Maize silage and ensiled beet pulp were fermented under anaerobic condition to MeH-rich biogas. Addn. of enzymatic additives resulted in increasing the biogas yield by 28% and 7%, resp., up to 620 Nm(3)/t dry mass after 30 days for maize silage and up 680 Nm(3)/t dry mass after 15 days for ensued beet pulp. The additives did not affect the MeH content in the biogas.