Wastewater-borne microalga Chlamydomonas sp.: A robust chassis for efficient biomass and biomethane production applying low-N cultivation strategy

Abstract

Biogas/biomethane generation from microalgae biomass via anaerobic fermentation is increasingly gaining attention as CO 2-neutral energy source. Intensive research has shown, however, that microalgae represent a rather challenging substrate for anaerobic digestion (AD) due to their high cell wall recalcitrance and unfavourable protein content. Previously, the utilization of nitrogen-limited (low-N) microalgal biomass for continuous AD-processes was demonstrated (as proof-of-concept) with remarkable biomethane productivity. The present study shows the efficient portability of the low-N cultivation/fermentation strategy on a robust, wastewater-borne microalga isolate that tolerates high temperature and light conditions and can perfectly cope with microbial contaminations. Continuous long-term anaerobic digestion was characterized by stable and efficient specific biogas and biomethane productivity (765 ± 20 and 478 ± 15 mL N g-1 volatile solids (VS) d-1, respectively), equivalent to volumetric methane productivity of 1912 mL N L-1 d-1. The present work underlines the applicability of low-N-biomass of wastewater-borne, robust microalgae as mono-substrate for highly efficient continuous methane generation.