Recycled wastewater from anaerobic digestion of lipid extracted algae as a source of nutrients

Nutrient supply, especially nitrogen and phosphorus, is one of the key obstacles limiting industrialization of algal biofuel. To help enhance nutrient utilization efficiency, our research focused on recycling of nutrients from lipid extracted algae biomass by the method of anaerobic digestion. Two methods of lipid extraction were performed, nutrients were released during anaerobic digestion of the lipid extracted biomass, the recycled nutrients were collected for algae cultivation, and the cycle was repeated: cultivation-extraction-digestion-cultivation. The results show that anaerobic digestion released nitrogen and phosphorus, and methane as a gaseous by-product. The algae grew well on the recycled nutrients. Ammonia is the limiting macro element, and extra trace elements enhanced algae production as well. Ash free dry weight, lipid content and lipid components were monitored and did not vary when the cycle was repeated. This system for recycling nutrients with supplementary nutrients holds potential for producing biofuel from algae.