Cultivation of microalgae using flash hydrolysis nutrient recycle

Algal biofuels have the potential to provide a scalable source of renewable fuels. The high nutrient use in algae cultivation and its recovery and recycle is one of the challenges that may limit the scalability and sustainability of algal biofuels. The present study evaluates the use of hydrolysate obtained after Flash hydrolysis (FH) of Scenedesmus at 280 °C as a nutrient source for microalgae cultivation. FH hydrolysate nutrient recycling was compared with low temperature batch Hydrothermal Liquefaction (HTL) nutrient recycling. Oocystis and Scenedesmus were cultivated using hydrolysate as a partial phosphorous (P) and nitrogen (N) source. The study shows that hydrolysate from FH could satisfy 50% of the nitrogen and phosphorus demand in the culture media. Ammonia toxicity was identified as one potential limitation to higher percentages of N replacement using HTL aqueous phase as it resulted in a high soluble ammonia concentration in the media. This effect was most pronounced in the 50% P HTL replacement treatment where minimal algae growth was observed during the first 11 days of cultivation.