| Energy is the foundation and motivation of human society development. With the explosive growth of productivity since the industrial revolution, energy began to have an profoundly impact on national development and people’s life. The traditional fossil energy, such as oil, natural gas, coal and so on is about to run out due to reliance on petrochemical energy excessively. Looking for new renewable energy to replace the traditional fossil fuels has become very urgent. However, the production of microalgal biofuels has not yet sufficiently cost-effective to reach commercial production level, and one of the limiting factor is lack of excellent strains. Nannochloropsis oceanica can grow fast, has high oil content and strong resistance, and has been regarded as the potential to exploit.In this paper, six Nannochloropsis strains (named 3-5,4.38,3-25,3-26, KA2 and 75B1 respectively) are selected to be as research objects and evaluated under the laboratory, pilot, and large-scale culture conditions.The main results are as follows:(1) The 6 strains treated with chemical mutagen were purified and cultured with ventilation and their growth rates, total lipids, neutral lipids and fatty acid compositions were also evaluated under laboratory conditions. The results showed that the 6 strains had smaller gaps in terms of specific growth rates, and their total lipids contents were more than 30% of dry weight, and fatty acid compositions contained a large proportion of saturated fatty acids and monounsaturated fatty acids. To sum up, the 6 strains had great potential for biodiesel production.(2) 6 strains of Nannochloropsis oceanica were cultured and evaluated at pilot scale. After ten days of culture,2 algal strains named 3-25 and 75B1 were selected due to their high total lipids, which were 33.49% and 29.36%, respectively. What’s more, their oil productivity reached 10.04 mgL-1d-1 and 8.07 mg L-1d-1,respectively. The C16 and C18 series contents of the two algal strains accounted for 72.71% to 68.05%, respectively, and were found to consist largely of the saturated fatty acid (SAFA) palmitic acid (C16:0) and the monounsaturated fatty acid (MUFA) palmitoleic acid (C16:1), which is ideal for biodiesel production.Strain 4-38 performed better than the other five as it contained higher amounts of triacylglycerols and fatty acids (The C16 and C18 series contents reach up to 76.32%), which are used for biodiesel production.(3) The high cost of microalgae biodiesel production restricted the industrialization of biodiesel. Highly effective and economically feasible biomass generating techniques are essential to realize such potential. Flue gas from coal-fired power plants may serve as an inexpensive carbon source for microalgal culture, and it may also facilitate improvement of the environment once the gas is fixed in biomass. In this study, among the 6 algal strains,3 strains of the genus Nannochloropsis (4-38, KA2 and 75B1) survived this type of culture and bloomed using flue gas from coal-fired power plants in open raceway ponds. Lower temperatures and solar irradiation reduced the biomass yield and lipid productivities of these strains. Strain 4-38 performed better than the other two as it contained higher amounts of triacylglycerols and fatty acids, which are used for biodiesel production. Further optimization of the application of flue gas to microalgal culture should be undertaken.In conclusion, this research successfully verified the feasibility using Nannochloropsis to produce biodiesel.3 algal strains with stable growth were selected using flue gases as carbon source generated from power plants. This kind of training mode can not only effectively reduce power plant flue gas emissions, but also minimize the cost of microalgal cultivation. In consequence, it is feasible for large scale cultivation, and worth spreading. |
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