Case Story United Kingdom

ICKNIELD FARM BIOGAS

An Integrated Farm Enterprise

August 2018

MISSION AND VISION

This biogas plant with biomethane production, which began operation in 2014, is an integral part of the farm system. The project was led by David Bermingham (a local resident and employee of Scotia Gas Networks). David sought a suitable location for a biomethane facility that could feed into the local gas pipeline, which serves the villages along its route. The farm provided the optimum site. The gas pipeline runs under the 700 ha Icknield Farm, owned by Guy Hildred (a mechanical engineer) and his family. This mainly arable farm operates as a Family Partnership in association with a nearby farm which together form a contract farming business servicing over 3,000 ha of mainly cereal growing land.

PLANT DESCRIPTION

The plant (figure 1) consists of 2 x 28m diameter digester tanks sunk 5m below ground to minimise any visual impact in this Area of Outstanding Natural Beauty. Three silage clamps are used to store maize and hybrid rye through the year. The digestate is stored above ground in two ultra-flexible polyethylene gas storage bags. The biogas upgrading unit is housed in containers adjacent to the CHP engine and control station. The annual biomethane output is sufficient to supply 4,000 homes along the Thames Valley. The biogas is produced from a total input of 34,000 tonnes, all locally sourced.

An EnviThan polymer membrane is used for the first time in the UK to clean the biogas (figure 2). This produces approximately 99% biomethane at a pressure sufficiently high to inject directly into the grid without an additional compression process. This innovative technology exploits the smaller size of the CO2 molecules which can migrate quicker through the membrane. This simple and environmentally friendly treatment is cost effective as there is no need for further processing, chemicals or water. This process produces 4.4 million m3 of biomethane (47.3 million kWh) annually for injection into the gas pipeline. This is eligible to receive payments through the Renewable Heat Incentive. A containerised 360 kW CHP engine provides all the heat and power needed to operate the plant (Table 1). Any surplus is exported to the electricity distribution network.