Is better biogas the next big thing in the world of cars?

Releasing methane into the atmosphere is far more destabilising for the climate than CO₂. Oil drilling and refining is a major methane source. Other sources are waste tips and farming/livestock. Methane emerges when organic matter in piles of waste and dung decays in the absence of oxygen – anaerobic digestion (AD).

Fortunately, AD can be harnessed, so the methane can be collected and used productively. A large gas-tight vessel holds the waste while the process happens naturally. It’s not new. Many local councils in Britain are already sending collected food waste to AD. But sulphur compounds, CO₂, oxides of nitrogen and water vapour also come out of the digester, and it has been hard to separate them out.

Recent developments look promising. Suzuki makes two-fifths of India’s cars, and many run on CNG – which is mainly methane. India has 200 million cows. That’s a lot of dung. So Suzuki has developed new optimisations for refining the output of ADs. But what about the lost dung, which is a good fertiliser and displaces the artificial stuff? Fortunately the solid matter that comes out of AD is also good for the soil.

The resulting fuel helps fight climate change. Even if only burned, the tailpipe CO₂ is less aggressive than the methane it displaces, and anyway the source of the CO₂ in the first place is the growing of grass which the cows ate, which abstracts CO₂ from the atmosphere. Of course that’s an inefficient process compared with humans eating plants, but turning the world vegan is probably a bigger ask.

Meanwhile in Brittany, Sublime Energy has developed a process to liquefy the output of small on-farm ADs. It then goes in tankers to a central processing hub to separate the methane from the by-product gases. Otherwise you’d need expensive separation equipment on each farm.

So these projects, if scaled, could support rural economies, improve energy sovereignty and green the energy system.

Also the methane, AKA biogas, can of course fuel gas power stations, or go into the gas network for home and industrial heat. Liquefied gas is also a pretty good fuel for trucks and buses – Oslo has converted its entire bus fleet. But there’s too little waste to fuel more than a small fraction of the world’s vehicles.