Northern Ireland has more than 80 anaerobic digestion plants making biogas, most of them supported by a renewables obligation that closed to new entrants in March 2017, and one pioneering site, in Dungannon, that injects biomethane into the gas distribution network. The Department for the Economy and the Department of Agriculture, Environment and Rural Affairs now want a policy for what comes next. Their joint consultation on a biomethane strategy and policy framework was published on 20 October and stays open until 5 pm on 15 December; Energynews summarised it on 10 November.
The paper covers financial support, grid connections, gas quality, nutrient management, and certification and sustainability. It cites academic research according to which local feedstocks could produce more than 80% of the demand on the region's gas distribution network, approximately 7.6 TWh.
Money for industrial heat first
On support, the departments' preferred option is a capped subsidy in pence per kilowatt-hour for biomethane used for industrial heat, Energynews reports. It would be paid from residual annually managed expenditure and only until an end date. No rate or cap has been published. In parallel the Department for the Economy has opened a call for information on commercial supply and demand to build the business case; it is explicitly neither a grant application nor a funding commitment. The Treasury has agreed to the proposal being worked up, nothing more.
On gas quality, the consultation notes that the health and safety regulator already allows up to 1% molar oxygen for biomethane injection under a class exemption, and that the Utility Regulator modified gas conveyance licences in March 2026 for biomethane entry points. Proposals described by Energynews include aligning the oxygen limit between transmission and distribution and reducing propane addition over time where safety allows. Final positions follow after the responses have been analysed.
When the engine leaves, so does the digester's heat
A plant built for an electricity subsidy typically burns its biogas in a CHP engine on site, and the engine's cooling water heats the digester. Take the gas away to an upgrading unit and a grid entry point, and the digester still wants to be kept at temperature every day of the year. The heat has to come from somewhere else: the upgrading plant's compressors, a boiler on a slipstream of biogas, or a heat pump.
That is a heat recovery job with awkward fluids. Digestate and slurry foul; compressor cooling circuits are clean but only lukewarm. Where a site also pasteurises its feedstock, heat is recovered from the treated stream to the incoming one. Exchangers on the dirty side need wide passages and easy opening. On the clean circuits - compressor cooling, hot water loops, the industrial user's own process - standard gasketed plate units are the normal choice.
Anyone planning a conversion would do well to draw the site's heat balance before the gas contract is signed. Selling every kilowatt-hour of biomethane looks good until the digester gets cold in January.
Sources: Energynews, Department for the Economy
