Preliminary study of biomethane production of organic waste based on their content of sugar, starch, lipid, protein and fibre

The biomethane potential (BMP) of five organic sources with different proximal composition have been investigated during anaerobic digestion (AD). The organic sources have been selected among different Ecuadorian biomass residues according to the criteria, that each one has a high content of one parameter of interest. Therefore, the five organic sources are: blackberries as a residue high in sugars, avocado for high content in lipids, soybean representing high protein content, green plantain peel for starch and sugarcane bagasse for high fibre content. The experimental setup was developed in batch reactors at the mesophilic regime (35^°C). All experiments are prepared with a reactive mixture composed of inoculum, basal nutritive medium (BM) and the organic material (OM) diluted in water with approximate 10% total solids. The experiment of each biomass was performed in three sequential times. The feed and the final reactive mixture were analysed according to the following parameters: chemical oxygen demand (COD), total solids (TS), total volatile solids (VS), pH, volatile fatty acids (VFA) and nitrogen (N). The biogas production is measured by the water displacement method, while the methane content was analysed by GC-TCD / FID. The results showed that the first experiment with high protein content showed the highest cumulative biogas production with 2300 mL in 21 days, while the three experiments with high sugar content produced in average the most biogas (23 mL/day). The high fibre experiment presented the highest methane content as well as the lowest concentration of VFA with 2667 ± 103 (mgCH3COOH/L). Since the VFA profiles presented higher values for the different concentrations, which was also related with low final pH values of reactive mixture, the lowest pH value (4.6 ± 0.8) was observed for reactors charged with high sugar content.