Burton Agnes Renewables Ltd was set up in 2015 as a joint venture between the Dewhirst Farming Group and the Burton Agnes Estate with the purpose of building an anaerobic digestion (AD) plant on the Burton Agnes Estate. The plant is fed on energy crops (maize and hybrid rye), pig manure, poultry manure and wheat straw. Much of the energy crops (and the wheat straw) are grown on the Dewhirst and Burton Agnes arable farms, but there is also a proportion grown on neighbouring farmers’ land on Grower Agreements. All of the manures come from the Dewhirst pig and poultry enterprises.
The digester (which is actually made up of a primary and a secondary digester in a “power ring” design) is fed daily with a strictly adhered to diet of energy crops and manure. The digester is heated and mixed in anaerobic conditions to encourage the production of raw biogas. This biogas is captured and fed into 2 consumers. The 500kW Combined Heat & Power (CHP) engine consumes around 25% of the raw biogas produced and in so doing generates all of the electrical power required to run the plant and also all of the heat required by the digester. All of the rest of the raw biogas goes through the site’s 3 gas upgrading units, converting the raw biogas into biomethane, which is injected into the 17 bar gas main that runs through the site. This is used to power industry and homes across the region.
The bi-product of the process comes in the form of solid and liquid digestate. This is spread on the Dewhirst and Burton Agnes arable land as a valuable natural fertiliser, reducing the need for expensive fossil fuel based bagged fertiliser and thus reducing our carbon footprint.