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Will buying green gas help tackle climate change?


At Big Clean Switch, we make sure that all our tariffs guarantee that the electricity you use is matched by 100% renewable energy. So why don’t we make the same promise for green gas? Here, we explain why conventional gas has to go, but why using green gas as a replacement isn’t quite so straightforward.

What’s wrong with natural gas?

Our reliance on natural (non-renewable) gas is really bad for the planet. In the UK, warming our homes is behind one quarter to one third of the UK’s greenhouse gas emissions. That’s more than 10 times the amount of CO2e created by the UK aviation industry, which gets a much worse rep. Around 85% of homes use gas-fired central heating, and gas cookers are still very common, so we’ve got a big challenge ahead.

One of the renewable alternatives already out there is green gas. Green gas (or biogas) is already contributing – albeit often in a relatively small way – to the gas supply of around one million homes. This could hit 10 million by 2050 – or just under half the homes in the UK currently currently supplied by gas. 

What is green gas?

Green gas is made by turning sewage, manure and other waste organic matter (such as plants or vegetables) into biomethane through anaerobic digestion. It’s a process that’s been around for millions of years and occurs naturally in bogs, landfill sites and sewers.  

Some of the most efficient anaerobic digesters are cows. Organic matter – grass, in their case – is broken down by bacteria in the stomach, which is an oxygen-free environment (the word anaerobic means ‘without oxygen’). The cow then ‘releases’ biogas in the form of belches and other, even less polite, emissions. 

The green gas industry mimics a cow’s digestive process, capturing the gas emissions and removing the carbon dioxide before pumping it into the National Grid. 

Is green gas good for the planet? 

What’s great about biogas is that it diverts waste products from landfill and sewers and converts them into something everybody needs. Not only is the feedstock renewable, it’s a brilliant opportunity to tackle our huge food waste problem in the UK. Every year we waste around 10 million tonnes of food – that’s the equivalent of 50 thousand blue whales! That waste then produces double the amount of methane and carbon dioxide emissions (20 million tonnes). The global warming effect of methane is 21 times more powerful than CO2, so by capturing it and redirecting it into the national grid supply, we can significantly reduce our environmental impact. 

The process is entirely natural and doesn’t require outside energy to work. Less landfill means fewer toxins and cleaner waterways, while anaerobic digestion neutralises nasty pathogens and parasites, so there are fewer waterborne diseases going around.  And finally, a byproduct of the process is a rich natural fertilizer that’s much more environmentally friendly than commercial chemical ones.

Biogas has an exciting future ahead. Cadent, the UK’s largest gas distribution network, has enough biogas production plants to meet the heating demand for up to 243,000 homes – that’s a city the size of Manchester. It’s also an increasingly popular fuel choice for some of the UK’s largest HGV fleets, helping hauliers and retailers drastically cut their carbon and other harmful emissions – not to mention costs.

Is green gas bad for the planet?

So far so good. But are there any downsides? Well, yes. 

The reality is that while sewage, food and farm waste would be ideal feedstocks, we currently don’t have the infrastructure to divert them all to green gas plants. This means that most of the organic matter used is actually purpose-grown crops, which requires a lot of space to grow. 

One of our suppliers, Bulb, works with green gas generators who source around three quarters (74%) of their feedstocks in this way. Food and farm waste amounts to only 18% of their raw material, with residues (e.g. vegetable peelings and cereal straw), making up the rest. As only 4% of their gas is green gas (instead, they’ve decided to adopt carbon offsetting – find out more here) this isn’t a huge amount, but it does raise issues around scalability. 

As a densely populated island, it’s hard to see how we could be self-sufficient if we switched over to green gas en masse without changing this ratio. We did a few back of beermat calculations, and in order for UK homes to be powered by 100% green gas, half of the country’s agricultural land would have to be turned over to feedstock production. If we maximised our energy efficiency, this would drop to one third – which is still a lot. It’s likely, therefore, that feedstock demand would be met by imports from developing countries, increasing transportation emissions and risking deforestation of the sort we’ve seen due to demand for palm oil

That’s not to say that things might not change in the future, and it’s certainly not a reason to give up on biogas. According to ADBA (the Anaerobic Digestion and Bioresources Association), the anaerobic digestion of food leftovers could cover a third of the gas or power demand in the UK. Last year German biogas plant manufacturer, Weltec, constructed a biomethane plant near Pontefract, West Yorkshire. The plant took only six months to build, and produces enough biogas to supply 9,600 homes with round the clock sustainable energy – roughly half of Pontefract. Over half of the feedstock is food waste.

So, what’s the verdict?

Here at Big Clean Switch, we believe that while it’s not the perfect solution, green gas is still a good alternative to dirty natural gas. At the moment, choosing green gas certainly won’t do any harm, but if we all do it, we’ll have a big problem on our hands because of the land use impacts, which is why we aren’t going out of our way to actively encourage it. 

The more demand for it there is, the more investment there’s likely to be, and we’re all for that investment to focus on making human and food waste a larger proportion of the feedstock. In which case, we’ll be shouting it from the rooftops! Until then, we’ll be sure to keep you up to date with new developments. 

Green gas tariffs 

If you’d like to try a green gas tariff, Ecotricity offers one through our site. 12% of their gas is produced by anaerobic digestion, and they are working hard to build green gas plants to bring this up to 100% in the future. They’re planning on sourcing their feedstock from permanent pasture, which by definition can’t be ploughed, and therefore won’t release a whole load of carbon into the atmosphere. In the meantime, they’re offsetting the residual carbon emissions from the rest of their supply by investing in carbon reduction schemes. 

Good Energy aren’t far behind, offering 10% green gas, and working with ClimateCare to offset the rest. Other suppliers on our site, like Octopus and Bulb, also offer 100% carbon offsets. 

One of our favourite renewable tariffs comes from Bristol Energy, which offers 100% green electricity and 15% green gas, powered by Bristol sewage. Now that’s progress!

Up next…

Want to find out what the alternatives are? Keep an eye out for our next blog