PNNL

Abstract

Atmospheric carbon dioxide (CO2) concentrations are increasing and will cause unknown deleterious environmental effects if left unchecked. The Intergovernmental Panel on Climate Change (IPCC) has predicted in its latest report a 2ºC to 4ºC increase in global temperatures even with the strictest CO2 mitigation practices. Global warming can be attributed to in large part to the burning of carbon-based fossil fuels, as the concentration of atmospheric CO2 is directly related to the burning of fossil fuels. Biofuels which do not add CO2 to the atmosphere are presently generated primarily from terrestrial plants, i.e., ethanol from corn grain and biodiesel from soybean oil. The production of biofuels from terrestrial plants is severely limited by the availability of fertile land. Lipid production from microalgae and its corresponding biodiesel production have been studied since the late 1970’s but large scale production was determined to be economically unfeasible due to the large costs of sterile growing conditions required for many algal species. This study focuses on the potential to use the halophilic microalgae species Dunaliella salina as a source of lipids and subsequently for biodiesel production. The lipid production rates were compared for D. salina cultured in replicate photobioreactors under high light and low light as well as nitrogen sufficient and nitrogen deficient culture conditions. The results show (a) cellular lipid content ranging from 16 to 44% (wt), (b) a maximum culture lipid concentration of 450 mg lipid/L, and (c) a maximum integrated lipid production rate of 46 mg lipid/L culture*day. The high amount of lipids produced suggests that D. salina, which can be mass-cultured in non-sterile outdoor ponds, has a strong potential to be an economically valuable source for renewable oil and biodiesel production.