Increased biogas production from lignocellulosic biomass by soaking in water

Due to its large production worldwide, lignocellulosic biomass represents a substrate with great potential to produce biogas. However, this type of biomass is characterized by a complex and solid structure, which is difficult to decompose by anaerobic microorganisms. Applying the correct pre-treatment method can increase its biodegradability. Lignocellulosic substrate was pre-treated by soaking in water for one day at room temperature to increase biogas production and monitoring of long-term operation of laboratory models of anaerobic reactors for anaerobic digestion of such pre-treated maize waste was employed. Monitoring results in two reactors, R1 with biogas produced from a substrate soaked in water for one day and R0 with the production of biogas from a substrate mixed with water just before dosing into the reactor, were compared showing positive effect of the pre-treatment method. This was expressed by higher values of biogas production and higher methane content in biogas from the substrate soaked in water for one day. The achieved specific biogas productions during four different phases of reactor operation in reactor R1 were in the range of 190–335 mL g-1 of VS (volatile solids) and 101–221 mL g-1 of VS in reactor R0. Methane content of biogas during reactor operation was 49.3–55.2% in reactor R1 and 42.5–45.5% in reactor R0. During long-term operation of another reactor, pre-treated maize waste was used as a co-substrate for maize silage, in the ratio of 1:1 based on VS of the substrates proving as a suitable co-substrate for maize silage, as the achieved average value of specific biogas production during reactor operation at OLR (organic loading rate) = 1.75 kg VS m-3 d-1 was 510 mL g-1 of VS and during first 67 days at OLR = 2 kg VS m-3 d-1 it was 454 mL g-1 of VS.