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Home , Kerbside collection

Quantifying Household Diversion by Home Composting and Kerbside Collection

Principal Investigator: Dr Stephen R. Smith Research Student: Olympia Mitaftsi

Funder: The Norlands Foundation Collaborating Organisation: Runnymede Borough Council

The Centre for Environmental Control and (CECWM) in the Department of Civil and Environmental Engineering at Imperial College has recently completed a major programme of research for The Norlands Foundation, in collaboration with Runnymede Borough Council (RBC), on the effectiveness of home composting at waste diversion from disposal. The project was established to address uncertainty relating to the reductions in waste disposal potentially achieved through promoting home composting of garden and kitchen waste in the community. Waste inputs to home composters were measured for a two year monitoring period by a volunteer group of 64 households in the Borough of Runnymede, representing the largest and most comprehensive data set on home composting available in the UK. The monitoring programme demonstrated that within this group of homeowners, the mean input of garden, kitchen and waste to the bins was 400 kg per household per year. The number of households purchasing a subsidised bin from Runnymede Borough Council was equivalent to approximately 20 % of homeowners in the Study Area (over 800 bins were distributed in the Study Area and the total number of properties in the Area was approximately 4000). If this level of participation were extrapolated to the whole of the Borough, the amount of waste diverted from landfill disposal would be equivalent to approximately 10 % of the total quantity of waste arising from door-to-door collection.

Home composting represents potentially one of the most sustainable options for managing putrescible household waste because the individual generating the waste is also the processor and user of the treated end-product. However, the analysis of gross waste statistics based on weighbridge data did not show a significant fall in general waste arisings, although the patterns in from the rounds in the Study Area did not increase in line with the national average value suggesting that home composting may have contributed to stabilising waste generation in the Study Area, at least in the short-term. However, the gross analysis approach to estimating impacts on waste arisings is relatively insensitive, and does not take account of the other factors that can influence waste disposal practices such as demography and other /disposal activities and changes in behaviour, such as the willingness of homeowners to take their waste to Civic Amenity (CA) sites. Analysis and measurement of disposal practices at the individual household level is necessary to fully understand the impacts of changes in waste management practices that are implimented at the householder level.

Home composting is recognised as having a central role in the waste strategy for , but because of uncertainty about the actual quantities of waste diverted from landfill disposal by this practice, Local Authorities do not receive payments under the Recycling Credits scheme for promoting home composting. This is suggested as a principal factor disuading Local Authorities from continuing to promote home composting. However, DEFRA would reconsider this policy if an appropriate and robust monitoring protocol could be developed to demonstrate the extent of waste diversion from landfill disposal by home composting.

The conference on Home Composting – Can it Make a Difference?, organised by CECWM in May 2002 concluded that home composting required active support from the Local Authority to engage the public to increase its effectiveness as a waste management option. The lack of Recycling Credits is a disincentive to supporting home composting, but the potential cost savings by both the waste collection and disposal authorities are significant and justify a proactive approach to promoting this activity. Nevertheless, information on the most effective techniques of promotion to ensure optimisation of resources would assist Local Authorities in planning appropriate promotional measures and strategies. Previous attempts to study impacts of different methods of supporting home composting have failed to produce results on waste diversion based on gross waste generation because of inconsistent collection rounds and data recording. This further emphasises the need for a more innovative and novel approach to recording household waste statistics at the individual household level.

Runnymede Borough Council has established a kerbside collection scheme for dry recyclates, and includes the same collection rounds used in the Home Composting Study. The Council and IC have data base records of the distribution of recycling bins and home composters to individual homeowners. This provides a unique opportunity to quantitatively examine the impacts of both diversion/recycling activities on waste generation for this large sample group of households. So far, little attention has been paid to measuring the effects of these types of practice on the actual amounts of waste generated by households that is landfilled. This information is essential to:

1. Determine the effectiveness of /recycling measures in reducing the amounts of landfilled waste; 2. Assess whether removing material from the wheeled bin by these measures encourages household waste disposal – there is anecdotal evidence to suggest that this may be the case. For example, homeowners may be less willing to take waste to a CA site for disposal if space is created in the wheeled bin due to kerbside recycling/home composting; 3. Provide management optimisation information in terms of the required frequency of waste collections from households and waste bin size. For example, where recycling/minimisation measures are effective in reducing the amount of waste placed in the wheeled bin for disposal, the frequency of collection could be reduced; 4. Provide a technical case and quantitative information to present to DEFRA to reevaluate the awarding of Recycling Credits for waste diversion by home composting.

Technology is now available for collecting dynamic waste data for individual households by fitting refuse collection vehicles (RCV) with automatic weighing and data logging equipment. This provides a critical and flexible tool for measuring waste collection from a large number of households, which is necessary in quantitative, statistically designed waste management research. To date, however, there are no examples of waste management research projects where this technology has been deployed.

The Environment Agency has expressed an interest in obtaining further information on the consequences of expanding home composting on the release of greenhouse gases, - particularly methane (CH4) and also on nitrogen (N, principally nitrate [NO3 ]) transport in leachates from home compost bins. The Home Composting Study measured CH4 concentrations in the interstitial gas of composting residues and found only traces of the gas were present. However, quantitative emissions of greenhouse and other gases (CH4, carbon dioxide [CO2] and also ammonia [NH3], which is now becoming the focus of increased environmental control from the bins were not measured. This would require an alternative experimental approach enclosing the entire bin in a gas collection chamber.

Problems were also encountered in advising homeowners participating in the Home Composting Study regarding the suitability of different types of waste packaging, card and paper, for adding to composting waste, which is important to balance the moisture status and improve the rate of waste and quality of the end-product. Achieving good end-product quality is important in maintaining the continuity of interest by homeowners in home composting activities as a waste diversion method. Little progress appears to have occurred in labeling packaging to indicate its suitablility for composting and further work is necessary to identify suitable types of packaging materials and to encourage producers to develop compostable packaging.

This programme of research by the CECWM at Imperial College London, in collaboration with the Environmental Protection Division of RBC and funded by the Norlands Foundation aims to quantify the impact of home composting and kerbside collection on household waste disposal, adopting an innovative approach to measure waste diversion/disposal using a dynamic, automatic weighing system for individual refuse bins. The research also addresses a number of key issues that emerged from the earlier Home Composting Study in terms of maximising waste processing by small-scale home composters, environmental emissions (gaseous and aqueous) and the suitability of packaging materials for home composting.

The aims of the research are as follows:

• To quantify the impacts of home composting and kerbside recyclate collection on waste generation, composition and disposal.

• To provide management optimisation information on the frequency of waste collection rounds and refuse bin size.

• To develop a protocol for measuring actual waste diversion statistics by home composting and provide recommendations for consideration by DEFRA regarding approaches to quantifying waste diversion by home composting.

• To assess the effectiveness of different promotional strategies for home composting on the amount of diverted from landfill by this practice.

• To quantify maximum potential of small-scale home compost bins and management factors governing end-product quality.

• To assess the significance of environmental emissions from home compost bins in - the gaseous (CO2, CH4 and NH3) and aqueous (NO3 ) phases. • To test the biodegradability of different packaging materials for use as bulking agents and develop recommendations on the suitability of these for home composting inconjunction with the packaging industry.