Technique Research For Oil-producing Chlorella Vulgaris Cultured In Biogas Slurry

As one of the main materials of producting biodiesel, microalage is one of the hot renewable energy research spot, which has unique advantages such as not competing with human beings, not competing with the domesticated animals and not competing with livestock feed. But the cost of producting microalgae biodiesel is high, one aspect is high cost of culturing microalgae, this paper conducted studies on microalgae technology as to reduce training costs and purify water, the main research contents and conclusions are as follows:At first, by collecting water samples, purification and preliminary screening, four chlorella algae species were obtained which have higher oil production rate and optimum biodiesel quality indicators Water samples were collected in Beijing river basin such as Xiaoyue river, microscopy and separate microalgae species by spread plate method and dash plate method,8green microalgae species were obtained, which were named as BJ01-BJ08. The chlorella vulgaris which was supplied by project coorperation partner was named BJ09. Culturing the9species of microalgae in the4common green algae medium, oil productivity as a evaluation indicator, the oil productivity of chlorella vulgaris BJ01, BJ05, BJ07, BJ09were higher than other species of microalgae. As viscosity (Vis), iodine value (IV), cetane number (CN) and cold filter plugging point (CFPP) the evaluation indicators, referring to the biodiesel standards of United States, European union, Germany and China, by established mathematical model between fatty acid methyl ester (FAME) carbon chain structure and biodiesel quality items, to evaluate the quality items of4species microalgae biodiesel.Secondly, determination of other active ingredients of the4species to supply the basis of the ultization. The results showed that, the four chlorella cell components in protein, fat and lignin content accounting for about80%, cellulose followed, accounting for about10%. Among the amino acid score(AAS)and essential amino acid index(EAAI) as an indicator of the value of food and forage protein amino acids were evaluated and found that the four kinds of chlorella have high protein of edible and feed value.Thirdly, high oil productivity chlorella and biogas effluent medium were breed and optimized. By different proportional biogas slurry and nutritional deficiencies experiment with oil productivity as an index, to acquire the highest oil productivity microalgae and biogas slurry medium was chlorella vulgaris BJ05in the1/4biogas slurry medium, the highest level achevied was0.294g/L, and the oil productivity of chlorella vulgaris BJ05was not affected without sodium and citrate acid.At last, the culturing conditions were optimazed, and the oil productivity of algae species BJ05was significantly improved. By single factor and orthogonal experiment, the culture conditions (light intensity, temperature, pH and brightness ratio) optimized were light intensity70001x, temperature36℃, pH6and brightness ratio18:6, the oil productivity of chlorella vulgaris BJ05was0.392g/L, which was 1.3times more than0.17g/L on the conditions which was not optimized. The medium breeded and the conditions optimised were well validated when cultured in small-scale in four photoreactors, the oil productivity of chlorella vulgaris BJ05was0.388g/L. The removal rates of Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus (TP) and NH4+-N were90.80%、68.0%、74.04%and80.83%, respectively which can meet the Chinese aquaculture effluent standard.