Story of methane

I thought of writing about methane. It is a curious molecule consisting of a single carbon atom surrounded by four hydrogen atoms around it which pretty strong bonds with the carbon atom. The entire molecule is relatively small and exists in gaseous form at room temperatures. It is naturally occurring and comes out of natural processes that involves anaerobic bacteria actions. It is a fuel that can be combusted to produce carbon dioxide and water vapour.

It also happens to be a greenhouse gas. Each methane molecule is thought to have 25 times more global warming potential than carbon dioxide. Natural gas is largely made up of it; hence it is a greenhouse gas by itself though combusting it will also produce carbon dioxide which itself is a greenhouse gas though with lower potential.

The focus on carbon emissions is a result of the recognition that we have spewed so much of this particular greenhouse into the atmosphere that it is having extreme effects on the global climate due to the warming potential. The world needs to move towards low-carbon and that means having activities that are emitting less carbon dioxide into the atmosphere. In general, fossil fuel based carbon holds the largest responsibility in anthropogenic carbon emissions.

Interestingly, you could produce methane through anaerobic biological process. And cows are known to release methane into the air because of the bacteria actions in their stomach. The dairy industry therefore becomes a rather larger emitter of greenhouse gas for this reason. That is where stuff gets a bit fuzzy when you’re counting global warming potential, anthropogenic emissions and so on.

So biomethane is the methane produced through anaerobic digestion of organic matter can be captured and used as a fuel. When combusted it likewise produces carbon dioxide and water. But this carbon dioxide belongs to the short carbon cycle due to its organic/plant heritage and hence is excused from what typical constitutes carbon emissions. Yet when biomethane leaks or is released into the air, the methane’s global warming potential is counted and the carbon-equivalent emissions actually forms part of the emissions from processes whenever biomethane is used. This ‘short cycle’ argument doesn’t seem to apply.

This may not seem very consistent and can potentially create a lot of confusion around the truly ‘green’ identity of biomethane. One could see how biomethane, or renewable natural gas as it is known in the US, is going to suffer from being conflated with fossil fuel natural gas.