Kinetic Modeling of Anaerobic Co-Digestion Of Plant Solid Waste with Sewage Sludge: Synergistic Influences of Total Solids and Substrate Particle Size in Biogas Generation

Anaerobic co-digestion is a complex process; therefore, understanding the factors related to kinetics is a prerequisite for optimizing biogas production. In this sense, this study addressed the anaerobic co-digestion of solid waste from vegetables and fruits and anaerobic sewage sludge, focusing on the kinetic modeling of biogas production and investigated synergistic effects of the concentration of total solids (TS) and substrate particle size (SPS). For that, a Factorial Design 3 (2-0) was used in which the controlled variables were TS (29.2, 39.9, and 50.5 g/L) and SPS (1.68, 2.9, and 3.36 mm), with tests carried out in 2-L reactors for 200 days to quantify the biogas produced. The modified Gompertz (MG), function transfer (FT), logistic function (LF), modified first-order (FO), and Cone (CN) kinetic models were evaluated in the description of biogas production using the Akaike Information Criterion (AIC) and NRMSE, resulting in the following performance order: LF>CN>FO>MG>FT. The SPS influenced the cumulative biogas production ( M max ) and the hydrolysis constant, so that M max increased 221% when the SPS has been reduced from 3.36 to 1.68 mm. TS had an effect on the latency phase time and maximum biogas production rate ( R max ), so that R max was optimized by 40% when TS was adjusted from 50.5 to 29.2 g/L.