Biomethanisation: Putting Microbes at Work


In a country that is rapidly urbanising, municipal solid waste brings a huge financial and managerial liability for the municipalities. Strong laws and policies stand published, but lack of public awareness and willingness to pay for scientific management of one's own waste is highly disregarded. An average of 20% of the waste in typical Indian cities is organic and compostable, indicating it can be efficiently decomposed to yield beneficial by products that have the ability to nourish the soil with the nutrients they are made of. Composting, is thus highly recommended by environmentalists and policy makers alike. The process, though very enriching, usually occurs in uncontrolled environmental conditions and produces gases like carbon dioxide and methane when anaerobic conditions prevail. Both methane and carbon dioxide are greenhouse gases and contribute to global warming. The global warming potential of methane is known to be much higher than that of carbon dioxide. A slight modification in the system harbours the potential to trap methane and use it as a source of energy for lighting and cooking. The process, called biomethanisation is an upgradation of the traditional practice of biogas production.

This involves collection and shredding of the organic waste and subsequently feeding it into an anaerobic digester which has been fed with a primary culture/inoculum from the previous batch to stimulate the anaerobic digestion process. The methanogenic bacteria produce methane which is trapped in a gas balloon for use, preventing it from escaping into the atmosphere and subjecting it to productive use.

One successful biomethanation plant has been functioning in Bhopal since December 2016. The capital city of Madhya Pradesh, Bhopal, produces about 800 metric tonnes of solid waste daily. A staggering 28% of this is organic waste that can be composted. The municipality has taken the initiative to reduce its waste quantum from commercial centers like vegetable markets and commissioned a biomethanation plant for producing biogas from the Bittan Market Sabji (vegetable) bazaar and MP Nagar zone 1 and 2 hotel and restaurant kitchen waste. The plant has been funded by the Bhopal Municipal Corporation and is designed and operated by Ikos Mailhem Environment Pvt. Ltd. The firm has been contracted to maintain and operate the plant for a period of 5 years. It has contracts with hotels and restaurants within a 2km radius of the plant to collect and drop their kitchen waste at the centre.

With a capacity to accommodate 5 tonnes of waste per day to produce 300 cubic meters of biogas, the plant is a successful and financially sustainable model. The resultant gas from the digester is then fed into a 50kWh genset and converted to electricity to light up the market area in the evening. The extra power is used to run the plant. The sludge produced as a by-product of the process is regularly retrieved. Being rich in organic nutrients, it functions as good quality manure for plants. The BMC purchases 30 metric tonnes of the sludge for greening and nourishing its landscapes.

This initiative under the Swachh Bharat Mission is highly lauded. Uptake of this process has the enormous benefit of reducing methane emissions from Indian landfills where organic waste is thoughtlessly dumped, giving rise to self-igniting piles which are a common occurrence these days. Better funding opportunities and demand for responsible waste management by communities can push the government for establishment of such sustainable waste management models.

Visits to Bhopal and interactions with authorities, Swachh Bharat Mission (Urban) database

Kavya Arora

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