Biogas plants still need quite a bit of harvested biomass added tp the manure. Manure by itself has too low a Carbon/Nitrogen ratio, and without supplementation

Biogas plants still need quite a bit of harvested biomass added tp the manure. Manure by itself has too low a Carbon/Nitrogen ratio, and without supplementation, it will over-produce Ammonia, inihibiting the anaerobic bacteria that digest the feedstock. So you have to add sileage or switchgrass.