Intensifying Clean Energy Production Through Cultivating Mixotrophic Microalgae from Digestates of Biogas Systems: Effects of Light Intensity, Medium Dilution, and Cultivating Time
High-strength wastewaters after being digested for biogas production in anaerobic digesters still contain substantial nutrients and organics. The anaerobic digestates from four major industries in Thailand were tested with batch cultivation of Chlorella sp. for oil production potentials. Pig farm digestate was found most suitable as the growth medium generating 0.95 g/Lmedium (dry biomass), which was 1.16–3.06 times of other digestates tested. Considerable removals of nitrogen and phosphorus achieved were an added benefit to the goal of ultimate treatment of these wastewaters. Light intensity had strong influence on growth and heterotrophic metabolism up to 78 μmol/m2/s, while the dilution of digestate above 2.4× diminished growth potential and lipid production. A quadratic regression model was constructed to describe interaction of light intensity, dilution factor, and time of cultivation to lipid production with a satisfactory precision. Light intensity could influence fatty acid composition, although palmitic acid was found predominant at 47.1 %. The algae oil generated could potentially increase the total energy output from anaerobic digesters of a typical pig farm by 22 %.
KeywordsChlorella sp. Lipid Light Digestate Dilution Biogas
This research was financially supported by the Annual Research Budget of the Prince of Songkla University (PSU) contract no. ENG570183S and Graduate School of PSU, Thailand. The authors would like to recognize the full support for research facility of the Biogas and Biorefinery Research Laboratory, Faculty of Engineering, Prince of Songkla University, Thailand.
- 1.Thaibiogas. (2015) Thailand Energy Policy and Planning Office. 2015. http://www.thaibiogas.com/index2.php. Accessed 20 Mar 2015
- 10.George B, Pancha I, Desai C, Chokshi K, Paliwal C, Ghosh T, Mishra S (2014) Effects of different media composition, light intensity and photoperiod on morphology and physiology of freshwater microalgae Ankistrodesmus falcatus—a potential strain for bio-fuel production. Bioresour Technol 171:367–374CrossRefPubMedGoogle Scholar
- 15.Dumrattana P, Tansakul P (2006) Cultivation of the hydrocarbon-rich alga, Botyococcus braunii in secondary treated effluent from a sea food processing plant. Songklanakarin J Sci Tech 28:99–105Google Scholar
- 16.APHA, AWWA, WPCF (2012) Standard methods for examination of water and wastewater. American Public Health Association, Washington, DC.Google Scholar
- 19.Folch J, Lees M, Stanley GHS (1957) A simple method for the isolation and purification of total lipids from animal tissues. J Biol Chem 266:497–509Google Scholar
- 20.Collos Y, Berges JA (2004) Nitrogen metabolism in phytoplankton, Encyclopedia of Life Support Systems (EOLSS). EOLSS Publishers, OxfordGoogle Scholar
- 23.Khan M, Yoshida N (2008) Effect of L-glutamic acid on the growth and ammonium removal from ammonium solution and natural wastewater by Chlorella vulgaris NTM06. Bioresour Technol 99:572–582Google Scholar
- 27.Saifuddin N, Saltanat A, Refal H (2014) Enhancing the removal of phenolic compounds from palm oil mill effluent by enzymatic pre-treatment and microwave-assisted extraction. Chem Sci Trans 3:1083–1093Google Scholar
- 29.PCD (2015) Water Pollution Regulation, Pollution Control Department of Thailand. http://www.pcd.go.th/download/en_regulation.cfm?task=s3. Accessed 26 April 2015
- 37.Droop MR (1973) Some thoughts on nutrient limitation in algae 1. J Phycol 9:264–272Google Scholar
- 39.DEDE (2006) Technology for biogas production and utilization. Department of alternative Energy Development and Efficiency, Bangkok, ThailandGoogle Scholar