Semi-continuous anaerobic digestion of solid poultry slaughterhouse waste: effect of hydraulic retention time and loading.
We studied the effect of hydraulic retention time (HRT) and loading on anaerobic digestion of poultry slaughterhouse wastes, using semi-continuously fed, laboratory-scale digesters at 31 degrees C. The effect on process performance was highly significant: Anaerobic digestion appeared feasible with a loading of up to 0.8 kg volatile solids (VS)/m3 d and an HRT of 50-100 days. The specific methane yield was high, from 0.52 to 0.55 m3/kg VS(added). On the other hand, at a higher loading, in the range from 1.0 to 2.1 kg VS/m3 d, and a shorter HRT, in the range from 25 to 13 days, the process appeared inhibited and/or overloaded, as indicated by the accumulation of volatile fatty acids and long-chain fatty acids and the decline in the methane yield. However, the inhibition was reversible. The nitrogen in the feed, ca. 7.8% of total solids (TS), was organic nitrogen with little ammonia present, whereas in the digested material ammonia accounted for 52-67% (up to 3.8 g/l) of total nitrogen. The TS and VS removals amounted to 76% and 64%, respectively. Our results show that on a continuous basis under the studied conditions and with a loading of up to 0.8 kg VS/m3 d metric ton (wet weight) of the studied waste mixture could yield up to 140 m3 of methane.
Salminen
Esa A
EA
Department of Biological and Environmental Science, University of Jyväskylä, Finland.
Rintala
Jukka A
JA
D000003:Abattoirs; D000641:Ammonia / Q000032:analysis; D000818:Animals; D001421:Bacteria, Anaerobic / Q000502:physiology*; D019149:Bioreactors; D005227:Fatty Acids / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D011200:Poultry; D012037:Refuse Disposal / Q000379:methods*
D005227:Fatty Acids; D000641:Ammonia; D009584:Nitrogen