Application of biotechnology to construct a sustainable biodiesel production system on wastewater

The potential of microalgae biodiesel is unlimited. The ingenious combination of microalgae biomass exploitation, decontamination of municipal wastewater, and CO₂ fixation may gestate the ultimate hope for solving the problem of liquid alternative fuel. However, the municipal wastewater has some characteristics, such as high content of nitrogen and phosphorus, low C/N ratio, fluctuation of loading rate, toxicity of heavy metal, etc. To overcome these problems, studies are currently underway in our laboratory. In this paper, an idea of constructing a sustainable biodiesel production system from microalgae on wastewater is assumed. The system could realize CO₂ fixation, decontamination of municipal wastewater, and production of high value-added biodiesel by microalgae. Firstly, municipal wastewater is used as the cultivation media and CO₂ as gaseous fertilizer for mass culture of Shuihua microalgae. So with the harvest of large quantities of low-price Shuihua microalgae, the nitrogen, phosphorus and heavy metals can be removed from the wastewater, and the emission of greenhouse gas can be reduced. Secondly, try to breed a high-oil content engineering microalgae by heterotrophic cultivation which could realize high-density growth through the conjunction of the advanced methods of fermentation engineering with the microalgae breeding technology. Finally, make the high-oil content engineering microalgae cultivated on the decomposed Shuihua microalgae cells, and try to make the high-oil content engineering microalgae grow rapidly in the initial stage and start oil accumulation when nitrogen is exhausted by controlling the conditions of fermentation.