Bio-CNG: The future fuel

India is currently reeling under a severe fuel crisis. The price of fossil fuel is skyrocketing and is adversely impacting the country’s inflation rate. The country is importing more than 35 per cent of its fuel needs from Russia. The internal production is just a trickle compared to the total demand. Do we have a reliable alternative for the future? It is in the light of this grim situation that the need for a reliable energy source of organic origin, unlike fossil-based petroleum, assumes importance. And that is “compressed natural gas,” or bio-CNG.

Bio-CNG is an advanced version of biogas produced from organic sources such as animal manure (farm yard manure) and food waste, which have been traditionally used in India’s rural landscape. Its calorific value is similar to that of Compressed Natural Gas (CNG), which is used sparingly in India. Bio-CNG production involves the commercial refining of biogas to enhance its methane content to above 90 per cent. Waste products are decomposed to produce biogas, which is purified to enhance its methane content. The raw material is at least 90 per cent segregated biodegradable waste or crop residues, which are stored in a deep bunker inside the production plant. This waste is then sent to trommel mills, where unwanted materials are separated.

Next, a hammer mill grinds the waste and converts it into a slurry, which is sent to a pre-digestor and kept for two days for the hydrolysis to take place (decomposing in aerobic conditions). The slurry is then sent for methanogenesis, where it is decomposed for a fortnight (15–20 days) in aerobic conditions, which produces raw biogas, which has 60–65 per cent methane. The biogas is then passed on to a storage balloon. The left-over is passed through a solid-liquid separator.

The liquid is then returned to the predigestor. Remaining solids are used as bio-fertilisers in agriculture. Removing carbon dioxide and hydrogen sulphide from the raw gas converts it to purified methane containing 95 per cent methane, which is compressed and filled into cylinders and sent to CNG plants for fuelling vehicles.

What are some of the attractions of bio-CNG? India’s huge agricultural waste, primarily crop stubble—currently burned, causing severe air pollution, as in Punjab—is, along with municipal waste, the best raw material for bio-CNG production. The proposed bio-CNG plants, 75 of which will be in urban areas, are part of the Gobardhan (Galvanising Organic Bio-Agro Resources Dhan) scheme under the Union Ministry of Drinking Water and Sanitation.

India launched a serious exploration of the possibilities of producing clean fuel in June 2018 with the announcement of the National Policy on Bio-Fuels. Last October, the Union Ministry of Petroleum and Natural Gas rolled out its ambitious project, ‘Sustainable Alternatives Towards Affordable Transportation’ (SATAT), with a target to establish 5,000 bio-CNG plants by 2023–204, of which only 40 currently operate, as per data collected by the Gobardhan scheme, with a pathetic production of just 311 tonnes as against the potential of 62 million tonnes. SATAT targets a 15-million-tonne production by 2023.

Bio-CNG produced only from municipal solid waste and wastewater can generate enough energy to reduce India’s daily diesel consumption by 4,054 tonnes. Bio-CNG is also a decentralised clean energy form that can be produced at the point of consumption right through the year and at all times of the day, which sets it apart from other renewable sources such as solar or wind energy, which are subject to climatic fluctuations.

Pitfalls

India lacks a robust ecosystem for fuel uptake, leading to only a few takers operating comfortably. Plant owners complain that SATAT only guarantees a buyer for the fuel, does not support plant establishment or the procurement of quality feedstock, and makes fuel manufacture the exclusive responsibility of owners. Problems exist at each level.

It costs Rs 25–30 crore to set up a plant, of which the central finance from the Union Ministry of New and Renewable Energy under the “Waste-to-Energy Programme” is just Rs 4 crore, with a cap of Rs 10 crore per 4.8 tonnes of bio-CNG produced, while budget provision is just Rs 600 crore, which is insufficient to set up 5,000 plants. Uttar Pradesh provides a subsidy of Rs 75 lakh per tonne. The industry recommends a production-linked incentive scheme along with attractive interest rates on bank loans.

Finance Minister Nirmala Seetharaman, in her recent budget speech, pledged to set up 200 bio-CNG plants. Despite the technical difficulties like sourcing good raw materials and efficient segregation, the bio-CNG is not only environmentally sound but can save the country foreign exchange. It is, in my opinion, the “future fuel.”

(The writer is former professor, National Science Foundation, The Royal Society, Belgium.)