Environmental benefits of construction and demolition debris recycling: Evidence from an Indian case study using life cycle assessment

Journal Pre-proof Environmental benefits of construction and demolition debris recycling: Evidence from an Indian case study using life cycle assessment V.G. Ram, Kumar C. Kishore, Satyanarayana N. Kalidindi PII:

S0959-6526(20)30305-X

DOI:

https://doi.org/10.1016/j.jclepro.2020.120258

Reference:

JCLP 120258

To appear in:

Journal of Cleaner Production

Received Date: 19 November 2019 Revised Date:

22 January 2020

Accepted Date: 24 January 2020

Please cite this article as: Ram VG, Kishore KC, Kalidindi SN, Environmental benefits of construction and demolition debris recycling: Evidence from an Indian case study using life cycle assessment, Journal of Cleaner Production (2020), doi: https://doi.org/10.1016/j.jclepro.2020.120258. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.

Credit Author Statement VG Ram: Conceptualization, Software, Investigation, Writing- Review & Editing, Visualization, Supervision. Kishore C Kumar: Methodology, Software, Formal analysis, Investigation, Writing- Original Draft Satyanarayana N Kalidindi: Resources, Supervision, Project Administration

Environmental Benefits of Construction and Demolition Debris Recycling: Evidence from an Indian Case Study using Life Cycle Assessment VG Ram a*, Kumar C Kishore b, Satyanarayana N Kalidindi b a b

Department of Civil Engineering, Indian Institute of Technology Madras, India. Department of Civil Engineering, Indian Institute of Technology Tirupati, India. * Corresponding author. E-mail: [email protected]

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Environmental Benefits of Construction and Demolition Debris Recycling: Evidence from an Indian Case Study using Life Cycle Assessment Abstract The adversarial effects of construction and demolition (C&D) waste on the environment are on the increase. While materials such as metals, wood, glass and plastics are segregated and diverted for reuse/recycling, C&D debris consisting of concrete, bricks and tiles are landfilled in most of the countries. LCA studies have indicated a clear preference for recycling. However, it has been inferred that the environmental credits obtained in these studies were mainly from recycling of metals and wood and studies focusing on environmental impacts/benefits evaluation of C&D debris recycling is limited. This is particularly relevant in the cases of developing countries like India, where C&D debris forms a bulk of C&D waste generation. Therefore, this paper evaluates the environmental impacts of four different scenarios for managing C&D debris comprising the present (S1) and future (S2) landfilling options and recycling options without transfer stations (S3) and with transfer stations (S4). LCA according to ISO methodology is performed based on locally sourced data supplemented with Ecoinvent database. IMPACT 2002+ impact assessment method has been applied for environmental impact quantification using SimaPro software. Landfilling of C&D debris generates environmental impacts, and recycling scenarios generate environmental benefits in all 15 impact categories. Single score values of landfilling scenarios are 1.83 mPt (S1) and 2.78 mpt (S2) and that of C&D debris recycling are -2.56 mPt (S3) and -1.91 mPt (S4). The robustness of the results was shown through sensitivity analysis. Recycling remains beneficial compared to landfilling as long as the diesel and electricity consumption of C&D debris recycling facility remains less than 475% of the current consumption. Furthermore, even if the transportation distance from quarry to crushing unit is reduced to zero, recycling still remains a better alternative. The merit of considering the future landfilling scenario in the decision making has been discussed since the challenges that might be encountered in setting up new landfills are underestimated. The implications of the findings and their relevance to urban local bodies have also been discussed to help policymakers take informed decisions while facing challenges of managing C&D debris. Keywords: Construction and demolition waste; C&D debris; LCA; Landfill; Recycling; Transfer station 1. Introduction The urban ecological footprint is on the rise, globally. The resource demand and consumption has already crossed the bioregenerative capacity of the earth. To produce the resource needed and to assimilate the generated waste, there is severe stress on the environment owing to rapid urbanisation activities, especially in fuelling development in cities (Rees, 1999). Global urban population is expected to witness an increase of 60% (addition of 2.5 billion people) by 2050 and almost 90% of it is projected in Asia and Africa. Some of the world’s most populous cities are Tokyo (37 million inhabitants), New Delhi (29 million), Shanghai (26 million), Sao Paulo (22 million), and Mumbai (20 million). Tokyo’s population is expected to decline, and therefore, Delhi is anticipated to become the most populous city by 2028 as it is continuously growing (UN DESA, 2018).

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Rapid urbanisation often leads to massive amounts of construction activities resulting in both the consumption of raw materials and generation of construction and demolition (C&D) waste. For instance, C&D waste generation in China is estimated to be between 1.6 to 2.5 billion tonnes (Duan and Li, 2016). India generates about 112 to 431 million tonnes every year (Jain et al., 2018), and Brazil is reported to generate about 100 million tonnes of C&D waste (Rosado et al., 2019). A major portion of this waste is either landfilled or being dumped in unauthorised places such as sidewalks, roadsides, canals, and lakes in most of the countries (Di Maria et al., 2018). Unauthorised disposal practices lead to several undesirable effects on the environment. For example, illegal disposal of C&D waste was identified as one of the primary reasons for floods in Chennai due to choking of sewers in the city. In China, an illegal construction landfill collapsed, claiming 75 lives and damaged many infrastructures. While the literature recommends recycling of C&D waste, the city corporations responsible for the management of C&D waste dispose of the waste in landfills. Several barriers such as lack of awareness, inadequate policies, weak enforcement, and negligible incentives impede the development of infrastructure for recycling C&D waste in India and other developing countries (Hossain et al., 2016; Ram and Kalidindi, 2017). Studies have shown the need for government interventions to nurture a recycling ecosystem. For example, Brazil, China, Hong Kong, USA, and many European countries have developed policies to offer incentives and subsidies in the form of financial grants and tax rebates for setting up C&D waste recycling facilities (Lu and Tam, 2013; Söderholm, 2011; Wang et al., 2018). Recycling rates in countries such as Australia, Belgium, Japan, UK and Taiwan has been found to be greater than 50% of total generated C&D waste (Bio Intelligence Service 2011; WBCSD 2009). However, the installed capacity for recycling C&D waste in India amounts to only about 2.5% of total waste generation. The statistics of recycling rates from many other developing countries are not encouraging as well. This can be attributed to the lack of awareness and knowledge on benefits arising from recycling C&D waste. Studies quantifying the environmental impacts of C&D waste management have reported significant benefits of recycling. It was inferred that the environmental credits obtained in these studies were mainly from the recycling of metals, wood, and plastics (Blengini, 2009; Di Maria et al., 2018; Kucukvar et al., 2014; Rosado et al., 2019, 2017; Wang et al., 2018). Authors could not find literature focussed on evaluating the environmental benefits of recycling C&D debris. In recent years, materials such as metals and wood are being diverted for reuse/recycle to a large extent (Rosado et al., 2019); whereas, C&D debris comprising concrete, brick masonry, excavated earth and ceramics are landfilled, especially in developing countries (Mah et al., 2018). There is a pressing research need to quantify the impacts of recycling C&D debris to facilitate decision making in countries generating significant amounts of C&D debris. Therefore, the primary aim of this study is to quantify the environmental impacts of recycling C&D debris. 2. Literature Review 2

Landfilling, recycling and incineration are commonly depicted waste management scenarios for C&D waste management (Ortiz et al., 2010). Landfilling was found to be generating the highest environmental impacts (Penteado and Rosado 2016) and also resulted in highest economic costs (Di Maria et al., 2018). Recycling has been shown to be a better alternative in a number of studies using various comparative methods including life cycle assessment (LCA) techniques such as process LCA and hybrid LCA (Kucukvar et al., 2014; Ortiz et al., 2010). Moreover, an increase in the percentage of recycling was found to reduce environmental impacts. Environmental benefits have been reported in 13 out of 14 impact categories for C&D waste recycling (Blengini and Garbarino, 2010). The ratio of prevented to produced impacts of a C&D waste recycling facility equals 7.9 in the case of primary energy consumption and 10.8 for CO2eq emissions (Coelho and Brito, 2013). Thus, prevented impacts due to recycling outweigh the produced impacts of operating a recycling facility. C&D waste recycling plants powered by electricity were found to generate very low environmental impacts as compared among plants that are run by diesel (Borghi et al., 2018). Recycling systems with no storage operations (transfer stations) and reduced transportation distances were found to perform better comparatively. LCA studies have also been combined with the willingness to pay (WTP) approach to quantify the environmental costs and benefits. Landfilling was found to cause an environmental cost of $1.73 (¥12.04) against recycling that showed environmental benefits of $0.17 (¥1.21) for every tonne of demolition waste handled. Likewise, concrete and steel recycling were reported to yield environmental benefits, unlike brick & mortar recycling (Wang et al., 2018). However, C&D waste recycling was not found to be beneficial in certain situations. Transportation distances influence the environmental impacts generated (Mercante et al., 2012), and a definite preference between off-site recycling and landfilling could not be established (Vossberg et al., 2014). There are various methods for quantification of environmental impacts such as carbon footprint, substance flow analysis, environmental impact assessment, eco-labelling and life cycle assessment (LCA) (Jolliet et al., 2015). LCA technique is found to be widely adopted in the literature on C&D waste management (Bovea and Powell, 2016). Table 1 summarises various LCA studies in C&D waste management and the environmental credits considered in those studies. The dominance of parameters like metals and wood recycling could be inferred. However, in India and other developing countries, C&D waste predominantly consists of C&D debris and is devoid of materials that cause the highest environmental credits reported in other studies (Mah et al., 2018; Ram and Kalidindi, 2017). Steel, electrical wires, wooden doors, glass windows and other materials which have high economic value and a robust informal recycling network are seldom disposed in landfills. It is necessary to exempt the environmental credits from these materials to understand the exclusive benefits of C&D debris recycling. In such scenarios, it is not clear if recycling C&D debris is still beneficial. This research gap has been observed by Blengini and Garbarino (2010) as well.

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Table 1 Environmental credits considered in LCA studies of C&D waste management Country Spain USA Cape Town, South Africa Brazil, South America Flanders, Belgium Malaysia Lombardy, Italy Shenzhen, China Brazil Spain Portugal Turin, Italy Turin, Italy Italy

Author

Focus Mr



Ortiz et al. 2010 Kucukvar et al. 2014 Vossberg et al. 2014 Penteado and Rosado 2016 Di Maria et al. 2018

Consideration of environmental credits Wr Pr Par Cr Dr Gr V














L





C&D waste management scenarios










Mah et al. 2018 Borghi et al. 2018 Wang et al. 2018

















Rosado et al., 2019 Mercante et al. 2012 Coelho and Brito 2013 Blengini and Garbarino, 2010 Blengini 2009 Vitale et al. 2017





















C&D waste recycling

End-of-life phase



























Note: Mr - Metals recycling (Metal includes iron, steel, aluminium), Wr - Wood recycling, Pr - Plastics recycling, Par - Paper recycling, Cr - Cardboard recycling, Dr - Drywall recycling, Gr - Glass recycling, V- Virgin aggregate replacement, L - Landfill avoidance

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Furthermore, about 90% of the LCA studies on C&D waste were from European countries, the US and China (Bovea and Powell, 2016). Studies from developing countries such as India are limited and empirical data ascertaining the environmental benefits of recycling over landfilling from these regions is important owing to the regional differences in practices and composition of waste generated. Therefore, the objective of this research is to evaluate the environmental impacts of C&D debris recycling and identify a sustainable C&D debris management scenario among landfilling and off-site recycling scenarios. 3. LCA methodology LCA methodology in accordance with ISO 14040 and 14044 (2006a; 2006b) is adopted for evaluating the environmental impacts and benefits, and it involves four stages namely, (1) Goal and scope definition, (2) Life cycle inventory, (3) Life cycle impact assessment, (4) Interpretation and results. 3.1. Goal and scope The goal is to quantify and compare the environmental impacts of C&D debris management scenarios. Chennai, the capital city of the state of Tamil Nadu and the fourth largest Metropolitan City in India with a population of 4.6 million (Census, 2011) has been chosen as the case for this study. C&D debris recycling facility is currently unavailable in Chennai city, but the Greater Chennai Corporation (GCC), the municipal body, is taking measures to set up recycling facilities. The dumpsites in Chennai occupy about 180 hectares in total and are almost overflowing. The height of the dump in one of the dumpsites in Chennai has reached 15m already (Peter et al., 2019). Because of the regulatory restrictions on the maximum height of dumping, the municipal body is searching for a new dumping ground to cater to the disposal needs of the city. A significant portion of C&D debris dumped in these landfills can be recycled. The municipal body is faced with a dilemma of pursuing either recycling or developing a new landfill for C&D waste management in the city. As environmental benefits accruing from C&D debris recycling are unclear, Chennai city presents a suitable case for our research. The current scenario of C&D waste management in Chennai is depicted in Fig. 1. The portion of waste which is separated and sold in the secondary market and the illegally dumped waste is excluded from the study. Thus, this study effectively considers C&D debris (the inert portion of C&D waste) which consists of concrete, masonry, tiles, boulders and soil. Functional unit One tonne of C&D debris is chosen as the functional unit for the study. The composition of C&D debris being dumped in landfills was determined by visual analysis of 100 truckloads that were randomly chosen from the dumpsites, and the results are shown in Fig. 2. Among C&D debris, concrete and masonry waste contribute to about 53%. Studies conducted in other Indian cities have also indicated similar waste compositions of C&D waste. Metals, bitumen, wood and other 5

waste contribute only 10% whereas C&D debris contributes to 90% of the total C&D waste (TIFAC 2001). System boundaries Since the study aims at comparing different waste management scenarios, common elements of the systems such as building demolition, waste handling and on-site storage are not considered. This practice is commonly adopted in the literature on C&D waste and is known as ‘‘zero burden assumption’’ (Ekvall et al., 2007). This simplification is justified as neglecting the common processes in the scenarios considered facilitates effective comparison especially in situations where the scenarios handle identical amounts of waste. The system boundaries considered for landfilling and recycling of C&D debris are shown in Fig. 3 and Fig. 4, respectively. The study considers the avoided burdens of NA production and the system boundary for the same is shown in Fig. 5.

Fig. 1. Current scenario of C&D waste management in Chennai

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Fig. 2. Composition of C&D debris landfilled in Chennai

Fig. 3. System boundary for C&D waste landfilling

Fig. 4. System boundary for C&D debris recycling

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Fig. 5. System boundary for natural aggregate production This study excludes the burdens due to the infrastructure of crushing facility, trucks, support structure and maintenance operations of both NA and RA production facilities. The processes and technology used by both NA and RA production facilities are largely identical, and therefore the exclusion does not result in any significant error and gives a balanced comparison (Vossberg et al., 2014). Additionally, the upstream material and energy spent for crusher manufacturing and assembly, and replacement of spares cause negligible environmental impacts as operation phase contributes to 94% of the life cycle emissions (Landfield and Karra, 2000). A similar approach has been followed in several other works in the literature (Mercante et al., 2012; Penteado and Rosado, 2016; Rosado et al., 2019). 3.2. Development of various scenarios In this study, the relative impacts of four different scenarios of C&D debris management have been analysed. Table 2 presents the classification of various end-of-life scenarios of C&D debris management considered. A brief description of each of these scenarios has been detailed in the subsequent sections. Table 2 Classification of end-of-life scenarios considered Waste management scenario Scenario S1 S2 S3 S4

Dumping/ Landfilling

Recycling

Usage of transfer stations

Avoided burdens of NA production

Avoided burdens of landfilling

Current/ Future state





C F C C














3.2.1 Current scenario of dumping C&D debris in landfill (S1) Estimates of C&D debris generation in Chennai city indicate about 1.14 million tonnes every year (Ram and Kalidindi, 2017). Out of that, only 0.4 million tonnes of C&D debris is being dumped in two active dumping grounds, namely Kodungaiyur and Perungudi. The collection and transportation network consists of trucks with 16-tonne and 21-tonne carrying capacities. The amount of C&D debris dumped in the landfills is obtained by analysing the records of 8

weighbridges operating in the dumpsites. From the data collected, it was found that the total quantity of waste dumped in Kodungaiyur in 2014 is 0.21 million tonnes and that in Perungudi is 0.18 million tonnes and the detailed inventory is presented in Table A.1 and Table A.2 respectively (Appendix A). It was estimated that one tonne of C&D debris is transported to 11.4 tonne-km. Since transportation distances play a major role in C&D waste management (Blengini and Garbarino, 2010; Borghi et al., 2018; Mah et al., 2018; Mercante et al., 2012), instead of assuming transportation distance from the geometric centre of each zone to their corresponding dumpsite, this study generated a weighted centroid for each zone based on the actual locations of waste generation. The actual location of waste generation is obtained based on details available in the demolition permits issued by the municipal corporation in one year. Waste generation points are plotted in QGIS (an open-source GIS platform), and the distribution of these data points as obtained from QGIS is shown in Fig. 6. The transportation distance from the weighted centroid to the corresponding landfill is calculated and is detailed in Table A.3 of Appendix A.

Fig. 6. Actual points of waste generation overlapped on the zonal map of Chennai 3.2.2 Scenario of dumping C&D debris in future landfills (S2) S2 represents a scenario of C&D debris dumping in future landfills under the assumption that the existing landfills are entirely depleted. As explained earlier, landfills in Chennai are overflowing, and a search for the location for constructing new landfills are already underway. The situation in other Indian cities is not very different. Moreover, the Indian urban population has been 9

projected to reach 600 million by 2031 from 377 million in 2011. Such rapid urbanization will result in city limit expansion, and subsequently, the waste will be transported over longer distances than the current practice. Therefore, additional environmental burdens will be generated in the future compared to the current scenario. Furthermore, the presence of commonly encountered NIMBY (not-in-my-backyard) syndrome among the public poses a significant challenge to locate future landfills within or near the city limits (Lu et al., 2016). NIMBY syndrome typically refers to the attitudes of community groups to oppose developments of noxious facilities such as landfill sites, hazardous waste facilities, and nuclear plants. While the residents recognise the necessity of such facilities, they are against developing them near their homes. Discounting those impacts in the trade-off during decision making might be more realistic and relevant. Based on the inputs given by GCC officials, tentative places expected to replace Kodungaiyur and Perungudi dumpsites are Minjur in the northern part of Chennai and Kuthambakkam in the southern part of Chennai respectively. These places are situated farther away from the city, and the distance calculations are made according to the procedure detailed in scenario S1. It has been estimated that one tonne of C&D debris will have transported 29.3 tonne-km for this scenario (S2), which is more than 2.5 times the current scenario (S1). The related data is presented in Table A.4 of Appendix A. 3.2.3 Recycling of C&D debris (S3) S3 presents a scenario where the waste is recycled instead of dumping in landfills. In this scenario, the waste is assumed to be sent directly for recycling from the waste generation sites. The municipal body (GCC) planned to set up recycling facilities in the existing dumpsites because of several challenges in identifying land within city limits for crushing activities. The idea of locating recycling facility in landfills is in line with the recommendations in the literature (Cheung & Rootham 1991). The distance travelled by one tonne of C&D debris remains the same in this scenario as that of scenario S1, i.e. 11.4 tonne-km. 3.2.4 Recycling of C&D debris aided by a network of transfer stations (S4) S4 presents a case where C&D debris from all the 15 zones will be sent to identified transfer stations before being transported to recycling facilities. C&D waste generation sites are geographically dispersed, and therefore, the GCC has planned to establish transfer stations within the city where the waste can be dumped by waste generators and later transported to recycling facilities. Setting up of transfer stations is considered to be beneficial as dispersion of generation sources complicates the management of C&D waste (Penteado and Rosado, 2016), and C&D waste generators incur lower costs for transporting to smaller distances and hence compliance might be high. In addition, the lack of a collection network has been attributed to cause illegal dumping and this scenario is expected to enhance the efficiency of C&D waste management

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system. Presently, the GCC has planned to develop 10 transfer stations for C&D waste collection, and the locations of those are shown in Fig. 7.

Location of T.S Location of landfill/recycling facility

Fig. 7. Location of transfer stations to be developed in Chennai The transportation distance from the weighted centroid to transfer stations and from transfer stations to recycling centres is detailed in Table A.5-A.7 (Appendix A). A tonne of C&D debris will be transported 4.15 tonne-km from weighted centroids to transfer station and 12.69 tonnekm from transfer stations to recycling centres. Scenarios S3 and S4 consider the avoided burdens of NA production and landfilling. It is assumed that every tonne of recycled aggregate produced will replace one tonne of natural aggregate. Thus, the substitution ratio in this study for NA to RA is 1:1. Additionally, recycling a tonne of C&D debris prevents a tonne of waste from entering the landfills. A 1:1 substitution is considered for the case of avoided burdens of landfilling. 3.3. Life Cycle Inventory (LCI) The LCI phase quantifies all environmental inputs (energy and raw material) and outputs (emission to air, water and soil) of the unit processes in a complete life cycle (ISO 14040 2006). 11

The data collected from two dumpsites, a natural aggregate crushing unit in Chennai, an aggregate quarry in Tirupati in the state of Andhra Pradesh and a C&D waste processing facility located at Delhi form part of our evidence for this research. The required data were collected inperson using questionnaires and interviews by the authors during the visits to each of the facilities mentioned. Telephonic discussions were conducted for validation and clarification of obtained data. Meanwhile, the required secondary data were retrieved from Ecoinvent v3.5 database using Simapro 9.0.0.41 (LCA software package). Suitable modifications based on available Indian data were made to the values obtained from the generic database. The usage of data from generic database due to the unavailability of proper local inventory data has already been discussed and followed by many other C&D waste management studies from countries such as Brazil, Spain and South Africa (Mercante et al., 2012; Penteado and Rosado, 2016; Rosado et al., 2019; Vossberg et al., 2014). 3.3.1. C&D waste recycling facility The chosen facility for the study was commissioned in Burari, New Delhi in the year 2009 (oldest facility in India) with a capacity to handle 2000 tonnes per day (TPD). The recycling facility occupies 2.83 hectares of land and receives waste from 70 collection centres situated across New Delhi. The facility had processed 284,325 tonnes of C&D waste during its 340 operational days in the year 2018. The process flow of this facility has been mapped and is shown in Fig. 8. Various materials such as whole bricks, wood, plastics, metals and rags are manually sorted and sent for recycling and the rejects are landfilled. Sorted waste concrete and mixed C&D debris are processed to obtain output sizes ranging from 75 µm to 20 mm.

Fig. 8. Process flow of C&D waste recycling facility in Burari, New Delhi 12

From a tonne of C&D waste entering the facility, 0.725 tonnes of recycled aggregates (coarse & fine) is produced. Based on the data collected from the facility, the LCI has been developed and presented in Appendix B. This facility has been found to be consuming about 0.812 kWh of electricity, 1.35 L of diesel and 6.33 L of water for every tonne of recycled aggregates produced (considering gate-to-gate system boundary). 3.3.2. Natural aggregate production Natural aggregates are sourced from either river beds (sand as fine aggregate) or quarried rocks (crushed stone as both coarse and fine aggregates). An active quarry was selected in this study for developing the LCI. Quarry operations near city limits in India are negligible either because of regulatory restrictions or lack of adequate rock-deposits. Hence, materials are sourced from far away locations. In the case of Chennai, it has been found that the trucks travel an average distance of 40 km (one-way) to deliver the quarried rocks to crushing units. The crushing facility that was studied occupies 2.43 hectares of land and operates for 300 days in a year. It produced 206,625 tonnes during the year 2018. The process flow of the crushing unit under study is shown in Fig. 9. The average transportation distance to customer sites is assumed to be 15 tonne-km based on average distances hauled by trucks from this facility. The LCI data collected is detailed in Appendix B. The observed facility is found to be consuming 3 KWh, 2.22 L of diesel and 3.63 L of water for every tonne of natural aggregates produced considering cradle-to-gate system boundary.

Fig. 9. Process flow of natural aggregate crushing facility in Chennai 3.4. Life Cycle Impact Assessment The LCIA phase aims to evaluate the magnitude and significance of all environmental impacts using the results from the LCI phase (ISO 14040 2006). LCIA modelling has been performed using Simapro 9.0.0.41. IMPACT 2002+ (Jolliet et al., 2003) method has been adopted for LCIA in this study. IMPACT 2002+ method is commonly adopted in C&D waste management studies because of its superiority owing to the benefits it offers through the adaptation of existing LCIA methods such as Eco-indicator 99, IPCC and CML (Blengini and Garbarino, 2010; Hossain et 13

al., 2016; Rosado et al., 2019, 2017; Vitale et al., 2017). The Impact 2002+ method consists of 15 midpoint indicators which are mapped to four damage (end-point) categories (Jolliet et al., 2003). 4. Results and Discussion The characterization results of all scenarios are detailed in Table 3. Throughout the analysis, negative values denote environmental savings. Table 3. Characterization of impacts for all scenarios Impact category Unit Carcinogens kg C2H3Cl eq Non-carcinogens kg C2H3Cl eq Respiratory kg PM2.5 eq inorganics Ionizing radiation Bq C-14 eq Ozone layer kg CFC-11 eq depletion Respiratory organics kg C2H4 eq Aquatic ecotoxicity kg TEG water Terrestrial kg TEG soil ecotoxicity Terrestrial acid/nutri kg SO2 eq Land occupation m2org.arable Aquatic acidification kg SO2 eq Aquatic kg PO4 P-lim eutrophication Global warming kg CO2 eq Non-renewable MJ primary energy Mineral Extraction MJ surplus % variation compared to scenario S1

S1 0.017 0.052

S2 0.021 0.125

S3 -0.032 -0.119

S4 -0.026 -0.096

0.008

0.010

-0.008

-0.005

27.57

44.50

-36.08

-25.80

7.4E-07

12.1E-07

-8.3E-07

-5.5E-07

0.003 211

0.004 494

-0.002 -1483

-0.001 -1392

227

570

-786

-680

0.190 0.402 0.029

0.232 0.402 0.037

-0.143 -0.315 -0.032

-0.079 -0.289 -0.022

3.1E-04

4.9E-04

-6.6E-04

-5.5E-04

4.12

6.59

-6.41

-4.92

62.91

101.23

-89.93

-66.70

5.0E-04 -

7.8E-04 60.42%

-54.1E-04 350.19%

-52.5E-04 315.36%

4.1 Present landfills (S1) vs Future landfills (S2) Upon comparing the landfilling scenarios S1 and S2, it is found that depletion of existing landfills could lead to an overall rise in impact by about 60.42% due to increased transportation distances (2.5 times of the current distances). Landfilling one tonne of C&D debris generates 4.12 kg CO2 eq emissions and consumes 62.91 MJ energy for scenario S1. For the case of S2, it will generate 6.59 kg CO2 eq emissions and consume about 101.23 MJ energy. A significant increase has been observed in all of the impact categories except land occupation impact category. A change of more than 100% increase in the impact has been observed in three categories: Non-carcinogens (137.75%), aquatic ecotoxicity (133.57%) and terrestrial ecotoxicity (151.54%). 14

In several studies, recycling has been proved to be a better alternative as compared to landfilling based on reduced environmental impacts (Mah et al., 2018; Ortiz et al., 2010; Penteado and Rosado, 2016; Rosado et al., 2019; Vossberg et al., 2014). However, there are few studies that have reported that recycling is not always beneficial (Borghi et al., 2018; Mercante et al., 2012). This study shows the impact of the scenario wherein the existing landfills get depleted and thereby putting the authorities under pressure to identify alternative dumping grounds. The challenges in developing a new dumpsite are numerous and cannot be overstated. Even in the case of Chennai, several protests and public outcry were reported in the media in the places shortlisted for constructing new landfills (TOI, 2013). Moreover, obtaining environmental clearances for setting up landfill facilities in new places has been very challenging for GCC (The Hindu, 2013). The struggle faced by the GCC starting from 2013 and not being able to secure a place for future landfill yet, shows the magnitude of this problem to an extent. As found in this study, the impacts due to landfilling could only increase in the future because landfill spaces are limited. This effect will be more pronounced in rapidly urbanising countries, like India where landfilling is predominant. 4.2 Recycling vs Landfilling An overall reduction of 350% and 315% in impacts is observed in recycling scenarios (S3 and S4) compared to current landfilling scenario (S1). Lowest environmental benefits are noticed in terrestrial acidification/ nitrification (175%), and the highest benefits are seen in mineral extraction (1190%) impact categories. The high environmental benefits accrued from the recycling scenarios (S3 and S4) are primarily attributed to the avoided burden of natural aggregate production. The avoided burden of NA production is about 121% higher as compared to the avoided burden of landfilling. This result could be attributed to the higher benefits obtained due to avoided transportation from the quarry to the crushing unit. A sensitivity analysis for this parameter is carried out and presented in the following section. Recycling a tonne of C&D debris instead of landfilling will avoid 6.41 kg CO2 eq emissions (S3) and 4.92 Kg CO2 eq emissions (S4) from entering the atmosphere and saves 89.93 MJ (S3) and 66.7 MJ (S4) of primary energy. In addition, a saving of 0.316 m2 (S3) and 0.290 m2 (S4) organic arable land is possible if a tonne of C&D debris is diverted for recycling instead of landfilling (Table 3). If the avoided burden of future landfilling is considered in the scenarios S3 and S4, the environmental savings in global warming, non-renewable energy, and land occupation in the modified scenarios (S3.1 and S4.1) are shown in Table 4. Besides environmental savings, recycling is believed to create several social impacts as well. For instance, setting up recycling facilities will create employment opportunities and thereby boost the local economy. Governance performance of urban local bodies would greatly improve owing to better waste management system. Other benefits include enhanced social image and perceived health of the society. 15

Table 4. Characterization of impacts for modified scenarios Impact category Global warming Non-renewable energy Land occupation

Unit kg CO2 eq

S3.1

S4.1 -8.84

-7.36

MJ primary

-127.60

-104.37

m2org.arable

-0.316

-0.290

4.3 Recycling without transfer stations (S3) vs Recycling with transfer stations (S4) Recycling scenarios S3 and S4 show environmental benefits in all 15 impact categories. The overall environmental savings of 350% (S3) reduces to 315% (S4) because of the inclusion of transfer stations in recycling scenario. A reduction of only 10% (approx.) is observed in environmental savings if transfer stations are included in the recycling scenario. While this portion of savings might be lost if transfer stations are included, the potential benefits that might accrue are plenty including increased waste collection, lower transportation distances to small generators, and improved social image owing to decreased unauthorised disposal (Penteado and Rosado, 2016). Therefore, the decision to build transfer stations depends on the trade-off between the potential costs and benefits, which are contingent on the characteristics of the regions. The characterization results of individual unit processes of scenario S3 and S4 are shown in Fig. 10. In scenario S3, the environmental impact due to recycled aggregate production was almost 80%, and transportation (waste collection) contributed to about 19.6% of the total impacts. In the case of S4, transportation contributed to 24% of the total impacts, transfer station led to about 8% of the total impacts and RA production contributes the rest. Unlike other studies, the contribution of transportation to the total environmental impacts is found to be low owing to the strategic positioning of recycling infrastructure and the availability of land spaces according to the requirements in the case of Chennai. Therefore, a proper network design, including transfer stations coupled with land availability, might lead to lower environmental impacts as observed in the scenarios S3 and S4. The damage characterization factors used by Jolliet et al. (2003) to map mid-point indicators to end-point indicators is adopted in this paper. It can be inferred that landfilling scenarios cause greater damage and recycling scenario (S3) results in the least damage based on the four damage assessment indicators (details given in Appendix C). Among the four indicators, the highest damage due to landfilling and the lowest benefits from recycling occurs in human health category. This study utilised default normalisation factors proposed by Jolliet et al. (2003) (no weighting of data). The final stage consists of converting the end-point categories into a single score which is measured in milli-points (mPt), a dimensionless figure. A milli-point indicates the average impact in a specific category caused by a person during one year in Europe (Vitale et al., 2017).

16

70 60 50 40 30 20 10

%

0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 Carcinoge ns

Non-carci nogens

Respirator y inorgani

Ionizing radiation

Ozone lay er depletio

Respirator y organics

Aquatic ecotoxicit

Terrestrial ecotoxicit

Terrestrial acid/nutri

Land occu pation

Aquatic acidificati

Aquatic eutrophic

Global warming

Non-rene wable ene

Mineral extraction

Carcinoge ns

Non-carci nogens

Respirator y inorgani

Ionizing radiation

Ozone lay er depletio

Respirator y organics

Aquatic ecotoxicit

Terrestrial ecotoxicit

Terrestrial acid/nutri

Land occu pation

Aquatic acidificati

Aquatic eutrophic

Global warming

Non-rene wable ene

Mineral extraction

80 70 60 50 40 30 20 10 %

0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100

Avoided burden of NA production

Transportation of C&D waste (from weighted centroid to T.S.)

Transfer station

Avoided burden of landfilling

Transportation of C&D waste (from T.S. to recycling facility)

RA production

Fig. 10. Characterization results of Scenario S3 (top) and S4 (bottom) 17

The single score results obtained for all the four scenarios considered in this study are shown in Fig. 11. The single scores of landfilling scenarios are 1.83 mpt (S1) and 2.78 mpt (S2). Recycling generated single scores of -2.56 mpt and -1.91 mpt for scenarios S3 and S4 respectively. Thus, C&D debris recycling scenarios fare better than landfilling scenarios. The utility of single score results exists in simplifying interpretation and decision-making for the policymakers. The government intervention to push recycling of C&D debris in cities could be justified using the single score results.

Fig. 11. Single score environmental impacts of Scenario S1-S4 4.4 Sensitivity Analysis Sensitivity analysis determines the effect of variations in assumptions, methods and data on the results. Mainly, the sensitivity of the most significant issues identified is determined (ISO 14044 2006). It is to be noted that the highest environmental impact is caused due to crushing and sieving during RA production, and the highest environmental savings resulted from avoided burdens are due to transportation of rocks from quarry to crushing facility during NA production. Hence, a sensitivity analysis of the following parameters is carried out: 1. Diesel and electricity consumed (RA production); 2. Transportation from quarry to aggregate crushing facility (NA production). Each parameter is varied to identify the maximum increase/decrease till recycling with transfer station (S4) remains a suitable alternative instead of landfilling, based on global warming impact categories. In the current state, diesel and electricity consumed in RA production facility will have to remain less than 375% for recycling (S4) to be beneficial compared to landfilling. In the future state 18

(S4.1), the consumption of diesel & electricity can increase up to 475% to remain a beneficial alternative to landfilling. Recycling fares better than landfilling even if the second parameter, transportation distance from quarry to crushing unit, is reduced to zero. It has been established earlier that the highest environmental benefits were due to avoided burdens of NA production and transportation was found to have played a major role. Now, the sensitivity analysis reinforces the fact that this observation might not be invalidated due to changes in transportation distance (from quarry to crushing unit in NA production). Hence, the finding of this study, that recycling fares better than landfilling, is strongly implied. 4.5 Comparison with other studies The diesel and electricity consumption values of recycled aggregate (RA) and natural aggregate (NA) production facilities determined are compared with the values reported in the literature and presented in Fig. 12 and Fig. 13 respectively. The studied RA production facility utilises a diesel generator in addition to electricity obtained from the power grid, and hence, high diesel consumption value and low electricity value are observed. In the case of NA production, the electricity consumed by the facility is within the average values found in the literature. However, diesel consumption is very high due to high transportation distance from the quarry to the crushing unit. The sensitivity of these parameters has already been discussed and observed to be not affecting the scenario preferences.

1 - Estanqueiro et al., 2016; 2 - Blengini and Garbarino, 2010; 3 - Vossberg et al., 2014; 4 - Faleschini et al., 2016; 5 - Mah et al., 2018; 6 - Borghi et al., 2018; 7 - Ghanbari, 2018; 8 - Rosado et al., 2017; 9 - Mercante et al., 2012; 10 - Blengini, 2009; 11 - Ecoinvent data (Bovea and Powell, 2016)

Fig. 12. Diesel and Electricity consumption of RA production facilities 19

1 - Blengini and Garbarino, 2010; 2 - Vossberg et al., 2014; 3 - Faleschini et al., 2016; 4 - Mah et al., 2018; 5 Borghi et al., 2018; 6 - Ghanbari, 2018; 7 - Rosado et al., 2017;

Fig. 13. Diesel and Electricity consumption of NA production facilities The preferences established towards recycling scenarios over landfilling is in agreement with other studies in the literature. The slightly lesser benefits observed for the recycling scenario with transfer station over the recycling scenario with no transfer stations are as expected and also in agreement with Borghi et al. (2018). While some studies (Di Maria et al., 2018; Mah et al., 2018; Wang et al., 2018) strictly preferred not to develop transfer stations, we believe that the preference is contingent on the local conditions apart from the relative environmental benefits. In those regions that are plagued with weak enforcement, prevalent illegal dumping and adequate land availability with urban local bodies (as in Chennai city), setting up recycling facilities with transfer stations might be preferred. The chances to reduce illegal dumping and increased quantity of waste collection owing to the presence of transfer stations could outweigh the 10% loss in environmental benefits as compared to the recycling scenario with no transfer stations. 4.6 Relevance to urban local bodies and policymakers The need for governmental intervention in the form of taxes and subsidies is reinforced by the amount of environmental savings achieved in supporting C&D debris recycling initiatives. A projection of the quantum of environmental savings accrued from recycling is presented in Fig. C4-C6 in Appendix C for a ten-year period. In order to project the savings in the future, the growth rate of waste generation is assumed to be 10% and the existing landfill spaces in Chennai get entirely depleted by 2025. If recycling facility without TS is set up in 2019, about 78,290 tonnes of CO2 eq emissions, 1,116,969 GJ of primary energy and 322 hectares of organic arable 20

land can be saved by the year 2028. If recycling facility along with TS is set up, 63,107 tonnes of CO2 eq emissions, 879,760 GJ of primary energy and 295 hectares of organic arable land can be avoided by the year 2028. While the quantum of savings might differ for other cities and countries, depending on the transportation distances and quantity recycled, the result depicting exclusive environmental benefits in C&D debris recycling is not case-specific and hence, applicable for all regions and countries. Therefore, the results of this study will help policymakers in India and other developing countries where landfilling of C&D debris is predominant and will guide them to understand when and why recycling (with or without transfer stations) is a better alternative. The benefits shown in recycling C&D debris without considering the credits obtained from materials such as metals and wood forms one of the unique contributions of this work and might sensitise decisionmakers about the value in pursuing C&D debris recycling. In addition to analysing the environmental impacts/benefits generated for the waste management options (landfilling, recycling, and or incineration) of the current scenario, future scenario (with increased transportation distance) must also be taken into consideration as performed in this study. The consideration of potential costs of the impacts of future scenario could serve as the benchmark to decide on grant of subsidies for supporting recycling initiatives. Since there are environmental benefits from recycling, subsidies are not extra costs to the society but rather an upfront investment to reap those benefits as indicated in the results of the LCA study. Dust and noise emissions have not been included in this study. Moreover, the secondary data used for quantifying impacts is based on Eco-invent database which primarily is built from European studies. Lack of such secondary data from India also forms a limitation of this study as actual impacts might vary from the projected impacts for the Indian case. The dust and noise emissions from both natural aggregate and recycled aggregate production facilities could be measured to enhance the quality of the data. Quantifying the dust emissions from primary and secondary transportation of C&D waste would improve the accuracy of environmental impacts. While the secondary data for electricity consumption exists for India, other parameters such as diesel consumption and their upstream and downstream emissions needs to be developed to facilitate the accurate quantification of impacts for the local scenario. 5. Conclusion The environmental benefits of C&D waste recycling reported in the literature are derived mainly from the environmental credits obtained due to metals and wood recycling. The number of studies evaluating the environmental performance of C&D debris recycling is limited. The current C&D management system of Chennai, India in the year 2014 was evaluated and compared with recycling by applying the LCA methodology and SimaPro software. The study considered 15 mid-point indicators and 4 end-point indicators mapped to a single score, according to IMPACT 2002+ impact assessment method. QGIS tool was used to map the actual waste haulage distances and thus, sets apart from various other studies that approximate transportation distances. The following conclusions are drawn from the results: 21

•

An increase in transportation distance by about 2.5 times due to depletion of existing landfills leads to an overall rise in impact by about 60.42%.

•

Recycling scenarios show environmental benefits in all the 15 impact categories.

•

Recycling a tonne of C&D debris instead of landfilling will avoid 6.41 kg CO2 eq emissions (S3) and 4.92 Kg CO2 eq emissions (S4) from entering the atmosphere and saves 89.93 MJ (S3) and 66.7 MJ (S4) of primary energy. Additionally, a saving of 0.32 m2 (S3) and 0.29 m2 (S4) organic arable land can be achieved.

•

Sensitivity analysis indicated a strict preference to recycling over landfilling. For instance, even if the transportation distance from quarry to crushing unit is reduced to zero, recycling scenarios perform better.

•

Landfilling of C&D debris generates a net impact of 1.83 mpt (S1) and 2.78 mpt (S2). C&D debris recycling offers net environmental benefit having single scores of - 2.56 mpt (S3) and - 1.91 mpt (S4).

•

Over a ten-year time-frame, establishment of recycling facility with transfer stations in the city of Chennai could prevent 63,107 tonnes of CO2 eq emissions, 879,760 GJ of primary energy consumption and 295 hectares of organic arable land loss.

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Highlights • • • • •

Landfilling of construction and demolition debris generates a net impact of 1.83 mpt Environmental benefits are observed in all 15 impact categories for recycling Recycling offers net environmental benefit of 2.56 mpt Recycling avoids 6.41 kg CO2 eq emissions and saves 0.32 m2 land and 89.93 MJ energy Actual waste haulage distances have been computed to quantify CO2 eq emissions