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

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.

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.

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, 2018).

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 and 2.5 billion tonnes (Duan and Li, 2016). India generates about 112–431 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.