methane (CH4)
Also known as: natural gas · biogenic methane · CH₄
Methane (CH4) is a colourless, odourless hydrocarbon gas and the primary component of natural gas and biogas. It is the energy-bearing component of compressed biogas (CBG) and a potent greenhouse gas.
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What is methane?
Methane (CH4) is the simplest hydrocarbon — one carbon atom bonded to four hydrogen atoms — and the principal energy-carrying molecule in natural gas, biogas, and biomethane. It is colourless, odourless, lighter than air (specific gravity 0.55), and burns with a clean blue flame producing carbon dioxide and water, with no soot or sulphur dioxide. Its lower heating value of 35.8 megajoules per normal cubic metre makes it the most energy-dense common gaseous fuel; one Nm3 of methane delivers roughly the same useful heat as 1 litre of diesel.
In the context of Indian CBG production, methane is the target output that defines plant viability. Raw biogas contains 55–65% methane mixed with CO2 and impurities, with energy content of 21–24 MJ/Nm3. Biogas upgrading technologies — water scrubbing, pressure swing adsorption, membrane separation, and chemical scrubbing with amines — selectively remove CO2 and H2S to raise methane content above 95%, the threshold specified by IS 16087:2016 for bio-CNG sold as transport fuel. Upgraded biomethane at 97%+ purity has energy content of around 34 MJ/Nm3 and is chemically interchangeable with fossil-origin compressed natural gas.
Methane has a dual identity that is central to the climate case for CBG. As a fuel, combustion methane displaces fossil CO2 by converting renewable carbon (recently fixed by plants) into energy. As a greenhouse gas, atmospheric methane has a global warming potential 28 times that of CO2 over 100 years and 84 times over 20 years, making methane leakage the most consequential emission concern in any biogas system. Indian CBG plants must meet leakage targets of under 1% of methane production across the digester roof, gas storage, upgrading skid, and compression train. Methane is also explosive at concentrations between 5% and 15% in air (its flammability range), which dictates strict gas detection, ventilation, and electrical hazardous-area classification requirements for all biogas facilities under the Petroleum and Explosives Safety Organisation (PESO) framework.
Common questions about methane
Plain-English answers to what people most often ask.
What percentage of methane is in biogas?
Why is methane called a potent greenhouse gas?
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