Effect of nitrogen management in cultivation on the stability and microbial community of post-harvest Monoraphidium sp. algae biomass

Long-term storage is necessary to mitigate for seasonal variation in algae productivity, to preserve biomass quality and to guarantee a constant biomass supply to a conversion facility. While ensiling has shown promise as a solution, biomass attributes for successful storage are poorly understood. Storage studies of Monoraphidium sp. biomass indicate a strong correlation between nitrogen management in algae cultivation and stability of post-harvest algae biomass. Algae cultivated with periodic nitrogen addition were stored poorly (>20% loss, dry basis) compared to biomass from nitrogen depleted cultivation (8% loss, dry basis). A follow-up study compared the post-harvest stability of Monoraphidium biomass cultivated in nitrogen-deplete or nitrogen-replete conditions. Replete biomass experienced the largest degradation (24%, dry basis), while deplete biomass experienced the least (10%, dry basis). Dry matter loss experienced among blends of each correlated positively with nitrogen-replete biomass content. The composition of the post-storage algae microbial community was also affected by cultivation conditions, with Clostridia species being more prevalent in stored biomass obtained from nitrogen-replete cultivations. Nitrogen management has long been known to influence algae biomass productivity and biochemical composition; here, we demonstrate that it also strongly influences the stability of post-harvest algae biomass in anaerobic storage.