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What Place in Our Energy Future?

(Released April 2009)

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  by Ethan Goffman  


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Algae: Power from Pond Scum


Algal biofuel takes one of the most common, and often scorned, plants on earth, one that grows quickly in polluted and salty water, and turns it into energy for human consumption. Algae is often called a second or even third generation biofuel because it is being developed later than others, and because its proponents think it may be the final word in biofuels. Nevertheless, technically algal fuels "are a first-generation biofuel crop, producing hydrocarbons directly, without the need for a complex chemical process to break down cellulose" (Engineer 2008).

In the process of extracting energy from the sun, algae may be the best organic intermediary, since they "can double their size in a day, making them among the most efficient organisms at converting light energy into biomass" (Nowak). Oil is then extracted from the algae, creating a product "almost chemically indistinguishable from light, sweet crude oil, except that it is green in color" (Hiserodt). From the thousands of algae species, those high in starch are best, since "they need a good supply of carbon dioxide to grow at an acceptable clip, and they can feed on nutrients in sewage, raising the appealing prospect of producing fuel while treating sewage. They are aquatic, but can grow in salty or brackish water so they don't have to compete for the land and water needed to grow food crops" (Nowak).

biodiesel from algae

The difficulty is growing the right algae to make fuel and keeping it pure. In open ponds, algae "are susceptible to being killed off by invasive algae and bacteria"; furthermore "fluctuating temperatures and pH levels also can kill off algae" (Hiserodt). The alternative is a closed system known as a photobioreactor. This also has problems, since "algae produce oxygen, which is highly toxic to the blooms" (Clanton) and it is difficult to introduce "enough carbon dioxide (plant food) into the enclosed systems" (Hiserodt). Even were techniques perfected to grow a desired strain of algae in quantity, much experimentation remains regarding the best method of making fuel.

Algae have additional environmental advantages, notably their ability to sequester carbon, aiding the fight against climate change. GreenFuel Technologies is working on a system to directly siphon gasses from coal; "a coal plant's CO2 emissions, rich food for algae, could be piped into the GreenFuel system, inducing the algae to grow. Since the algae are essentially eating the coal emissions, there would be no need to capture and store the CO2" (Stipp). If implemented on a large scale, this could kill two environmental birds with one stone, producing clean fuel while capturing greenhouse emissions. This process is actually similar to the cycle envisioned for such cellulose plants as switch grass, but algae is far less resistant to being processed into ethanol.

Should the proper technology be developed, Algal fuels would create minimal land use disruption. Theoretically, "displacing gasoline use in the U.S. with hydrogen produced at algae farms would require an algae-growing area of 25,000 sq kilometers, equivalent to about one-tenth of the area the U.S. currently devotes to soybean production" says one researcher (Scott & Bryner). According to another estimate, "all the transportation fuels in the U.S. could be supplied by algae grown on less than 30 million acres of desert, an area equal to about 3% of the U.S. land devoted to farming crops and grazing for animals" (Stipp). The indirect land use problem is almost nil for Algae. Of course the technology is not there yet, but research is proceeding rapidly. Algal biofuel may soon be economically competitive. The trend is remarkable; "in 2006 it cost $3,000 to produce a gallon of algae oil, the price fell to $250 per gallon last year, and it will hit $20 a gallon by year-end [2008] " (Clanton). The U.S. Department of Defense is also working on using algae as a source of jet engine fuel.

Go To The Bigger Picture: Where Might Biofuel Fit in Our Energy Future?

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