Colby Laithes Farm – An Anaerobic Digestion Feasibility Study

Colby Laithes Farm is an organic dairy farm located in Cumbria. WRM were commissioned by the farm to conduct an anaerobic digestion feasibility study to explore the use of slurry arising on-farm as an anaerobic digestion feedstock. Colby Laithes Farm houses a 380 head Montbeliarde dairy herd and processes around 4,300m³ of slurry per year. The project was supported by the WRAP On-Farm AD grant scheme.

Colby Farms Ltd. were keen to explore an AD system to run on farm waste only (i.e. slurry) as all crops grown on-farm were high value due to the farm’s organic regime. Given the available AD feedstocks, WRM suggested the feasibility study focus on micro-scale (less than 50kW) anaerobic digestion of slurry. The feasibility study analysed the feedstock to understand AD generation capacity, assessed technology requirements and options, infrastructure changes or requirements and planning permission and permitting requirements which culminated in the production of a business plan and investment case, along with a detailed due-diligence risk assessment.

The feasibility study provided the farm with the information required to make an informed decision as to whether AD is a suitable technology option for the business at this point in time.

• Feedstock Analysis – Identified that the slurry arising could support up to a 22kW AD plant, however, due to the current grazing regime this would drop to 8kW during summer months.
• Technology Requirements- Suitable slurry-only technology was identified, and quotes from industry-leading slurry-only AD plant providers were scrutinised.
• Infrastructure – Necessary modifications to farm infrastructure were identified that required minimal changes to daily farm operations.
• Planning & Permitting – No planning challenges were identified and the project would likely proceed under Standard Rules permits.
• Business Case – An 11kW AD plant was identified as a technically feasible option, with a payback period of 11 years when all capital costs, processing costs and incomes are considered.
• Risk Assessment – Key risks identified included consistency of slurry supply in relation to grazing regime and RHI and FIT incentive tariff forecasts over the coming year.