Compressed Biogas, or CBG, is one of the more elegant ideas in clean energy. It takes waste that would otherwise rot, burn or pollute, and turns it into a renewable fuel that can directly replace compressed natural gas. For a country that imports most of its gas and struggles with agricultural and municipal waste, that is a powerful combination.
CBG has moved from a niche experiment to a national priority, backed by the SATAT scheme and a blending mandate. Here is what it actually is and how it is produced.
CBG is a purified, compressed form of biogas. Biogas itself is produced when organic matter breaks down without oxygen, releasing a mixture that is mostly methane and carbon dioxide. Once that raw biogas is cleaned to remove carbon dioxide and impurities, and then compressed, the result is a high-methane gas that is chemically very similar to the natural gas supplied as CNG.
Because it is so similar, CBG can be used in the same vehicles and the same pipelines as CNG, which is what makes it so useful. It is renewable natural gas made from waste rather than drilled from the ground.
The heart of the process is anaerobic digestion. Organic feedstock is fed into sealed digesters where micro-organisms break it down over time, producing raw biogas. That gas is then upgraded, removing carbon dioxide, moisture, hydrogen sulphide and other impurities, until it is rich enough in methane to meet fuel standards. Finally it is compressed and bottled or injected into a pipeline.
The feedstock is deliberately broad. Agricultural residue, cattle dung, press mud from sugar mills, food waste and the organic fraction of municipal solid waste can all feed a CBG plant, which is why the fuel doubles as a waste-management solution.
A CBG plant does not stop at gas. What is left after digestion is a nutrient-rich slurry that becomes Fermented Organic Manure, a valuable input for farms that has been formally recognised under fertiliser rules. The carbon dioxide separated during upgrading can also be captured for industrial use rather than released.
This is the circular-economy logic at work. Waste goes in, and out come clean fuel, organic fertiliser and usable carbon dioxide, with very little left to throw away.
India's CBG ambitions run through SATAT, short for Sustainable Alternative Towards Affordable Transportation, launched in 2018 by the Ministry of Petroleum and Natural Gas. Under SATAT, entrepreneurs set up CBG plants and sell the output to state oil marketing companies under long-term agreements, which removes much of the risk of finding a buyer.
Backed by capital subsidies, priority-sector lending and guaranteed offtake, SATAT set out to build thousands of CBG plants across the country. It is the foundation on which India's newer blending mandate now sits.
Whether it’s cleantech or technology, we’re happy to share what we know.