Storing E-Waste in Green Infrastructure to Reduce Perceived Value Loss Through Landﬁll Siting and Landscaping: a Case Study in Nanjing, China

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Article Storing E-waste in Green Infrastructure to Reduce Perceived Value Loss through Landﬁll Siting and Landscaping: A Case Study in Nanjing, China

Fu Chen 1,2,* , Xiaoxiao Li 2, Yongjun Yang 2, Huping Hou 2, Gang-Jun Liu 3 and Shaoliang Zhang 2

1 Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou 221008, China 2 School of Environmental Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221008, China; [email protected] (X.L.); [email protected] (Y.Y.); [email protected] (H.H.); [email protected] (S.Z.) 3 Geospatial Science, College of Science, Engineering and Health, RMIT University, Melbourne, Victoria 3000, Australia; [email protected] * Correspondence: [email protected]; Tel.: +86-5168-388-3501

Received: 31 January 2019; Accepted: 25 March 2019; Published: 27 March 2019

Abstract: Electronic waste (e-waste) represents a severe global environmental issue due to the fast upgrading and updating of electronic products and the high environmental risk. Current low recycling technology, high economic cost, and weak disposal capability make it difficult for e-waste to be rendered 100% harmless. E-waste disposal requires new site-selection methods and site-saving technology to take into account the loss of public perceived value. This study attempts to improve e-waste disposal through siting and landscaping to reduce perceived value loss. The first step is to determine the minimum distance for landfill siting by surveying the minimum loss of perceived value and to use the geographic information system (GIS) to sketch the suitable landfill site thereafter. To optimize the landfill landscape, a landscape infrastructure and its filling process have been designed to reduce the environmental risk and ensure future reuse potential. The application case showed that the minimum distance is 521 m, which was sensitive to the educational level and occupation of residents. The key to landfill landscaping is the construction of isolation layers and the integration of the landfill and urban landscape. The method described in this paper is characterized by minimizing the perceived loss of value to the public, reducing environmental risks, and preserving the resource value of e-waste. This design could provide an alternative to current electronic waste processing methods.

Keywords: electronic waste; urban planning; waste disposal; public attitude; NIMBY syndrome

1. Introduction Electronic products, such as computers, mobile phones, and TV sets, are indispensable equipment in people’s daily lives. With the improvement of technology and heightened consumer demand, the upgrading and updating of electronic products has become notably more rapid in recent years [1,2]. On average, a personal computer had a service life of 4–5 years at the end of the previous century, but at the beginning of the 21st century, its service life was reduced to 2–3 years [3,4]. Currently, the average service life of laptops and mobile phones is less than two years, and the annual scrap rate is equal to the annual update rate of certain electronics in China [5]. Electronic waste (e-waste) mainly comes from household appliances, entertainment electronics, ofﬁce equipment, communication equipment, and other electronic waste products [6,7]. The improper disposal of e-waste poses a signiﬁcant threat

Sustainability 2019, 11, 1829; doi:10.3390/su11071829 www.mdpi.com/journal/sustainability Sustainability 2019, 11, 1829 2 of 15 to water resources, soil, air, and public health, because it contains large amounts of heavy metals, such as copper, mercury, lead, gold, and silver [8–11]. China is the biggest producer and consumer of electronic products in the world. In 2015, approximately 1.68 × 109 mobile phones, 0.36 × 109 PCs, and 0.14 × 109 color TV sets were produced in China [12]. However, due to the lack of statistical data, Li et al. [5] noted that it is difficult to make a precise estimate of the volume of e-waste in China. According to an estimation method by the European Environment Agency [13], no less than three million tons of e-waste was produced in China in 2015, which has increased at an estimated average annual rate of 4–5%. Meanwhile, China is also the world’s largest destination for e-waste importers. Although the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal explicitly bans the export of e-waste [14,15], China accepted over 50% of the world’s total e-waste from 2001 to 2012 [16]. Guiyu, a small town in Guangdong Province, has become a globally notorious e-waste hub [8,17,18]. In addition, Longtang and Dali in Guangdong Province, Taizhou in Zhejiang Province, Huanghua in Hebei Province, Jiujiang in Jiangxi Province, and Nanjing in Jiangsu Province are considered to be main recycling and disposal cities for e-waste in China [17–21]. In 2004, the Chinese government drafted a first pilot for an e-waste disposal management scheme in Zhejiang Province [22], but the results of the pilot implementations were not satisfactory. Zeng et al. [23] considered that the failure might be due to the output of e-waste being very small, often ignored, and not even professionally classified directly into the production of waste disposal. Sanitary landfills are the most critical method for the nondestructive treatment of solid waste [24–27]. The Environmental Protection Agency (EPA) believes that there are, at least, major natural, economic, and financial risks that arise in the process of landfill site selection. The natural risks of landfills are comprehensively assessed with respect to topographic [28], hydrological [29], geological [28], soil [30], and land use factors [31]. Moreover, agricultural land, residential areas, industrial zones, and scenic spots are involved in the risks caused by such landfill sites [32–34]. Ekmekçio˘gluet al. [35] estimated the financial risks associated with landfill sites according to transportation cost. Thus, the best landfill site can be selected by considering all of the environmental, hydrological, and geological factors possible and using the combined geographic information system (GIS) and analytic hierarchy process or fuzzy logic reasoning [31]. However, landfills are still perceived as a nuisance to the public, no matter how scientifically grounded the site selection is. Simsek et al. [34] considered that landfill site selection is not a simple technical decision, and several unquantifiable political, sociological, and behavioral factors are also at stake. Therefore, above all else, public perceptions must be considered in landfill siting. Not-in-my-backyard (NIMBY) syndrome is one result of the awakening of public awareness of environmental protection, and NIMBY is characterized by opposition to any proposals for new construction that involves potential environmental risks [36,37]. Simsek et al. [34] argued that NIMBY syndrome is also a key factor affecting public perceptions. Emotional distress [38], declines in real estate value [39], or even discrimination against the residents living in the vicinity of the landfill [40,41] frequently occur as a consequence of landfill and dump site selection. Kao and Lin [42] and Shen and Yu [36] found that the more people who live or work near potential landfill sites, the less support there is for the landfills [43]. Similarly, Pampel [44] found that the greater the media coverage and public discussion, the greater the public attention and the greater the number people who switch from indifference to the new construction proposals to opposition. In addition, Greenberg and Truelove [45] discussed the impacts of gender, age, education level, social status, and the role played by the construction project on public perception. Unlike municipal solid waste, e-waste disposal requires more advanced technology, especially with respect to the extraction of trace elements. At present, only a small fraction of high-value metals is recycled, and most e-waste is burned, buried, or discarded randomly. Although a zero-emission solution is the best option for e-waste disposal, the proper storage of e-waste can be regarded as a stopgap for both environmental protection and future reuse in the current situation of inefficient Sustainability 2019, 11, 1829 3 of 15 recycling technology, low disposal capacity, and high economic cost. However, due to a lack of detailed evaluation criteria regarding the public perception of the value loss associated with landfills, several existing landfills are surrounded by urban sprawl, leading to the misuse of these landfills. Furthermore, modern methods have less frequently accounted for the loss of subjective value, environmental risk, and resource value. Therefore, new ideas and methods for landfill construction should be introduced to address these issues. The aims of this study are as follows: (1) to develop a method for determining the landfill site consideringSustainability 2019 the, 10 loss, x FOR of PEER subjective REVIEW value in order to discuss buffer distance and other influencing3 of 15 factors and (2) to design an e-waste landfill as landscape infrastructure to improve the overall local considering the loss of subjective value in order to discuss buffer distance and other influencing factors ecologicaland (2) environment. to design an e-waste landfill as landscape infrastructure to improve the overall local ecological environment. 2. Methodology and Data Collection 2. Methodology and Data Collection 2.1. Landfill Siting Considering Public Perception 2.1. Landfill Siting Considering Public Perception 2.1.1. Overall Technique Flow E-waste2.1.1. Overall is different Technique from Flow municipal solid waste and has greater environmental and health risks. Therefore,E-waste e-waste is different landfill from site selectionmunicipal requiressolid waste a two-stepand has greater evaluation environmental method. and The health first risks. step is to followTherefore, the method e-waste of generallandfill site landfill selection site requires selection, a two- andstep the evaluation second stepmethod. is to The consider first step the is to particularity follow of e-waste.the method A flow of general chart landfill for the sitesiting selection, of and e-waste the second landfills step is based to consider on the the minimizationparticularity of e-waste. of publicly perceivedA flow value chart for loss the was siting developed of e-waste (Figurelandfills1 based). on the minimization of publicly perceived value loss was developed (Figure 1).

Land use Settlement area Electronic industrial planning Public perception survey Soil type Agricultural area Distance of intolerable

Industrial… area Output of e-waste Geology

… … odor effects

Extraction Length of service Road Growth rate … landscape loss Slope Buffer zones … emotional distress

Subset of suitable areas Predict occupied area of landfill Dist. of public perception

Sliding box with buffer zones of public Scoring rules of the Evaluation unit perception distance perceived economic and ecological values Identify suitable areas where the value loss is minimum loss

FigureFigure 1. Flow 1. Flow chart chart for for the the siting siting of of electronic electronic wastewaste (e-waste) landfills landfills based based on onthe theminimization minimization of of publicly perceived value loss. publicly perceived value loss. Two steps are shown below. Two steps are shown below. (1) Subsetting of potentially suitable areas. The method employed in this step was developed by (1) Subsetting of potentially suitable areas. The method employed in this step was developed by Wilson, D.C. [40]. This method integrates analytical hierarchy process (AHP) and GIS. Several factors, Wilson,such D.C. as land [40 use,]. This soil methodtype, groundwater, integrates slope, analytical the settlement hierarchy area, process the agricultural (AHP) area, and and GIS. the Several industrial factors, sucharea, as land are considered use, soil type, by the groundwater, AHP method slope,[31,46]. theDifferential settlement analysis area, under the agriculturalthe ArcGIS 10.2 area, spatial and the industrialanalysis area, module are consideredwas performed. by theEach AHP criterion method was weighted [31,46]. by Differential AHP and mapped analysis using under GIS the techniques ArcGIS 10.2 spatial[46–48]. analysis The moduleoutput ofwas this step performed. is a small Each region criterion on the map was that weighted shows locations by AHP suitable and mapped for an e-waste using GIS techniqueslandfill. [ 46For– 48further]. The determining output of thisthe best step landfill is a small site in region the followin on theg mapstep, thatthe suitable shows area locations was then suitable for anrasterized e-waste with landfill. a resolution For further of 100 determiningm × 100 m. the best landfill site in the following step, the suitable area was(2) then Sliding rasterized box with with buffer a resolution zones of public of 100 perception m × 100 distance m. and identifying landfill units where the value loss is minimal. By referring to electronic industrial planning, the occupied area of the landfill (2) Sliding box with buffer zones of public perception distance and identifying landfill units can be predicted. A sliding box was created by using the predicted occupied area for the e-waste landfill where the value loss is minimal. By referring to electronic industrial planning, the occupied area of as the size of the box. The sliding box was moved within the rasterized landfill suitability map to generate the landfillpotential can landfill be predicted.units. A sliding box was created by using the predicted occupied area for the e-wasteBy using landfill a public as the perception size of thesurvey box. (Section The sliding 2.1.2), a boxbuffer was distance moved of public within perception the rasterized of different landfill suitabilitydegrees map of aversion to generate towards potential an e-waste landfill landfill units. can be determined. Here, four levels of buffer distance were considered during the public perception survey. As shown in Table 1, we formulated the value loss score of perceived value loss based on different levels of buffer distance and land use within the buffer zone. Combining the value loss scores of different buffer zones, we calculated the perceived value loss index of each potential landfill unit using Equation (1). Furthermore, the landfill unit where the value loss is minimal can be picked out by comparing the perceived value loss index. Sustainability 2019, 11, 1829 4 of 15

By using a public perception survey (Section 2.1.2), a buffer distance of public perception of different degrees of aversion towards an e-waste landfill can be determined. Here, four levels of buffer distance were considered during the public perception survey. As shown in Table1, we formulated the value loss score of perceived value loss based on different levels of buffer distance and land use within the buffer zone. Combining the value loss scores of different buffer zones, we calculated the perceived value loss index of each potential landfill unit using Equation (1). Furthermore, the landfill unit where the value loss is minimal can be picked out by comparing the perceived value loss index.

4 4 L = ∑ ai Fi/ ∑ Ai Fi × 100% (1) I=1 I=1 where L is the perceived value loss index, i is the number of buffer zones under consideration, ai is the area of construction land or farmland within the i-th buffer zone, Ai is the total area of the i-th buffer zone, and Fi is the value loss score of the i-th buffer zone.

Table 1. Scoring rules of perceived value loss.

Buffer Zone First Buffer Zone Second Buffer Zone Third Buffer Zone Fourth Buffer Zone All activities All activities except greening All activities except greening, Evaluation criteria Only affects housing except greening and agriculture agriculture, and industry Scoring rules 5 3 2 1

2.1.2. Survey on Public Perception The surveying of public perception is a critical step in landfill siting. The aim of our questionnaire was to understand the public perception of e-waste and its hazards and the impact of landfills. Aversion to the odor and appearance of landfills is the primary components of public perceptions. The odor is mainly due to the chemical reaction of the main components of e-waste in contact with the environment, such as water, acid, and soil. The dismantling, purification, and processing of e-waste in a recycling industrial park cannot prevent odor generation, but if buried e-waste can be guaranteed to be absolutely isolated from the environment, no odor will be produced after the closure of the landfill. Objectively speaking, it is obvious that the environment around an e-waste landfill has a huge impact on nearby residents’ living environment and physical health. The first reaction of most residents to landfills is “Do not enter my backyard.” However, what is the public’s perception of being various distances from the e-waste landfill? Because temporary e-waste landfills are already in existence, a questionnaire about landfill distances was distributed. Due to the real existence of NIMBY, it is necessary to investigate the impact of the extent of the e-waste landfill on public perception. Public awareness of an e-waste landfill site would affect the construction of such a landfill. To understand the attitudes and opinions held by a defined population toward the e-waste landfill, we designed a questionnaire consisting of four major parts (Table2). If the public surveyed did not understand the ideas underlying e-waste landfills, they could consult specially trained investigators to ensure the accuracy and reliability of the results of the questionnaire. The background knowledge needed to accurately respond to the questionnaire included the spread of waste odor, urban waste disposal standards, landfill health risks, and so on. After the questionnaire design was completed, the questionnaires were tested on a small scale in the network of surrounding residents. After confirming the validity of the small-volume data of the questionnaire, a large-scale investigation was carried out. An introduction of e-waste and its hazards comprised the first part of the questionnaire. Gender, age, educational level, and related job were the primary personal demographic characteristics sought; questions on these factors formed the second part of the questionnaire. The third part of the questionnaire related to the best way to dispose of e-waste, the main hazards of e-waste landfills, and the best solution for e-waste disposal in a landfill. The fourth part was comprised of questions regarding the distance of the four buffer zones. The first buffer zone is the minimal distance within which the resident will leave the area, and it represents all livelihood activities that are severely affected Sustainability 2019, 11, 1829 5 of 15 by the presence of an e-waste landfill. The second buffer zone is the distance within which the odor from an e-waste landfill can spread, and it represents the aspects of an e-waste landfill that are offensive to human olfaction. The third buffer zone is the distance within which the e-waste landfill fades to invisibility from residential or working areas. The fourth buffer zone is the distance at which no impact of anSustainability e-waste 2019 landfill, Sustainability10, x FOR is PEER reported. 2019 REVIEW, 10, x FOR PEER REVIEW 5 of 15 5 of 15

TableTable 2. Questionnaire 2. QuestionnaireTable survey survey2. Questionnaire on on public public perceptionsurvey perception on public of spatial ofperception spatialdistances of distances from spatial the distances e-waste from landfill.from the e-waste the e-waste landﬁll. landfill.

E-waste E-waste landfill Distance(m) Distance (m) E-wastelandﬁll landfill Distance(m)

DoDo youyou Know?Know? Do you Know? E-waste mainly includes household appliances, entertainment electronics, The improper disposal of e-waste poses a E-waste mainly includesE-waste household mainly includes appliances, household appliances, officeentertainment equipment, electronics, communication office equipment, equipment, and otherThe electronic improper disposal significantof e-waste poses threat a tosignificant water resources, soil, air, waste products. entertainment electronics, office equipment, The improperand public disposal health. of e-waste poses a significant communication equipment,communication and other equipment, electronic and waste other electronicthreat to waste water resothreaturces, to soil, water air, reso andurces, public soil, health. air, and public health. products. products.Gender Age Gender Gender Age Is your job Age related to waste Number of years of education Number of years ofNumber of years of disposal? Is your job related√ Is to your waste job disposal? related to waste disposal? Whateducation do you think is theeducation best way to dispose of e-waste? ( ) Incineration Dump Recycling What do you thinkWhat is the do best you way think to is the best way√ to What are main hazards of an e-waste landfill?Incineration ( ) DumpIncineration Landscape Dump Recycling Noise Recycling Odor Menticide dispose of e-waste?dispose (√) of e-waste? (√) Absolute WhatWhat isare the main best hazards solutionWhat areof foran main e-waste hazards disposal of an e-waste in a Anti-seepage √ Landscape NoiseLandscape physical Noise Odor OdorFixing Menticide agent Menticide landfill?landfill? ((√)) landfill? (√) treatment isolation Absolute Absolute What is the best solutionWhatWhat is for the shoulde-waste best solution be the minimalfor e-waste distance Anti-seepage from the landfill? Anti-seepage From which 1 physical physical Fixing agent FixingFirst buffer agent zone disposal in a landfill?disposal distance(√) in a landfill? will you (√ leave) your currenttreatment residential placetreatment or work? isolation isolation 2What should What be the isWhat the minimal maximalshould distance be distance the minimalfrom that the thedistancelandfill? odor fromFrom from the landfillwhich landfill? distance can From spread? which distance Second buffer zone 1 1 First buffer zone First buffer zone will you leaveWhat your iswill the current you distance leave residential atyour which current place the or landfillresidential work? fades place to invisibilityor work? from your 3 Third buffer zone 2 What is theresidential2 maximal What distance or is working the maximal that place?the odor distance from that landfill the odor can spread?from landfill can spread? Second buffer zone Second buffer zone What is the distance at which the landfill fades to invisibility from your 3 What isWhat the landfillis the distance distance at atwhich which the no landfill impact fades will to be invisibility produced fromThird on your buffer zone 4 3 Fourth bufferThird zone buffer zone residentialyour or working dailyresidential life? place? or working place? What is the landfillWhat distance is the at landfill which distanceno impact at willwhich be noproduced impact willon your be produced on your 4 4 Fourth buffer zoneFourth buffer zone daily life? daily life? 2.2. Criteria for Developing the E-waste Landfill as Landscape Infrastructure 2.2. Criteria for Developing2.2. Criteria the for E-waste Developing Landfill the asE-waste Landscape Landfill Infrastructure as Landscape Infrastructure Nowadays, recycled e-waste constitutes less than 30% of all e-waste in China. Most e-waste is not fullyNowadays, used. First, recycledNowadays, the currente-waste recycled constitutes technology e-waste less isconstitutesthan limited, 30% of less becauseall thane-waste 30 it% in cannot of China. all e-waste extractMost ine-waste allChina. the is Most not trace e-waste elements is not fully used. First, the current technology is limited, because it cannot extract all the trace elements of e- of e-waste [49].fully Second, used. recyclingFirst, the current certain technolo highlygy is toxiclimited, heavy because metals, it cannot such extract as all mercury, the trace elements cadmium, of e- waste [49]. Second,waste recycling [49]. Second, certain recycling highly toxic certain heavy highly metals, toxic such heavy as metals,mercury, such cadmium, as mercury, chromium, cadmium, chromium, chromium,and arsenic, and can arsenic,and be arsenic,difficult can candue be be difficultto difficultthe high due due cost. toto Thus, thethe high the cost.recycling cost. Thus, Thus, of the such the recycling heavy recycling metalsof such of has suchheavy been heavymetals metalshas been hasabandoned been abandoned by almostabandoned byall almostinformal by almost allrecycling all informal informal sectors, recyclingrecycling causing sectors, many sectors, seriouscausing causing en manyvironmental many serious serious problemsenvironmental environmental in problems in problemsChina. Third, in China. theChina. output Third, Third, of e-waste the the outputoutput is much of of e-waste larger e-waste th isan much isthe much capacitylarger larger th ofan e-waste the than capacity disposal. the of capacity e-waste The recycling disposal. of e-waste of The disposal.recycling of Thee-waste recycling not only ofe-waste e-wasteeffectively not not onlyalleviates onlyeffectively the effectively shortage alleviates of alleviates thenatural shortage resources the of natural shortage in China, resources ofbut natural also in China,contributes resources but also to contributes in China, to the green development of the world. Therefore, our idea is to store e-waste that cannot be dealt with by but also contributesthe green to the development green development of the world. of Therefore, the world. our Therefore,idea is to store our e-waste idea isthat to cannot store be e-waste dealt with that by current technologies,current economic technologies, costs, economicand disposal costs, capab andility disposal in an capabairtightility place in an instead airtight of placediscarding instead it, of discarding it, cannot be dealt with by current technologies, economic costs, and disposal capability in an airtight so that it can be sorecycled that it caneffectively be recycled in the effectively future to achievein the future zero wastage.to achieve zero wastage. place insteadThus, given of discarding theThus, potential given it, economic so the that potential it value can economic beof e-wast recycled e,value an effectively e-wasteof e-wast landfill,e, inan thee-waste as futurea temporary landfill, to achieve asbank a temporary for zero wastage. bank for potentiallyThus, given valuablepotentially the and potential untreated valuable economic e-wasteand untreated for value recycl e-waste ofing e-waste,and for reuse recycl anining the e-waste and future, reuselandfill, seems in the to future, asbe athe temporaryseems best to be the bank best forsolution potentially at the valuablemoment.solution However,at and the moment. untreated e-waste However, must e-waste be e-waste sealed for in recyclingmust a box be for sealed burying and in reusea boxto prevent for in burying the toxic future, tosubstances prevent seems toxic to substances be the bestof solution e-waste from at theof coming e-waste moment. into from contact However,coming with into water contact e-waste and withsoil. must Thewater sealed be and sealed soil.box proposedThe in asealed box by box for this proposed burying study is bymade to this prevent study is toxic made of impermeable and durable materials with an isolation layer and special protective functions. At the substances of e-wasteof impermeable from coming and durable into contact materials with with wateran isolat andion soil.layer Theand special sealed protective box proposed functions. by At this the bottom of the sealedbottom box, of thefour sealed layers, box, which four are layers, referred which to asare the referred drainpipe, to as rainwater the drainpipe, collection rainwater layer, collection layer, study is made of impermeable and durable materials with an isolation layer and special protective impermeable layer,impermeable and filtrate layer, monitoring and filtrate layer, monitoring were designed. layer, Thiswere sealed designed. box Thiscould sealed play an box important could play an important functions.role in storing At the e-wasterole bottom in storingwithout of the e-waste environmental sealed without box, fourinterference.environmental layers, Due which interference. to the are absolute referred Due physicalto the to asabsolute isolation the drainpipe, physical of the isolation rainwater of the collectionsealed box, layer, the design impermeablesealed ofbox, the the proposed design layer, ofe-waste and the proposed filtrate landfill monitoring e-wasteis different landfill from layer, is a differentmunicipal were designed.from landfill, a municipal because This landfill,sealed there because box could there playis anno biogas important collectionis no role biogas system, in storingcollection for example.e-waste system, The for withoutsealed example. box environmental isThe designed sealed boxto be is seal interference.designeded for toa periodbe seal Due ofed time,for to a the period absolute of time, physicalensuring isolation absoluteensuring ofisolation the absolute sealed and imperviousness isolation box, the and design imperviousness for 50–100 of the years. proposed for Thereafter, 50–100 years. e-waste if e- wasteThereafter, landfill landfills if e- isneedwaste different to landfills from need ato be uncovered for recyclable e-waste retrieval after closure, the sealed box greatly reduces the municipal landfill,be becauseuncovered there for isrecyclable no biogas e-waste collection retrieval system, after forclosure, example. the sealed The sealed box greatly box is reduces designed the environmental risksenvironmental and occupational risks and health occupational effects. We health hope effects. that e-waste We hope can that be more e-waste effectively can be more reused effectively reused to bewhen sealed technology forwhen a has period advanced.technology of time, has ensuringadvanced. absolute isolation and imperviousness for 50–100 years. Sustainability 2019, 11, 1829 6 of 15

Thereafter, if e-waste landfills need to be uncovered for recyclable e-waste retrieval after closure, the sealed box greatly reduces the environmental risks and occupational health effects. We hope that e-waste can be more effectively reused when technology has advanced. Meanwhile, e-waste landfills must not become a “forgotten space,” but should rather be transformed to make the city a better place by fulfilling ecological leisure purposes. Thus, when a center of e-waste disposal is closed, it can be preserved as an industrial heritage site that can display information about e-waste disposal with the public and improve the public’s awareness of environmental protection. In addition to an exhibition center, buried e-waste landfills can be used as urban green space to provide recreation services. To this end, any possible pollutant diffusion should be controlled, and the relationship between the landfill and the natural landscape should be coordinated. Based on the above considerations, the design of an e-waste landfill should adhere to the following criteria. (1) Determining the overall future development framework based on the natural conditions of e-waste landfills. A framework for pollution control technology and vegetation repair systems should be developed. A stable ecological protection system for controlling the future land use of the site should be established. The e-waste landfill should be decommissioned and transformed into part of the urban public space under the aegis of the established landscape once urban sprawl has reached the periphery of the existing landfills. (2) Using a sealed box for the burial of e-waste. The major benefit of a sealed box is to reduce pollution through layered burial while allowing for the reuse of the electronic waste bank. A separate sealed box can be arranged according to the terrain. After finishing the burial in one block, vegetation repair and ecological prevention should commence. To reduce the production of leachate, the leachate collection and drainage system should be designed separately for each block. Usually standing several dozens of meters high, the huge garbage mountain can be decomposed into a much lower height for proper management. The space overlying the top of the sealed box can be built into a platform for future landscape construction. In this way, the e-waste landfill will serve as an urban green space and low-carbon e-waste bank. (3) Conducting landscape construction step by step. First, the surrounding environment should be remediated. A public–private–partnership (PPP) model can be introduced to design and operate the e-waste landfill as a landscape project. This is very important for changing the conventional negative impressions of landfills. Second, e-waste landfill can be built and operated in connection with an e-waste recycling industrial park. The park is to be designed as an integrated system of waste decomposition, selection, recycling, and burial. The e-waste recycling industrial park can be rebuilt into a museum to introduce information about e-waste recycling to the public after the closure of the e-waste landfill. Third, road transportation networks and infrastructure facilities should be perfected. There will be gradual improvements of the planted vegetation on top of the sealed box for the formation of a greening system. The installation of sports, amusement, and leisure facilities will help separate different waste burial regions. The greening system will be constantly extended outwards and linked to the existing urban green space. Finally, the e-waste landfill will be integrated into the urban ecological environment to become part of the public leisure space.

2.3. Application Case and Data Resource To find a practical solution to design an e-waste landfill as landscape infrastructure, we selected Nanjing as an application case. Nanjing is the capital of Jiangsu Province and has a humid subtropical monsoon climate with an annual average temperature of 15.4 ◦C and an annual precipitation of 1106.5 mm. The total administrative area was 6597.2 km2 in 2015, with a built-up urban area of 923.8 km2 [50]. The entire municipal population was 8.24 million in 2015, and the urban population was 6.70 million. Nanjing’s gross domestic product (GDP) was 147.14 × 109 dollars in 2015, and the per capita GDP was 17,865.25 dollars. Contributing 35.79 × 109 dollars of local GDP in 2015, the computer, communications, and electronic industry is one of the pillar industries of Nanjing and is ranked the Sustainability 2019, 11, 1829 7 of 15 second largest such industry of all the cities in China. Nanjing has five landfills that process 8600 tons of domestic waste per day [51]. However, there is still no professional e-waste landfill in Nanjing, even though approximately 150,000 tons of e-waste is absorbed there annually. For landfill siting, a land use map with scale of 1:10,000, a geological map with scale of 1:50,000, a soil type map, and QuickBird remote sensing images for 29 July 2015 (spatial resolution of 0.61 m × 0.61 m) were collected. For investigating public perceptions, 11 postgraduate students undertook a field survey in the form of face-to-face interviews from July to September 2015. The staff who conducted the questionnaire interviews inquired and recorded the details of the information provided by the respondents. The field survey was conducted in three types of public spaces. The first public space consisted of 300 randomly interviewed respondents in downtown streets or public places. The second consisted of 200 randomly chosen interviewees in residential areas, office buildings, and enterprises near the existing landfill. The third consisted of 100 randomly chosen respondents in unsupervised suburban waste dumping sites. A total of 600 respondents were interviewed, including 33 waste disposal workers from the second group of investigated public spaces. In this application case, we applied the GIS-based sliding box sampling technique, social surveys, and scoring rules on the perceived economic and ecological values of the potentially suitable sites for e-waste landfills in Nanjing, China. SPSS 19.0 software was used to conduct statistical and correlation analyses on the survey results. ArcGIS 10.2 was used to conduct overlay analysis, and a buffer analysis was performed on the land use types, soil types, geological and hydrological information, and road distances. Once the site selection and design are finalized, this e-waste landfill could serve as a local natural landscape, providing the public with an ecological leisure space in addition to a landfill for e-waste.

3. Results and Discussion

3.1. Variety in Public Perception Regarding Spatial Distance from the Landﬁll The survey indicates severe underestimation and overestimation of the perceived distance from the landﬁll in some samples, especially with respect to the estimation of the radius of the fourth buffer zone. We took the sample value with the highest distribution frequency as the baseline X to increase the relative concentration degree of the samples. Next, the samples were selected within the range of [X/4, 4X], and the results are shown in Table3.

Table 3. Perceived distance from the landﬁll and valid samples.

Variable First Buffer Zone Second Buffer Zone Third Buffer Zone Fourth Buffer Zone Mean (m) 521.4 864.5 1976.3 5170.2 Standard deviation 171.6 576.8 478.9 916.3 Effective samples 579.0 571.0 573.0 546.0

According to the social survey, a radius of 521.0 m constitutes the area in which the presence of the landfill is unbearable, that is, the first buffer zone. This distance is very close to the minimal required distance from a landfill specified in the Standard for Pollution Control on the Landfill Site of Municipal Solid Waste [52], which requires that landfills should be at least 500 m away from residential areas [52]. In the first buffer zone, all livelihood activities are severely affected by the landfill, and only certain vegetation and trees for landscaping or protection purposes can be planted. There is not an allowance for any agricultural, gardening, or residential areas within the first buffer zone, in which there is a complete loss of perceived value. Therefore, establishing some economic compensation mechanism would be an effective method to communicate and reach consensus with residents regarding the first buffer zone. The perceived distance of odor spread from a landfill is 864.5 m, i.e., the second buffer zone. Odor has little impact on agricultural and gardening activities but may be offensive to human olfaction. Therefore, residential areas and industrial development zones are the primary sites of perceived value loss within the second buffer zone. The perceived distance of landfill visibility is Sustainability 2019, 11, 1829 8 of 15

1976.3 m, i.e., the third buffer zone, primarily impacting viewsheds. Therefore, there is a low degree of disturbance, and residential and office areas are the primary sites of perceived value loss within the third buffer zone. Corresponding to the fourth buffer zone, the perceived distance at which no disturbance exists is 5170.2 m, which was significantly higher than the perceived distance in the other three layers. In the fourth buffer zone, there are minimal effects on the productivity and life activities near the landfill aside from the psychological impact. Although the tangible impact of the landfill is absent at this point, the public still worries about the potential risks of the landfill, and there is still the existence of some psychological resistance, leading to a decline in the value of both real estate and investmentSustainability attraction. 2019, 10, x In FOR the PEER fourth REVIEW buffer zone, the impact of the landfill is considered extremely8 of 15 low, and residential and office areas are the primary sites of perceived value loss. of the landfill is considered extremely low, and residential and office areas are the primary sites of 3.2. Landfillperceived Site value with loss. Minimal Perceived Value Loss GIS3.2. Landfill and the Site analytical with Minimal hierarchy Perceived processValue Loss were used to determine the suitable sites for a landfill based onGIS the and flowchart the analytical in Figure hierarchy1. Threeprocess siteswere used qualified to determine as a landfill the suitable site, sites as for shown a landfill in based Figure 2: Qinglongshanon the flowchart in southeast in Figure Nanjing, 1. Three sites Tongjing qualified in as southwest a landfill site, Nanjing, as shown and in Ma’anshanFigure 2: Qinglongshan in west Nanjing. in The built-upsoutheasturban Nanjing, area Tongjing of Nanjing in southwest has nearlyNanjing, doubled, and Ma’anshan reaching in west 923.8 Nanjing. km2 Thein built-up the past urban 10 years. Becausearea they of Nanjing are already has nearly surrounded doubled, byreaching the built-up 923.8 km urban2 in the area, past 10 the years. Shuige Because Landfill they andare already Tianjingwa Landfillsurrounded should noby longerthe built-up be used urban (Figure area, the2 a).Shuige Landfill and Tianjingwa Landfill should no longer be used (Figure 2a).

FigureFigure 2. Location2. Location ofof (a) the the study study area area and and (b) a ( bsuitable) a suitable site with site minimal with minimal perceived perceived value loss. value loss.

AccordingAccording to theto the 2015 2015 Nanjing Nanjing Bulle Bulletintin onon the thePollution Pollution Control Control and Management and Management of Solid Waste of Solid and Overall Environmental Planning of Nanjing (2013–2030) [53], the volume of e-waste was Waste and Overall Environmental Planning of Nanjing (2013–2030) [53], the volume of e-waste was approximately 150,000 tons in Nanjing in 2015. Within the next fifteen years, this volume is expected to approximately 150,000 tons in Nanjing in 2015. Within the next fifteen years, this volume is expected to grow at a rate of approximately 4% annually. In 2015, the e-waste disposal capacity of Nanjing was only grow at90,000 a rate tons of per approximately year. Residues 4% are annually. about 1/3 Inof the 2015, tota thel mass e-waste and still disposal need to capacity be buried of after Nanjing recycling. was only 90,000These tons perresidues year. contain Residues certain are highly about toxic 1/3 ofheavy the totalmetals, mass such and as mercury, still need cadmium, to be buried chromium, after recycling.and Thesearsenic, residues which contain can be certaindifficult to highly recycle toxic due to heavy cost or metals,technology. such Therefore, as mercury, approximately cadmium, 30,000 chromium, tons and arsenic,of residues which and 60,000 can be tons difficult of untreated to recycle e-waste due need to to cost be temporarily or technology. saved Therefore,in a sealed box approximately of an e- 30,000waste tons landfill of residues each year. and The 60,000 design tons operational of untreated service e-waste life of the need e-waste to belandfill temporarily is 20 years. saved Considering in a sealed box ofthe an available e-waste depth landfill of the each disposal year. of 60 The m for design 10-laye operationalred burial, the service floor area life of of the the e-waste e-waste landfill landfill is is estimated to be approximately 50,000–60,000 m2. Thus, the size of the sliding box should be designed to 20 years. Considering the available depth of the disposal of 60 m for 10-layered burial, the floor area of be 250 m × 250 m, and the four buffer zones must be considered in the design of the landfill, with the the e-waste landfill is estimated to be approximately 50,000–60,000 m2. Thus, the size of the sliding distance thresholds being 521.4 m, 864.6 m, 1976.3 m, and 5170.2 m, respectively. The areas of different box shouldland use be types designed within each to be buffer 250 mzone× are250 obtained m, and by the sliding four the buffer box over zones themust rasterized be considered suitable sites. in the designThe of perceived the landfill, value with loss index the distanceis calculated thresholds using Equati beingon (1), 521.4 identifying m, 864.6 the site m, with 1976.3 the minimal m, and index 5170.2 m, respectively.value, as Theshown areas in Figure of different 2b. land use types within each buffer zone are obtained by sliding the

3.3. Landscape Infrastructure of E-waste Landfills According to the criteria for developing an e-waste landfill as landscape infrastructure, the process of landscaping an e-waste landfill in Qinglongshan is shown in Figure 3a. Unlike municipal waste, sealed e-waste does not produce biogas and harmful leachate. It is only necessary to collect rainwater. Therefore, in a sense, an e-waste landfill is more like an e-waste storage bank than a sanitary landfill. The section Sustainability 2019, 11, 1829 9 of 15 box over the rasterized suitable sites. The perceived value loss index is calculated using Equation (1), identifying the site with the minimal index value, as shown in Figure2b.

3.3. Landscape Infrastructure of E-waste Landfills According to the criteria for developing an e-waste landfill as landscape infrastructure, the process of landscaping an e-waste landfill in Qinglongshan is shown in Figure3a. Unlike municipal waste, sealed e-waste does not produce biogas and harmful leachate. It is only necessary to collect rainwater. Therefore, in a sense, an e-waste landfill is more like an e-waste storage bank than a sanitary landfill. TheSustainability section 2019 diagram, 10, x FOR of PEER thesealed REVIEW box referenced to the research of Yang and Cui [54] and detailed9 of 15 design specifications and dimensional standards are shown in Figure3b. At the top of the sealed box, diagram of the sealed box referenced to the research of Yang and Cui [54] and detailed design seven layers are designed for imperviousness and landscaping. The impermeable layer is an excellent specifications and dimensional standards are shown in Figure 3b. At the top of the sealed box, seven layers water or vapor barrier at the bottom. The mixed territorial layer is used as a re-protection barrier and are designed for imperviousness and landscaping. The impermeable layer is an excellent water or vapor is filled in between the two impermeable layers. The drainage blanket, geotextile layer, and compacted barrier at the bottom. The mixed territorial layer is used as a re-protection barrier and is filled in between soil are then added. The plant layer is used as the landscape element for the top layer. Only shrubs the two impermeable layers. The drainage blanket, geotextile layer, and compacted soil are then added. and flowers can be used as landscape elements. On one hand, it prevents the roots of tall plants The plant layer is used as the landscape element for the top layer. Only shrubs and flowers can be used as from intruding the other engineering cover layers, and on the other hand, it prevents the plant layers landscape elements. On one hand, it prevents the roots of tall plants from intruding the other engineering from becoming too heavy and causing the collapse of the sealed box. Some engineering measures are cover layers, and on the other hand, it prevents the plant layers from becoming too heavy and causing the performed before the landfilling process, including field preparation, which is determined using the collapse of the sealed box. Some engineering measures are performed before the landfilling process, minimal perceived value loss. Next, a landfill ditch is dug, and the spoil is piled aside with a reserved including field preparation, which is determined using the minimal perceived value loss. Next, a landfill microstome. After completing these initial steps, the classified e-waste can be added. Shrubs and ditch is dug, and the spoil is piled aside with a reserved microstome. After completing these initial steps, flowers are allowed to grow on top of the e-waste landfill, and thus, a single landfill area is completed. the classified e-waste can be added. Shrubs and flowers are allowed to grow on top of the e-waste landfill, Finally, a landscape infrastructure will be formed, while more landfill areas are constructed and shaped and thus, a single landfill area is completed. Finally, a landscape infrastructure will be formed, while more into a complete terrain. landfill areas are constructed and shaped into a complete terrain.

Figure 3. 3. DesigningDesigning the the e-waste e-waste landfill landﬁll as asa green a green infrastructure infrastructure (a) (anda) and detailed detailed design design specifications speciﬁcations and dimensionaland dimensional standards standards of the ofsealed the sealedbox (b box). (b).

Because the construction of such a massive e-waste landfill requires a refined project management process, four stages of development were successively carried out (Figure 4). The first stage is planning and design. After the investigation and assessment of the e-waste site selection, the overall conceptual design of the landfill will be proposed. Moreover, in the framework of designing, regional revitalization, employment, and removal, three main principles are considered. The second stage is construction and operation. At this stage, all the materials will be transported to the site. Moreover, the sealed box will be constructed based on the design of Figure 3b. After the e-waste landfill is constructed, shrubs and flowers will be planted. Reasonable and regular water protection management measures will also be introduced. The third stage is growth and succession. With the promotion of e-waste market development and ecologic improvement, a diverse habitat will be formed. The fourth stage is adaptation and transformation. At the beginning of the design of the e-waste landfill, the long-term development has been Sustainability 2019, 11, 1829 10 of 15

Because the construction of such a massive e-waste landfill requires a refined project management process, four stages of development were successively carried out (Figure4). The first stage is planning and design. After the investigation and assessment of the e-waste site selection, the overall conceptual design of the landfill will be proposed. Moreover, in the framework of designing, regional revitalization, employment, and removal, three main principles are considered. The second stage is construction and operation. At this stage, all the materials will be transported to the site. Moreover, the sealed box will be constructed based on the design of Figure3b. After the e-waste landfill is constructed, shrubs and flowers will be planted. Reasonable and regular water protection management measures will also be introduced. The third stage is growth and succession. With the promotion of e-waste market development and ecologic improvement, a diverse habitat will be formed. The fourth stage is adaptationSustainability and2019, transformation.10, x FOR PEER REVIEW At the beginning of the design of the e-waste landfill, the long-term 10 of 15 development has been considered. Therefore, an ecological museum will be built as an urban public spaceconsidered. that illustrates Therefore, the an harmony ecological between museum man will and be built nature. as an urban public space that illustrates the harmony between man and nature.

Investigation and Construction Promote e-waste Long-term development market development program assessment Traffic Conceptual design Museum Regional revitalization Ecological Urban public space improvement Harmony between man Employment Water protection and nature Diverse Removal Planting trees habitat

Construction and operation Adaptation and transformation Planning and design stage stage Growth and succession stage stage

Figure 4.Figure Development 4. Development stages of e-waste stages of landfill e-waste and landﬁll landscape and formation landscape strategies. formation strategies.

4.4. DiscussionDiscussion

4.1.4.1. InfluenceInfluence of Individual Ch Characteristicsaracteristics on on Landfill Landfill Siting Siting LandfillsLandfills havehave aa tremendoustremendous impactimpact onon theirtheir surroundingsurrounding environment.environment. However, However, making making a a reasonablereasonable evaluationevaluation of of these these impa impactscts is is difficult difficult because because of ofthe the diverse diverse standpoints standpoints and and interests interests of ofdecisionmakers, decisionmakers, businesses, businesses, and andthe general the general public. public. Because Because the treatment the treatment process processof e-waste of is e-waste a major is aexternality major externality under the under existing the economic existing and economic technical and conditions, technical in conditions, this study, inwe this focused study, on wethe focusedcriteria onfor the the criteriasiting of for e-waste the siting landfills of e-wastebased on landfills the publ basedic’s perceived on the value public’s loss perceived from a questionnaire. value loss fromThe aquestionnaire questionnaire. is generally The questionnaire organized and is generally implemented organized in strict andaccordance implemented with international in strict accordance common withpractice, international and the survey common data practice, is accurate and and the surveyreliable. data The isbasic accurate personal and information reliable. The gathered basic personal in the informationquestionnaire gathered mainly included in the questionnaire the gender, age, mainly education included level, and the gender,occupation age, of educationthe respondents. level, The and occupationpublic perception of the of respondents. spatial distances The was public mainly perception reflected of the spatial public’s distances requirements was mainly for the site reflected selection the public’sof the landfill. requirements Public perception for the site is selectionvery subjecti of theve, landfill.and the respondents’ Public perception age, gender, is very occupation, subjective, and and theeducational respondents’ background age, gender, strongly occupation, affect the results and educational(Figure 5). In background order to make strongly the evaluation affect thefairer, results the (Figuresurvey5 data). In orderwas classified to make for the statistical evaluation analysis. fairer, Pe therceived survey distance data was is not classified influenced for statistical by age, and analysis. there Perceivedwere no significant distance iscorrelations not influenced in the by perceived age, and dist thereance were of different no significant buffer correlationszones across inthe the age perceived groups distanceat a significance of different level bufferof 0.05 zones(Figure across 5a). As the for agethe impact groups of at gender, a significance the percei levelved distance of 0.05 of (Figure different5a). Asbuffer for thezones impact showed of gender,no significant the perceived differences distance except for of the different fourth buffer zone zones (Figure showed 5b). noFurthermore, significant differencesin all four buffer except zones, for the females fourth were buffer more zone sensitive (Figure to5b). the Furthermore, potential risks in of all e-waste four buffer landfills zones, than females males. wereHowever, more the sensitive number to of theyears potential of education risks is ofa sign e-wasteificant landfillsinfluencing than factor. males. Compared However, with thethe age number and ofgender years of of the education respondents, is a educational significant influencingbackground an factor.d occupation Compared had a with greater the impact age and on genderthe perceived of the respondents,distance. Compared educational with background the respondents and occupationreceiving less had than a greater six years impact of oneducation, the perceived the perceived distance. Compareddistance differed with thesignificantly respondents in the receiving respondents less receiving than six 6–9 years years of of education, education, 9–16 the perceivedyears of education, distance and over 16 years of education (Figure 5c). With the increase of educational years, the perceived distance to the landfill increases, which indicates that environmental awareness is enhanced by educational level. The survey shows that people with high education pay more attention to environmental issues. Moreover, the landfill distance perceptions vary depending on occupation, and the difference was statistically significant in all the buffers (Figure 5d). In addition, it is obvious that people who are engaged in waste disposal offer a much shorter perceived distance than those who are not. This finding coincides with the conclusions by Greenberg [55] but cannot overturn the “proximity hypothesis.” In general, landfill siting is influenced by many individual characteristics. When selecting sites for landfills, we should optimize site selection to ensure that a buffer zone is chosen that does not disturb the residents, enhances effective communication with the public, and raises environmental standards. Sustainability 2019, 11, 1829 11 of 15 differed significantly in the respondents receiving 6–9 years of education, 9–16 years of education, and over 16 years of education (Figure5c). With the increase of educational years, the perceived distance to the landfill increases, which indicates that environmental awareness is enhanced by educational level. The survey shows that people with high education pay more attention to environmental issues. Moreover, the landfill distance perceptions vary depending on occupation, and the difference was statistically significant in all the buffers (Figure5d). In addition, it is obvious that people who are engaged in waste disposal offer a much shorter perceived distance than those who are not. This finding coincides with the conclusions by Greenberg [55] but cannot overturn the “proximity hypothesis.” In general, landfill siting is influenced by many individual characteristics. When selecting sites for landfills, we should optimize site selection to ensure that a buffer zone is chosen that does not disturb the residents, enhances effective communication with the public, and raises environmental standards. Sustainability 2019, 10, x FOR PEER REVIEW 11 of 15

Figure 5. Impact of respondents’ age (a), gender (b), number of years of education (c), and occupation (d) onFigure the perceived5. Impact of distancerespondents’ to age the ( landﬁll.a), gender Error(b), number bars of represent years of education the standard (c), and error, occupation and different (d) lowercaseon the lettersperceived indicate distance signiﬁcant to the landfill. differences Error bars at representp < 0.05 accordingthe standard to error, Duncan’s and different multiple lowercase range tests. letters indicate significant differences at p < 0.05 according to Duncan’s multiple range tests.

4.2. Advantages and Disadvantages of the Design of a Sealed Box In this study, we propose the use of a completely impermeable sealed box, which is costlier than an ordinary landfill, but it will offer lower pollution risk and effective vegetation repair. The term "landfill mining" has long been recognized, but heavy metals, such as mercury, cadmium, and chromium, are still difficult to recycle. Burying a mixture of electronic and domestic waste is a common practice in China [56]. This process not only represents a huge potential environmental risk, but also causes the waste of resources [49,57]. The disposal of e-waste is also technically difficult and less economical, and the concept of “landfill banks” has been proposed to offset the environmental responsibility of e-waste in the future. In this new sealed box, the risk of heavy metal leakage from e-waste will be prevented. Furthermore, as a landscape infrastructure, it provides urban residents with recreational venues. However, this sealed Sustainability 2019, 11, 1829 12 of 15

4.2. Advantages and Disadvantages of the Design of a Sealed Box In this study, we propose the use of a completely impermeable sealed box, which is costlier than an ordinary landfill, but it will offer lower pollution risk and effective vegetation repair. The term “landfill mining” has long been recognized, but heavy metals, such as mercury, cadmium, and chromium, are still difficult to recycle. Burying a mixture of electronic and domestic waste is a common practice in China [56]. This process not only represents a huge potential environmental risk, but also causes the waste of resources [49,57]. The disposal of e-waste is also technically difficult and less economical, and the concept of “landfill banks” has been proposed to offset the environmental responsibility of e-waste in the future. In this new sealed box, the risk of heavy metal leakage from e-waste will be prevented. Furthermore, as a landscape infrastructure, it provides urban residents with recreational venues. However, this sealed box also has some deficiencies, such as its high construction cost and complex maintenance management. As a new methodology, innovation and practice are necessary, and difficulties are encountered, which require global joint efforts to address.

4.3. E-waste Landfill for a Green Future “Pollution first, treatment later” is a long-standing principle of economic development in China that needs to be renounced. To conform to the social trend toward harmony between man and nature, the design of environmental protection facilities should be updated. Landfills are usually constructed as a remedial measure against garbage-based disasters in developing countries [58]. The long-term development goals of landfills are rarely considered during the planning and design stage [59]. The ecological repair measures currently used are mainly for preventing environmental deterioration due to landfill pollution [46]. The ecological repair of landfills in China currently lags far behind those on the global scale, and remedial measures are not sufficient. Throughout the world, landfills seem to be one of the most unattractive dimensions of urban development [25,41]. The primary reason for this is the profound lack of understanding of the value of landscaping in landfill siting. It is time to consider the future of landfills as more than a remedial project for environmental protection, but as a unique landscape infrastructure from the very beginning [41]. The landfill construction process should integrate the ecological repair of the landfill. From siting, burial, pollution management, and vegetation planting to habitat reconstruction, every step of landfill construction must be placed under overall planning. This is the inevitable pathway leading to the integration of e-waste landfills into urban green public space. In fact, an e-waste landfill design was published in March 2016 and has received widespread public and media discussions in Nanjing, China. The local community has actively supported the planning scheme, as they see a more beautiful future than the current situation. After the innovation of the e-waste landfill, the recycling and disposal of e-waste have become a reality, and we have moved closer to a green future.

5. Conclusions E-waste is the fastest-growing category of garbage around the world. Residual burial after recycling specific valuable materials seems to be the only solution for e-waste management. However, an e-waste landfill should not be a forgotten and unattractive place in a city, and it must be integrated into the future urban space. The combination of three methods, namely, a GIS-based sliding box technique, social surveys on the public perception of landfill distance, and the scoring of the perceived values of lost biology and plants, can help us identify landfill sites with minimal public perceived value loss. An independent sealed box not only stores residual e-waste as valuable materials for the future, but also prevents soil and groundwater pollution. By designing e-waste landfills as landscape infrastructure, e-waste landfills will become part of the urban public green space. The results showed that the minimum distance accepted by local residents is 521 m, an opinion which was mainly influenced by the respondents’ educational level. The key to landfill landscaping is the construction Sustainability 2019, 11, 1829 13 of 15 of isolation layers and integration of the landfill and urban landscape. This study highlights that in the process of creating an e-waste landfill, it is key to minimize the perceived value loss to the public, reduce the environmental risk, and preserve the resource value of e-waste. Our study provides an alternative option for the improvement of e-waste landfills in developing countries, especially where e-waste has grown substantially.

Author Contributions: Conceptualization, F.C. and G.L.; Data curation, F.C. and H.H.; Formal analysis, X.L.; Funding acquisition, S.Z.; Investigation, F.C., X.L., Y.Y. and H.H.; Methodology, F.C., Y.Y. and H.H.; Project administration, G.L. and S.Z.; Resources, G.L.; Software, F.C., X.L. and Y.Y.; Supervision, G.L. and S.Z.; Writing—original draft, F.C., X.L., Y.Y., H.H., G.L. and S.Z.; Writing—review & editing, F.C., X.L., Y.Y., H.H., G.L. and S.Z. Funding: This work was supported by the Major Project in the Fundamental Research Funds for the Central Universities under No. 2017XKZD14. Acknowledgments: The authors would like to thank Nanjing Environmental Protection Bureau and Department of Land and Resources of Nanjing City for the support during the research. The authors would also like to thank MDPI English Service for providing linguistic assistance during the preparation of this manuscript. Conﬂicts of Interest: The authors declare no conﬂict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

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