Pre-dimensioning of Small-Scale Anaerobic Reactors of Food Waste Through Biochemical Methane Potential Assays and Kinetic Models

The potential for obtaining renewable energy from organic substrates such as food waste (FW) and biowaste has generated increasing interest in the anaerobic digestion process. Kinetic models are used to analyse the impact of different parameters on biological processes and thus, to optimize them to achieve and to increase the quality and quantity of biogas. This study presents an approximation of the pre-dimensioning of semi-continuous anaerobic reactors treating FW, based on: (i) biochemical methane potential (BMP) assays, in different conditions of substrate-inoculum ratio (S/I: 0.5 and 4.0 g volatile solid-VSsubstrate·g VSinoculum−1) and nutrients (with macro-nutrients (N and P) and micronutrients, only micronutrients (Ni, Co, Mo and Fe) and without nutrients), and (ii) the kinetic performance through three kinetic models (transfer function-TF, logistic function-LF and modified Gompertz-MG), using Pmax (maximum methane production) and Rmax (maximum rate of methane production) as kinetic parameters related to the hydraulic retention time. The best S/I ratios were below 1.0 gVSsubstrate·gVSinoculum−1 with nutrients. Although the three kinetic models obtained a good fit (R2 > 0.9 and RMSE < 15), the TF model overestimated methane production, due to its high sensitivity for the kinetic parameters, which can lead to oversizing in reactor design.