Effect of flocculants and pretreatment on the co-digestion of microalgae biomass to methane production

Microalgae biomass is a promising feedstock for the production of biofuels, while the harvesting process is still a bottleneck. This study tested the hypothesis that flocculants and pretreatment do not influence the methane production through the co-digestion of microalgae biomass with sewage sludge. The following flocculants were applied to the microalgae biomass: cationic starch, modified tannin and aluminum sulfate. Sodium hydroxide at 27°C for two hours was used as pretreatment. Microalgae culture lasted 7 days until the harvest. Before the pretreatment, the highest methane volume was observed on modified tannin flocculated biomass. Differently, after pre-treatment, the highest methane production was detected on cationic starch biomass. Only the experiments with aluminum sulfate showed a non-significant difference between before and after pretreatment. Finally, organic flocculants and pre-treatments can contribute to the recovery of microalgae biomass and the increase in methane production.