Biomethane, the future of green gas

Decarbonisation of heat is one of the biggest challenges for the mitigation of climate change. 85% of UK households currently use gas for their heating.

The most plausible strategy for decarbonisation is to retain the gas grid, but to decarbonise the gas within it. Currently the gas grid is served by natural gas, which is largely methane, but with small amounts of propane and ethane. Methane from fossil sources can be replaced by methane manufactured from renewable sources, such as municipal waste, or biomass. This is referred to as biomethane.

Biomethane can be manufactured by two different processes.

Anaerobic Digestion (AD), which is the decomposition of the fuel without the presence of oxygen to produce a mixture of gases, which is then purified to create biomethane.

Gasification, which is the heating to high temperature of the fuel without combustion, similar to burning toast, which produced a mixture of gases, including hydrogen, which is then converted to biomethane (also known as bioSYN).

Through government support with Feed-in-Tariffs, AD is already an established industry, but has a constrained potential for growth due to difficulty of finding capacity in the grid during the low demand summer months. In contrast, bioSYN has the future potential to supply up to 50% of UK demand.

A strategy of blending the gas in the grid with bioSYN, biomethane from AD, and up to 20% hydrogen, combined with decreasing the requirement for energy use for heating by improving the thermal efficiency of properties, would provide a cost effective and plausible route to decarbonisation.

Gasification is proven technology, but requires assistance to move from its current development status to become commercially mature, but is future proofed for the plant to continue to be used if there is a future shift to hydrogen.

Sadly, the government is proposing to only support AD through Feed-in-Tariffs, and there is a lack of strategic commitment to developing gasification technology.