(421ad) Enhanced Biocrude Production by Activated and Anaerobic Digester Sludges Via Cultivation In Sugar-Fed Aerobic Bioreactors

The utilization of microbial communities in municipal sewage anaerobic digester and activated sludges for the production of biofuel feedstock lipids was investigated. Previous studies have found that lipid concentrations in activated sludge increased by 70 % after aerobic cultivation in a high carbon-to-nitrogen (C:N) ratio wastewater supplemented with biomass sugars. Anaerobic digester sludges contain both obligate and facultative anaerobes, the latter of which may be able to grow and accumulate lipids under aerobic conditions similar to activated sludge. This process could potentially reduce waste sewage sludge outputs and utilize existing wastewater treatment plant infrastructure as biorefineries. Anaerobic digester and activated sludges were cultivated in batch bioreactors with glucose as the carbon source at high (70:1) and low (10:1) C:N ratios. The results showed an enhanced lipid content in anaerobic digester sludge similar to activated sludge (13 – 15 % CDW) after fermentation of glucose at high C:N ratio. However, the saponifiable fractions useful for biodiesel production in anaerobic sludge lipids were significantly lower (2 % CDW) than those in activated sludge (7 % CDW). Analysis of the solvent fractions also showed higher triacylglycerol (TAG) accumulations in activated sludge that with anaerobic digester sludge, indicating possible formation of other products. This hypothesis could be supported by the observed formation of pigmented biopolymer-like materials insoluble in hexane during the fractionation process, subject to further characterization.