Biogas Production from Lipid-Extracted Algal Residue

Waste-grown microalgae is a potentially important biomass for wastewater treatment, meanwhile lipid extracted from the algae could be further converted into biofuels. The lipid-extracted algal residues as major by-products mainly consist of carbohydrate and protein, which makes anaerobic digestion an efficient way to recover energy. The conversion of lipid-extracted algal residues into methane plays dual role in renewable energy production and sustainable development of microalgal biodiesel industry. Therefore, an anaerobic fermentation process for investigation of methane production potential of algal residues was conducted in this paper. The effect of inoculum to substrate ratios (ISRs) on the methane production by anaerobic digestion of Chlorella sp. residue in single stage was evaluated. The stability and progress of the reaction from algal residues to methane were monitored by measuring the pH, volatile fatty acids (VFAs), total ammoniacal nitrogen (TAN), methane volume. Due to the characteristic of high content of protein in algal residues, the inhibition would occur resulting from the generation of ammonia. Thus two stage technology was proposed and more suitable to improve the methane yield.