Current UK biomethane injection stands at 6 TWh annually (around 1% of gas demand). Five feedstocks could drive scale-upGrassland (29 TWh potential), rotational crops (27 TWh), sequential crops (17 TWh), agricultural residues (15 TWh) and livestock waste (11 TWh) represent the highest-growth feedstock mix. And gas grid constraints — already limiting injection in summer months — will intensify if overall gas demand falls or biomethane production accelerates; propanation (supplementing biomethane with propane for calorific value) adds cost friction. Production costs comparable to hydrogen; policy support criticalLevelised production costs range £73–£135/MWh, roughly matching projected hydrogen costs (£73–130/MWh) but significantly above natural gas with carbon pricing (£26–70/MWh by 2050). However, most plants would require CO₂ trucking to access piped networks, making infrastructure and policy frameworks for non-pipeline transport critical.