Optimization of the production and quality of biogas in the anaerobic digestion of different types of biomass in a batch laboratory biodigester and pilot plant: Numerical modeling, kinetic study and hydrogen potential

Abstract

The study aims to evaluate the biogas production and quality from four biomasses (microalgae (MB), sorghum (S), corn stubble (CS), rapeseed oil (RO)) in a digestion process carried out in two batch reactor (6 L) and pilot plant (1.5 m3) agitated mechanically.

The substrates were characterized and anaerobic digestion was carried out as batch tests in mesophilic conditions for 30–35 days. Inoculum/substrate ratio was 1:1–2:1. Gas composition and total gas volume produced were monitored. Methane yields of 306, 345, 419, and 740 NL kg VS−1 were obtained for MB, CS, S, and RO, respectively, in laboratory tests, while in pilot plant tests were 182, 151, 397 and 655 NL kg VS−1. CH4 percentage in biogas was 49–60%. The yield of H2 generated for the four biomasses in the two types of biodigesters has been estimated, obtaining values between 16 and 39 mL g VS−1.

First-order, Modified Gompertz, and Cone models have been applied to evaluate the kinetic parameters on the methane produced in the batch and pilot plant tests, obtaining an excellent fit. ADM1 model with 19 biological processes (disintegration of biomass composite, enzymatic hydrolysis, and digestion of soluble materials mediated by organisms), acid-base equilibria, kinetic study, and liquid-gas transference has been used to fit the cumulative methane volume.