Anaerobic digestion (AD) plants vary in their cost of construction, but some guidance of costs can be provided.
Most estimates have been made to include not just the AD equipment to produce the biogas, but also for an adjacent combined heat and power (CHP) plant.
The first step is to identify the energy needs, usually in kilowatt-hours (kWh) per year.
Then, the power rating of the equipment can be determined, a 1 kW-rated plant would provide 1 kWh of energy every hour, assuming it was 100% efficient (which they aren’t).
The capital cost is effectively the price to build and install an AD plant and associated CHP unit.
The capital cost doesn’t include annual maintenance, operation, insurance or feedstock costs. Accurately factoring in all of the data to give a realistic cost-per-kWh is complicated and not attempted here, but it is possible to give ballpark figures as a rough idea.
An International Energy Agency survey quoted by the NatWest bank in 2020, gives a mean cost of about £5,000 per kW of installed capacity in the UK.
The report uses a basis that slurry from 200 dairy cows would require 200 cubic metres of digester space and would produce about 20 kW of continuous power.
On this basis, the capital costs would come to about £100,000.
Adding a mean 12.5% of that figure to cover an initial feasibility study, planning permission, assessment and licencing would bring the total to around £112,500.
This brings the cost for a modest-size plant closer to £6,000 per installed kW of capacity when adjusted for inflation.
On a larger scale of circa 2.0 MW capacity, costs may dilute to circa £4,000 per installed kW.
Page Last Updated: 23 April 2022