FACTORS INFLUENCING BIOGAS PRODUCTION DURING FULL-SCALE ANAEROBIC FERMENTATION OF FARMYARD MANURE

Farmyard manure was subjected to anaerobic fermentation in airtight di gesters for approximately 30 days. The annual biogas production was 0. 9 m(3) per large animal unit per clay with three different production levels evident: a summer period, a transitional period and a winter pe riod, when biogas production was 1.1, 0.75 and 0.55 m(3) per animal un it per day, respectively The research focused on the factors influenci ng equipment operation for farmyard manure anaerobic fermentation and biogas production. The factors discussed in this paper can be divided into three different groups: (i) main independent factors (natural con ditions, transition to summer and/or winter feeding); (ii) main factor s affected by the operational conditions (composition of feed, aerobic stage); and (iii) secondary factors that may nor influence fermentati on under optimum operational conditions (feed quality, quantity and qu ality of bedding, technology of farmyard manure removal). Once the inf luence of secondary and partly, main controllable factors had been eli minated, higher biogas production could be expected mostly in the tran sitional and winter periods, up to 0.85 and 0.65 m(3) per large animal unit per day; the annual average biogas production would then reach 0 .95 m(3) per large animal unit.