Chris Huhne is right to say that the UK faces a false choice between more North Sea drilling and greater reliance on imports of gas (Letters, 21 April). But presenting biomethane as a straightforward solution overlooks the serious environmental and health risks of its expansion.

Biogas can reduce emissions when produced from waste. Yet a growing share of feedstock for anaerobic digestion comes from purpose-grown energy crops, increasing pressure on land, competing with food production and risking wider environmental harm.

Nor is the process leakage-free. Studies suggest that up to 13% of methane produced at anaerobic digestion sites can escape, no small issue given methane’s powerful warming effect. Current requirements around detecting leaks and repairing them are not mandated or well enforced.

Expansion of biogas production also risks worsening air quality and damaging ecosystems. Ammonia emissions from the sector are rising, produced when the nitrogen-rich feedstock is broken down in digesters. Ammonia contributes to the formation of particulate matter (PM2.5), a harmful air pollutant, and damages sensitive habitats.

While biogas has a role to play in decarbonising the gas grid, it is no magic bullet and, according to some estimates, is unlikely to meet more than 18% of current gas demand.

Without stronger safeguards, its expansion risks substituting one set of environmental problems for another.
Dr Matilda Dunn
Policy analyst, Green Alliance