Cocoa residues as viable biomass for renewable energy production through anaerobic digestion

• Published in: Bioresource technology 2018-10, Vol.265, p.568-572
• Main Authors: Acosta, Nayaret, De Vrieze, Jo, Sandoval, Verónica, Sinche, Danny, Wierinck, Isabella, Rabaey, Korneel
• Format: Article
• Language: English
• Subjects: Agricultural residues; Bio-energy; Biogas; Cocoa waste; Methane
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2018.05.100

•Cocoa waste is a feasible biomass resource for energy production through anaerobic digestion.•Dry anaerobic digestion of cocoa waste has more stable performance.•Up to 88% of the electricity demand of a small region in Ecuador could be potentially covered. The aim of this work was to evaluate the bioenergy potential of cocoa residue via anaerobic digestion. Batch and fed-batch lab-scale reactors were operated under low and high solids conditions. In the batch tests, 59 ± 4% of Chemical Oxygen Demand (COD) was recovered as methane. This corresponded with an average methane yield of 174 (wet) and 193 (dry) L kg−1 volatile solids fed, whereas a series of fed-batch reactors produced 70 ± 24 (wet) and 107 ± 39 (dry) L CH4 kg−1 volatile solids fed during stable conditions. A case study was developed for canton Balao (Ecuador) based on our experimental data, operational estimates and available cocoa waste in the area. Annually, 8341 MWh could be produced, meeting 88% of the current electricity demand in Balao. This case study proves the potential for cocoa waste as a source of renewable energy in rural areas.