Collect, process, generate

Managing urban waste is a major challenge local bodies and corporations are faced with. What better way than tackling the problem with an integrated waste to energy management project. Ramky Enviro Engineers Limited, a Hyderabad-based company specialising in waste and environment management solutions, has set up a ₹650 crore Municipal Solid Waste Management project in Delhi, which not only tackles tonnes of waste generated every day but uses the solid waste to generate electricity through a 24 MW power project.

Delhi MSW Solutions Limited, the special purpose vehicle, and a subsidiary of Ramky group bagged the project in 2009 to collect, process and dispose the waste. The processing facility has capacity to treat 2,000 tonnes per day from select zones of Rohini and Civil Lines in Delhi.

“This is the country’s largest waste to energy plant,” says M Gautham Reddy, Managing Director of Ramky Enviro Engineers Limited. “Most urban bodies require such projects as waste management is a major problem. This can be replicated and urban areas and smart cities will offer big opportunity to set up such projects.” Even today, less than 10 per cent of the 22,000 tonnes of waste generated per day is scientifically managed. The country requires a number of such projects, he said.

In what the company describes as a ‘cradle to grave’ approach, multiple processes have been deployed in the project. These include composting, refuse-derived fuel and thermal processing. Thermal processing involves waste to energy conversion to minimise the waste put into landfills.

The municipal waste is segregated into wet and dry. The wet waste is aerobically treated for compost as a soil conditioner and the dry waste is converted into thermal power. Thus the refuse derived fuel, as it is known, is burnt in a boiler through a process called MSW combustion. The reciprocating grate, referred to as fuel, is burnt and the resultant heat is converted into steam. The steam thus generated runs the turbine, which in turn generates electricity that is then supplied to the grid.

“We have two combuster plants at Bhuvana industrial area in Delhi. They have capacity to handle 4.8 lakh tonnes of waste per annum. The 24 MW power plant generates 130 to 135 million units per annum. This is supplied to the discoms at ₹7.03 per unit,” Associate Vice President, DBSSR Sastry, explained.

After generating power, the residue is further treated. The gas coming out of the two combusters gets treated with milk of lime and activated to reduce heavy metal pollutants. The neutralised effluent is used to quench the bottom ash and partly used to control dust emission within the waste pit. The process is as required by the Delhi Pollution Control Board, with emissions monitored online.

At the same time, the biodegradable composted material, which is around 150 tonnes of soil enricher, goes to fertiliser selling units. The plant has residues of about 25 per cent of the waste. This goes as landfill. Efforts are on to explore alternative use of the bottom ash generated from the incinerator.

The environment ministry has accorded clearance to expand the power plant capacity by another 24 MW. Meanwhile, the company is executing another project. This time in Hyderabad.

“It will have the potential for 2,400 tonnes of waste and a 48 MW waste to energy power plant. However, in phase one, which will be completed by end of 2018, 19.8 MW unit is proposed to be operational,” Sastry explained.