Improvement of the energy conversion efficiency of Chlorella pyrenoidosa biomass by a three-stage process comprising dark fermentation, photofermentation, and methanogenesis.

Highlights: [•] Saccharification of C. pyrenoidosa is promoted by steam heating with diluted acid. [•] Dark H2 production is remarkably enhanced by using hydrolyzed biomass as feedstock. [•] H2 yield is dramatically increased by the combined dark and photo fermentation. [•] Energy conversion efficiency is markedly improved via co-generation of H2 and CH4. [Copyright &y& Elsevier]