Co-digestion of Sargassum sp. with glycerol and waste frying oil: optimization of the biomethane production using a design of experiments

A response surface methodology was adopted to assess the optimal conditions for methane production from the macroalgae Sargassum sp. Three variables were tested: % total solids of algae (%TSsargassum); co-substrate concentration (gwaste L-1); and, co-substrate type (glycerol or waste frying oil (WFO)). The Biochemical Methane Potential (BMP) of Sargassum sp. was 300 ± 3 L CH4 kg-1 COD. The co-digestion with glycerol and WFO increased the BMP by 72% and 68% respectively. The methane production rate (k), showed similar behavior as the BMP, increasing 45% and 29% with glycerol and WFO, respectively. The higher BMP (517 ± 13 L CH4 kg-1 COD) and k (78± 4 d-1) was obtained in the assays with 0.5% TS and 3.0 g glycerol L-1. Co-digestion with glycerol or WFO is a promising process to enhance the BMP from the macroalgae Sargassum sp