Abstract
Microalgae-derived biodiesel has been regarded as a promising alternative for fossil diesel. However, the commercial production of microalgal biodiesel was halted due to its high cost. Here, we presented a pilot study on the industrial production of algal biodiesel. We began with the heterotrophic cultivation of Auxenochlorella protothecoides in a 60-m3 fermentor that produced biomass at 3.81 g L−1 day−1 with a neutral lipid content at 51%. Next, we developed plate-frame filter, natural drying, and ball milling methods to harvest, dry, and extract oil from the cells at low cost. Additionally, algal biodiesel was produced for a vehicle engine test, which indicated that the microalgal biodiesel was comparable to fossil diesel but resulted in fewer emissions of particulate matter, carbon monoxide, and hydrocarbon. Altogether, our data suggested that the heterotrophic fermentation of A. protothecoides could have the potential for the future industrial production of biodiesel.
Highlights
We will eventually have to face the time when all fossil fuels, i.e., petroleum, natural gas, and coal, run out
Two liters of A. protothecoides cells at the exponential stage was inoculated into each fermentor, for which the temperature, pH, aeration rate, and agitation speed were initially set at 28 ± 0.5°C, 6.3 ± 0.1, 25 m3 h−1 (1:1 vvm), and 360 rpm, respectively
We found that the carbon monoxide (CO) emissions were 35 and 53% lower from the combustion of MBD20 and MBD100, respectively, than that from petroleum diesel (PD) when the engine speed was below 1900 r min−1 and the engine load was below 20% (Figures 5A,B)
Summary
We will eventually have to face the time when all fossil fuels, i.e., petroleum, natural gas, and coal, run out. Climate change might destroy the entire planet if we continue to rely heavily on fossil fuels as we have, and we are already experiencing warming of over 1°C (http://news.yahoo.com/not-run-fossil-fuels-op-ed-231243174.html). Recent advances in drilling and hydraulic fracturing technology to explore shale gas (Weber and Clavin, 2012) are exciting and may relieve concerns about fossil fuels for some time. Even this resource may eventually be exhausted, as it is still not infinite. There continues to be interest in developing new technologies to utilize other renewable and sustainable energy sources, such as solar, wind, geothermal, and biomass (Hidy, 2012)
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