Welcome to Lutra

Biogas design, innovation and research

About Lutra

Lutra is a biogas business set up by Michael Chesshire, who has been in the AD industry since 1975. The previous companies he founded were Farmgas (pioneers of pre-fabricated sewage sludge digesters), Greenfinch (pioneers of food waste AD) and Evergreen Gas (pioneers of plug-flow digesters).

Lutra provides two consultancy services: design of plug-flow biogas plants, and biological & analytical support for major AD plants.

Lutra research is concentrated on the operation of 1500-litre pilot plants and the community food waste AD digester (known as BMAD). Current areas of research include the biomethanation of hydrogen and carbon dioxide (“power-to-gas”), biopropane, and biochar.


Michael Chesshire is a Cambridge engineering graduate. After a brief spell in the nuclear industry (including cold commissioning of Hinkley B), he set up his first AD business in 1975 in the wake of the Middle-East oil crises. Over the years his companies have built more than 100 biogas plants and have employed more than 200 people in South Shropshire. Furthermore, employees from these companies have gone on to start their own new biogas businesses within the industry – notably Marches Biogas.

Since 2008, he has been a visiting professor at the University of Southampton, teaching both at the university and at summer schools in Finland. More recently his association with the university has been on research projects.

He has been an active participant in trade associations, as a Director of the Renewable Energy Association (2009 to 2017), Director of Renewable Energy Assurance (2011 to date), and a Board Member of the European Biogas Association (2017 to date).

MJC profile

Plug-Flow Digesters

Plug-flow digester design has advantages over the traditional continuous stirred tank reactor (CSTR) design, and is particularly suited for on-farm AD.

MJC profile

Design Consultancy

Michael Chesshire pioneered the development in the UK of the below-ground plug-flow digester. Lutra offers a complete process design service, including: project feasibility, process calculations, piping & instrumentation diagrams, mechanical design, electrical design, process control and commissioning.

engineering drawings Fig: P&IDs and plug-flow digester with 250kWe CHP unit


R&D and innovation have been key features of Michael Chesshire’s career in anaerobic digestion. Since 2001 much of his R&D work has been in partnership with Professor Charles Banks and Professor Sonia Heaven at the University of Southampton, notably in relation to the anaerobic digestion of food waste. The latest project is the development of biomethanation (“power-to-methane”), also working with the University of Sheffield and the University of York.

Community Food Waste AD

With Greenfinch, and supported by Charles Banks at the University of Southampton, Michael Chesshire started developing the anaerobic digestion of food waste in 1996; first, with a feasibility project processing food waste from a cafe-bar; second, with a demonstration project, in 1999, digesting source-segregated food waste from 1200 households in South Shropshire; and third in 2004, with the design, construction and operation of the Defra demonstration digester in Ludlow, known as “Biocycle”.

Since March 2014, Lutra has been operating a small community food waste AD plant near Ludlow in Shropshire; the plant is known as “BMAD” – Barrett’s Mill Anaerobic Digester. Lutra has been collecting about one tonne per week of food waste from local pubs, restaurants and schools as part of a privately-funded feasibility study into the economics and logistics of small-scale food waste AD. The food waste has also been co-digested with other feedstocks – potatoes, poultry manure and grass cuttings.

BMAD is comprehensively monitored with daily records taken of many key parameters. Plant performance is verified using the principle of mass balance – in the 124-week period of operation when the only feedstocks were food waste and grass cuttings, the mass balance was accurate to within 1.5%. Methane production has been higher than expected, possibly due to the plug-flow design, and over the same 124-week period the methane production was 128m3 per tonne of food waste.

BMAD has been temporarily closed for redesign.


The concept of P2M is based on the microbiology of anaerobic digestion, which is a multi-stage process with intermediate products. One of these stages is acetogenesis, by which volatile fatty acids are converted to acetic acid, hydrogen and carbon dioxide. The final stage, methanogenesis, converts acetic acid, hydrogen and carbon dioxide into methane. The microbes which convert hydrogen and carbon dioxide into methane are known as hydrogenotrophic methanogens. The principle of P2M is to use these same hydrogenotrophic methanogens to combine an external source of hydrogen with an internal or external source of carbon dioxide to produce methane. P2M has the potential to address the two major challenges referred to above: by using surplus or low-cost electricity to produce hydrogen through electrolysis; by using this hydrogen to produce methane; and by injecting the methane into the national grid which has a large storage capacity. This process therefore enables energy storage and electricity grid balancing to be achieved by using the gas grid as storage as well as by batteries.

Theory and Concept: The efficiency of the conversion of electricity to hydrogen is about 75% (excluding heat production) and the efficiency of the conversion of hydrogen to methane (excluding heat production is about 80%). The efficiency of the combination of electrolysis plus biomethanation is therefore about 60%, the balance being heat.

Formula for the electrolysis of water:

2H2O + electricity → 2H2 + O2 + heat

Formula for biomethanation:

4H2 + CO2 = CH4 + 2H2O + heat

Combined formula for electrolysis plus biomethanation:

2H2O + CO2 + electricity = CH4 + 2O2 + heat

Ex-Situ Biomethanation: Most commercial research and development into P2M has been focussed on “ex-situ” biomethanation. This involves an anaerobic reactor in which hydrogenotrophic methanogens are cultivated and into which hydrogen and carbon dioxide are injected. Ex-situ biomethanation has the significant benefits that it can be switched on and off, and that the methane quality is not adversely affected by variable flow of input gases.

In-Situ Biomethanation:In-Situ biomethanation involves the injection of hydrogen into a stable working AD plant which is being fed in the normal way. The hydrogen combines with the carbon dioxide fraction of the biogas to form methane, with the potential to produce biogas with a concentration of 95% methane. The advantages of in-situ are that no special reactor is required and that the process replaces biogas upgrading. The disadvantages are that there are biological issues to be overcome and that the process needs a continuous rather than intermittent source of hydrogen if a consistent gas quality is to be achieved.

IB Catalyst H2AD: The University of Southampton, in partnership with the University of York and the University of Sheffield, successfully bid for a BBSRC (Biotechnology and Biological Sciences Research Council) research grant under the “Industrial Biotechnology Catalyst Early Stage Translation” scheme to carry out research into the biomethanation of carbon dioxide in anaerobic digestion plants – “H2AD”. The four-year project started in June 2015 and is due to be completed by the end of 2019: Southampton is researching reactor biology through the operation of eight 1-litre laboratory digesters; York is researching genome identification of the hydrogenotrophic microbes; and Sheffield is researching process modelling and optimisation. As well as the universities, there are four industrial partners H2AD – United Utilities, Fera, ITM Power, and Lutra.

Lutra H2AD Pilot: As a supplement to the BBSRC project, the University of Southampton successfully applied for grant funding to set up and operate a 1500-litre pilot plant, which has been set up and operated by Lutra in Shropshire. The feedstock is cow slurry collected by Lutra from a local dairy farm.


Michael Chesshire has been appointed as a consultant to C3 Biotechnologies, a partner in eForFuel (www.eforfuel.eu).
eForFuel is developing industrial biotechnology that uses electricity and microorganisms to convert CO2 into hydrocarbon fuels, thus providing a sustainable replacement of fossil carbons without the need for sugar-based biofuels. One potential pathway is the electrochemical reduction of CO2 to produce formic acid which is converted to propane or isobutene by E.coli strains.


Lutra is investigating the feasibility of producing biochar by the pyrolysis of waste biomass. Biochar is a high value carbon product which has the potential to enhance the process of anaerobic digestion and to sequestrate carbon in the soil.

Contact Lutra

Barrett’s Mill, Ludlow, Shropshire, SY8 4AH

Please ignore your SatNav and use the map provided. Travelling South on the A49 towards Leominster, as you come over the railway bridge we are the next left, down a farm track. If you reach The Salwey Arms you've gone too far. Travelling North on the A49 towards Ludlow, as you pass The Salwey Arms, the road bears right handed as indicated by chevrons, just around that corner turn right down the farm track. If you cross the railway bridge you've gone too far and it is safest to turn around at the lay-by at Ashford Bowdler. Leaving Lutra - it is suggested for safety reasons that when leaving Lutra, regardless of your route, that you turn left and head South on the A49 initially. It is easy to subsequently turn around to head North and much safer due to the restricted view when pulling out of the junction.

Barret's Mill map