Biochemical methane potential of agro-wastes as a renewable source alternative for electrical energy production in Cuba

The present Cuban economic model focuses on renewable sources of energy production, according to sustainable development strategies for 2030. However, the strategies do not consider biogas (or methane) due to, among other reasons, a lack of knowledge of its actual potential. Following the methodology of the batch anaerobic digestion process, the study shows the biomethane potential contained in the most critical agricultural solid wastes generated in Cuba, i.e., rice straw, cane straw, corn straw, bean straw, banana straw (leaves), coffee husk, and parchment coffee. Biochemical Methane Potential (BMP) was assayed by lab-scale (585 ml) batch reactors, using the pig manure anaerobic sludge as inoculum under mesophilic conditions (35 +/- 2 degrees C). Physicochemical parameters (total volatile solids, pH, alkalinity, volatile fatty acid concentration, and alkalinity ratio) were determined for process stability, quantifying the biogas production daily. Subsequently, the BMP was calculated for all substrates. The results showed that corn straw (0.42 l CH4 per gram of volatile solids) contained the highest biomethane potential. Stability on all systems was obtained, demonstrating the viability of the inoculum used to start digesters that treat this waste. The total potential methane obtained was 1258 106 m3/year, which is enough to generate 3,750 GWh of power per year-equivalent to 18 % of the total annual electricity generation in the country.