Effect of temperature and the Carbon-Nitrogen (C/N) ratio on methane production through anaerobic co-digestion of cattle manure and Jatropha seed cake

Abstract

Anaerobic digestion is a method of agricultural residue transformation used in bioenergy, making these activities energy efficient. However, it can be limited on a larger scale by the availability and diversity of organic residues related to carbon-nitrogen (C/N). Therefore, the anaerobic co-digestion of bovine manure and Jatropha seed cake (Jatropha curcas) were evaluated, with three different C/N ratios, under two conditions: mesophilic (30ºC) and thermophilic (50ºC). Biodigesters were mounted with three replicates for each C/N ratio. The highest production of CH4 was registered after 30 days of processing in the thermophilic condition (C/N 25:1) with 633.95 ± 5.59 mL of CH4 g-1 VS. In contrast, the lowest production was in the mesophilic condition (C/N 20:1) with 208.66 ± 2.61 mL of CH4 g-1 VS. The feasibility of co-digestion of agricultural residues in the production of CH4 as a possible bioenergetic alternative in short periods was demonstrated.