There’s considerable enthusiasm about renewable energy such as wind or solar, or the alluring prospect of affordable green hydrogen, on the long road to a decarbonised economy.

There’s far less talk – and policy attention – focused on “renewable” gases or low-carbon fuels such as the biomethane created by crops, food and other organic, animal and yes, human, waste. Perhaps it’s because the processing of such waste sounds less sexy – certainly messier and murkier – than the image of clean, green renewable power.