Ireland could need up to 80 farm anaerobic digestion (AD) plants by 2030 under Government plans to introduce a renewable heat obligation.
The public consultation on the obligation is currently open and would mandate suppliers of fuel to the heat market to ensure a proportion of that fuel is from renewable sources.
The obligation rate would start low, at 0.5% from 2023, and gradually be increased over the decade to at least 3% by 2030.
Eligible renewable fuels under the obligation will include green hydrogen, biomass, bioliquids and biomethane (upgraded biogas) which can be imported.
However, the consultation highlights how indigenous biomethane produced from AD plants and injected directly into the national gas grid is likely to be the lowest cost source of renewable fuel for suppliers.
The 2030 target of a minimum of 3% equates to around 1.6TWh (terawatt hours) of renewable heat. Due to the extra cost associated with upgrading biogas to biomethane, relatively large AD plants will be required.
It is assumed a typical farm-sized AD plant in Ireland will have a biomethane output of 20GWh (gigawatt hours). For context, this is twice the size of a farm-based plant in Northern Ireland.
Therefore, up to 80 AD plants would be required to satisfy the obligation.
Under the Renewable Energy Directive II, strict sustainability criteria applies to renewable fuels. For example, biomethane must reduce emissions by 70% when compared to natural gas.
This dictates the type and quantities of feedstock which can be used to supply a plant. Therefore, on average, a typical 20GWh farm AD plant will require approximately 400ha of forage feedstock sourced within 10km and a further 16,000t of slurry sourced within 3km to 5km.