One million homes in Britain are now using “green gas” for heating and cooking after a surge in energy produced from farm and food waste.

Biomethane plants – there are now 60 in the UK – use food leftovers, cattle and chicken manure as well as grass silage and hybrid rye to create gas.

According to the Green Gas Certification Scheme, the number of homes supplied with green gas has leapt 13-fold since 2017. Campaigners say it could supply as many as 10m UK homes by 2050.

Should you be joining them? Most big suppliers now have green tariffs, although few are 100% renewable, and only one, Green Energy UK, guarantees that all its gas is green.

Research earlier this month by Switchd, an automated energy switching platform, found the big six energy companies are still charging over the odds for green tariffs.

It claimed the worst offender is British Gas, whose cheapest green tariff costs £230 more per year than its cheapest non-green tariff. “What’s perhaps even more shocking is that SSE doesn’t even offer a green tariff,” said Switchd.

Some green tariffs are much cheaper than the cheapest tariffs at the big six. But consumers should check the suppliers’ green credentials and service.

When Money checked dual-fuel (gas and electricity) deals this week on energyhelpline.com, Lumo’s green tariff was cheapest, but only 33% of its electricity is provided by generation from renewable sources, with no information about its gas. The company is relatively new, and scores just three out of five on the comparison site’s quality ratings.

Bulb, the most popular cheap green tariff, scores a five-star rating, but while 100% of its electricity is from renewable sources, just 10% of its gas is green.

Green Energy UK promises 100% green gas and electricity, but on our test was the priciest tariff, although only a shade above the cost of the British Gas standard dual fuel price.

Doug Stewart of Green Energy UK said: “Since launching green gas 2 years ago we have seen a 209% increase in customers wanting us to supply them with green gas. Green gas is not only better for the environment, but it means millions of tonnes of organic waste which would otherwise be send to landfill, incinerated or simply left to rot gets put to good use heating our homes.”

Energy minister Claire Perry – who last year was spearheading the UK’s renewed push into fracking – said the government has invested £656m into biomethane to reduce dependence on natural gas extracted from the ground.