Effect of Acid Pretreatment on the Anaerobic Codigestion of Sewage Sludge, Chicken Litter, and Sugarcane Waste (SCW) for Biogas Production

In Mexico, productive activities related to poultry farming and the sugarcane industry generate large amounts of three byproducts, sewage sludge, chicken litter, and sugarcane wastes, which have high concentrations of organic matter and lignocellulosic material. Therefore, the objective of the present study was to evaluate the effect of acid pretreatment with different doses of acetic acid (2%, 3%, and 4% v/v) and exposure times of 30, 60, and 90 min on the solubilization of organic matter and biogas production in the anaerobic codigestion of a mixture of agroindustrial wastes. The biodegradability and biogas production were evaluated by anaerobic digestion for 30 days. Finally, for 90 days of semi-continuous operation, the increase in applied organic load of 1 KgVS/(m3.d) was considered with Δ1 KgVS/(m3.d) every 30 days until reaching 3 KgVS/(m3.d). Acid pretreatment with a dose of 4% acetic acid and an exposure time of 90 min improved the solubility and hydrolysis, considering the limiting stage of the anaerobic process, reducing the hydraulic retention time from 19 to 11 d to reach –Δ 38% VS, and increasing biogas yields (Ybio = 609 ± 11.7 to 1857.2 ± 7.5 Lbio/gVSrem) and methane yields (YCH4 = 426.9 ± 8.19 to 1392.9 ± 5.65 LCH4/gVSrem).