The importance of green gas

If we take a look at where energy is used in the home, the biggest slice of the pie goes to heating. The second is hot water. Renewable sources of electricity may be proliferating, but renewable heat is the next big challenge. Until we can decarbonise heating, we won’t be able to reduce household emissions all that far.

The long term answer is zero carbon homes, whether new build or retrofitted. But we need emissions to come down faster than the housing stock cycles through, and that means looking for new solutions within our existing infrastructure.

Most of us in Britain heat our homes with gas, and we have a sophisticated and highly efficient gas grid to supply it. So let’s start there. Can we produce gas without fossil fuels, inject it into the grid, and cut emissions without any great revolution in either technology or behaviour?

We can certainly try, and several companies are on the case. I wrote about my own energy supplier, Ecotricity, earlier this year. Their plan is to build biogas plants that run on grass. Grass can be grown on less favourable land or as part of crop rotation, so that it doesn’t need to compete with food production. The grass is then mown and fed into a bio-digester, which produces methane. The gas is scrubbed and fed into the grid as an almost carbon neutral fuel.

Like renewable heat overall, biogas is almost invisible in the climate change debate and scarcely recognised in policy circles. But it’s an up-and-coming energy source. At the end of 2015 there were 50 biogas plants operating in Britain – enough to heat 190,000 homes. That’s less than 1% of households, but considering that there were no biogas plants at all in 2012, that’s not bad going. We’re starting from a low base.

There will be more, because there are lots of advantages to growing a biogas industry. As well as low carbon heat, Ecotricity’s Green Gas Report estimates that we could create thousands of jobs and put billions of pounds into the rural economy. That could be quite important as Britain leaves the EU and potentially loses the subsidies that currently keep our farmers in business.

Another benefit is that a by-product of the gas process is digestate, a nutrient-rich fibrous material that can be spread on the land as fertilizer. Here’s another solution to the soil loss that I was writing about last week – biogas could be a restorative technology that helps to improve soil. And since farmers would be spreading digestate instead of artificial fertilizers, it would reduce the use of chemicals and help to stop run-off and pollution problems.

Finally, biogas is in direct competition with fracking. All the reasons that the government gives for supporting fracking are true of biogas too – reducing our dependence on imports, keeping bills down, and creating jobs. If more MPs and ministers were aware of the potential for biogas, the impetus for fracking would evaporate. So don’t just protest against fracking, share the alternative as well.

Ecotricity is working on grass as its primary input, and has planning permission for its first plant. Others are using different sources. A company called Xergi has been installing plants that use food waste, and digesters on farms that run on post-harvest waste. A scheme in the US aims to use manure from dairy farms as a feedstock. Projects in India have experimented with biogas from public toilets, and in California it’s been produced at municipal wastewater treatment plants. A number of Britain’s leading waste companies are capturing landfill gas.

All of these are useful alternative energy sources, all helping to chip away at our fossil fuel use. Some of are better than others, as there’s the risk of perverse incentives – ideally we want to reduce food waste, so we don’t want to sign contracts guaranteeing a long term supply for anaerobic digestion. Grass has the most benefits, but we should also be tapping landfill and sewerage as part of the circular economy.

It’s early days yet, but I expect to hear more about green gas in the coming years.