Assessment of the Biohydrogen Production Potential of Different Organic Residues In Colombia: Cocoa Waste, Pig Manure and Coffee Mucilage

Abstract

Colombia has a great potential to produce biofuels based on biomass residues due to the importance of agroindustry in the country’s economy. The diversity of this industry guarantees the availability of different residues which are susceptible to be valorised through biological processes. There are several works, in the country, focused on biomass use to produce bioethanol and biodiesel. Nevertheless, the biohydrogen production using residual biomass has been scarcely studied. Dark fermentation and anaerobic digestion processes allow the degradation of substrates such as agricultural biomass and agroindustrial waste in order to produce hydrogen and methane, respectively. These residues are highly biodegradable, have low cost and have high availability. In this study, an assessment of the biohydrogen production potential by various organic residues (coffee mucilage, cocoa waste and pig manure) was carried out. The biohydrogen production potential of each residue was conducted in batch reactors (250 mL bottles). In order to maintain a mesophilic condition, an immersion thermostatic bath was used. Biological methane potential was evaluated to compare the energy recovery through hydrogen and methane for each substrate. Soluble products as volatile fatty acids and total reducing sugars were measured to characterize the dark fermentation process. The batch experiments were evaluated until the production rate of hydrogen and methane was reduced substantially. In all cases, the biomass demonstrated its versatility and capacity to produce biohydrogen. Maximum production was reached during dark fermentation process of coffee mucilage with a cumulative hydrogen production of338.9 mL and a maximum hydrogen production rate of 47.0 mL/d. However, the dark fermentation experiments showed instability with high standard deviation for production values. Despite the instability, the energy recovery from coffee mucilage through dark fermentation was 10 times above the energy produced by anaerobic digestion.