Bubbling up very nicely

Bubbling up very nicely


The concept of anaerobic digestion is certainly not a new one. But nestling in a tucked-away corner on the south Shropshire border, a new company is developing a product that could transform the way the county’s farmers power their businesses, become more energy self-sufficient and reap a good financial harvest.

Now widely used as a source of renewable energy and recognised by the United Nations Development Programme as one of the most useful sources of energy supply, scientific interest in anaerobic digestion was reported as far back as the 17th century.

AD is common in developing countries such as India, Pakistan and many African countries where simple anaerobic digesters are used to generate biogas from household waste, manure and human excrement for cooking.

Larger anaerobic digesters have become a familiar sight on the agricultural landscape in countries such as Germany and Austria where they benefit from an economy of scale to generate significant amounts of electricity for export into the distribution grid. Such businesses can be financially very rewarding, and AD is also used to produce gas that is cleaned of impurities and injected into the natural gas grid.


But in Britain, the nature of farming, the rural landscape and the lack of availability of finance and incentives have led to large anaerobic being less commonplace than elsewhere in Europe. AD technology providers from Europe have been having some success in the UK market, but AD plants designed to operate at a scale that matches typical farming operations have been few and far between, until now.

Michael Chesshire with one of the company's gas-powered vans.

Evergreen Gas, based at Barrett’s Mill, near Ludlow, is the brainchild of Michael Chesshire and Will Llewellyn, who have developed a range of small-scale modular AD plants designed specifically for farms and rural communities.

Anaerobic digestion is a process in which biomass (plant and animal material) is converted by micro-organisms in the absence of oxygen to create a methane-rich gas called biogas and a biofertiliser called digestate. The biogas is made up of roughly 60 per cent methane, and 40 per cent carbon dioxide. The biogas can be burned to generate clean, renewable energy either in a combined heat-and-power unit or a boiler, or even cleaned of impurities and turned into vehicle fuel.


Biomass from a variety of sources including animal slurries and manures, crops, foodwaste and agricultural residues can be digested to produce biogas.

The unique feature of Evergreen Gas plants is the design of the digester itself, which is a radical departure from conventional tank design, reducing both capital and operating costs.

Michael Chesshire is renowned as one of the UK’s leading AD engineers. After graduating in engineering from Cambridge and working briefly in the nuclear industry, he founded Farm Gas, which designed and built digesters for farms, abattoirs and the water industry.

The company grew to more than 100 employees before being acquired by Anglian Water in 1990. Two years later Michael founded Greenfinch Ltd which pioneered the anaerobic digestion of food waste, which through a series of research projects culminated in the construction of the Ludlow food waste digester. In 2008, the company was acquired by leading food waste operator Biogen, to create Biogen Greenfinch, of which Michael remains a non-executive director.

Will Llewellyn talks to farmers at a trade show

Will, who originates from just over the Shropshire border in Herefordshire, read Biology and French at university before working in shipping in London.


A father of two small boys, he decided to embark on a career change after first hearing about anaerobic digestion from a friend, then deciding to investigate the subject further.

The two met when Will requested an informal chat with Michael to learn more about his new subject.

Will said: “Michael said he would see me for an hour. That became an afternoon and at the end of it he said he might be looking for an assistant.” Will joined Biogen Greenfinch in 2009.

Will left Biogen Greenfinch in 2011, and in October that year the pair started to develop the Evergreen Gas approach to low-cost, small-scale AD plants and designed their range of AD plants which look quite different from the traditional models.

Evergreen Gas was founded in response to both government policy and perceived market demand. The government made a commitment to work towards a ‘zero waste’ economy in the Coalition Programme in 2010, and to introduce measures to increase energy from waste through anaerobic digestion, which was later incorporated into Defra’s business plan.


Will said: “The benefits are so clear – AD can produce carbon-neutral electricity, displacing the use of fossil fuels, as well as making good financial sense from a feed-in tariff set at 14.5p per kWh for AD plants up to 250kW electrical output, and an export tariff where surplus electricity is sold for around 4.5 p per kWh. Then the ‘soup’ left over after the process is extremely good fertiliser.”

Operating with their team from a restored mill on the bank of the river Teme, the idyllic setting belies the company’s fast pace as already Michael and Will have taken on more staff to keep up with the enquiries Evergreen Gas are receiving.

And it doesn’t stop there. Will, refusing to be drawn on the full extent of future R&D plans for Evergreen Gas, said: “We are building a full-scale R&D digester here on our premises, which will generate heat and electricity for us and for export, and we are seriously looking at powering vehicles and machinery with our gas . . .”. Of course!