Algal biofuels have the potential to provide a scalable source of renewable fuels in the near future. The high nutrient use in algae cultivation and its recovery and recycling 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 50% of the phosphorus required in the culture media could be replaced with Hydrolysate from FH; also, 50% nitrogen was provided from the same source. Ammonia toxicity is one limitation for the higher percentages of N replacement in this study. The HTL aqueous phase had a near continuous high soluble ammonia concentration in the media. The effect was significant for the 50% P HTL replacement treatment where almost no algae growth was observed in the first 11 days of the experiment
