Anaerobic digestibility of algal bioethanol residue

The aim of this work was to investigate anaerobic digestibility of algal bioethanol residue from saccharification and fermentation processes. A series of batch anaerobic digestion tests using saccharification and fermentation residue showed that the maximum methane yields of saccharification residue and fermentation residue were 239 L/kg VS (Volatile Solids) and 283 L/kg VS (Volatile Solids), respectively. Energy recovered by anaerobic digestion of the residue was 2.24 times higher than that from the ethanol produced in the main process. 5-HMF (5-hydroxymethylfurfural), a saccharification byproduct, could retard methanogenesis at over 3 g/L however, the inhibition was prevented by increasing cell biomass concentration. Anaerobic digestion of residue has the potential to enhance bioenergy recovery and environmental sustainability of algal bioethanol production.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Algal ethanol production generates residue retaining >70% of biomass as energy basis. ► Anaerobic digestion of residue recovered energy 2.24 times higher than ethanol. ► Maximum CH4 yields of algal ethanol residue ranged 239–283 L/kg VS. ► Inhibition of a saccharification by product can be prevented by increasing cell biomass..