Enhanced anaerobic digestion of brewers’ spent grain: effect of inoculum, poultry manure application and iron (iii) chloride supplementation on biogas production and its kinetics

The brewery industry generates a huge quantity of brewers’ spent grain (BSG) which can pose waste disposal and pollution problems. Anaerobic digestion of BSG, a recalcitrant lignocellulosic waste, is slow but can be enhanced by bioaugmentation, biostimulation and co-digestion to obtain a higher biogas yield. Hence, the effect of inoculum from brewery wastewater sludge (BWWS), iron (III) chloride (FeCl₃) and co-digestion with poultry manure (PM) on the production of biogas from BSG was investigated. Cumulative biogas and biomethane yields of 588.19 NL/kgVS and 400.34 NL_CH4/kgVS, respectively, were obtained from a slurry consisting of a blend of 60% BSG and 40% PM plus 15 mg L^-1 FeCl₃ in BWWS, after 30 day retention time at 37 ^oC. However, mono-digestion of BSG in only water yielded 402.17 NL_biogas/kgVS and 262.86 NL_CH4/kgVS. The synergistic effects of inoculum from BWWS, FeCl₃ and poultry manure on anaerobic digestion of BSG resulted in 46% and 52% increases in biogas and methane yields, respectively, compared with BSG mono-digestion. The biogas and biomethane production kinetics were well described by the dual pooled first order, logistic and modified Gompertz models.