JOIN USEfficient operation of waste to energy plants
India’s waste-to-energy sector, which kicked off in 1987, is still searching for a successful role model even after tens of millions of dollars of investment. The Narendra Modi government’s quest for an efficient solid waste management (SWM) system has prompted it to look westward, where countries such as Sweden, Denmark and Germany manage their waste with clockwork precision.
Sweden’s sophisticated system that handles waste and convert them into energy, is so good that it has run out of waste to feed the plant. But hype aside, Sweden does a pretty impressive job of keeping its municipal solid waste (MSW) — household garbage — out of landfills because it receives largely segregated, high calorific value wastes to feed its waste-to-energy (WTE) plants that is easy to manage.
So, why are WTE plants struggling to survive in India while they are doing reasonably well in Sweden? India’s experience with WTE has been lacklustre until now. The progress of the WTE sector in India is hampered by multiple issues including poor quality of municipal waste, high operation and maintenance cost of WTE plants and lack of successful projects. According to a recent study by the Centre for Science and Environment, nearly half of India’s WTE plants are defunct. The fundamental reason is the quality and composition of waste.
Bengaluru generates around 5,000 tonnes of waste on a daily basis. In a bid to solve garbage-related issues in Bengaluru, the BBMP is set to establish five WTE power plants in public-private partnership model in and around the city as part of Swacch Bharat Mission as well as Atma Nirbhar mission. The first WTE power plant being set up in Bidadi would generate 11.5 MW power using 600 MT processed waste every day - built at a cost of Rs 260 crore - followed by other four projects around Bengaluru.
There are many challenges and speed bumps in the efficient operation of the existing WTE projects. One of the biggest challenges encountered in MSW-fired boilers are the increased tendency for bed agglomeration and increased fouling of convective heat transfer surfaces, associated with increased corrosion due to their ash constituents such as sulphur, chlorine and phosphorous. This is one of the reasons for the unforeseen shutdown of the MSW-fired boilers resulting in constant repairs thereby adding to the running cost. These problems can be eliminated by avoiding the use of mixed waste and totally eliminating the presence of chlorinated hydrocarbons like PVC and paying attention to the materials used in the boiler.
Union Power and Renewable Energy Minister R K Singh said in a written reply in Parliament: “The compositional characteristics of waste in India are very distinct compared to those in developed countries. Waste generated in the country has more organic components, more moisture content and low calorific value compared to waste generated in developed countries, which has a direct influence on the efficiency of electricity generation.”
Smells emanating from the landfill have also triggered widespread opprobrium among citizens when the plant location is not isolated. Hence, the waste should be stored in an enclosed area with a negative pressure, which prevents unpleasant odours from escaping and the air drawn from the storage area is sent into the boiler.
Heap of garbage
The crashing down of massive heap of garbage has sometimes been fatal. On September 1, 2017, a massive heap of garbage came crashing down from the Ghazipur landfill site near Delhi, killing two people on the spot and sweeping away several vehicles. This incident captures the seriousness and importance of the subject of MSW management.
The presence of chlorinated hydrocarbons like PVC in waste results in the release of dioxins and furans, which are extremely difficult and costly to measure. They are known to be carcinogenic. SWM Rules 2016 require that PVC be phased out in incinerators by April 2018. But it is impossible to identify and remove PVC beverage labels, from mixed waste streams. As a preventive measure, the National Green Tribunal directed the Ministry of Environment and Forests to consider the phase-out of such single-use short-life PVC by July 2017. Their failure to do so till date is inexcusable. Appropriate efficient filtering mechanisms need to be installed to prevent the emission of dioxins and furans.
There will be wastewater discharge as leachate from waste collection, storage and processing areas and effluent from the power generation process to avoid groundwater pollution which invites public protest demanding the closure of the plant. Leachate management is very critical and appropriate filtering mechanisms need to be installed.
The total amount of ash produced by WTE plants ranges from 15% to 25% by weight of the original quantity of waste and the fly ash amounts to about 10% to 20% of the total ash. The fly ash, by far, constitutes more of a potential health hazard than does the bottom ash because fly ash contains toxic metals such as lead, cadmium, copper and zinc as well as small amounts of dioxins and furans. The bottom ash may or may not contain significant levels of health hazardous materials. Hence, ash is tested for toxicity before disposal in landfills. If ash is found to be hazardous, it can only be disposed of in landfills which are carefully designed to prevent pollutants in ash from leaching into underground aquifers.
In the above context of existing WTE projects, the state government should give due consideration to the above challenges. Rather than blindly ape Sweden, we should try to learn from the Swedish example and adapt the learning to the Indian context. If the government fails to initiate corrective measures to alleviate the root cause or causes while executing the project, the government will not only fail to appease the local residents, which may exacerbate the situation, but also may fail in the successful operation of the projects.
(The writer is retired Deputy Director of Boilers, Government of Karnataka)