Energy
Digestate
Digestate is the material left after anaerobic digestion has taken the methane out of organic waste. It is rich in nutrients and goes back to the field as organic manure, so a biogas plant produces a soil input as well as a fuel.
It closes a loop that is otherwise open. Residue leaves the field, and the nutrients in it return to the same land.
Handled well it reduces the need for bought fertiliser on the block, which shows up as a cost saving rather than as a carbon claim.