Improving the biogas production in two-phase anaerobic digester of food waste using sugarcane bagasse-derived biochar

The impact of conductive additives on the two-phase anaerobic digestion (AD) process has been limited. Consequently, in this study, we investigated the impact of different doses of biochar (5, 10, and 15 g/L) on a batch two-stage AD, consisting of acidogenic (1st phase) followed by methanogenic (2nd phase). First, sugarcane bagasse was used as a precursor for the preparation of biochar. The prepared biochar was then employed as a conductive material in two-phase AD of food waste. Compared to the control, the hydrogen and methane production were improved in the biochar-amended digesters. Notably, 10 g/L of biochar dose was optimal for both stages. Additionally, the addition of biochar ameliorated the generation of volatile fatty acids (VFAs) during hydrogen production and the degradation of VFAs during methane production. Principal component analysis (PCA) interpreted the relative performance of the AD conditions with various biochar doses. Hydrogen was detected during the first 10 days as the main component of the biogas with a maximum ratio of 85.6% and maximum yield of 583.2 mL/g VS in the case of using biochar dose 10 g/L, while the highest methane yield (114.5 mL/g VS) was detected on the 15th day using the same biochar dose, and the highest methane ratio was 81.6%. The low content of CO₂ during the biogas production as well as the high biogas production and the effective biodegradation of food waste can support the application of the proposed system on a wider scale.

Graphical abstract