To resolve the twin problems of urban solid waste disposal and urgent requirement of soil for construction of embankments, the Ministry of Road Transport and Highways (MoRTH), through the National Highways Authority of India (NHAI), recently undertook two pilot projects for utilisation of inert (sand, concrete and demolition waste) municipal solid waste material. The first pilot project has been carried out in Delhi-NCR on the urban extension road and DND Sohna spur of the Delhi-Mumbai Expressway, the second on the Ahmedabad-Dholera Expressway. At a point of time when road and highway construction activity is peaking, the Indian Government is drafting a policy to integrate this initiative with the Swachh Bharat Mission 2.0, which will involve incorporation of inert material from solid waste for construction of embankments along National Highways (NHs) and state roads. Carbon footprint reduction “The maximum carbon emissions are from asphalt production, energy consumption, steel and cement production, transportation, mining, etc, while the execution contributes only 3-6 per cent,” says Subodh Dixit, Former Executive Director, Shapoorji Pallonji. “Apart from this, India is the world’s second-largest steel-producing country, generating around 20 million tonnes of steel slag as solid waste per year, which is projected to increase to a staggering 60 million tonne by 2030, with each tonne of steel production resulting in about 200 kg of steel slag waste. Recycled plastic, fly ash and steel slag alongside construction waste could substantially free up the land area. Also, new techniques can reduce recyclable waste in aggregates, pavement layers and subbases along with new technology in highway construction.” “Of all municipal solid waste (MSW) generated in India, about 13 million tonne of legacy MSW is at the Ghazipur landfill in Delhi,” says Dr Vasant Havanagi, Chief Scientist (retired), Geotechnical Engineering Division, CSIR-Central Road Research Institute. “CSIR-Central Road Research Institute research indicates that trommels (to separate materials) can segregate about 65-75 per cent of MSW waste into different fractions of the requisite capacity. Segregated MSW can then be suitably used for road embankment construction. Conventional good quality soil used for embankment construction is available at large lead distances, especially in urban areas, due to mining restrictions. The utilisation of locally available MSW significantly reduces the carbon footprint. However, a lifecycle analysis needs to be carried out to estimate the reduction in carbon emissions.” Cost reduction According to Dixit, cost reduction can be achieved in two stages. “One by reducing the production cost of raw materials such as steel by using low-carbon hydrogen instead of the coal route. About 60 per cent of landfill plastic is recyclable and can be processed into low-grade bitumen for low-density road asphalt usage. Second, small granules can be created to coat aggregates for better binding and strength. Steel slag can replace or be mixed with aggregate; in turn, it will reduce stone mining, plant cost and resultant carbon emissions and free up the landfills. Another possible use of steel slag is mixing it with asphalt to make road embankments, shoulders and pavement bases more durable. Air-cooled blast furnace slag for highway construction will give it high strength, low bulk density and high durability, resulting in a low maintenance cost and minimising transportation, energy and mining cost. Overall cost reduction will come from multiple fronts – raw material production, transportation, energy saving in running equipment in mining alongside reduction in maintenance cost, freeing up the landfill for forestation (one more way to reduce the Co2e), and reduction in water pollution. A comprehensive study has to be undertaken by the Government and authorities to arrive at the tangible and intangible cost benefits.” For his part, Dr Havanagi says, “Segregated MSW replaces conventional soil for road embankment construction and its use significantly reduces the project cost. Also, the cost of an MSW road project reduces considering the need to pay royalty to the Government for soil excavation as against the free supply of MSW for road construction from municipal authorities. Indirect benefits are savings in terms of freed land and a significant reduction in health costs.” Global gains Sharing some innovative approaches internationally on Co2e emissions and the use of innovative approaches, Dixit says, “The Netherlands has created lightweight durable structures by using plastic with inbuilt drainage facilities from shredded recycled plastics; the UK has experimented on warm instead of hot mix asphalt, reducing emissions by about 20 per cent by using asphalt pavements that get mineralised owing to carbon capture; Sweden has undertaken studies on solar-powered road surfaces to reduce energy requirements; and Indonesia, Costa Rica and other European countries have studied the use of iron slag along with aggregates and also use plastic granules as a binding agent in asphalt and for coating on slag to improve its bonding ability.” Meanwhile, Dr Havanagi says, “There is no literature available indicating the use of segregated municipal waste in road construction, which may be due to differences in the type of MSW available in India and in other countries. The legacy waste in our country has construction and demolition waste (C&D), apart from kitchen waste. But in developed countries, there will not be any mixed waste as they follow strict segregation at the source.” Exploding landfill sites Indeed, disposal of solid waste is a major environmental challenge in urban areas, with an estimated 10,000 hectare of land locked in dump sites. These landfill sites are nearing maximum capacity and pose environmental and health hazards. To put things in perspective, as per the ministry’s assessment, about 170 million tonnes of waste accumulates across 2,304 dump sites in the country. The draft guidelines propose that all projects, whether in the bidding or detailed project report (DPR) stage, will be eligible to use inert material. Deleterious materials, if any, such as paper, polythene or glass, will be removed at the site. “Of India’s total waste every year, about 50 million tonnes goes into land,” points out Dixit. “A majority of this is biodegradable and the rest is plastic, construction waste and other solid waste. The problem of waste management in India is open dumping, which creates social issues, apart from Co2 emissions. If this continues unabated, the total landfill area in the next 15 years will be the size of the Delhi capital region.” “India’s commitment to reducing its carbon footprint and addressing environmental concerns is underscored by its ambitious targets for waste reduction, particularly in diverting waste from landfills,” says Sanjay Kumar Nirmal, Secretary General, Indian Roads Congress (IRC). “Over the past five years, India has made significant strides in this regard, with a remarkable reduction of waste being disposed of in landfills. Through the concerted efforts of IRC in waste management, recycling initiatives and promoting sustainable practices, India has effectively diverted tonnes of waste away from landfills, thereby mitigating harmful methane emissions and reducing the overall carbon footprint.” To the extent of how the new initiative will free up landfills, possibly to construct affordable housing, Dr Havanagi says, “Sixty-five to 75 percent of segregated MSW from landfills can be used for road embankment construction and the remaining can be used as refuse-derived fuel (RDF) in waste-to-energy plants. Waste plastic present in MSW (about 5-7 per cent) can also be used in bituminous mixes for long-term durability of constructed roads. By following this methodology, we can free up 90-95 per cent area of landfills. The freed land can then be used for developmental work for society, including housing for the needy.” In conclusion “Looking ahead, India remains steadfast in its commitment to further reduce its carbon footprint by continuing to implement innovative waste management strategies, investing in infrastructure for waste segregation and recycling, and fostering public awareness and participation in waste reduction initiatives,” says Nirmal. “By working towards these goals, India aims to continue its trajectory of waste reduction, contributing significantly to global efforts to combat climate change and build a more sustainable future for generations to come.” And Dixit concludes, “Even if India creates management efficiency like the western world, which produces much more waste, it will free up 50 per cent of land area and recycle about 40 percent of it.” - R SRINIVASAN