Anaerobic Co-Digestion of Sugarcane Vinasse and Elephant Grass Juice for Biomethan Production

Abstract

In the present study, biogas production was investigated by co-digesting elephant grass juice (EGJ) and sugarcane vinasse using batch reactor. Some factors that influence biomethane production were observed, including initial pH, inoculum concentration and proportions of each substrate. Two tests were carried out. In Experiment I, the following proportions (%v/v sugarcane vinasse/elephant grass juice) were tested: A - 25/75, B - 50/50, C - 75/25, D - 100/0, E - 0/100. In Experiment II, the effect of adding alkalizer to the condition that showed the highest methane production (in Experiment I) was also evaluated. In the Experiment I, the highest accumulated production was observed for the proportion 1:1 corresponding to 50% of EGJ and 50% of vinasse (370.94 mLCH4/gVS). Experiment II showed the higher values of accumulated methane production of 1,364.1 mLCH4/gVS. Regarding addition of alkalizing, a maximum production of 836.18 mLCH4/gVS was obtained in the experimental condition with 50% EGJ and 50% vinasse, but with the lowest addition of alkalizer tested (0.05 g HCO3/gCOD). In general, the use of elephant grass caused the acidification of the reactors and was unfavorable for biogas production.