Prevention of algaculture contamination using pesticides for biofuel production

Abstract Compared to terrestrial biofuels, algal biofuels have the advantages of high areal productivity, high oil content and the ability to be cultivated using non-potable water on non-arable land. However, just like terrestrial agricultural crops, algae can be grazed by a wide variety of organisms, particularly in open pond systems. Algal grazers can be controlled using pesticides to make a more sustainable source of biofuels. In this study, we choose Chlorella kessleri as the model freshwater algal producer and select the freshwater rotifer, Brachionus calyciflorus and the freshwater ciliate, Colpoda sp. as the model algal grazers. The pesticides - quinine (QN), niclosamide (NC), 3-trifluoromethyl-4-nitrophenol (TFM), rotenone (ROT) and protons (pH) are used to inhibit algal grazers. C. kessleri is not affected by TFM and NC at concentrations up to 39 and 31 μM respectively, while inhibition of B. calyciflorus is achieved at concentrations of 18 and 14 μM respectively. Colpoda sp. is inhibited by NC at 8 μM, while, QN, TFM and ROT inhibit Colpoda sp. at 30 μM. A pH range between 8.4 and 10.3 inhibits B. calyciflorus and allows C. kessleri to grow well. Compared to previous results using ROT, the findings presented in this study demonstrate that algal grazers may be effectively controlled by using QN, NC and TFM yet may require higher doses than ROT.