I have been unbundling the challenge of handling the garbage that we produce as a society. The response has to begin with the segregation of the solid waste at source (be it households or commercial establishments), and go on to ensure that the waste goes through the different streams of recycling and resource recovery till the much reduced final residual is deposited scientifically in sanitary landfills.
In India, the segregation of waste at source is rare. Recycling is mostly with the informal sector, although some municipalities are trying to integrate this sector into their waste management systems. More than three-fourths of the municipal budget on solid waste management goes into collection and transportation, which leaves very little for processing/resource recovery and disposal. This neglect is perhaps due to lack of awareness, in our cities, of the hugely adverse impacts of poor waste disposal on the air we breathe and the water we drink.
How else do we explain this? We still have to imbibe the basic truth that waste out of sight does not mean that it is no longer a threat to our health.
Where does waste-to-energy fit into all this? Ideally, it fits in the chain after segregation (between wet waste and the rest), collection, recycling, and before getting to the landfill, although this is not always the case. The energy from waste is a crucial element of waste management because it reduces the volume of waste for disposal and also helps in converting the waste into renewable energy and organic manure. It is not necessarily the most efficient or most economical means of generating energy.
Which technology is most appropriate in converting waste to energy depends on what is in the waste — that is biodegradable vs non-biodegradable component — and its calorific value. The biodegradable component of India’s municipal solid waste is currently estimated at a little over 50 per cent. Biomethanation offers a major solution for processing biodegradable waste. If only we were to segregate our biodegradable waste from the rest, this could reduce the dimensions of the challenge of solid waste management to half, at one stroke.
“Biomethanation process degrades biological or organic compounds to generate biogas and manure. Biogas is a mixture containing carbon dioxide and methane in varying proportions and a small quantity of hydrogen sulfide gas. Methane is a harmful gas if released in the environment as it is one of the four major gases responsible for global warming. But it is an excellent fuel.” This is how Sharad Kale explains the phenomenon of biomethanation. He was the force behind the installation of the first biomethanation plant in Pune using nisargruna technology which was developed by him at the Bhabha Atomic Research Center, Mumbai. There are 250 biomethanation plants across India which use nisargruna technology of biomethanation. ranging in capacity from 0.25 TPD to 20.0 TPD, producing biogas and manure.
Some years ago in my column, ‘Postcards of change,’ I had written about a major initiative of decentralised biomethanation cum power generation plants in Pune. The city has taken new initiatives to try biomethanation on a medium-scale. While the decentralised small -scale biomethanation cum power generation plants have increased from 17 in 2012 to 25 in 2016 and their total capacity has increased from 83 TPD to 121 TPD, they still treat only about six per cent of the total municipal solid waste in the city.
Notwithstanding their limited share in the total waste that needs processing, the decentralised plants have made a significant contribution in solid waste management of the city in so far as they use methane as a source of renewable energy to produce electricity which is used to power street lights in surrounding areas. Not only do these plants provide a major energy saving from reduced transportation, but they also generate additional annual revenue of close to Rs 3 crore from electricity generation besides meeting their own demand for electricity.
A major new attempt at scientific management of solid waste has come forth again from Pune where the Pune Municipal Corporation and Nobel Exchange Environment Solutions, a private company have come together to commission a bio-CNG plant with a capacity to convert 300 TPD of biodegradable waste into 15,000 standard cubic meters of bio-CNG. This plant takes the process of biomethanation one step forward. Using anaerobic digestion to produce biogas and organic manure, it further processes the biogas to higher standards. The gas that is obtained can be used as an alternate fuel for natural gas vehicles or can replace other fossil fuels such as LPG/CNG and diesel.
Sources in the company indicate that the plant at present is processing 170 TPD of biodegradable waste and generating 9,000 kg of bio-CNG per day. While this is being sold as industrial fuel, the plant is also attempting to generate bio-CNG which could be used for city buses. This requires further refining of the processes to meet the necessary standards and also setting up of the requisite infrastructure with the help of the Pune Municipal Corporation.
Another medium scale initiative in biomethanation is the 400 TPD plant of Organic Recycling Systems, another private company at Solapur in Maharashtra. Based on thermophilic biomethanation process, this plant is currently accepting 200 TPD of biodegradable waste and generating 2 MW of electricity and 40 TPD of manure. The company has been awarded a contract for setting up a plant of 500 TPD capacity to process biodegradable waste in Pune.
It is too early to tell how much difference these new ventures of biomethanation will make. Will scaling-up work? In any case, the solution will only work if we are able to segregate municipal solid waste at source. Reform must begin at home.