As cities grow, so too do the quantities of waste generated. Sustainable waste management marked by efficient management of resources can address the growing waste challenge by reducing, reusing and recycling the waste. A wide range of technologies enable cities to minimise the negative impacts of urban waste while producing local, renewable fuels. Converting waste into fuel in India is reaping rewards.
Need to convert waste into fuel
Municipal solid waste (MSW), sewage and industrial effluents must be well managed to avoid serious environmental impacts. MSW typically has around one-third the energy content of coal.
Many technologies are available to convert waste into fuels for the generation of heat and/or electricity, as well as for use in transport. These include the capture of landfill gas (a mixture of methane and CO2), anaerobic digestion of solid and liquid wastes (to produce biogas) and the direct combustion of solid wastes (to generate electricity and/or heat for district heating systems, for example).
Landfill gas and biogas can either be burned directly to produce heat and/or electricity or upgraded to biomethane, a renewable natural gas that can be pressurised and injected into gas pipelines or used as a transport fuel.
The recovery of landfill gas is widely deployed in cities around the world. In 2017, Sabarà (Brazil) completed a gas recovery plant at its local landfill with the capacity to produce 5.7 MW of electricity. To the north-east, the city of Jaboatão dos Guararapes was completing a 12.8 MW landfill gas system, large enough to meet the electricity needs of an estimated 52,000 people.
SATAT initiative to the rescue
Anaerobic digestion, a biological approach to treating sewage and other liquid effluents (as well as agricultural and industrial wastes), results in the production of biogas, which can be used to heat and/or power the wastewater treatment plant or exported for other uses. The biogas produced can be upgraded to biomethane. The government’s Sustainable Alternative Towards Affordable Transport (SATAT) initiative is expected to support the opening of 5,000 biomethane plants by 2023.
Compressed Bio-Gas (CBG) is exactly similar to the commercially available natural gas in its composition and energy potential. The government plans to roll out 5,000 Compressed Bio-Gas plants across India in a phased manner, with 1,000 plants by 2022 and 5,000 plants by 2025. These plants are expected to produce 15 million tonnes of CBG per annum, which is about 40% of current CNG consumption of 44 million tonnes per annum in the country.
At an investment of approx. Rs. 1.7 lakh crore, SATAT is expected to produce 50 million tonnes of bio-manure for crops. The plants would use agricultural waste, MSW and cattle manure to produce up to 15 million tonnes of biomethane annually, displacing up to half of the country’s natural gas imports.
SATAT holds great promise for efficient municipal solid waste management and in tackling the problem of polluted urban air due to farm stubble-burning and carbon emissions. Use of CBG will also help bring down dependency on crude oil imports and in realising the Prime Minister’s vision of enhancing farmers’ income, rural employment and entrepreneurship.
Converting waste into fuel in India is good for the environment since waste-derived fuel can have a smaller carbon footprint than fossil fuels. Even though carbon dioxide is emitted when the fuel is burned, this is partly offset by the carbon dioxide captured by the plants that produced the materials in the first place.
