Hydrogen production from coffee pulp by dark fermentation.

Abstract

Coffee pulp (C.P.) is a waste of coffee production that needs to be controlled. Due to its high moisture and sugar content, a diagnostic study that characterizes the pulp was conducted and the potential for hydrogen production was evaluated. Subsequently, the kinetics of hydrogen production in a bioreactor were evaluated. A biodegradability index of 0.91 (DBO5/DQO) was calculated, initial pH of the sample was 4.16 ± 0.05, a concentration of total volatile solids (TVS) of 58.1 ± 0.94 [g/L], and total sugar of 19.6 ± 0.79 [g Dextrose/L]. The yield was at 49.2 [NmL H2/g DQOInitial], the hydrogen production per fresh coffee pulp kilogram was 4.18 [L H2/kg C.P.], the energy density was determined at 0.045 [MJ/kg C.P.]. Modified Gompertz parameters were 585 [NmL] for Hmax, 4.1 [NmL H2/g DQO-h] for Rmax and a lag phase (λ) of 92.70 [h]. Because the yield of hydrogen production of coffee pulp estimated was similar to complex substrates like tequila vinasses, and there was a DQO reduction of 13.58%, based on some substrate restrictions, dark fermentation could be a stage of pretreatment of wastewater with coffee pulp in a biogas process to produce two relevant economic and energy products (hydrogen and biogas).