Pilot-scale Assessment of Biohydrogen and Volatile Fatty Acids Production via Dark Fermentation of Residual Biomass

Abstract

This article determines the hydrogen and volatile fatty acids production from a pilot plant's dark fermentation (DF) process, using residual biomass available in Colombia. Previous studies over the biochemical production of hydrogen (BHP) allowed determining the optimum operative conditions to scale the process. The following biomass was used as substrates: pig manure (PM), coffee mucilage (CFM), and cocoa mucilage (CCM). The inoculum was pre-treated by thermal shock to eliminate the methanogenic microorganisms. Based on the physicochemical characterization of the substrates and the inoculum, the experiment was carried out using an organic load of 10 g VS, substrate/inoculum ratio (S/X) of 1:1, and a carbon/nitrogen ratio (C/N) of 35. The pilot plant was operated under mesophilic conditions (35 °C), a pH of 5.5, and a working volume at 80% of the reactor capacity, corresponding to 4 L. The cumulative bio-hydrogen production (CHP) was 3,674.021 mL H2, corresponding to 91.85 mL H2 g VS-1, and the amount of VFA was 4,952 mg COD L-1. The removal of VS was 84.4 %; this, together with the production of VFA, allows suggesting secondary processes associated with biorefinery schemes.