Kavita Srinivasan is a Senior Analyst at the CCC, looking at how Agricultural emissions reductions should form part of the Governments wider strategy for meeting carbon budgets. Here Kavita tells us about an Anaerobic digestion plant installed on a farm…
Members of the CCC Secretariat last week visited Crouchlands Farm, a 750 cattle dairy farm located in West Sussex, to tour the farm’s newly installed 1 MW anaerobic digestion (AD) plant and to discuss GHG emissions reduction from agricultural activities with representatives of the National Farmers Union (NFU).
Faced with increased Nitrate Vulnerable Zone restrictions, which would require installation of expensive manure storage facilities, farmer (and NFU Vice President) Gwyn Jones opted to invest in a £2 million AD plant which converts agricultural waste into renewable energy.
The plant consists of two digester towers, which are fed on a combination of slurry collected from the dairy farm as well as maize (produced at a local arable farm on poorer quality land) and grass silage, which together form an optimal feedstock mix.
The feedstocks are mixed in the towers on a 90-day cycle, producing a biogas which is then converted into electrical energy, which is sold directly into the national electricity grid.
At completion of the digestion process, a nutrient-rich digestate is produced from the waste products which is then separated into solids and liquids. The solid digestate is spread back to cropland (used to grow maize) and the liquid slurry to pasture land, providing a nutrient recycling system and saving the farm in fertiliser costs.
As a renewable energy generator, the plant will earn returns from the ROC scheme as well as tariffs received from selling the electricity generated. Gwyn anticipates a payback for his investment in 4 to 5 years.
The CCC’s 2010 progress report to Parliament identified cost-effective opportunities to reduce methane emissions arising from livestock manures by increased installation of on-farm and centralised anaerobic digestion plants (approximately 0.6 MtCO2e in savings). At present methane emissions arising from manures account for 3 MtCO2e, or 6% of total agricultural GHG emissions.
The CCC report also noted that achieving greater uptake of abatement measures in the agriculture sector will require new approaches to address current barriers. Gwyn and NFU colleagues noted a number of potential barriers faced by farmers interested in installing AD systems, ranging from planning and compliance processes to accessing financing for smaller scale plants.