ABSTRACT
The operation and performance of five full scale plants installed in breeding farms are analyzed in this paper. The digesters were operated at an HRT from 10 to 40 days with pig, pig and cattle and cattle waste. The digesters, fed by pig waste, gave an average biogas yield of between 0.30 and 0.55 m .Kg−1 VSo.d−1, 0.80 and 1.20 m3 .Kg−1 VSr.d−1 at an HRT of 10–15 days, at an average organic loading rate of 0.84 – 1.95 Kg VS.m−3.d−1, and at a digestion temperature of 28–40°C; TS, VS, COD removal was respectively 30–47%, 46–57%, 42–59%. One of the plants fed by mixed waste and operated at an organic loading rate of 0.60 – 1.78 Kg VS.m−3.d−1 gave an average biogas yield of 0.46 m3 .Kg−1 VSo.d−1, at an HRT of 20–35 days and at a digestion temperature of 30–34°C; TS, VS, COD removal was respectively 35%, 46%, 50%. The experimental plug flow plant operating on cattle waste gave a biogas yield of 0.24 – 0.41 m3 .Kg−1 VSo.d−1 at an HRT of 24 – 40 days, at an organic loading rate of 2.7 –4.5 Kg VS.m−3 .d−1 and at a digestion temperature of 33–37°C.
