Biomethane from waste
Biomethane is a renewable gas. Ws made from biodegradable matter such as food waste, sewage or energy crops. When these start to rot, they generate the gas we call biomethane.
It's likely that food waste and sewage will continue to be part of our society for many decades to come, so finding a use for them - instead of letting the gas simply escape into the atmosphere- is beneficial to us all.