Planet Portfolio

Powering Farms with Captured Methane

Covering waste slurry lagoons to convert fugitive methane emissions into liquified fuel.

Cornwall, United Kingdom

About this Project

Slurry lagoons are man-made basins on farms that collect and concentrate waste produced by animals and livestock. These uncovered lagoons emit methane, which is biologically produced through the anaerobic decomposition of organic matter by bacteria. Not only does this release planet-warming methane many times more powerful than carbon dioxide into the atmosphere, it represents an untapped source of energy.

Bennamann is a company that supports farms to cover their lagoons, collect excess methane, refine it, and liquify it through a technology that took 11 years to develop. Liquefaction is a critical step in the process — in gas form, methane has to be stored in steel cylinders with regulated pressure, limiting the quantity of fuel that can be stored or transported. When cryogenically liquified, the volume is reduced by over 600 fold but stays at low pressure, allowing it to be transported by road and stored easily and efficiently in non-cylindrical tanks. This means its energy density is comparable to diesel making it perfect for use on heavy duty applications such as tractors and other farm equipment and the aggregation and distribution has no reliance on the natural gas or electrical grid. It can be captured from anywhere and used anywhere.

Unlike fossil Liquid Natural Gas (LNG), Bennamann’s patented zero venting technology enables the Liquid Fugitive Methane (LFM) to be stored indefinitely and safely with no release of methane in the form of boil-off gas. The high density, efficient stored and zero venting capability makes LFM a perfect replacement for diesel enabling off grid back-up power to fill in the intermittent nature of renewables such as wind, solar and tidal.

This project finances the coverage of one slurry lagoon 25 x 25 meters, along with the capture, refinement, and liquefaction of methane that otherwise would have been emitted from the lagoon. This program is truly innovative — 20% of the profits from the sale of the liquid biomethane fuel goes into a trust fund that covers the cost of additional follow-on slurry lagoon covers enabling the impact of this project to grow continuously, touching more farms and amplifying its environmental benefits.

Why We Picked This Project

Bennamann’s local aggregation and distribution model leverages local biogas storage and process preparation, providing a new source of income to farmers, while displacing fossil fuels. The unique approach provides de-centralised & de-synchronised biogas processing, liquefaction and storage to dramatically reduce capital cost, increase flexibility and provide resilience to fluctuations in price and demand. This project utilizes a novel business model to capture fugitive methane, generate revenue for farmers, displace diesel, and re-invest profit in additional projects.

Complying with UK law on the Renewable Transport Fuel Certificates, Bennamann is able to provide precise and frequent audit reports and updates on the amount of fugitive methane captured, liters of fossil fuel displaced, and amount of additional funding generated to expand the program.

Our Assessment of this Project

Project Developer

Standards & Certifications

  • Renewable Transport Fuel Obligation


Jun 2023 - Lagoon Covered

Slurry lagoon sized 25 x 25 meters covered on 1 farm in Cornwall

Jun 2023 - Trust fund established

Trust fund for profit share from sale of fuel established

Dec 2023 - Liquid fuel produced

First batch of methane collected to produce liquid fuel

Benefits & Impact


  • Increased profitability enabling investment into farming infrastructure and sustainable practices

  • Reduced environmental contaminants, slurry run-off, nitrate leaching

  • Reduced smells, slurry movements and pests

  • Low cost fuel at fixed prices for typically 2-5 years

  • Displacement of fossil fuels

Sustainable Development Goals

This project supports the following UN Sustainable Development Goals:

Affordable and Clean EnergyIndustry, Innovation and InfrastructureClimate ActionLife On Land

Additional Information

Additionality Summary

Funding for this project directly finances the cover for a slurry lagoon that otherwise would remain uncovered.