Psychrophilic anaerobic digestion of lignocellulosic biomass: A characterization study

Psychrophilic (20 °C) specific methane (CH4) yield from cellulose (C), xylan (X), cellulose/xylan mixture (CX), cow feces (CF), and wheat straw (WS) achieved (Nl CH4 kg−1 VS) of 338.5 ± 14.3 (C), 310.5 ± 3.4 (X), 305.5 ± 29.6 (CX mixture), and 235.3 ± 22.7 (WS) during 56 days, and 237.6 ± 17.7 (CF) during 70 days. These yields corresponded to COD recovery of 73.3 ± 3.1% (C) = 69.1 ± 0.76% (X) = 67.3 ± 5.8% (CX mixture) > 52.9 ± 2.6% (CF) > 46.5 ± 2.7% (WS). Cellulose-fed culture had a lower and statistically different initial CH4 production rate from those calculated for cultures fed X, CX mixture, CF and WS. It seemed that the presence of hemicellulose in complex substrate such as wheat straw and cow feces supported the higher initial CH4 rate compared to cellulose. Biomethanation of the pure and complex lignocellulosic substrates tested is feasible at psychrophilic conditions given that a well-adapted inoculum is used; however, hydrolysis was the rate limiting step.