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| Fig. 1: An image depicting an algae harvester. (Source: Wikimedia Commons) |
For over a decade, we have been converting biomass into biofuels to supplement other transportation fuels, such as gasoline. Corn, sorghum, barley, and sugarcane--among other agricultural products--go into the production of ethanol; ethanol is currently blended into nearly all of the gasoline in the United States. As highly productive flora, the organisms that make up algal blooms provide a promising solution for the worlds alarming dependency on fossil fuels. However, the technology for algae conversion is still in its infancy and nowhere near the scale of corn digestion. While many eagerly push for the development of algae-based fuel sources, there are several obstacles to overcome before algae-based biofuel is a viable alternative to fossil fuels.
Algae refers to a wide range of chlorophyll-containing organisms. It can be microscopic unicellular, like phytoplankton, or large and multicellular, like kelp. [1] Which type of algae is most productive for biofuel purposes? Researchers are still working to answer that question. Some variations perform better in different climates with ranges of nutrients. Additionally, there are multiple ways to collect algae in developed and developing countries. One of these methods is shown in Fig. 1.
Algae's high productivity per given acreage is essential to its promise as a renewable energy source. Microalgae have significantly faster growth rates than terrestrial crops. It is reported that the per unit area yield of oil from algae is estimated to be from 20,000 to 80,000 I per acre, per year. This is 7‐31 times greater than the next best crop, palm oil. [4] The most optimistic researchers believe that an acre of algae can produce about 5,000 gallons of biodiesel, whereas an acre of corn can only produce about 500 gallons of ethanol. This should be taken with a grain of salt as the claim has not been publicly documented. With that said, a study has produced results that algae growth supplied fuel at a rate that would yield 1,200 gal/acre/year, if sustained for a year. [5] Additionally, algal growth does not require potable water or arid land, which means that unlike corn, algae farming will not take up resources that could be used for growing food. [1]
However, the amount of space needed to grow these algae fields is significant, as is the amount of water required to grow them. [2] In order to harvest algae on a large scale, researchers must also find a way to provide nutrients, such as iron, sulfur, and nitrogen. Algae require these nutrients and carbon (most commonly carbon dioxide), but to produce these blooms consistently and on a massive scale, researchers must find an efficient way to provide these nutrients en masse. [2] Some of these nutrients are also in high demand by food-bearing agricultural systems. While algae can sequester some carbon dioxide from the air and remove nitrogen from wastewater, atmospheric levels of CO2 may not be high enough to spur exponential algal growth. This is why companies like Solix began siphoning waste carbon from other facilities. In 2007, Solix partnered with New Belgium Brewery to utilize the CO2 generated during their beer's fermentation and boiler processes. They later moved next door to a coal-fueled power plant to maximize CO2 reclamation". [3]
Researchers still require time and resources to establish the most efficient solutions for producing algae to a commercial scale within a range of biomes and for extracting its lipids. Though the environmental costs of algae-based fuel will be substantially lower than that of fossil fuels, the initial selling point of algal fuels will be approximately twofold higher than petroleum. [2] While researchers might be able to find the ideal organism that can fit into the current infrastructure and make sense economically, they will more likely need to splice a variety of organisms.
© Frank Buncom IV. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. Milledge and S. Heaven, "A Review of the Harvesting of Micro-Algae For Biofuel Production," Rev. Environ. Sci. Bio. 12, 165 (2013).
[2] M. Hannon et al., "Biofuels From Algae: Challenges and Potential," Biofuels 1, 763 (2010).
[3] L. Wagner, "Biodiesel from Algae Oil," Mora Associates, July 2007.
[4] A. Demirbas, "Importance of algae oil as a source of biodiesel," Energy Conservation and Management, January 2011.
[5] I. Woertz et al., "Algae Grown on Dairy and Municipal Wastewater for Simultaneous Nutrient Removal and Lipid Production for Biofuel Feedstock," J. Environ. Eng. 135, No. 11 (November 2009).
