The Flux of Macro Plastic from the Scheldt Basin Towards the Sea

Home , Haine, Scheldt, Senne (river)

INTERUNIVERSITY PROGRAMME ADVANCED MASTER OF SCIENCE IN ‘TECHNOLOGY FOR INTEGRATED WATER MANAGEMENT’

THE FLUX OF MACRO PLASTIC FROM THE SCHELDT BASIN TOWARDS THE SEA

Laurens Hermans Studentnumber UGent: 017121533 Studentnumber UAntwerpen: 20176277

Promotor: Prof. dr. Stefan Van Damme Copromotor: dr. Tom Maris Supervisor: drs. Bert Teunkens

Master's dissertation submitted in partial fulfilment of the requirements

for the degree of Master of Science in ‘Technology for Integrated Water Management’

Academic Year: 2017 - 2018

Abstract

Plastic contamination is an increasing environmental problem. Many aquatic species and birds get entangled, wounded or ingest plastic fragments with devastating effects. Besides is plastic also found to effect plants and even humans. Most of the plastic in the sea originates at land and is transported via the wind, rivers and coasts to the sea. Based on data of the plastic waste production of the inhabitants of the Scheldt basin, the waste production of inland navigation and waste created in the ports, this study modelled the flux of macro plastic from the Scheldt basin towards the sea. This flux is between 7.9 and 48.6 tons a year with the average scenario indicating 18.2 ton. This is a small number compared to major rivers in Europe and could be, besides the fact that the basin is much smaller than the other basins, related to the good waste management with only 0.6% of the yearly plastic waste production which is littered.

Using limited data on the cleaned-out materials and by estimating a waste input per kilometre, a second model was made to study the spatial behaviour of the macro plastic distribution in the waterways. While this model could not be correct calibrated, an indicative calibration using the modelled flux showed that the Maritime Scheldt delivers double the amount of plastic compared to the ‘kanaal Gent-Terneuzen’. The large cities are the major contributors of plastic litter within the basin.

To reduce the flux of macro plastic towards the sea, it is important to reduce the amount of plastic waste generated and to improve the management of plastic waste further. Also, additional research is necessary to determine the plastic waste hotspots and to test the effect of different measurers to reduce plastic waste.

Acknowledgments

This thesis was written with the primary aim of fulfilling the requirements for the degree of Master of Science in ‘Technology for Integrated Water Management’. Secondly this thesis contributes to the research of pollution within the Scheldt basin.

Writing a thesis requires a lot of support not only for the knowledge but also motivational support. Therefore, I like to thank everyone who contributed to my thesis or supported me. Especially thanks to Tom Maris and Bert Teunkens, who helped me by giving knowledge, feedback and justified criticism. Also, thanks to my promotor prof. Stefan Vandamme for helping me to understand the basic dynamics and processes present within the Scheldt basin.

Last but not least I have to thank my parents for their financial and motivational support, my sister Karolien for correcting my English and my family, my classmates and friends for their support and assistance.

Table of contents

Abstract ...... I Acknowledgments ...... II Table of contents ...... III List of Figures ...... V List of Tables ...... VI List of Abbreviations ...... VII 1. Introduction ...... 1 1.1. Problem statement...... 1 1.2. Relevance ...... 5 1.3. Research objectives and questions ...... 5 2. Study area ...... 7 2.1. Situating ...... 7 2.2. The ports and waterways ...... 10 3. Material and methods ...... 13 3.1. Top-down model: Downscaling of global models ...... 13 3.1.1. River pathway ...... 14 3.1.1.1. Mismanaged plastic waste (MPW) in the Scheldt basin ...... 14 3.1.1.2. Plastic load towards the sea based on Lebreton et al. (2017) ...... 15 3.1.1.3. Plastic load towards the sea based on Schmidt et al. (2017) ...... 15 3.1.2. Inland shipping and port pathway ...... 16 3.1.2.1. The amount of plastic entering the water via inland shipping and port activities .. 17 3.1.2.2. Transport losses ...... 17 3.2. Bottom-up block model ...... 19 3.2.1. Plastic entering the district ...... 22 3.2.2. Cleaned out plastic ...... 23 3.2.3. Plastic losses due to blockages ...... 23 3.2.4. Calibration of model ...... 24 4. Theoretical framework ...... 25 4.1. Definitions ...... 25 4.2. The production of plastic ...... 26 4.3. Types of plastics ...... 27 4.3.1. Low-density polyethylene ...... 28 4.3.2. High-density polyethylene ...... 28 4.4. The usage of plastic ...... 29 4.5. Plastic waste ...... 30 4.5.1. Selectively collected plastic waste ...... 30 4.5.2. Plastic via domestic waste ...... 31 4.5.3. Littered plastic ...... 32

III

4.5.4. Industrial plastic waste...... 34 4.5.5. Total land-based plastic waste ...... 35 4.5.6. Water-based plastic waste ...... 36 4.6. The degradation of plastic ...... 38 4.7. Distribution and spreading of plastics in the aquatic environment ...... 39 4.8. The effects of plastic in the aquatic environment ...... 41 4.8.1. The effect of macro plastics ...... 41 4.8.2. The effect of micro plastics ...... 42 4.8.3. The effect of chemicals attached to plastics ...... 43 4.9. Plastic litter legislation in Europe ...... 44 5. Results ...... 47 5.1. Top-down model ...... 47 5.1.1. The MPW produce with the Scheldt basin ...... 47 5.1.2. The river pathway ...... 49 5.1.3. Water-based plastic ...... 50 5.1.4. Total macro plastic entering the sea ...... 51 5.2. Bottom-up model ...... 52 5.2.1. Plastic entering the district ...... 52 5.2.2. Cleaned out plastic waste ...... 54 5.2.3. Results of bottom-up model ...... 54 5.2.4. Model calibration ...... 56 6. Discussion ...... 59 6.1. Top-down model: Downscaling of global models ...... 59 6.1.1. The mismanaged waste ...... 59 6.1.2. The river pathway of plastic waste ...... 60 6.1.3. The water-based plastic ...... 62 6.1.4. The total plastic amount delivered to the sea ...... 62 6.2. The added value of the bottom-up model ...... 63 6.3. Solutions to decrease the amounts if plastic ...... 63 6.3.1. Reduce the plastic waste ...... 64 6.3.2. Improve the waste management ...... 64 6.3.3. Get the plastic waste out of the rivers ...... 65 6.3.4. Transformation towards bioplastics ...... 66 6.4. Scope for further research ...... 66 7. Conclusion ...... 69 References ...... 71

List of Figures

Figure 1-1: Evolution of the plastic production over the last decades ...... 2 Figure 1-2: Estimated mismanaged plastic waste per million Mton for the population within 50 km of the coast ...... 3 Figure 2-1: The Scheldt basin with its major rivers and canals ...... 7 Figure 2-2: Distribution of the Scheldt basin area over its different regions ...... 8 Figure 2-3: Land use in Scheldt basin ...... 9 Figure 2-4: Population density within the Scheldt basin ...... 10 Figure 2-5: Port of Antwerp ...... 11 Figure 2-6: Freight transported in the Scheldt basin ...... 12 Figure 3-1: Macro plastic model From Land to Sea ...... 13 Figure 3-2: Basic structure of the top-down model...... 14 Figure 3-3: Linear regression model between the macro plastic load measured in the literature and the MPW ...... 16 Figure 3-4: Different ways to use the transport distance to estimate the transport losses...... 19 Figure 3-5: Basic block of the bottom-up block model with plastic in- and outflows ...... 20 Figure 3-6: Different districts in the study area; ...... 21 Figure 3-7: Block model scheme ...... 21 Figure 3-8: Discharge management around Ghent under normal weather and discharge conditions . 22 Figure 3-9: Example of plastic blocked behind a sluice ...... 24 Figure 4-1: Distribution of plastic production over the world ...... 27 Figure 4-2: The distribution of plastic types in some of the main rivers of Europe ...... 28 Figure 4-3: Plastic demand in Europe ...... 29 Figure 4-4: A) Distribution of European (EU28+NO/CH) plastics over main market sectors in 2016 ... 29 Figure 4-5: Plastics demand by polymer and market segment of 2015 ...... 30 Figure 4-6: A) Selectively collected plastic ...... 31 Figure 4-7: Sort analysis of Domestic waste in Flanders in 4 different groups subdivided ...... 31 Figure 4-8: Total amount of domestic waste and the fraction plastic ...... 32 Figure 4-9: Sort analysis of litter ...... 34 Figure 4-10: Plastic waste in Belgium by sector 10³t ...... 34 Figure 4-11: Plastic packaging production and the amount recycled and incinerated for energy production ...... 36 Figure 4-12: Recycling rate of packaging waste in Europe ...... 36 Figure 4-13: Collection of waste via the containers in the Port of Antwerp ...... 37 Figure 4-14: Origins of plastics found in the North Sea at Ostend ...... 40 Figure 4-15: The weight density of floating plastic modelled around the world ...... 41 Figure 5-1: Defining 'Centrum cities', 'Medium cities' and 'Small cities' ...... 47 Figure 5-2: Litter density map ...... 48 Figure 5-3: Accumulated MWP along the natural streams ...... 49 Figure 5-4: Additional litter density map based on packaging plastic in Belgium ...... 53 Figure 5-5: Result output in function of buffer distance/ width with different percentages of blocked plastic ...... 55 Figure 5-6: Result output in function of percentage blocked by sluice/ lock at the end with different buffer widths ...... 55 Figure 5-7: Model outflow of each district using a 100m buffer width and 70% of blockage ...... 56 Figure 5-8: Model outflow of each district using a 200m buffer width and 85% of blockage ...... 57 Figure 6-1: The relation of the micro plastic concentration and the population density and land uses 61

List of Tables

Table 1-1: Large European rivers with their plastic load ...... 4 Table 2-1: Average rain in parts of the Scheldt basin ...... 8 Table 2-2: Population of the Scheldt basin ...... 9 Table 3-1: Regression coefficients for the conversion of the MWP to the plastic load ...... 15 Table 3-2: Extrapolation factors based on total freight volume of ports ...... 17 Table 3-3: Transport loss coefficients used in the 'From Land to Sea' model ...... 18 Table 3-4: Districts managed by Waterwegen en Zeekanaal NV 2012-2015 ...... 20 Table 3-5: Different buffer distances around the waterways ...... 23 Table 4-1: The most common types of plastic polymers, their application and their demand ...... 28 Table 4-2: Organisations and agencies responsible for removal litter ...... 32 Table 4-3: Estimations of total littered waste ...... 33 Table 4-4: The amount of litter for different municipality types ...... 33 Table 4-5: Total plastic waste generated a year for Flanders ...... 35 Table 4-6: Estimation of Water-based plastic waste in the Port of Antwerp ...... 37 Table 4-7: Degradation rates of different plastic materials ...... 39 Table 4-8: Example of hazardous additives of plastic ...... 43 Table 4-9: European directives which could decrease the amount of marine litter ...... 44 Table 5-1: Plastic litter amounts for each city type ...... 47 Table 5-2: Monthly average catchment runoff in mm/day ...... 49 Table 5-3: Results of flux towards the sea from the river pathway ...... 50 Table 5-4: Port contributions in tons a year ...... 50 Table 5-5: Amount of plastic from inland shipping which reach the sea in tons a year ...... 50 Table 5-6: Amount of plastic from port activities which reach the sea in tons a year ...... 51 Table 5-7: Model output for the Scheldt basin in tons a year ...... 51 Table 5-8: Water-based plastic waste input ...... 52 Table 5-9: Litter input in districts in tons a year ...... 53 Table 5-10: Based on measurements in ZS - 1 percentage of inorganic waste ...... 54 Table 5-11: Waste cleaned out of the different districts ...... 54 Table 6-1: MPW calculations in different studies ...... 59 Table 6-2: Calculated plastic litter from the Scheldt basin to the sea ...... 60 Table 6-3: Large European rivers with their plastic load ...... 63

List of Abbreviations

AK: Albert Kanaal (Management department of ‘Vlaamse Waterweg nv’)

ANB: Agentschap voor Natuur en Bos (Flemish agency for nature and forests)

AWV: Agentschap Wegen en Verkeer (Flemish agency for road maintenance)

ArcGIS: Software packet for geospatial data analysis

BS: Bovenschelde (Upper Scheldt; Management department of ‘Vlaamse Waterweg nv’)

ESRI: GIS company and developer of ArcGIS

FVW/GFT: Fruit and vegetable waste (groente, fruit en tuinafval)

GLDAS: Global Land Data Assimilation Systems (surface modelled and data assimilation derived data products)

BKV GmbH: German plastic producer

GT: Gent-Teneuzen (District Management by Maritime Toegang)

KK: Kempische Kanalen (Management department of ‘Vlaamse Waterweg nv’)

MPW: Mismanaged plastic Waste

NOAH: Land surface model

OVAM: openbare Vlaamse afvalmaatschappij (Flemish waste management company)

PMD: Plastic, Metals and drink cartons (waste collection system)

SPW: Service public de Wallonie (Statistic service of Wallonia)

SRTM: Shuttle Radar Topographic Mission (elevation data)

UNEP: United nations environmental programme

USGS: United States Geologic survey

VMM: Vlaamse Milieu Maatschappij (Flemish environment agency)

VNF: Voies navigables de France (French waterway management)

VNSC: Vlaams-Nederlandse Schelde Commissie (Flemish-Dutch Scheldt Commission)

ZK: Zeekanaal (Management department of ‘Vlaamse Waterweg nv’)

ZS: Zeeschelde (Management department of ‘Vlaamse Waterweg nv’)

VII

VIII

1. Introduction

1.1. Problem statement

Over the last decades, there is an increasing interest in plastic debris in the aquatic environment. This is because a large amount of studies show the negative impact of plastic elements on fauna and flora. Already more than 663 species are found to be impacted by marine plastic debris, with entanglement and ingestion as the main effects causing wounds, blockages, bio-accumulation, hormone imbalances, oxidative stress, impaired reproduction or even direct death (Baldwin et al., 2016; Eriksen et al., 2013; van der Wal et al., 2013). Since the early 1970s the plastic pollution in the oceans is widely studied. The fluxes from land towards the sea, however, where not yet estimated and only recent studies try to make rigorous estimations of this yearly flux towards the oceans. A first estimation for a global waste flux happened in 1975. The National Research Council (1975) estimated a flux of 5.8 Mtons of waste coming from passenger vessels, merchant shipping, recreational boating, commercial fishing and other sources. They mention, within these fluxes, high percentages of plastic litter. However, the measurements for this percentage in waste were too limited and too diverse to make global estimations of the plastic fluxes. Even when the exact percentage of plastic would be present, this calculated flux would no longer be representative today. This is because the discharge of plastic from at-sea vessels is banned since 1988 (IMO, 1988) and this study underestimates the amount of plastic coming from land sources, while this is 80% of all the marine debris (Jambeck et al., 2015). Worldwide the use of plastic has increased dramatically. In 1977 only 50 Mton was produced yearly (PlasticsEurope, 2016), while this was 335 Mton in 2016 (Figure 1-1). This is an increase of 710%. In Europe the production seems to be stabilized nowadays, meanwhile the production in the world is still increasing. Jambeck et al. (2015) is one of the first studies, which tries to estimate the yearly global plastic flux towards the oceans. The study uses the amount of mismanaged plastic waste (MPW) generated annually by the population living within 50 km of the coast to calculate the yearly input. This is calculated for each country with the following formula:

푀푃푊 = 푚푝푝 With: MPW the mismanaged plastic waste mwaste the mass of waste generated per capita annually pplastic the percentage of waste that is plastic pmismanaged the percentage of plastic waste that is mismanaged

400 350 300 250 200 150 100

Plasitcproduction (Mton) 50 0 2005 2007 2011 2012 2013 2014 2015 2016

Europe World

Figure 1-1: Evolution of the plastic production over the last decades in the world and Europe (in Mt)(Based on PlasticsEurope, 2017)

The MPW gives the amount of plastic that has the potential to enter the ocean. To convert this to marine debris this study uses three conversion rates (15%-25%-40%) to have a minimum, average and maximum scenario (Jambeck et al., 2015). These rates are loosely based on a study of the water quality data from the San Francisco Bay, where a maximum rate of 61% was found (BASMAA, 2012). This method results in a final estimation of a global flux between 4.8 and 12.7 Mton of plastic. Jambeck et al. (2015) also looks at the spatial distribution of the MPW (Figure 1-2). The contribution per country varies between 1.1 ton to 8.8 Mtons a year and the top 20 contributors are responsible for 86% of the waste and are mostly located in Asia. The annual waste generation is mostly a function of the population size of the coastal region, however also the percentage of mismanaged waste is important. In many of the countries with a high MPW, there is a fast-growing economy, while the growth of the waste management infrastructure is lacking. For Belgium the study estimates a yearly flux between 411 ton and 1097 ton (Jambeck et al., 2015). Although, not only the first 50 km from the coast contributes plastic towards the sea and river networks can facilitate the transport of plastic debris over longer distances into the sea. This is already proved by studies for terrestrial sediments, organic carbon, nitrogen and various other solutes (Gruber & Galloway, 2008; Ludwig & Probst, 1996; Schmidt et al., 2017). Therefore Lebreton et al. (2017) and (Schmidt et al., 2017) adapted the model of Jambeck et al. (2015) to a river basin based model.

Figure 1-2: Estimated mismanaged plastic waste per million Mton for the population within 50 km of the coast in 2010 (Jambeck et al., 2015)

Lebreton et al. (2017) still uses the MPW and the population density, furthermore, the catchment runoff and the presence of artificial barriers, in the form of large reservoirs, that act as particle sinks are also included. This study uses the following formula:

푀 = 푘푀푅 With Mout the plastic mass release at the outflow (kg/d) Mmpw the mass of MPW produced inside the catchment downstream of artificial barriers (ton/year) R the monthly averaged catchment runoff (mm/d) a and K regression parameters

The regression parameters are determined by known values of plastic loads in different basins around the world found in literature. This method helps to overcome one of the weaknesses of the approach of Jambeck et al. (2015) where conversion rates are used and for each country the assumption was made that 2% was littered (Jambeck et al., 2015).The resulting estimation is a global flux between 1.15 and 2.41 Mton of plastic, with a similar spatial distribution as in Jambeck et al. (2015). However, because the calibration based on literature mentions mostly buoyant plastic, the result could be an underestimation of the real number. Additional, this model does not take in account the littering near beaches. The study estimates a contribution of the Scheldt between 4.2 and 23.3 tons a year, which is low compared to for example the Rhine (718 – 2263 ton).

Schmidt et al. (2017) has a similar approach but does not include runoff and sinks. This study tries to find a relationship between the measured plastic loads out of the literature and the MPW, therefore a power-law model is used. Schmidt et al. (2017) has the first model that makes a clear distinction between macro- and microplastics (the particles larger than 5 mm or smaller). The global estimates for macro plastics flux are between 51 kton/yr and 440 kton/yr, with a median of 150 kton/yr. For the total flux (micro and macro plastics) the estimates are between 210 kton/yr and 4 380 kton/yr, with a median of 470 or 2 750 kton/yr depending on the set up of the model. The first setup includes all datasets found in the literature, while in the second case only the datasets which includes both micro as macro plastic measurements are included. The results of this study clearly have a large uncertainty range, but this study also shows the dominance of Asia as contributor of plastics. For the Scheldt this model calculates 1.46 ton/yr for macro plastics and 0.6 ton/yr or 2.2 ton/yr for micro plastics, depending on the different setups of the model.

So, the existing models have a wide range of plastic load estimations within and between them (Table 1-1) for both the Scheldt basin as for the global fluxes. One of the reasons for these large differences is the large variety of basins that exist. They differ by population density, levels of urbanization and industrialization, rainfall rates and presence of barriers such as weirs and dams. While only a limited amount of these parameters is included in the existing models, many of them parameters are indicated to influence the possible amount of plastic loads (Lebreton et al., 2017; Schmidt et al., 2017). On the other hand, also extrapolations of measurements show results which are far off from the model outputs (Table 1-1). In most cases the models seem to have overestimated the plastic load. But it is also possible that the extrapolations are an underestimation because of the episodic character of plastic fluxes, related to storm events which are not often measured (van der Wal et al., 2015). Because both techniques have their weaknesses it is useful to try to improve them both.

Table 1-1: Large European rivers with their plastic load based on 1) extrapolations of field measurements (van der Wal et al., 2015); 2) extrapolation of volumetric measurements of the load in the Rhine, Meuse and Scheldt converted to mass based on estimate 1 (van der Wal et al., 2013); 3) Modelled loads from Schmidt et al. (2017); 4) Modelled loads from Lebreton et al. (2017)

River Area of Average Plastic load Plastic load Plastic load catchment discharge extrapolated modelled 3 modelled 4 (10³ km²) (m³/s) (ton/yr) (ton/yr) (ton/yr) Rhine 185 2900 20-30 1 180-582 718-2263 Po 74 1500 120 1 6.5 -13.2 34-154 Danube 800 7000 500 1 1008-4273 287-1014 Scheldt 22 120 (2-4) 2 2.09-3.67 4-23 Meuse 35 350 (4-6) 2 8.2-16.9 18-32

1.2. Relevance

Within in my master of TIWM (Technology for Integrated Water Management) one of the main objectives is: ‘How to manage a basin to protect both humans and the environment in a sustainable way’. Within this domain plastic is a relative recent studied threat for both the water quality, different aquatic species and even humans. Like earlier mentioned plastic can affect organisms in different ways. To reduce this threat and to prohibit a future increase it is important to have an idea of the magnitude of the plastic fluxes from land towards the sea. This could help to identify the pollution hotspots and the effect of some plastic reducing measurers. Because continuous measurements are difficult, expensive and not standardized a realistic model is necessary. For this reason, this study tries to model the macro plastic flux for the small, heavily urbanized and dense populated Scheldt basin. Based on the results of this study, the models could be broadened by including micro plastics and calculate the total plastic fluxes.

1.3. Research objectives and questions

First of all, this study tries to estimate the annual macro plastic flux at the basin scale, this scale is chosen because this is the scale where the extrapolation models and global models meet. To set up the models the Scheldt basin is selected as a case study. This is a relative small, highly industrialized and urbanized and dense populated basin with a good waste management status. While this basin has many characteristics, which are often related to a high plastic load like the high degree of urbanization and dense population (van der Wal et al., 2015; Yonkos et al., 2014), this basin seems to have a relative low plastic load based on both extrapolations and the models (Table 1-1).

The first method that will be used is a top-down method, where it is tried to downscale the existing global models for plastic fluxes. The second method is a bottom-up method where it is tried to extrapolate the limited amount of plastic waste measurements in the Scheldt basin. Then the estimations of both techniques will be compared to see if the final fluxes are of a similar magnitude and the results will be compared to existing model outputs and measurements from the literature. Finally, possible measurers are discussed and the use of models to see their effectiveness.

The corresponding research questions are:

. How large is the annual flux of macro plastic from the Scheldt basin towards the sea based upon the downscaling of global models? . How large is the annual flux of macro plastic from the Scheldt basin towards the sea based on upon extrapolations of plastic waste measurements within the Scheldt basin? . Do both the bottom-up and top-down models show similar estimates of the annual macro plastic flux? . How do the results of both models compare to other plastic flux estimations in the world? . Is it possible to use the plastic flux models to estimate the influence of measures to decline the plastic pollution?

The next chapter will introduce the Scheldt basin, this is followed by a chapter which describes how the global models are downscaled and how limited data will be upscaled. Next more information will be given about plastic and the influence of plastic on the environment and the legislation towards plastic in the theoretical framework. Then will both the bottom-up as top- down model be applied to the Scheldt basin and in the final part these results will be discussed and compared against existing literature.

2. Study area

2.1. Situating

The Scheldt basin is 22 116km² and is located within France, the Netherlands and Belgium. Of this latter all three regions are partly located within the basin (Flanders, Brussels and Wallonia) (VMM, 2004; Figure 2-1). With 45% is most of the basin located in Flanders, followed by France with 31% (Figure 2-2). The northern part of the basin is mainly flat and the highest part is 212 m above sea level and is located in Wallonia (VMM, 2004). The area is characterised by polders, these are low lying areas which are reclaimed by dykes (VMM, 2004). The river Scheldt itself has a length from source, Gouy (FR), to mouth, Vlissingen (NL) of 350 km (VNSC, 2018).

Figure 2-1: The Scheldt basin with its major rivers and canals

The river section between the source and the sluice in Merelbeke (Ghent) is called ‘the Upper Scheldt’, between Ghent and the Belgian-Dutch border the ‘Maritime Scheldt’, and beyond this border we’re talking about ‘Westerscheldt’ (van der Wal et al., 2013). The Scheldt has many tributaries of which the Durme, Scarpe, Sensée, Haine, Dender, the Lys and the Grote and

Kleine Nete, Dijle and Zenne via the Rupel are a few important ones. Many of these streams are canalised for navigation purposes, for the same reason the basin has a dens canal network (Figure 2-1). In total 1434 km of waterways is navigable in the basin. Also, the main part of the Scheldt is canalised, with more than 250 weirs and locks (VMM, 2004). The maritime Scheldt and the Westerscheldt together form the estuary where there is a tidal influence. At Vlissingen twice, a day more than 1 billion m³ flows in and out of the Scheldt. The annual net river discharge is estimated on 4 billion m³ (VMM, 2004).

Figure 2-2: Distribution of the Scheldt basin area over its different regions

The Scheldt basin has a temperate maritime climate with a relative wet summer and mild winter. Table 2-1 shows the rainfall, this amount is distributed quite homogenous over the area throughout time, without clear dry seasons. But in the spring and summer the rain has often higher intensities (Vandaele & Poesen, 1995).

Table 2-1: Average rain in parts of the Scheldt basin (VMM, 2004)

Average rainfall (mm/yr) France 805 Walloon region 842 Brussels 780 Flemish region 845 Netherlands 775

The Scheldt basin is highly urbanized, with a high percentage of urban area (Figure 2-3). The area has some major industrial areas around Kortrijk, Ghent, Antwerp, Vlissingen Terneuzen, along the Antwerp-Brussels-Charleroi axis, in the Lille-Roubaix region, along the Albert Kanaal … (VMM, 2004). Agriculture is however still the land use which covers most of the area. Forests, on the other hand, are very limited.

Figure 2-3: Land use in Scheldt basin based on VMM (2004)

The Scheldt basin is very dens populated, in total 11.1 million people are living within its borders (Table 2-2). Almost 50% lives in Flanders and only 2% in the Netherlands. Figure 2-4 shows that the population density is quite scattered and is especially high around the larger cities of Antwerp, Ghent, Brussels, Lille, Arras and Lens.

Table 2-2: Population of the Scheldt basin (Based on CBS StatLine (2017); Data.gov.fr (2017); IBZ (2017))

France 3 053 906 Brussels 1 183 545

Flanders 5 377 052 Wallonia 1 286 061 The Netherlands 217 074

Total 11 117 638

Figure 2-4: Population density within the Scheldt basin (Based on CBS StatLine (2017); Data.gov.fr (2017); IBZ (2017))

2.2. The ports and waterways

As mentioned in previous chapter not all plastic waste is coming from inland areas, also the ports and the shipping on the waterways play an important role. The Port of Antwerp is the most important industrial area of the basin (Figure 2-5), it is approximately 13 000 ha (van der Wal et al., 2013). Besides this port, the ports of Ghent, Brussels, Lille and the Zeeland ports (ports of Terneuzen and Vlissingen) are also important in the basin, the latter two (Ghent and Zeeland ports) are merged into the ‘North Sea port’ at the end of 2017 (the places are indicated on Figure 2-6). The port of Antwerp, however, is focussed upon to calculated the plastic waste within this study because this port is relative close to the mouth of the river and has a freight 3 times higher than the other ports combined (Port of Antwerp, 2017).

Figure 2-5: Port of Antwerp (Port of Antwerp, 2014)`

Like mentioned earlier many rivers are canalised and many additional canals are available for shipping in the basin. The boats generate waste and are therefore also an important source for waste. Additional the locks and weirs, build for navigation, are places were waste gets stuck and is removed from the system (Schmidt et al., 2017). Figure 2-6 shows the freight per waterway, this figure shows clearly that the traffic from Antwerp is dominant, but also the Gent- Terneuzen kanaal is an important connection. Inland are the Albert Kanaal, the Maritime Scheldt, the Ringvaart of Ghent, the Lys and the ‘Gent-Brugge kanaal’ important.

Figure 2-6: Freight transported in the Scheldt basin (based on De Vlaamse Waterweg nv (2017); Port of Antwerp (2017); SPW (2017) ; VNF (2017); WDP (2016)) and the places with the most important ports

3. Material and methods

3.1. Top-down model: Downscaling of global models

The first model is a hybrid model of the ‘From Land to Sea model’ (developed by BKV GmbH (2017)) and the earlier mentioned model of Lebreton et al. (2017) and model of Schmidt et al. (2017). Figure 3-1 show how to ‘From Land to sea model’ is structured. First an estimation is made of the amount of plastic waste which is generated in an area, next is estimated how much of this waste is improperly disposed (the 0.3% is based on data of the city of Bayern). Then is assumed that the largest part of this litter will end up on land and only 30% of this waste will go towards waterbodies. Finally, this amount of waste will travel via four different pathways towards the sea: the river, the coast, inland shipping or ports. In practice this model calculates for all of these different pathways the amount of litter which ends up in this pathway and multiplies this with a transport coefficient. This coefficient is the account for the losses of plastic by waterway management, sedimentation in nature, the blockage at sluices and locks …

Figure 3-1: Macro plastic model From Land to Sea (BKV GmbH, 2017)

The model of this research uses three pathways: the river, shipping and the ports (Figure 3-2). The coast pathway is not included for the Scheldt basin because the length of the coastline of the Scheldt basin is small (Figure 2-1). The amount of plastic entering the sea via the river pathway is based on the mismanaged plastic waste and is calculated in two different ways

13 using the methods of Lebreton et al. (2017) and Schmidt et al. (2017). For the other two pathways similar to the ‘From land to Sea model’, first the total amount entering this pathway is estimated using existing literature and this amount is multiplied with different transport coefficients.

Figure 3-2: Basic structure of the top-down model

3.1.1. River pathway

In the model this pathway is used to transport all the mismanaged waste by the inhabitants of the basin towards the sea. To assess the amount of this waste enters the sea, the two earlier discussed models from the introduction are used (Lebreton et al. (2017) and Schmidt et al. (2017)), which are both driven by the MPW.

3.1.1.1. Mismanaged plastic waste (MPW) in the Scheldt basin

In this model the MPW will be approximated with the total amount of plastic littered by the inhabitants of the basin. This amount will be discussed together with the total amount of plastic waste in the next chapter. The amount of litter will then be converted to a litter density map which shows for each location in the basin how much litter is generated per square kilometre. To converse these values to a MPW for the whole basin, the same method as in Lebreton et al. (2017) is used. In this study is assumed that the inland plastic accumulates by following natural drainage patterns derived from the space borne elevation data. In this case the SRTM elevation data with a resolution of 1 arc-second are used (USGS, 2000). This data is however slightly adapted to get the natural drainage pattern closer to the real pattern, this is done to cope with the human influences which reformed the basin, as mentioned in Chapter 2. Therefore, the elevations at the border of the basin are enlarged, so that the water cannot flow out via this border, for this original border the border found on Scheldemonitor (2015) is used. This elevation data combined with the plastic litter density are with the flow accumulation toolset from ESRI’s ArcGIS software converted to the total mass of inland MPW upstream of the outflow.

3.1.1.2. Plastic load towards the sea based on Lebreton et al. (2017)

The convert the MPW to a load of plastic Lebreton et al. (2017) uses the following formula as mentioned earlier:

In the research three different scenarios are used based on different extrapolations to enlarge the dataset out of the literature. The three final scenarios are a low, average and high load scenario and the corresponding regression parameters are can be found in Table 3-1. The average catchment runoff in millimetres a day was calculated using GLDAS driving the NOAH land surface model (Rodell et al., 2003). The model computes the daily average 3h surface and subsurface runoff globally on ¼ degree resolution, for this runoff the monthly average of the sum of both runoff values is used converted to a mm/d format. The GLDAS-data is used in the initial plastic load model because these data exist at a global level. This study uses this data, however they give often a small underestimation of the flow (Lebreton et al., 2017), still because the model of Lebreton et al. (2017) is calibrated by using

GLDAS-data. Only more recent data (2017) will be used. To find out of these Mout-values the final yearly load the different daily loads are multiplied with the corresponding days a month and these monthly values are summed.

Table 3-1: Regression coefficients for the conversion of the MWP to the plastic load (Lebreton et al., 2017)

k a Average 0,00185 1,52 Low 0,00107 1,61 High 0,00446 1,42

3.1.1.3. Plastic load towards the sea based on Schmidt et al. (2017)

Schmidt et al. (2017) tried to find a direct relation between loads of plastic entering the sea from literature and the MPW. As mentioned in the introduction a power-law model is used to account for the nonlinearity and the regression coefficients b1 and b0 are estimated b linear least-squares regression (see formula below).

푙표푔(퐿) = 푏 + 푏푙표푔(푀푃푊)

With L the plastic load entering the sea (ton/yr) MPW the mismanaged plastic in the basin (ton/yr) b0 and b1 regression coefficients

The linear regression model gives the black line on Figure 3-3. In this study will however besides the x on y regression used in Schmidt et al. (2017) also the y on x regression and the bisector regression be included. The reason this is done, is because a small deviation from the regression line in a power model can lead to a difference in an order of magnitude. To increase the range (and possible worst-case scenarios), this study made the choice to include the additional regression lines which leads to three different scenarios (low, average, high). The MPW that will be calculated could then be directly transformed using these regressions into a low, average and high load.

Figure 3-3: Linear regression model between the macro plastic load measured in the literature and the MPW of the basins (based on Schmidt et al. (2017))

3.1.2. Inland shipping and port pathway

Both the inland shipping and the port pathway are quite similar structured in the model. In both cases first the total of plastic entering the water via shipping and port or quay activities is estimated. Next is this amount, based on the location were this plastic enters the system, multiplied with a fraction of this plastic waste that enters the sea to account for the transport losses due to blockages and so on.

3.1.2.1. The amount of plastic entering the water via inland shipping and port activities

Like mentioned earlier, these amounts are mainly determined by literature in next chapter. For the plastic waste coming from inland navigation, the total waste is converted to an amount of waste per kilometre of waterway. This is mainly done to make it possible to extrapolate the values to values for the whole basin. However, additional does this method make it possible to give a spatial component to the waste values. This spatial component is important because in certain transport losses, proposed in next section, have a specific value for each specific place in the basin.

In case of the ports the calculation gets a little more complex, this is mainly due to a lack of data and because all ports are managed by different authorities. Therefore, only the amount of plastic waste that enters the water will be calculated for the ‘Port of Antwerp’ in next chapter. This value is then extrapolated to the other ports assuming that this amount of plastic waste is proportional to the total freight volume in of the ports. This results in the extrapolation factors of

Table 3-2.

Table 3-2: Extrapolation factors based on total freight volume of ports (based on (Port of Antwerp (2017))

Port Freight Mt Extrapolation factor Brussel 5 0.02 Lille 8 0.04 Ghent 29 0.14 Zeeland seaports 33 0.15 Antwerp 214 1

3.1.2.2. Transport losses

The amounts of plastic waste calculated are then transformed towards a load of plastic that reaches the sea. This is done using four different calculation for transport coefficients. The first one is based on the original values that are used in the ‘From Land to Sea’ model (Table 3-3). From these values the base values of 80% and 20% are used (Table 3-3), this means that 20% of the plastic that ends up in the river/waterway via inland shipping ends up in the sea, while this is 80% for plastic in the ports. Because these values are based on only limited field data for the Rhine, the applicability of these values for the Scheldt basin is questionable. Therefore, the three other coefficients are added.

Table 3-3: Transport loss coefficients used in the 'From Land to Sea' model (BKV GmbH, 2017)

Variable/scenario Min Base Max Incorrectly disposed of waste 0.2% 0.3% 0.5% Transport loss macro plastics (river) 96% 80% 64% Transport loss macro plastics (inland shipping) 96% 80% 64% Transport loss macro plastics (ports) 24% 20% 16%

These three values are all based on a similar assumption: the transport loss is in function of the transport distance. If plastic waste enters the river at the mouth of the river or at the coast 0% of the plastic will be lost, while plastic that enters the basin at its headwater border will probably never enter the basin and therefore 100% is lost. Although this is a simple concept the implementation is more difficult. This is mainly because the transport distance is difficult to define. This study made three different assumptions to approximate this distance. First of all, the natural flow distance is used, this is a distance calculated based on the DEM if the area based on the flow accumulation tools of ArcMap (Figure 3-4a). Because of the earlier mentioned large human influences in the basin, the flow pattern is no longer realistic and therefore the two other methods are added. The second method uses the distance towards the coast (Figure 3-4c). Plastic can arrive much faster via different canals towards the sea than following the flow network, therefore this distance is added as shortest distance for each location to the sea. Finally, in the third method the distance toward the river mouth is used (Figure 3-4e), this distance is the shortest distance for each point towards the mouth of the river and assumes in contrary to previous distance all plastic has to still pass the mouth of the river in this calculation but similar to previous one it could go quicker by following canals. All these three distances are inversed normalised, which gives Figure 3-4b,d,f. Each percentage indicates how much plastic which enters up at that location will finally enters up in the sea.

These raster data need than to be multiplied with the plastic waste amounts estimated for the inland navigation and ports converted to raster data and the total sum of this final raster will give the total amount of water-based plastic entering up in the sea. Which can be summed with the earlier calculated river-based plastic to find the total tonnage of plastic entering up in the sea via the Scheldt basin.

Figure 3-4: Different ways to use the transport distance to estimate the transport losses. a) The natural flow distance; b) This distance inverse normalised form 0 to 1; c) The Euclidean distance towards the coast; d) This distance inverse normalised form 0 to 1; e) The Euclidean distance towards the river mouth; f) This distance inverse normalised form 0 to 1.

3.2. Bottom-up block model

In the bottom-up model only the major waterways are included, this is mainly to reduce the complexity and the lack of data for many small streams. For this model, a block model is used in which each block represents a district (Figure 3-5) and each district has an inflow from previous district and an outflow to next district. Further has each district additional inputs from littering in the area and mismanaged waste from inland shipping. If there is a port within the district an additional input of the port will be present. Finally, will also a part of the plastic be

19 cleaned out by or ordered to clean out by the water manager and will there be losses of plastic due to blockages etc.

Figure 3-5: Basic block of the bottom-up block model with plastic in- and outflows The district is chosen as main block because the cleaning and management of the waterways in Flanders happens per district. For the different districts which were managed by ‘Waterwegen en Zeekanaal NV’(

Table 3-4), the tonnages cleaned out of the waterways are available. Additional to these districts in this research 3 additional district are added: ‘Kanaal Gent-Terneuzen’ (GT), the ‘Westerscheldt’ (WS) and the ‘Albert Kanaal & de Kempense Kanalen’ (AK&KK). Figure 3-6 shows all of the districts included in this study.

Table 3-4: Districts managed by Waterwegen en Zeekanaal NV 2012-2015

District Waterways Remark BS-1 Gentse waterwegen BS-2 Upper Scheldt BS-3 Lys BS-4 Dender, oude Dender, Moervaart & Boven Durme BS-5 Kanalen oost (i.a. Kanaal Gent-Brugge) BS-6 Kanalen West (i.a. Kanaal Passendale-Nieuwpoort) BS-7 Ijzer ZS-1 Scheldt & Durme Division organic waste & other waste ZS-2 Lower Maritime Scheldt, Upper Martitme Scheldt (East) & Rupel ZS-3 Nete (Grote en Kleine) Cleaned by contractor floating wood ZS-4 Lower Senne, Dijle & Demer ZK-1 Sea Canal Charleroi-Schelde ZK-2 Kanaal Leuven-Dijle & Netekanaal

Figure 3-6: Different districts in the study area; the different colours symbolise different departments (Black= out of study area)

These districts lead to the block model shown by the scheme in Figure 3-7. Around Ghent the districts are related to multiple districts. To find what the contribution is towards the different districts, we assume a similar distribution as the discharge distribution in this area. Based on the average discharge management carried out by ‘De Vlaamse Waterweg nv’ (who manages this discharge) 33% percent of the plastic coming out of the Lys district will go to the Ghent (BS-1) district and 66% is going out of the system (Figure 3-8). The outflow of Ghent is divided over ‘Kanaal Gent-Terneuzen (29% GT), the ‘Maritime Scheldt-Durme’ (66% ZS-1) and also a minor part will leave the Scheldt basin (4%).

Figure 3-7: Block model scheme; green arrows or input flows from other districts not mentioned; the black box represents an outflow out of the system

Figure 3-8: Discharge management around Ghent under normal weather and discharge conditions (D. Maes, 2018)

3.2.1. Plastic entering the district

Plastic can enter the district in four ways: via another district, via littering in the district, via mismanaged waste coming from inland navigation or via mismanaged waste from ports in the district (Figure 3-5). The whole outflow of a district is assumed to enter the next district or will be divided over multiple districts (using the distribution earlier mentioned). Only the inflows at the borders of the defined system (green arrows on Figure 3-7) are in this study assumed to be 0 tons a year. This will be an underestimation, but these values are set in this way because (1) of the large distance towards the outlet of the system, because (2) there is a lack of data concerning the management in the French part and because (3) many of the plastic will flow out towards the sea in the west or towards the Meuse.

For the ports and the inland shipping similar values are used as the values used in the top- down model. Only for the plastic litter the calculation is more complex. The litter that finally goes to the sea is litter that is not managed at all. Because this plastic is not managed, no numbers of the real amounts are existing. Although some numbers can be found for the total amount of plastic packaging produced in Belgium, together with the total amount of this plastic that is managed (See Figure 4-11). An assumption can be made that all the additional plastic, which is produced but not managed, is littered. Thus, the tonnage of additional plastic litter can be converted to an additional litter rate per person. Together with the population density data, this rate can create a map of the additional plastic litter density, which gives as spatial dimension to the additional plastic waste. How much of this additional litter ends up in the river stays however a large unanswered question. We try to estimate this amount by assuming that

‘all’ litter within a certain distance from the major waterways within the district will end up in this waterway. The magnitude of this distance is, however, unknown. To make up for this several distances are used as shown in Table 3-5, by calibration later on the optimal distance will be selected. For each of the districts a buffer with this distance will be made around the waterways (using Arcmap software) and all of the plastic waste within this buffer will be assumed to enter the district. A disadvantage remains that the smaller streams and waterways are not included, a district with many incoming waterways would probably have a larger buffer than a district without incoming waterways

Table 3-5: Different buffer distances around the waterways of each district which are used to estimate the input from litter in each district

Different buffer distances around waterways 100m 200m 500m 1000m 2000m 3000m

3.2.2. Cleaned out plastic

In each district management cleans out a certain amount of waste among which a certain amount of plastic. Besides these clearances, there is also an additional cleaning out of floating material in the Port of Antwerp. The data for this management operations is available for the period of 2012- 2015 for the districts managed by the ‘Waterwegen en Zeekanaal NV’ ( Table 3-4). For each district all the floating and littered waste is summed and the average is made over the years which have a continue set of measurements. This gives only the amount of waste cleaned out. To convert this to the total amount of plastic waste, the measurements of ZS-1 are used. These measurements made a difference for 2014 – 2016 between organic and inorganic waste, the average of this years is used to convert the total waste fished out to solid waste. This amount will then be converted into plastic using the later on discussed contribution of plastic towards litter. For the port of Antwerp, a similar approach is used. For the other districts GT and AK&KK were no measurers were available, we assume ‘worst case’ that there is no management.

3.2.3. Plastic losses due to blockages

Locks and sluices are important sinks in the plastic waste budget (Figure 3-9), Lebreton et al. (2017) even indicated that artificial barriers in rivers could retain 65 % of all the plastic. This is because they form a physical barrier and they reduce locally the flow rate which leads to

23 sedimentation of waste. Because almost all of the districts of a lock or sluice close to their confluence (except for the WS), each district will be multiplied with a loss fraction between 0 and 1. This loss will, just as the earlier discussed buffer distance, be determined by calibration, because it is difficult to put a real amount or percentage on the blockage by a sluice or lock and while some areas have only 1 sluice other have multiple. In practice this number will not be equal for each district, because the number of sluices and the discharge will probably affect this number. The Albert Kanaal for example will probably have higher losses compared to the Maritime Scheldt. But due to a lack of calibration data a similar loss for each district is assumed.

Figure 3-9: Example of plastic blocked behind a sluice (Topping, 2018)

3.2.4. Calibration of model

Finally, this model has to be setup, ideally this would be done with measured outflow fluxes for as many districts as possible. These values are, however, not available for any of the districts. Therefore, for the calibration the output values of the top-down model are used to find numbers for the loss fraction and the ideal buffer distance. This however leads to the fact that the output value of this model is not very useful, because it will be similar to the top-down model. However, the distribution over the different districts can give a better inside in the plastic waste hotspots and if in the future measurements are available this model could be used to estimate a flux towards the sea.

4. Theoretical framework

4.1. Definitions

Plastic is an all-encompassing word referring to a family of synthetic polymeric materials (UNEP, 2014). Plastic is often the preferred option for a range of applications because of its versatility and low price. It is relatively strong, has a low weight and is malleable. In addition plastic has also social benefits: the plastic packaging keeps food fresh and safe and it has many medical applications (UNEP, 2014). Furthermore, it has some environmental benefits. The amount of CO2 that is prevented to by emitted by the reduction of food losses by plastics, is , for example, lower than the CO2 emitted while manufacturing the material (Pilz et al., 2010). Despite these qualities, plastic has a range of negative environmental and social impacts throughout its lifecycle. Chemicals could escape in the environment, a lot of non-renewable petroleum is used for the manufacturing and as earlier mentioned one of the most important environmental problems is the generation of plastic litter (UNEP, 2014). In this study all the different plastic elements will be included with a certain size as will be mentioned later on.

There are many different types of plastic waste. Most plastic waste in Flanders is collected for recycling or incineration via separately collection of plastics, or via the collection of household waste. However most plastic waste which does enter the aquatic environment is plastic litter. Litter is any piece of misplaced solid waste (Geller, 1980). While most people are aware that littering has major environmental impacts, a study in the USA showed that 17% of the individuals in this research littered during the observation period (Schultz et al., 2013; Williams et al., 1997). Littering is not related to a specific gender. Younger people however, show to litter more compared to older people. Littering happens both on purpose and by leaving things behind by accident. The most common littered items are food wraps and containers, beverage containers, paper products and cigarettes (Williams et al., 1997). Many of these products consist out of plastic and are therefore the main source of the plastic that ends up in to the river systems towards the sea.

In the aquatic environment plastic litter is classified in to two categories: marco plastics (particles larger than 5 mm) and micro plastics (particles smaller than 5 mm) (van der Wal et al., 2013). Besides these dominant forms and terminology, other often used terms in literature are meso plastic and nano plastic. This first indicates plastic between 5mm and 25mm and nano plastic is smaller than 100nm (González et al., 2016; Koelmans et al., 2015). This study will, focus mainly on macro plastic and to a lesser extent on micro plastic. The macro plastics includes, among others, packaging of foods and drinks, households items such as combs, toothbrushes and pens, shopping bags … (Fendall & Sewell, 2009). These plastics enter the

25 environment by littering or are displaced by the wind (UNEP, 2016). The micro plastics, on the other hand, can enter the aquatic environments in a number of ways. Primary sources include manufactured plastic products such as scrubbers in cleaning and cosmetic products, as well as manufactured pellets used in feedstock or plastic, which can enter the water via spillages or via effluent streams of waste water (Baldwin et al., 2016; Eerkes-Medrano et al., 2015). Secondary sources of microplastics and dominant one, include fibres or fragments resulting from the breakdown of larger plastic items via photodegradation and/or mechanical breakdown (Baldwin et al., 2016; Eerkes-Medrano et al., 2015). Especially these micro plastics are harmful for the environment, measurements for this size of elements is however missing, or very limited for the Scheldt basin, therefore this study focusses on macro plastics.

4.2. The production of plastic

The production of plastic starts from crude oil or biomass, which is in a refinery separated into different fractions of which the naphtha fraction is one. The naphtha is then transferred to a petrochemical factory where it is treated in a steam cracker at a temperature of 800 °C in the presence of water vapour. This results into the naphtha splitting into light hydrocarbons olefins (ethylene, propylene, butylene and butadiene) and aromatics (benzine, toluene and xylene) (Planète Énergies, 2015). Next out of these elements polymers are formed. For these two processes are used: polymerization and polycondensation. In the polymerization process, polymers are formed by low-molecular compounds which gradually attach to each other. In the polycondensation process polymers are formed by combination of different monomers. This second process happens often by the release of various subsidiary low-molecular product. The main difference is that in polymerization, the composition of the monomer and polymer is identical, while this can significantly differ in the polycondensation process (MEL Science, 2017). Fossil fuels are still the dominant source of plastic, but this is only 4-6% of the total usage of them within Europe each year (Plastics Europe, 2017).

The end product of these factories are granules or powders, which are then transported for further processing, they can be kneaded, heated, supplemented with other chemical products, cooled or even moulded (Planète Énergies, 2015). This results in hundreds of different materials with a wide variety of properties, which could be designed in such a way to meet the needs of each single application in an efficient manner (Plastics Europe, 2017). There are mainly two types of plastics: thermoplastics and thermosets. The former is a family of plastics that can be melted when heated and hardened when cooled. Therefore, these transformations are reversible. The latter is a family of plastics which undergo chemical changes when heated. Therefore, this plastics cannot be re-melted or reformed (Plastics Europe, 2017).

Like mentioned in the introduction, the plastic production between 1977 and 2016 increased with 710% towards 335Mton a year. 50% of this production takes place in China. Europe is responsible for 19% of the production (Figure 4-1).

Figure 4-1: Distribution of plastic production over the world (only thermoplastics and polyurethanes (280Mt)), with NAFTA = North Atlantic Free Trade Agreement (Canada, USA, Mexico) and CIS = Common wealth of independent states (Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan and Uzbekistan)(Plastics Europe, 2017)

4.3. Types of plastics

Table 4-1 shows the most commonly used plastic polymers in Europe. Polypropylene and polyethylene together contribute to almost half of the European demand (49.1%).

If the demand of the polymers is compared with their occurrence in the main rivers of Europe (Figure 4-2), another distribution can be seen. In the rivers 50 to 80 percent of the plastic is polyethylene, while polypropylene stays at 10 -20% for the micro plastics and between 10-30% of the macro plastics. Also, polystyrene (PS), has a higher abundance than expected from the total European demand. Finally, a strange observation is that in the Danube, while almost no PVC was found as micro plastics, it has a significant macro plastic contribution. A possible explanation for the high amount of PE and PS, could be find in their application, which are packagings, bags, bottles, plastic cups … These materials are often littered as mentioned before. The absence of PVC could be a lower degradability but is not further mentioned in van der Wal et al. (2015).

Table 4-1: The most common types of plastic polymers, their application and their demand (Plastics Europe, 2017)

Type Thermoplast/ Applications Demand in Thermoset Europe (2016) Polypropylene (PP) Thermoplast Food packaging, sweet and snack 19.3% wrappers, hinged caps, microwave - proof containers, pipes, automotive parts, etc. 4.3.1. Low-density polyethylene Thermoplast Reusable bags, trays and 17.5% (LDPE) containers, agricultural film, food packaging film, etc. 4.3.2. High-density polyethylene Thermoplast Toys, milk bottles, shampoo 12.3% (HDPE) bottles, pipes, houseware, etc. Polyvinyl chloride (PVC) Thermoplast Window frames, profiles, floor and 10% wall covering, pipes, cable insulation, garden hoses, inflatable pools, etc. Polyurethane Thermoset Building insulation, pillows and 7.5% (PUR) mattresses, insulating foams for fridges, etv. Polyethylene terephthalate Thermoplast Bottles for water, soft drinks, 7.4% (PET) juices, cleaners, etc. Polystyrene (PS) Thermoplast Eyeglasses frames, plastic cups, 6.7% egg trays; packaging, building insulation, etc. Others: 19.3% Acrylonitrile butadiene styrene Hub caps (ABS) Polybutylene terephthalate (PBT) Optical fibres Polycarbonates (PC) Eyeglasses lenses, roofing sheets Touch screens Poly (methyl methacrylate) (PMMA) Polytetrafluoroethylene (PTFE) Cable coating in telecommunications Etc.

Figure 4-2: The distribution of plastic types in some of the main rivers of Europe A) percentages of micro plastic; B) percentages of macro plastic (Based on van der Wal et al. (2015))

4.4. The usage of plastic

Figure 4-3 shows that Belgium, the Netherlands and France, which are the three countries of the Scheldt basin, are in the top plastic demanding countries of Europe. Therefore, there is a large possibility for plastic waste generation.

Figure 4-3: Plastic demand in Europe, includes plastic materials (thermoplastics and polyurethanes) and other plastics (thermosets, adhesives, coatings and sealants). Does not include the following fibres: PET-, PA-, PP- and polyacryl-fibres. In total the demand is 49 mt (2015) (PlasticsEurope, 2016)

Almost 40% of this plastic within Europe is used for packaging. Building and construction is the second most usage of plastic and the auto industry the third (Figure 4-4-A). Figure 4-4-B shows for some rivers in Europe the source of the macro plastic, which is cleaned out of the rivers. For more than 50% the source cannot be determined, one of the main reasons for this is degradation of the plastic elements. However, from the main litter which could be determined industrial packaging is the main source. Urban waste, like bottles, bags, … is the second most determined source. A third major source are industrial materials.

Figure 4-4: A) Distribution of European (EU28+NO/CH) plastics over main market sectors in 2016 (based on Plastics Europe, 2017); B) Composition of Litter by Source in the Danube, Rhine, Dalavan and Po (based on van der Wal et al., 2015)

To get a better idea over the composition of plastic litter in rivers Figure 4-5 can be compared with Figure 4-2. The dominance of PP and PE for packaging, could explain dominance of these materials in rivers. The limited amount of PVC could be related to the limited amount of building and construction, which litter more difficult compered to packaging.

Figure 4-5: Plastics demand by polymer and market segment of 2015 (PlasticsEurope, 2016)

4.5. Plastic waste

Like mentioned in 4.1, plastic waste has several forms. A part is selectively collected, another part ends up in the domestic waste and a third part is littered. Besides these types of household plastics, additional industrial waste is present in the study area. Because the most part of the basin is located in Flanders, only the waste distribution in Flanders will be discussed and extrapolated to the whole study area.

4.5.1. Selectively collected plastic waste

Selectively waste collection has as purpose to recycle materials, or to remove materials in a controlled and environmental-friendly way (OVAM, 2017). For plastic the reason is mainly recycling. The amount of plastic that is collected is increasing, because of the increasing amount of recycle centres. The collection of plastic waste happens mainly in three ways: PMD collection (plastic bottles, flasks, metal cans and drink cartons), plastic collection at the recycling centre and, since 2016, more and more cities collect plastic packaging material separately (P+MD -project) (OVAM, 2017). Figure 4-6 shows that the collected plastic waste is increasing each year to 12.5 kg per person in 2016. Most of these plastics are packaging materials, followed by mixed plastic and hard plastic. More than half of this plastic is collected via the PMD collection and in total more than 81 000 ton of plastic was collected in 2016.

Figure 4-6: A) Selectively collected plastic (based on (OVAM, 2014a, 2015, 2017); B) Types of selectively collected plastic (based on OVAM, 2017)

4.5.2. Plastic via domestic waste

Figure 4-7: Sort analysis of Domestic waste in Flanders in 4 different groups subdivided (OVAM, 2014b)

Domestic waste is defined in this research as waste which is not selectively collected and can therefore only be eliminated by definitive removal (mostly incineration for energy production) (OVAM, 2017). In total 988 804 ton of domestic was collected in Flanders in 2016. OVAM (2014b) organised recently a sort analysis to study the distribution of waste types of domestic waste. For this study they made a difference between urban and rural regions and regions were a separately FVW (fruits and vegetables waste; in dutch ‘GFT’) collection existed (GFT- Region) and where not (Green Region). The results are displayed on Figure 4-7, the largest difference is that regions with a FVW collection have less organic waste, as you could expect. This is probably also to reason why the percentage of plastic is higher in these regions. On

31 average the report mentions that 13.73% of the domestic waste are plastics. The total amount of domestic waste is slowly decreasing in recent years (Figure 4-8), mainly due to tariff changes in 2014 (OVAM, 2017). However, on average, still more than 20 kg/pp a year of plastic ends up in the domestic waste, which is higher than the amount separately collected (Figure 4-6).

Figure 4-8: Total amount of domestic waste and the fraction plastic based on the 13.73% of OVAM (2014b) (based on OVAM, 2017)`

4.5.3. Littered plastic

As mentioned, the most important waste directly related to the environment is litter. Litter is partly removed by different organisations in Flanders, the organisations are mentioned in Table 4-2.

Table 4-2: Organisations and agencies responsible for removal litter (KplusV & OVAM, 2015)

Cities and - Placing of public trash cans intercommunales - Machinal+ Manual sweepings ‘In de vuilbak’ & Flemish - Communication steering committee - Research - Funding projects Flemish agency AWV (Agency for roads and traffic) - Maintenance 6288 of roads ANB (Agency for nature and forest) - Maintenance of 75000ha De Vlaamse Waterweg nv (Agency - Maintenance 1500km of for management waterways) waterways and berms Provinces - Maintenance provincial domains

A Study of KplusV & OVAM (2015) estimated that at least 17 508 ton of litter is collected each year, which is equivalent to 2.3 kg/pp (Table 4-3). This is however an underestimation of the total collection of litter because the data for the waterways are only partly included and there

32 are no data for the agency of nature and forests (see ‘WaterWegen & Zeekanaal NV’ and ‘ANB’ in Table 4-3). A new estimation based on more recent data of AWV, the data of 1 cleaning project of the ANB and the average amount of waste collected on the Flemish waterways in the period 2010-2014 shows that the total amount of litter is certainly higher and a recalculation for the amount per person for 2016 gives 3.1 kg/pp (Table 4-3). However, this could be an overestimation because the total of collected litter of the waterways will have a large amount of organic material in it, which is not really litter.

Table 4-3: Estimations of total littered waste based on the estimation of KplusV & OVAM (2015); *1 AWV (2017) ;*2 Based on 1 collection in March 2016 (ANB, 2016); *3 Based on combined data of the Flemish waterways (Vlaams Parlement, 2015)

Organisations Estimation KplusV & OVAM More recent estimation (2015) Cities and intercommunal 14981 t 14981 t AWV 2 500t 2 995 t1 ANB Unknown 20 t2 WaterWegen & Zeekanaal NV Unknown 2510 t3 nv De Scheepvaart 27 t Total 17 508 ton 2.3kg/pp 20 506t3.1kg/pp

This litter is not homogeneous distributed: larger cities have a larger contribution compared to small rural cities (Table 4-4). Therefore, they are often hotspots for litter because they also have a large population density. To transfer these numbers to the amount of plastic litter, like for the domestic waste, a sorting analyses is used. This resulted in the distribution shown by Figure 4-9. This pie-chart shows that for litter, the contribution of plastic is much higher than it was for domestic waste (21.0% compared to 13.7%). If this distribution is used, 3677ton of plastic litter is collected each year or an average 0.5 kg/pp. Estimations for the amount of litter which enters the environment but is not collected, does not yet exist for Flanders.

Table 4-4: The amount of litter for different municipality types (KplusV & OVAM, 2015) (1 The amount of litter for coastal cities is low due to a lack of waste data concerning these type of municipalities) ; 2 Based on conversion rate of 21%

Type Centrum city Coastal Average Small rural municipality municipality municipality Risk of litter High risk High touristic risk Average risk Low risk Average amount 117 000 18 000 25 000 13 000 of inhabitants Amount of litter 3.7 2.01 2.7 1.4 (kg /inh.) Amount of plastic 0.8 0.4 0.6 0.3 litter (kg/inh.)2

Figure 4-9: Sort analysis of litter (Wael, 2008)

4.5.4. Industrial plastic waste

Figure 4-10: Plastic waste in Belgium by sector 10³t (Statbel, 2014)

Besides the household waste, there is the industrial waste. This waste is collected partly by the municipalities as ‘similar industrial waste’ but the largest part is collected by private companies (OVAM, 2017). ‘Similar industrial waste’ is waste that is in composition similar to household waste. In 2015, 780 kton of this type of waste was collected by the municipalities of which, by estimation, 18.7% was plastic (OVAM, 2017). This results in approximately 146 kton additional plastic waste. Based on Figure 4-10 however, this is only a small part of the industrial waste, the figure shows for Belgium the total plastic waste production. The industry is clearly

34 the largest contributor of plastic waste. The selectively collected plastic, the plastic in the domestic waste and the plastic litter could be mostly linked to household and service waste. The industrial plastic waste is however, almost three times as big (375kton versus 989 kton (Statbel, 2014)). Together with the construction and agricultural sector an additional plastic waste of 1030 kton is generated for Belgium. If assumed that the distribution of the industrial waste is quite homogenous, this number can be converted to 92 kg/pp and could be assumed representative for Flanders and the Scheldt basin.

4.5.5. Total land-based plastic waste

The total plastic waste rate estimated in Flanders is thus quite high, with a total of 125.7 kg/pp (Table 4-5). If, this rate is extrapolated to the Scheldt basin, with a population in the Scheldt basin of 11.12 million (Chapter 3), in total 1.4 Mton of plastic waste a year is generated. This is similar to the plastic waste production generated in Belgium (sum of Figure 4-10;1.4 Mton).

Table 4-5: Total plastic waste generated a year for Flanders

Selectively collected plastic waste 12.5 kg/pp Plastic via domestic waste 20.8 kg/pp Littered plastic 0.5 kg/pp Industrial plastic waste 91.9 kg/pp Total 125.7 kg/pp

Despite the high load of plastic waste within the basin, the amount of mismanaged plastic is only limited. Figure 4-11 shows for Belgium the total amount of produced plastic packaging waste compared to the amount recycled and incinerated. The difference between these in 2015 was only 18.4 kton. So only 5% of the packaging material is not incinerated or recycled. If you take into account the time gap between the moment production of the packaging waste and the processing of this waste, this is even less (the total amount recycled + incinerated of 2015 not far off from the produced packaging waste in 2014). Like mentioned in 4.4 packaging is the dominant form of plastic which is found in the rivers, and if only maximum 5% is mismanaged the amount that would end up in the river is relative small. An important reason for this is that Belgium is within Europe the top recycler of plastic packaging material (Figure 4-12). While the total plastic waste load is high in Belgium and the Scheldt basin, because of a good waste management together with a high recycling rate the total mismanaged plastic waste is only limited.

Figure 4-11: Plastic packaging production and the amount recycled and incinerated for energy production (StatBel, 2016); the reused plastic is the sum of the recycled and the incinerated packaging material.

Figure 4-12: Recycling rate of packaging waste in Europe (Fost Plus, 2016)

4.5.6. Water-based plastic waste

Besides land-based waste many plastic waste is also water-based, the Port of Antwerp is a major contributor of this waste. Waste of ships is divided into fluid and fixed waste, both are collected in the port. The fixed waste is collected in containers on the quay, the fluid waste is pumped out the vessels by a tanker (Maes et al., 2000). Table 4-6 shows an estimation for the

36 part of Antwerp of the additional plastic waste, which is estimated on almost 2500 ton/yr in 1998. Maes et al. (2000) indicated that the handling of this waste can cause losses of 0.1- 0.2%, which means that 2.5 to 5 ton plastic enters the Scheldt directly from the harbour and the shipping. Assumed that all waste evolved with the same trend as the waste collected in the containers of the quay in the period from 1998 to 2016 (Figure 4-13), this amount is enlarged over the years with a factor 2.3 towards 5.8 - 11.5 ton/year.

Table 4-6: Estimation of Water-based plastic waste in the Port of Antwerp based on Maes et al. (2000) & van der Wal et al. ( 2013); 1) Assumed that same composition domestic waste (13.73% plastic); 2) Based on Maes et al. (2000) if all other freight would be plastic for marine freight; 3) Based on Maes et al. (2000) if all other freight would be plastic for inland freight

Type Waste Estimated plastic waste (ton/yr) (ton/yr) Domestic waste Sea-going vessels 2 300 315 (1)

Domestic waste inland navigation 2 100 290 (1)

Packaging waste 18 700 1 500 Waste generated while loading sea vessels 1 000 300 (2)

Waste generated while loading inland shipping 300 60(3)

Total 24 400 2 465

Figure 4-13: Collection of waste via the containers in the Port of Antwerp based on Port of Antwerp (2016) & van der Wal et al. (2013)

The waste created by inland shipping is in Flanders collected in 4 different waste collection spots of which 3 are located within in the port area of Antwerp (Noordkasteel-, Lillo- and Kallo- park. One in Evergem (near to Ghent) is managed by the ‘Vlaamse Waterweg nv’ (Verlinden et al., 2014). Together with these 4 parks are there at almost sluices containers for domestic waste. In the northern part of France (in the Lille region) the waste also collected at the sluices (Verlinden et al., 2014). In 2012, 3 220 ton of domestic waste coming from inland shipping in

Flanders was gathered in this way (Verlinden et al., 2014). If assumed a similar percentage of plastic as in the domestic waste of households (13.73% (Section 4.5.2)) this generates an additional plastic load of 422 ton/year. If similar losses are assumed as the losses of the sea- vessel losses in Antwerp (0.1-0.2% (F. Maes et al., 2000)), 0.4 - 0.8 ton additional plastic enters up in the waterways each year. Together with this collected waste also some waste is generated with loading and unloading of ships for plastic this is however difficult to estimate. To get from this number to a number for the whole basin, these numbers are transformed to a waste weight per kilometre. In total Flanders has 1375 km of waterways of which approximately 1078 km is navigable for transportation (Polfliet, 2014). Because most waste is coming from this latter category only this part is seen as waste generating, so between 0.37 and 0.74 kg plastic waste per kilometre is generated. In total the basin has 1434 km of navigable waterways so between 0.5 and 1.1 ton of plastic a year could end up via inland shipping in the basin.

This additional 6.3- 12.6 ton a year, however, will not all end up in the see, some of the waste will get stuck behind the dykes and a large part will be cleaned up out of the waterways or out of the port. In the port Condor is removing daily floating waste, this is on average 90 ton/yr (Port of Antwerp, 2016). The main part is however vegetation and only 1/3 is other solid waste of which then only a fraction is plastic (van der Wal et al., 2013) . The waterways, on the other hand, are mainly managed by the’ Vlaamse Waterweg nv’. The estimation of the floating plastic removed by this organisation will be estimated based on measurements later on.

4.6. The degradation of plastic

Degradation of plastic is the destruction of the polymer chain and a reduction of the molecular weight of the plastic material (GESAMP, 2015). First the plastics are degraded to micro plastic particles, which could be further degraded into plastics in the Nano range and mineralized (Lassen et al., 2015). Degradation of plastics is mainly in function for environmental factors and the properties of the polymer (GESAMP, 2015). In aquatic environments, for example, is the degradation retarded, as a result of the lower oxygen concentrations and the lower temperature (Andrady, 2011). Therefore the depth at which a plastic object or partible is present is very important because each depth has a certain dissolved oxygen level, amount of sunlight and temperature (Lassen et al., 2015). Plastic also degrades faster on beaches, where the decay depends on UV-radiation, temperature and mechanical abrasion (Lassen et al., 2015). Certain additives of the polymer could prolong the degradation and fouling of plastic, as possibly a biofilm can form a protected layer against UV-radiation (Lassen et al., 2015).

A first degradation mechanism are cracks which form at the surface of the plastic, because of the exposure to environmental conditions. This weakens the plastic and is followed by

38 embrittlement and micro fractionation, which generates powdery plastic fragments in various sizes (Andrady, 2011; GESAMP, 2015). A second possible mechanism is light-initiated oxidative degradation, this is the fastest degradation process. In this process the plastic is exposed to UV-B radiation in sunlight which initiate photo-oxidative degradation. This process can go on as long as oxygen is present in the environment (Andrady, 2011; Lassen et al., 2015). A third possible degradation mechanism is biodegradation. Microbial colonies use, in this process, the carbon in the polymer, which is converted into CO2 and incorporated into the marine biomass (Andrady, 2011).

Table 4-7 gives some indicative degradation rates for plastic in an aquatic environment. The fact that these go quickly up to 400 to 1000 years, is one of main reasons why plastic litter is so dangerous. A newspaper takes for example only between 6 weeks and 4 months to degrade

(Lassen et al., 2015).

Table 4-7: Degradation rates of different plastic materials (Lassen et al., 2015)

Material Degradation rate (yrs) Plastic beverage holder 400 Plastic bags 1 - 1000 Disposable diapers 50 - 450 Plastic bottle 100 -1000 Foamed plastic cup 50 Monofilament fishing line 600 Polystyrene case 100 - 1000 Telephone and top-up cards 1000

4.7. Distribution and spreading of plastics in the aquatic environment

Durability is one of the properties of plastic which makes it very interesting. However as mentioned before the degradation is slow and therefore plastic will be transported via different ways into the environment. A lot of plastic is land-based and the waste could be transported by the wind from collection points to the rivers and seas. Besides the winds, littering is a major reason how plastic materials end up in rivers and beaches and finally enters the seas and oceans (UNEP, 2016). But plastics also enter the rivers directly via industry, thereby a lot of plastic resin pallets is found in the Westerscheldt, downstream from the Port of Antwerp. Beside land-based, also a lot of plastic ends up directly in the sea. Fishery aquaculture, commercial and touristic/recreational shipping are the main contributors for the sea-based plastics (UNEP, 2016). A study of Arcadis estimates for the North Sea the origins of the plastics (Figure 4-14; Acoleyen et al., 2014). It shows that while earlier Jambeck et al. (2015) mentions that 80% of the plastic is land based, in the North Sea only 49% is land-based of which 29%

39 is coming in the sea by activities on the shore and shore littering, so the contribution of land- based plastics seems to be lower in the North Sea compared to its global contribution.

Figure 4-14: Origins of plastics found in the North Sea at Ostend (Acoleyen et al., 2014)

In the aquatic environment one of the most important characteristics which determines the distribution of litter, is if the plastic floats or sinks. This is determined by the density of the polymer and the density of the water (salt water has another density compared to fresh water) (UNEP, 2016). The buoyancy can however change due to attachment of some species like sessile organisms (Lobelle & Cunliffe, 2011).

The circulation of surface waters of the oceans is characterised by a broad pattern of persistent surface currents. These currents together with the influence of local currents, such as the current created at river mouths, and prevailing winds, transport plastic fragments around the globe (Eriksen et al., 2014; UNEP, 2016). In all the five compartments of the ocean (coastlines, surface/upper ocean, the main water column, the seabed and biota) plastic can be found. Plastic is accumulating in the centres of the ocean basins for both the northern as southern hemisphere with a similar order of magnitude (Figure 4-14; Eriksen et al., 2014). Eriksen et al. (2014) estimated with a model that 250 kton of plastic material floats on the ocean surface. A more recent study found out that this is an underestimation. The mass of the micro plastics is not 35kton as suggested by Eriksen et al. (2014) but varies between 93 and 236 kton (Van Sebille et al., 2015). However, even with this additional tonnage, these numbers do not match with a yearly global input from plastic between 0.2 and 12 Mt coming from the land. The main explanation for this gap, is that a lot of the plastic sinks because of the higher density than water, or due to hydrodynamic processes (Eriksen et al., 2014; Van Sebille et al., 2015). Recently they also found out that 17.6 ton of plastic is accumulated on some small remote islands (McAdam, 2017). But as shown on Figure 4-15, especially the micro plastic load is

40 smaller than expected, based on the macro plastic load. This suggests that micro plastic is depleted out of the system. This could be by a buoyancy loss or by ingestion by animals (Eriksen et al., 2014; Van Sebille et al., 2015), especially this later is dangerous as will be mentioned in next section.

Figure 4-15: The weight density of floating plastic modelled around the world in 4 different size fractions (Eriksen et al., 2014)

4.8. The effects of plastic in the aquatic environment

4.8.1. The effect of macro plastics

Besides the possible effects of micro plastic, which will be discussed in next section, macro plastics have in themselves become an increasing problem for aquatic biota all over the globe (Lassen et al., 2015). A first danger is entanglement: many sea-leaving species are entrapped. Records of entanglement exist for sea turtles, sea birds, fishes and even marine mammals as the sea otter (Laist, 1997). The animals can be strangled, wounded, become more immobile which could lead to starving or exclusion from their family and has many more effects (Laist, 1997). Besides entanglement is ingestion the second major problem for animals in the sea (Laist, 1997). Especially seabirds are prone to ingest plastic, the plastic can pile up in their stomach which leads to blockages (Acampora et al., 2014). Some seabirds showed tendency to select specific plastic shapes and colours, which indicates that they may be mistaking the plastics for potential prey (Moser et al., 1992). Van Franeker et al. (2011) indicates that 95% of the Northern Fulmars in the North Sea have a level higher than 0.1g of plastic in their body. At the

41 other hand is this situation improving, for different birds species in the North sea area, the amount of birds exceeding the 0.1g threshold decreased from 62% to 40% over a period of 25 years (Kühn & van Franeker, 2012; Van Franeker & Law, 2015). The problem is however not only limited to seabirds, Bravo Rebolledo et al., (2013) found out that 11% of the seals studied had plastic in their stomach. This is not only related to primary ingestion, but also secondary ingestion. Also turtles show on different places in the world a certain amount of plastic in their bodies (Schuyler et al., 2014). da Silva Mendes et al. (2015) thinks this is among other things because turtles see plastic bags in the ocean as jellyfish. Finally, also fish show to ingest plastic, the fraction macro plastic is in this limited because consumption is often difficult because of the size. But in the Mediterranean sea, large pelagic fish were found to ingest plastics (mainly micro plastics). This has large implications because humans consume these fishes (Romeo et al., 2015) and nano particles could migrated towards human tissues, the effects however are not jet studied in detail. Another increasing problem is that several bird species use plastic as material to build their nests. Birds doe get often entangled while trying to fetch the plastic and the quality of the nest is often decreasing, one of the reasons is for example a poor drainage because of the use of the plastic (Hartwig et al., 2007). Besides these commonly known problems macro plastics can also lead to other problems an example of this is that plastics may be potential vectors in the dispersal of aggressive and invasive marine organisms, who endanger the endemic biota (Gregory, 2009).

4.8.2. The effect of micro plastics

Over 663 species of marine life are impacted by marine debris (Dias & Lovejoy, 2012). The extent of the impacts depends on the levels of exposure. Plastic in the micro and nano range can be taken up in aquatic organisms by oral ingestion or through the gills (Watts et al., 2014). Physical hazard of this ingestion can include obstruction of the digestive system, clogging of feeding appendages, oxidative stress, impaired reproduction or even death (Baldwin et al., 2016). The availability of micro plastics to organism depends on their density as this leads to their location in the water column, other factors which are of influence are the size and colour (prey item resemblance) and abundance (Wright, Thompson, et al., 2013). Micro plastic are found among other animals in harbour seals, herring, cod, whiting, haddock, mackerel, gurnard, fulmar, blue shark, mussels … the frequency and concentrations however have large ranges (Lassen et al., 2015). Due to their size, micro plastics are available for ingestion by a wide range of animals, both vertebrate as invertebrate species (Ivar do Sul & Costa, 2014). Filter-feeding zooplankton and other planktonic organisms are among these species customary and they mistake the particles for prey (Cole et al., 2011). Additional the particles

42 could adsorb onto biological surfaces. The algal photosynthesis can for example be affected (Bhattacharya et al., 2010).

Besides the direct ingestion studies show that micro plastic are also transferred via the food- web from one trophic level to another (Farrell & Nelson, 2013; Setälä et al., 2014). The rate is, however, depended: does the primary feeder digests or translocate the micro plastic particles (Lassen et al., 2015)? At higher trophic level micro plastics can also be passively ingested under normal feeding behaviour (Wright, Rowe, et al., 2013).

4.8.3. The effect of chemicals attached to plastics

Micro plastics can transport also hazardous substances, these substances can have two different origins: 1) hazardous substances can already be present in the plastic particles, this are mostly additives which give the plastic the specific usage and specific characteristics; 2) hazardous substances present in the environment can adsorb on the surface of the plastic (Lassen et al., 2015).

Table 4-8 shows several hazardous additives which are often used in plastic. When the plastic degrades through UV-radiation, salinity and turbulence the additives leach out in the environment (Suhrhoff & Scholz-Böttcher, 2016), especially PE and PVC are prone to leach. Mato et al. (2000) demonstrated in a study in Japan, that PP plastic resin released PCBs, DDE and nonylphenols in the environment. Tanaka et al. (2013) found PBDE in seabirds originating from flame retarders in plastic.

Table 4-8: Example of hazardous additives of plastic (Nerland et al., 2014)

Additive goals Example hazardous additives Plasticizers (Improve DIHP, BBP, DEHP, DMEP, DBP, DiBP, TCEP flexibility and durability) Flame Retardants Short and medium chain chlorinated paraffins, Boric acid, Brominated flame retardants Stabilizers Arsenic compounds, Organic tin compounds, Triclosan, BPA, Cadmium compounds, Lead compounds, Nonylphenol compounds, Octylphenol Curing agents MDA, MOCA, Formaldehyde Colorants Titanium Dioxide, Cadmium compound, Chromium compounds, Lead compounds, Cobalt di-acetate

The sorption of hazardous materials depend on the physico-chemical properties of the substances and the plastic materials (Nerland et al., 2014). POPs and PBTs, including polycyclic aromatic hydrocarbons (PAHs) and the other petroleum hydrocarbons, are chemicals which can be sorbed on plastic (GESAMP, 2015). PS, PE and PP plastics have a great affinity for these substances (Teuten et al., 2007). ‘Micro plastic particles have been shown to hold concentrations of PCB’s more than 1 million times higher than those in the surrounding water’ (Betts, 2008). Besides sorption to plastics themselves, hazardous

43 substances may be accumulated in bio-films formed at the surface of plastics (GESAMP, 2015). Plastics as media can transport hazardous substances for a long-range (Mato et al., 2000), Zarfl & Matthies (2010) suggest even that several tons of these substances are transported to the Arctic areas each year.

4.9. Plastic litter legislation in Europe

Within Europe some legislation exists to decline to amount of plastic litter that could enter the marine environment. Table 4-9 shows some EU legislation tools which are indicated in a study of Arcadis as tools which could decline the marine litter (Acoleyen et al., 2014).

Table 4-9: European directives which could decrease the amount of marine litter in order of relevance and feasibility (Acoleyen et al., 2014)

Directive Reference 1 Packaging and packaging waste directive Directive 94/62/EC 2 Waste Framework Directive Directive 2008/98/EC 3 Micro and nano plastics in cosmetics Cosmetic products Regulation (EC) 1223/2009 REACH regulation (EC) 1907/2006 4 Port Reception Facilities Directive Directive 2000/59/EC 5 Water Framework Directive Directive 2000/60/EC 6 Green Public Procurement and Eco-Labelling Communication “Public procurement for a better environment” (COM (2008) 400) Ecolabel Regulation (EC) 66/2010 7 Marine Strategy Framework Directive Directive 2008/56/EC 8 Landfill Directive Directive 199/31/EC & Decision 2003/35/EC 9 Ship-source Pollution Directive Directive 2005/35/EC 10 Eco-design Directive 2009/125/EC 11 Urban Waste Water Treatment Directive Directive 1991/271/EEC 12 Integrated Coastal Zone Management (ICZM) Recommendation 2002/413/EC Recommendation and Maritime Spatial Planning Publication of MSP Directive Directive pending 13 Bathing Water Directive. Directive 2006/7/EC

Based on this study these are the 7 most effective and feasible measurements:

1 Packaging and a packaging waste directive

This directive aims to harmonise national measures in order to prevent or reduce the impact of packaging and packaging waste on the environment and to ensure the functioning of the internal market. Because packaging takes a large proportion this is an important directive. The

44 goal is to improve recycling and collection, which will have large effects on the amount of litter which will be able to enter the environment.

2 Waste Framework directive

This directive sets out the basic concepts and definitions related to waste management, such as definitions of waste, recycling, recovery. The idea is to reduce the waste generation by expanding the lifespan of products, increase recycling, improve recovery from incinerators. More care in the final disposal of waste. Because the goal is to reduce the total waste this directive will also directly have large influences on the amount of litter.

3 Micro and nano plastics in cosmetics

Micro plastics found in cosmetic products are finding their way to the marine environment, these are generally not filtered out by the treatment plants, therefore Europe has some regulations for the cosmetic sector. This allows Europe to withdraw a product from the market when certain regulations are not met. Micro plastic shows to have a larger influence as thought in the past, so the regulations for the use of micro plastics have to be stricter (updated in 2017 (Scudo et al., 2017)).

4 Port Reception facilities Directive

This Directive has the same goal as the Marpol Convention of 73/78, which is to prevent pollution by ships. This directive wants to decline dumping and to oblige vessels to transfer their waste to port authorities. A more efficient management of waste in ports and more controls could even decrease the amount of waste that could enter from vessels in to the water.

5 The Water Framework Directive

This is a directive to protect all surface waters, groundwaters, transitional waters and coastal waters. The goal is to get all these waters to a good ecological and chemical status by reducing pollution and promoting sustainable water use and environmental protection. For litter it is mainly related to the chemicals which can now pollute the waters if the pollution has to decline, the plastic must also decline. However, no direct link to plastic is included.

6 Green Public Procurement and Eco-Labelling Green Public Procurement is a process whereby public authorities seek to procure goods, services and works with a reduced environmental impact throughout their life cycle when compared to those with the same primary function that would otherwise be procured. The EU Ecolabel may be awarded to products and services which have a lower environmental impact than other products in the same group. Because these measures have effect on the material

45 used, they also have an effect on the amount of marine litter produced. A further focus on recyclability could even further decrease the plastic waste generation.

7 Marine Strategy Framework Directive

The aim of this directive is to protect and restore Europe's marine ecosystems and to ensure the ecological sustainability of economic activities linked to the marine environment in European Seas. The final goal is to achieve a good environmental status (GES) in the marine waters. This directive states that the status of this environment can only be good if marine litter does not cause harm to the coastal and marine environment. Because of a large lack of data and because most of the litter is coming from the land, this directive is expected to have only a small effect.

The other 6 still have an effect but this expected to be smaller than the effect for the previous mentioned directives. Besides the members, states in Europe can have still their own goals of reducing plastics. Belgium, for example, has the goal the reduce the amount of plastic in the Fulmars to higher than 0.1g for maximum 10% of the population of the species (Acoleyen et al., 2014). Also, some collaborations exist like the “North-East Atlantic – OSPAR” in which also guidelines are set to improve the amount of litter entering the environment.

5. Results

5.1. Top-down model

5.1.1. The MPW produce with the Scheldt basin

Table 4-4 showed the total amount of litter and the contribution of different types of cities. The recalculations in Table 4-3, show that the litter amount is on average 3.1 kg/pp each year. Based on this increase with a factor 1.35 from 2.3 to 3.1 kg/pp, Table 5-1 is set up were this increase is implemented on the litter for the different type of cities. These amounts are conversed into plastic amounts based on the 21% of plastic in litter (Wael, 2008).

Table 5-1: Plastic litter amounts for each city type

Type Average Centrum city Medium city Small city Amount of litter (kg /pp) (2015) 2.3 3.7 2.7 1.4 Amount of litter (kg/pp) (2017) 3.1 5.0 3.6 1.9 Amount of plastic litter (kg/pp) 0.7 1.1 0.8 0.4

To translate this litter amounts to spatial data first ‘Centrum cities’, ‘Medium cities’ and ‘Small cities need to be defined’. In KplusV and OVAM (2015) this different types are not clearly defined but there is mentioned that besides a high population density, centrum cities are characterised by a touristic value. Based on this knowledge Brussels, Antwerp, Ghent, Lille Leuven and Lens were selected as ‘Centrum cities’. Furthermore, all the remaining cities with a population density higher than 500 persons/km² are selected as medium cities and the remaining cities are small cities (Figure 5-1).

Figure 5-1: Defining 'Centrum cities', 'Medium cities' and 'Small cities'

Combining this information with the population density information leads to the litter density map (Figure 5-2). This map shows that while almost all cities produce only between 0 and 1 ton a litter per square kilometre a year, these numbers can go up to almost 30 tons a square kilometre in the area around Brussels.

Figure 5-2: Litter density map

Next the adapted elevation data is used combined with this litter density map to find the MPW, which symbolises how much mismanaged plastic accumulates, if it would flow natural, at the mouth of the river. The result is shown by Figure 5-3, which show how the mismanaged plastic accumulates natural starting from a 100 ton accumulation. In total finally 8 006 214 kg of MPW accumulates at the outlet. The map, however, shows also the importance of cities as major contributors of plastic. Almost all the places were the first 100 ton is accumulated are close to larger cities (Arras, Hasselt, Valenciennes) and also the major shifts in magnitude are also happening at the large cities (before Ghent line is still yellow, while orange downstream of Ghent). Finally, this map shows also the importance of human influences in the basin. While you can say that the stream next to Kortrijk still follows more or less the Lys, the stream next to Tournai follows the Scheldt and the stream next to Aalst the Dender for example. The whole

48 flow network is, however, very different from the real flow network as it was shown on Figure 2-1.

Figure 5-3: Accumulated MWP along the natural streams

5.1.2. The river pathway

The MPW can now, using both the method of Lebreton et al. (2017) end Schmidt et al. (2017), be converted towards a load of macro plastic towards the sea. The monthly average runoff calculated from GLDAS for this first method can be found in Table 5-2. Together with the coefficients of Table 3-1 this leads to the total loads in Table 5-3. For the second technique the formulas on Figure 3-3 are used, also these results are shown in Table 5-3.

Table 5-2: Monthly average catchment runoff in mm/day

R (mm/d) R (mm/d) January 0.49 July 0.48 February 1.25 August 0.46 March 1.36 September 0.43 April 0.73 October 0.35 May 0.52 November 0.35 June 0.47 December 1.28

Table 5-3: Results of flux towards the sea from the river pathway

Low Average High Lebreton et al. (2017) 7.1 ton/yr 13.5 ton/yr 36.4 ton/yr Schmidt et al. (2017) 1.6 ton/yr 4.6 ton/yr 13.3 ton/yr

So, between 1.6 and 36.4 tons of plastic ends up in the sea via the littering next to the river.

5.1.3. Water-based plastic

Like mentioned in section 4.5.6 inland navigation leads to an input of the waterways of 0.5 - 1.1 tons of plastic a year or 0.37-0.74 kg per kilometre of waterway. In this same section the plastic input for the port of Antwerp is estimated on 5.8-11.5 tons a year. Based on these values, the values for other ports are calculated based on the conversion factor of Table 3-2. In total between 7.8 and 15.5 tons of plastic a year enter the waterways by the ports.

Table 5-4: Port contributions in tons a year

Port Minimum Plastic Average Plastic Maximum Plastic Brussels 0.1 0.2 0.2 Lille 0.2 0.3 0.5 Ghent 0.8 1.2 1.6 Zeeland seaports 0.9 1.3 1.7 Antwerp 5.8 8.7 11.5 TOTAL 7.8 11.7 15.5

Based on these numbers of plastic waste, the amount of plastic that goes to the sea can be calculated using the four different methods of transport loss. Table 5-5 gives the results for inland shipping, which shows that all the different techniques have very similar results. Only the fixed has slightly lower numbers for the amount of plastic getting to the sea.

Table 5-5: Amount of plastic from inland shipping which reach the sea in tons a year

Minimum Plastic Average Plastic Maximum Plastic Fixed transport loss 0.1 0.2 0.2 Transport loss in function of 0.4 0.5 0.7 flow distance Transport loss in function of 0.3 0.5 0.6 distance to the coast Transport loss in function of 0.3 0.5 0.7 the distance to the mouth

For the ports the variation between the different methods is larger. A major reason is that the fixed transport loss, the lower, this can be contributed to the locations of the ports on which this data is based. The order of magnitude is however similar, which indicate that all 4 techniques could be used separately. But because the fixed transport losses are very location specific, this model will use averages of the other three techniques for the ports and the inland navigation. The changes between the other techniques can be mainly explained by the weight that the port of Antwerp gets in by the three different length techniques.

Table 5-6: Amount of plastic from port activities which reach the sea in tons a year

Minimum Plastic Average Plastic Maximum Plastic Fixed transport loss 6.2 9.4 12.4 Transport loss in function of 5.8 8.6 11.5 flow distance Transport loss in function of 4.3 6.5 8.6 distance to the coast Transport loss in function of the 4.4 6.5 8.9 distance to the mouth

5.1.4. Total macro plastic entering the sea

The total flux of macro plastic towards the sea can be seen in Table 5-7 were the three different pathways are summed. In all scenarios the fixed transport losses are not used as mentioned before. For the minimum and maximum scenario, the lowest and highest values found are used for the river pathway and the for the average scenario the average of the two techniques is used. For the water-based plastic the flow-distance technique is used as optimal technique. This is based on the assumption that the discharge in the canals will be lower and more plastic gets blocked in these shortcuts, which takes away the advantage of the shortcut. In this way the flow length can be assumed as most realistic. Table 5-7 shows that finally between 7.9 to 48.6 tons of plastic will enter up in the sea, with the average scenario indicating 18.2 tons a year. Depending on the scenario the ports or the river pathway is the largest contributor.

Table 5-7: Model output for the Scheldt basin in tons a year

Minimum Scenario Average Scenario Maximum Scenario River pathway 1.7 9.1 36.4 Inland navigation pathway 0.4 0.5 0.7 Port pathway 5.8 8.6 11.5 TOTAL 7.9 18.2 48.6

5.2. Bottom-up model

5.2.1. Plastic entering the district

The plastic which enters the waterways via the ports and inland shipping activities is calculated similar to this amount in the Top-down model. Only the average values are used, so for inland shipping is assumed that 0.56 kg of plastic waste is generated per kilometre and for the port of Antwerp is assumed that 8.65 tons of plastic enters the waterways. Together this leads to the values in Table 5-8 as input for each district.

Table 5-8: Water-based plastic waste input

Districts Length (km) Shipping (ton/year) Ports (ton/year) BS-1 59.1 0.03 1.17 BS-2 71.8 0.04 BS-3 65.0 0.04 BS-4 70.0 0.04 ZK-1 65.1 0.04 0.20 ZK-2 42.1 0.02 ZS-1 72.0 0.04 ZS-2 59.2 0.03 8.65 ZS-3 60.8 0.03 ZS-4 63.1 0.04 AK&KK 210.2 0.12 GT 35.5 0.02 WS 63.0 0.03 1.33

The estimation of the litter starts at Figure 4-11, which shows the total amount of plastic packing waste produced each year and the total managed amount. Section 4.4 showed that packaging is the dominant use of plastic especially when you look at which types of plastic enters up in the river/waterway. Therefore, these data can be used to calculate the plastic input of the system if the amount which is produced but not managed is assumed to be all littered. The data of this graph shows that in Belgium, in 2015, 339 690 tons of plastic packaging waste was created, while only 321 322 tons was managed. So, in total 18 368 tons of plastic waste was not managed or 1.6 kg of plastic per person in Belgium. Using this amount, it can be estimated that in the whole basin 17 788 tons of plastic is not managed and is therefore assumed to be littered. Together with the population density data this amount of additional waste is given a spatial distribution showed by litter density map (Figure 5-4). As in Figure 5-2, again the larger cities are dominant litter hotspots. The increased resolution of this map towards hectares is done to make it possible to work with smaller buffers than 1 km.

Figure 5-4: Additional litter density map based on packaging plastic in Belgium

Next is assumed that all litter within a certain distance or buffer around the waterway districts end up in the waterway. 6 different buffers are used and the input values are shown in Table 5-9. As aspect is the litter input almost linearly increasing with the buffer width. Together with the values of Table 5-8 and the inflow of previous districts, the input values for each district are formed.

Table 5-9: Litter input in districts in tons a year based on different buffer widths applied on Figure 5-4

Buffer Districts 100m 200m 500m 1km 2km 5km BS-1 24.2 47.7 115.1 203.3 308.1 482 BS-2 9.1 18.5 46.5 92.3 180 570.7 BS-3 16.7 33.6 83 164.7 324.3 714.3 BS-4 16.5 33.1 82.1 165.1 328.4 722 ZK-1 52.7 106.2 271.7 561.3 1145.8 2404.2 ZK-2 11.1 22.4 56 111.3 212.1 457.8 ZS-1 14.2 28.6 72.4 146.1 284.8 638 ZS-2 35 68.7 171.4 329.7 565.4 1128 .ZS-3 11.1 22.3 55.8 108.9 209.6 472.5 ZS-4 14.3 28.2 69.1 133.9 239.1 523.5 AK&KK 32.1 64.3 158.9 314.3 611.4 1374.4 GT 9.5 19.1 47.8 93.6 179.9 330.1 WS 21.5 25.8 43.1 77.7 151.6 367.6

5.2.2. Cleaned out plastic waste

Section 4.5.6 already mentioned that by management a lot of floating materials were taken out of the system. Although most of this material will be organic material like branches, also plastic will be fished out of the water. The amount of the total waste that is inorganic is based on calculations in the ZS-1 district (Table 5-10) and thus 11.3% of all waste that is cleaned out of the river is assumed to be inorganic. However, two exceptions are made on this percentage. (1) For the amount that Condor collects in the port of Antwerp, is similar to van der Wal et al. (2013) a inorganic fraction of 33% is assumed. (2) For district ZS-3 is only a 5% assumed to be inorganic, in this section the management done by a contractor specialised in wood (Table 3-4), therefore is assumed that he would avoid plastic if possible.

Table 5-10: Based on measurements in ZS - 1 percentage of inorganic waste

2014 2015 2016 Average Percentage inorganic 10.2% 13.4% 10.4% 11.3%

The convert these tonnages of inorganic waste towards plastic waste, similar to normal litter a percentage of 21% is used (Wael, 2008). This results in the plastic amounts found in Table 5-11. The amount of waste cleaned out at the port of Antwerp is added the WS district but could also be part of the ZS-2 district as it is on the border between both.

Table 5-11: Waste cleaned out of the different districts

Districts Ton floating waste + litter Ton Inorganic waste Ton Plastic Waste BS-1 56.3 6.2 1.3 BS-2 21.3 2.3 0.5 BS-3 26.9 3.0 0.6 BS-4 49.5 5.4 1.1 ZK-1 174.1 19.2 4.0 ZK-2 139 15.3 3.2 ZS-1 484.3 53.3 11.2 ZS-2 269.5 29.6 6.2 ZS-3 762.9 38.1 8.0 ZS-4 177.3 19.5 4.1 AK&KK GT WS 90 30.0 6.3

5.2.3. Results of bottom-up model

With the outflows and inputs established to final output of the model can be calculated. Figure 5-5 and Figure 5-6 show the results in two different ways taking into account the variables of percentage blocked by the sluice/ lock and the buffer width. These figures show that depending

54 on the choice of these variable values still a large range of possible outputs exist. Especially the percentage blocked by the sluice/lock plays a very important role, if this percentage is low the plastic flux towards the sea increases quickly.

12000 100% 95% 90% 10000 85% 80% 75% 8000 70% 65% 60% 6000 55%

Ton/year 50% 45% 4000 40% 35% 30% 2000 25% 20% 0 15% 0 1000 2000 3000 4000 5000 6000 10% Buffer width (m) 5% 0% Figure 5-5: Result output in function of buffer distance/ width with different percentages of blocked plastic

12000

10000

100m 8000 200m 500m 1km 6000 2km

Ton/year 5km

4000

2000

0 0% 20% 40% 60% 80% 100% 120% Blocked by sluice/lock

Figure 5-6: Result output in function of percentage blocked by sluice/ lock at the end with different buffer widths

5.2.4. Model calibration

To work with the model the previous variables need to be calibrated. Because a lack of measurements makes a normal calibration impossible, the outputs of the Top-down model are used instead. For the calibration the maximum scenario (Table 5-7) is used because this symbolize the worst-case scenario and because a calibration of the average scenario is on the boundary of the existing model input and would need smaller buffer width which is impossible with the present resolution of the litter density data. The flux towards the sea is in this case 48.6 tons a year, two different setups of the model lead to a similar result: a buffer of 100m with a blockage percentage of 70% or a buffer (48.1 tons a year) and a buffer of 200m with a blockage percentage of 85% (48.3 tons a year). Because no additional data exist, it is difficult to say which of those two is the best representation of the reality.

Figure 5-7 and Figure 5-8 show all the outflows of each districts for these two possible set-ups for the model. While the set-up is different to main distribution between the two outputs is very similar with an input of ZS-2 which is the double of the GT input and 5 times higher than the input from the AK&KK district and also here a large influence of the cities can be seen the major outflows are seen at ZK-1 of which Brussels is part, BS-1 in which Ghent is located and ZS-2/WS in which Antwerp plays a dominant role. However due to the high blockage rates in both models the produced litter in the own district is far more dominant and important in this model than the contribution of the litter (compare numbers in Figure 5-7 and Figure 5-8 and Table 5-9)

Figure 5-7: Model outflow of each district using a 100m buffer width and 70% of blockage

Figure 5-8: Model outflow of each district using a 200m buffer width and 85% of blockage

6. Discussion

This chapter discusses the results of the top-down model and compare them to other existing estimates for the Scheldt basin and also to estimates of other large rivers in Europe. Next is the added value of the bottom-up model discussed. Then several measures to reduce the plastic load towards the sea are examined and finally some additional research is proposed concerning the different themes of this study.

6.1. Top-down model: Downscaling of global models

6.1.1. The mismanaged waste

Both Schmidt et al. (2017) and Lebreton et al. (2017) used the MWP calculations of Jambeck et al. (2015). In this study the total waste production per person is estimated and this is multiplied with the percentage plastic and the percentage of mismanaged waste and this amount is multiplied by the population. While these studies use the same technique, the difference is more than 1000 tons a year (Table 6-1). This difference can be explained by the use of other population data and a different basin delineation. While this study starts from the litter amount instead of the total amount of waste and uses the spatial differences created by the population density differences, the total amount of MWP is in the same order of magnitude. The fact that two different techniques leads to similar amounts of plastic, is a confirmation that this amount is realistic.

In Section 4.5.5 it is estimated that 1.4 million tons of plastic waste are generated each year within the basin. Thus, while 8000 tons is still a lot of plastic, only 0.6% of the plastic wased is mismanaged and this implies a good waste management system in the Scheldt basin. To protect the environment to an optimal extent, this final percentage of mismanaged waste needs to decrease even further.

Table 6-1: MPW calculations in different studies

MWP (ton/year) Schmidt et al. (2017) 7768 Lebreton et al. (2017) 8854 Calculation 5.1.1 8006

6.1.2. The river pathway of plastic waste

To convert this to the macro plastic load, different techniques are used (Table 6-2). Already the original models gave different outputs for the Scheldt basin. This difference is not only related to the difference in MPW discussed in previous paragraph, but also the calculation technique. Because, while both studies use more or less the same dataset of studies which calculated amounts of micro and macro plastic in different rivers, the use of this dataset is very different. Lebreton et al. (2017) makes no differentiation in his final flux values between macro and micro plastic and based on values calculated in Schmidt et al. (2017), the percentage of micro plastic could be between 30 and 60% of the total amount of plastic. This is thus also the main reason why all the values of Lebreton et al. (2017) are higher. On the other hand, the power-model of Schmidt et al. (2017) can be critical reviewed. The problem with this model is that a small variation is the MPW can lead to a difference in orders in magnitude of the load. To minimize this effect this study did not only use the existing regression but added two alternatives. When comparing these models to the new calculated values (Table 6-2), all the new values are higher than the original values. For the values based on Schmidt et al. (2017), this difference is only related to the higher MPW. While this MPW is decreasing compared to the value of Lebreton et al. (2017), the plastic load is increasing. This can be explained by the new runoff data of 2017 which has higher values than those used in the original study. In Table 6-2 also a value for the ‘From Land to Sea model’ this is based on the values in Table 3-3 and shows similar values to the recalculated Schmidt et al. (2017) values. While this gives no certainties, because this ‘From Land to Sea’ model is a very empirical model, this result indicates that for the real macro plastic flux the results of the model of Lebreton et al. (2017) are probably an overestimation.

Table 6-2: Calculated plastic litter from the Scheldt basin to the sea; for the number for the ‘From Land to Sea model’ the MPW is used multiplied with the incorrectly disposed percentage and transport losses for macro plastic in Table 3-3

Techniques Min Average Max (ton/year) (ton/year) (ton/year) Schmidt et al. (2017) 1.46 Lebreton et al. (2017) 4.2 8.3 23.2 From Land to Sea model 0.6 4.8 14.4 Calculation based on Lebreton et al. (2017) (5.1.2) 7.1 13.5 36.4 Calculation based on Schmidt et al. (2017) (5.1.2) 1.6 4.6 13.3

However, both global models can still improve by different changes to improve their estimates. These improvements will need many additional fieldworks to estimate the yearly or monthly plastic fluxes from different river basins to make better regressions with the MPW. But also,

60 other improvements are possible, mentions Lebreton et al. (2017). For example, the influence of urbanization, industrialisation and artificial management on the plastic load, but except for large dams, nothing is done with these relations. While other studies as Yonkos et al. (2014) clearly indicate that the land use can have large influences on the available plastic. Indicated by Figure 6-1, the different land uses are related to the micro plastic concentrations measured. If more measurements for plastic loads within basins would be available, sub regressions between catchments with, for example different industrialisation rates, could give better relations with the MWP. Also, in some way should artificial dams, like sluices or locks, need to be included because these elements are responsible for blockages of plastics. This could best be done in the calculation of the MPW with additional plastic losses in the accumulation method.

Figure 6-1: The relation of the micro plastic concentration and the population density and land uses (Yonkos et al., 2014)

6.1.3. The water-based plastic

The water-based plastic is in most models not taken into account, while Table 5-7 shows that especially the ports are still large contributors. In the low scenario it is even the largest contributor. This is in line with the earlier mentioned study of Acoleyen et al. (2014) (Section 4.7), which indicated that more than half of the plastic in the North Seas was coming from shipping. Based upon this information, the ports need to be pushed to increase their waste management. Based on Table 4-6 this is mainly packaging material, so stricter rules on packaging waste would help to reduce this number.

The three transport loss methods based on the three different distances show, while they are very different, quite similar results. Only the flow distance for the ports give higher results (Table 5-6), which is probably related to the lower transport loss for the Port of Antwerp compared to techniques using the distance to the mouth and the coast distance. But because the final results are in the same order of magnitude for future modelling only one technique has to be selected, or an alternative method has to be found which indicates better the possible losses from the point where the plastic enters the water to the sea, keeping the infrastructure into account.

6.1.4. The total plastic amount delivered to the sea

Table 6-3 shows the amount of plastic from different European rivers coming from extrapolations of measurements. These results show that the plastic contribution of the Scheldt is minor compared to other rivers e.g. the Danube and the Po. But taken into account the catchment area, population and discharge, even lower numbers could be expected. While the management seems to be very good, the contribution of plastic is higher than one would expect, if you compare to the numbers of the Rhine.

Even more clear is that the numbers modelled in this study are much higher than the values based on the van der Wal et al. (2013). This could have different reasons. An overestimation of this model based on too low transport losses, or like mentioned earlier maybe the relation between the MWP and the plastic load could improve. On the other hand, this could also be due to gaps the research of van der Wal et al. (2013), large loads of plastics are transported during storm events, if these events are not measured the existing data will give an underestimation. Another reason for underestimation could be a wrong conversion rate to go from volume to weight. In the worst case the load of macro plastic is similar to this load in the Rhine which has an 8 times larger area and more than 20 times higher discharge. While these

62 numbers of the Rhine could be an underestimation, it still indicates that additional measurements are necessary in the Scheldt basin.

Table 6-3: Large European rivers with their plastic load based on 1 extrapolations of field measurements (van der Wal et al., 2015); 2) extrapolation of volumetric measurements of the load in the Rhine, Meuse and Scheldt converted to mass based on estimate 1 (van der Wal et al., 2013); 3)Based on Lechner et al. (2014); 4) Based on Gasperi et al. (2014)

River Area of Population Average Plastic load extrapolated catchment (million) discharge (ton/yr) (10³ km²) (m³/s) Rhine 185 49 2900 20-30 1 Po 74 16 1500 120 1 Danube 800 80 7000 500 - 1500 1,3 Meuse 35 9 350 (4-6) 2 Seine 79 16 560 27 4 Scheldt 22 12 120 (2-4) 2 (This study modelled) 8 - 49

6.2. The added value of the bottom-up model

While because of too limited plastic load measurements within the basin, it was impossible to calibrate the bottom-up model towards a realistic situation and get a correct value for the plastic material entering the sea, this model could still be very interesting. Because the previous model and the values in Table 6-3, give only an idea of the flux towards the sea, they do not contribute to a solution. On the other hand, this bottom-up model could help to get a view of the plastic waste hotspots and the spatial pattern of plastic accumulation. Looking back at Figure 5-7 and Figure 5-8, these figures indicate for example that the largest problems are in the districts BS- 1, GT, ZS-2 and ZK-1 and therefore could indicate that management has to focus first on these areas. To calibrate this model correctly still a lot of additional research is necessary because, besides the outflow measurements to calibrate the model, also additional losses has to be included. For the moment only the final lock/sluice is seen as loss factor. In many districts, however, there are 10 or more locks and sluices. Also, for the moment the tidal effect is neglected. In reality, this will also have a large effect in the Westerscheldt and the Maritime Scheldt. So, this model needs a lot of improvements and the model described in this study is only a first step towards a good bottom-up model which could lead to an optimal plastic management within the Scheldt basin.

6.3. Solutions to decrease the amounts if plastic

Like mentioned earlier still additional actions are necessary to decrease the amount of plastic entering the sea via the Scheldt basin, because it is creating many environmental effects as mentioned in Section 4.8. This is possible in at least four different ways: 1) by reducing the

63 amount of plastic waste which could up entering the environment, 2) by further improving the waste management, 3) by physical getting the plastic waste out of the rivers and waterways and 4) by transforming the plastic used to a more biodegradable sort of plastic.

6.3.1. Reduce the plastic waste

Like mentioned in Section 4.4, packaging is the primary use of plastic and is this the primary amount of plastic found in river systems. If the amount of packaging plastic would decrease, this would lead directly to a decrease in the amount of plastic entering the environment. Section 4.9 indicated already several existing legislations which try to deal with this but they are still insufficient.

In the whole basin area the governments are, however, aware that regulation about plastic could benefit the environment. This lead to a ban of plastic bags, which can be used only once, in the Netherlands (2016) and Brussels and the Walloon region (2017) (F&F Verpakkingen, 2017; Rijksoverheid, 2016). In Flanders this regulation is not active, but in the private sector in Flanders a change towards more sustainable bags is also being seen (Thijs, 2018). However, one strict policy over the whole basin would help the reduction of packaging plastic.

A new proposal of the European Commission for a directive for ‘Single-use plastics’ can also reduce the amount of plastic (European Commission, 2018). With the proposal they want to reduce 70% of the marine litter. Specifically, they want to ban certain products like plastic cotton buts, cutlery, plates, straws, drink stirrers and sticks for balloons, which are not made from sustainable materials (paper or bioplastics (see 6.3.4)). Besides these ban, the countries have to set targets to reduce the use of plastic food containers and drinking cups and the top of a plastic bottle needs to be attached to the bottle (European Commission, 2018). This additional regulation proposed by the European Commission shows the importance of the problems and together with local regulation such as the plastic bags ban the amount of plastic waste could be lowered dramatically.

6.3.2. Improve the waste management

In the same proposal of the European Commission they mention that 90 % of the single-use drinks bottles need to be collected by member states. Figure 4-11 showed already that 95% of the created packaging waste is managed in some form in Belgium. However, the recycling rate still has a large opportunity to increase. Besides the total amounts of litter, Section 4.5.2 mentions that still 13.73% of the domestic waste is plastic in Flanders. So, if the selective collection of waste could be improved, the recycling rate could go up.

In some cities within the basin, like Leuven and Mechelen, besides the earlier discussed PMD, there are also since 2016/2017 separate collection of mixed plastic waste. In Leuven this lead in a year time to an increase with 52% of the collected plastics (Stad Leuven, 2018). But also, Fost Plus, which is the organisation responsible for collecting and processing of waste within Belgium, has taken action and will broaden the allowed materials within the PMD. Like mentioned in Section 4.5.1 this was limited to plastic bottles, flasks, metal cans and drink cartons. But starting from 2019 all soft plastic waste can be collected via the PMD bag. By these measurements Fost Plus aspires to recycle an additional 70 000 tons of plastic a year (Torfs et al., 2018).

Together with this broadening of plastic collection, also alternative collection of plastic bottles with deposit refund is promoted by the European Commission (European Commission, 2018). This form of bottle collection is already active in the Netherlands. In Flanders currently the introduction of deposit refunds for plastic bottles is discussed, but this measure would have a large additional cost and according to critics the additional collected plastic would be small (De Maeseneer, 2018).

Also starting from June 2018, firms need to improve their selective collection of waste in Flanders. Plastic foils, hard plastics and Styrofoam need to be collected separately, additional on the PMD they already have to separate. Because more than a million tons (Section 4.5.4) of plastic waste is created by the industry these actions could also have enormous effects on the management and recycling rates.

Finally, the European Commission also want to put some kind of ‘the polluter pays’ principle on plastic waste. In practice the idea is that the plastic producer will partly cover the costs of waste management and clean-up actions (European Commission, 2018). If this management could improve as promised, the plastic input towards the sea would decrease a lot.

6.3.3. Get the plastic waste out of the rivers

This third option is a very expensive and labour-intensive process. In practice this would mean that the number of cleanings in the waterway has to go up as well as the cleaning campaigns of litter on the river banks. Besides the costs, is the effectiveness of these measurements is limited. The litter entering the waters between cleaning campaigns could still be transported towards the sea. In addition to these labour-intensive works, also automatic trash removal systems exist, this is for example a device placed across the water body so that a flow occurs through a grid and sieves the plastic out. Another example is a device that can lift some macro plastic up by using a conveyer fitted with projecting teeth (Parakash et al., 2017). But these

65 machines are very expensive, which would for this reason only be implemented if the other measures seem to have no effect. Also, a good identification of the plastic waste hotspots is necessary via for example the bottom-up model, so that these devices are constructed in an optimal way and place.

6.3.4. Transformation towards bioplastics

As mentioned in Section 4.6 one of the major problems of plastic is the slow degradation. If plastic would better degrade, or even totally degrade into carbon dioxide, methane and water, the environmental effects of plastic would be reduced significantly (UNEP, 2015). Recently more and more plastics with these characteristics exist. They are often called bioplastics. This term is, however, not very clear because it could refer to plastic derived from biomass or quick biodegrading plastics (UNEP, 2015). Many recent researches focus on plastic with both those characteristics, mainly to reduce the price to make them more economical interesting. The KU Leuven developed for example a PLA (polyactic acid) based on lactic acid of cheese waste which can be developed quite fast (De Clercq et al., 2018).

A main problem, however, is that degradability is often related to environmental characteristics. So there is no certainty on the effect of all these bioplastics (Accinelli et al., 2012). Therefore many researchers are still very critical about the products labelled as ‘biodegradable,’ because many of these products will have no significant decrease either in the quantity of plastic entering the ocean or the risk of physical and chemical impacts on the environment (UNEP, 2015). This field of science still have to improve to be a safe solution to cope with the problems created by plastic. Therefore, most attention has to be given to a reduction of the waste and better waste management.

6.4. Scope for further research

While the flux of macro plastic from the Scheldt basin towards the sea is limited compared to other rivers and recently regulation is started to even further decrease the trends, there is still need for additional research.

a) Like earlier mentioned, an optimal management model could only be realised when the plastic waste hotspots are identified. Because if the contribution of the largest contributors is identified (touristic littering, waste dumping, ports …), more specific measures could be installed to realize quick changes. Therefore, the bottom-up model should be improved as suggested in Section 6.2 with a better calibration and with the incorporation of some important additional parameters which influence the plastic load.

66 b) Control studies of estimation are necessary to see the effect of all the measures summed up in Section 6.3. This flux estimations must however use a standardized form, otherwise there will always be a distorted picture of the effect. c) Like mentioned in the previous section bioplastics and alternative materials need to be further researched, so that they could degrade even faster under a wider range of conditions. d) In Section 6.1.2 several problems with the two existing global models are mentioned. Therefore, it would be useful to make a new global model which include land use and artificial barriers to a certain extent. A new model would need a lot of new data on plastic loads in rivers with a wide range of characteristics. e) Besides all these proposed studies about the plastic amount, it would also be good to study different ideas to protect animals from the existing plastic in the seas and rivers mentioned in Section 4.7. This could help the animals in a short period of time f) Finally, this study focusses on macro plastic, however micro plastic is as important or even more important, toward damaging the environment. So also, for these particles the contribution of the Scheldt basin should be estimated.

7. Conclusion

As plastic is one of the largest sources of pollution within the 21st century, it is studied by many researches. They conclude that many species are affected by both macro plastic, as micro plastic. They can suffer entanglement, wounds or can ingest the particles which can lead to blockages, bio-accumulation, hormone imbalance, oxidative stress, they can influence the reproduction … While researchers started, from the seventies on, to study the plastic pollution and its effect. Land-based plastic was already indicated as the most important source, only recent studies have been published which tried to estimate the plastic fluxes into the oceans and seas. This research studied the contribution of plastic waste generated within the Scheldt basin to the flux of macro plastics (fraction larger than 5 mm). The flux macro plastics is described instead of the total flux or the micro plastic flux because the data on micro plastic within the basin is too limited.

Literature shows that most of this macro plastic in river systems originates from packaging plastics and dominant forms of plastic found in rivers are polyethylene and polypropylene. While the waste management is quite good in the basin, many of this plastic still enters the river via litter. On average a person litters 3.1 kg waste each year in the basin, of which 0.7 kg is plastic. This is however only a small amount if you know that on average 125.7 kg plastic waste is generated in total by the inhabitants of the basin. So only 0.6% is mismanaged and especially packaging waste is in most cases used for recycling or energy production. This is however still too much because of the low degradation rate. A plastic bottle needs, for example, between the 100 and 1000 years to degrade.

To estimate the flux, first is tried to scale down the existing global models and use them only on the Scheldt basin. This leads to the ‘Top down-model’, a model which is based on three existing models: one of Lebreton et al. (2017), Schmidt et al. (2017) and the ‘From Land to Sea model’ of BKV GmbH (2017). The model includes plastic litter which ends up in the river system, plastic waste of inland shipping and waste of ports. In total it is calculated that between 7.9 and 48.6 tons of macro plastic enter the sea each year via the Scheldt Basin, with an average scenario indicating 18.2 ton. These estimations could however be fine-tuned by including the land-use and artificial barriers as parameters.

The second model which is explored in this study is the Bottom-up model. This model does not start at basin scale, as did the previous model, but tries to build up the plastic load accumulation. For this model a block model is used with each block representing a district (based on the management districts of ‘De Vlaamse Waterweg nv’). Each of these blocks have litter inputs and inputs from plastic waste from inland navigation. Additional some districts have an input form waste of a port. Almost all districts have additional transport losses due to

69 blockages of sluices or locks. This model has still too many data gaps to correctly quantify the plastic flux and will need additional data and research. However, when using the Top-down model to calibrate this model some small observations could be done: the Maritime Scheldt seems to be responsible for double as much plastic compared to the ‘kanaal Gent-Terneuzen’. And the district around Brussels seems to be one of the major plastic contributors. However, to get a real value out of the model, additional measurements of the load are needed and probably more processes as the tidal influence, or the influence of the additional locks or discharge have to be added.

For a river in Europe the contribution of the Scheldt is limited. However, compared to an estimation of the Rhine, you would expect an even lower flux of macro-plastic based on the smaller catchment area, population and discharge. While the contribution of the Scheldt is not that big, there is still a lot of progression possible. This is possible by converting to bioplastics or cleaning the plastic out of the rivers. But both techniques are still expansive and both need more research before they could be implemented. What should be already done is limiting the plastic waste and improve the management of plastic waste. The European commission has a proposal ready for a directive which should help to do this, but the main challenge is to implement this set of rules as quickly as possible and maybe go even further than the thresholds set out by Europe to make of the Scheldt a plastic free river.

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