The number of operational anaerobic digestion (AD) facilities in the UK now stands at 68, an increase of 20 per cent over the past year, according to latest figures.

Nearly a third of these are powered by farm feedstock only and are predominantly in the west of the country, reflecting the current dependence on livestock manures.

The 68 operational digesters combined process over a million tonnes of biomass each year, statistics published by the UK's National Centre for Biorenewable Energy, Fuels & Materials (NNFCC) and WRAP reveal.

Scotland, South West England and the East of England have the highest number of AD facilities per person, while Yorkshire & Humberside, Northern Ireland and London have the lowest. London has yet to build a single digester.

Speaking exclusively to edieWaste, NNFCC's head of biomass & biogas, Lucy Hopwood, said: "The increase in the number of facilities is in no small part thanks to the introduction of incentives encouraging the development of smaller-scale farm-fed digesters and support for renewable heat."

"We have been working closely with government to ensure these incentives are balanced fairly and correctly, to reduce our reliance on fossil fuels, help reduce our greenhouse gas emissions and encourage sustainable development in the AD sector."

The market has until now been dominated by larger AD facilities producing biogas from food waste, but farming also produces large amounts of waste which could be turned into valuable, renewable energy. However, this is usually at a smaller-scale and requires higher subsidies to make it economically viable.

The introduction of the renewable heat incentive (RHI) this year and changes to feed-in tariffs for smaller-scale farm-fed digesters are making AD an attractive proposition to many more energy investors and there are nearly a hundred new facilities in planning.

A map of the operational AD facilities can be viewed here.