Algae: fuel of the future?
Algae: fuel of the future?Environ. Sci. Technol., Article ASAPDOI: 10.1021/es902509dPublication Date (Web): September 2, 2009Copyright © 2009 American Chemical Society
Biofuels produced from algae, rather than from crops, have entered the spotlight lately, and several companies now say that they are close to overcoming the technical hurdles to making algae-derived biofuels competitive on a commercial scale. However, experts caution that significant obstacles still need to be dealt with to make algae competitive with energy from fossil fuels.
For several years, entrepreneurs, investors, and even oil companies have been quietly looking to turn the photosynthetic powers of the once lowly and obscure but now coveted green slime, algae, into energy. Industry giants such as Dow Chemical Co., ExxonMobil Corp., BP p.l.c., and Chevron Corp. have recently made major investments in companies seeking to develop renewable fuels from algae, pushing this group of prolific organisms to center stage.
With thousands of strains of algae to choose from—each possessing varying ratios of oils, proteins, and starch in their cells—experts are exploring a wide range of possibilities for harnessing energy from these microbes. For example, the algae can be indigenous strains or genetically engineered organisms. And companies can choose from a diverse range of growing techniques, from inexpensive open ponds to carefully controlled enclosed tanks, to coax algae into secreting the desired product, which might be ethanol, biodiesel, or pump-ready gasoline.
Algae thrive in the presence of sunlight, CO2, and water. They multiply quickly and can be harvested year-round. Unlike conventional biofuel feedstocks such as corn, soy, palm, and canola, algae do not require vast and often valuable tracts of land and ample freshwater to grow, advocates say. Instead, algae can be grown on nonagricultural land in a fraction of the space and with brackish water or wastewater.
In addition, algae are potentially far more productive than other leading oil crops such as palm, canola, and soy. Some companies are reporting that they can produce up to 6000 gallons of fuel per acre per year (gal/ac/yr) from algae, even though they’re not yet operating on a large scale. In comparison, palm yields 650 gal/ac/yr; canola, 150 gal; and soy, 50 gal. And because algae consume CO2, algae companies plan to link up with power plants, cement factories, and other industrial plants to capture heat-trapping CO2 that would otherwise waft into the atmosphere. “There are a lot of opportunities to address multiple problems that might make algae all the more attractive,” says Martha Groom, a conservation biologist who is at the University of Washington Bothell and studies land and habitat issues associated with energy development.
Although algae are relative newcomers on the alternative-energy scene, researchers have been investigating the promise of algae as an energy source for decades. The National Renewable Energy Laboratory (NREL) began researching algae for biodiesel production in 1978, but the program was shuttered in 1996 when the price of oil dropped so low that growing algae for biofuels did not seem economically feasible. NREL researchers also ran into difficulties with contamination by non-native algae species and with the replication of laboratory conditions in the field.
Companies have spent the past few years grappling with such technical hurdles and now say that they expect to be able to produce algae-based biofuels on a commercial scale. Harrison Dillon, cofounder and president of Solazyme, Inc., founded in 2003 and one of the first algae companies to emerge, says that his company has used algae to produce more than 10,000 gal of oil at a quality that meets existing fuel standards. Dillon believes that the company can produce oil from algae at a cost that is competitive with fossil fuels within two and a half years. Other companies are focusing on a similar time frame. Paul Woods, chief executive of the biofuel start-up Algenol Biofuels, says, “I’m a believer that we’re one, two, and three years away from having this on a commercial scale.” And Andrew Beck, vice president of public affairs at PetroAlgae, Inc., an emerging renewable energy company, says that his company is commercial-ready today and that they have signed a license deal for 10 commercial units to be built in China. They hope to begin construction later this year and say that the system will take one to three years to be completed.
Yet some experts warn that, although there is plenty of room for enthusiasm, significant challenges remain. “Just the logistics of bringing [this technology] to a large scale are mind-boggling,” says Jergen Polle, an algae physiologist at Brooklyn College of the City University of New York who has worked on algae for nearly two decades.
One issue is that algae cultures grown in an open pond can easily be contaminated and overtaken by invasive species. So, some companies have opted to grow their algae in enclosed containers that allow them to precisely control the light, CO2, and water conditions needed by various strains of algae. Doug Henston, CEO of the start-up company Solix Biofuels, says, “Closed systems have shown over time that they have significant yield benefits and merits over open ponds.” But others maintain that enclosed growth systems, commonly called “photobioreactors”, are far too costly to make algae competitive with fossil fuels. In addition to production costs, Polle notes that it’s equally important to consider the energy balance of building enclosed systems. “Even if a photobioreactor is 100 times more productive than an open pond, does it then work out in the economics and the energy balance?” says Polle. “All of the materials that go into a photobioreactor cost energy to make.”
Another hurdle is choosing which species of algae to work with from the tens of thousands available. During the 18-year NREL program, researchers sifted through more than 3000 strains of algae from across the U.S. before settling on 300 species that they thought were the most promising oil producers. Some species of algae can yield more than 50% of their weight in oil, while other strains are not as bountiful.
In addition to natural and indigenous species of algae, some companies are experimenting with the genetic engineering of certain algal strains to select for production of the desired product. Solazyme’s Dillon says that after extensive screening, his company found strains that thrive on biomass materials such as corn stover, wood chips, and sugar cane and then spit out oils that can be refined into anything from jet fuel to food oils. “Once we have the feedstock chosen and the product chosen, we use a lot of sophisticated biotechnology to make the conversion of feedstock into the target oil happen very rapidly,” says Dillon. Another company, Joule Biotechnologies, Inc., recently announced that it is working to produce a variety of products, including ethanol and biodiesel, from an undisclosed genetically engineered microorganism that its proprietors will only say is “not algae”.
Although many companies are focused on harvesting oils from algae, the biofuel start-up Algenol Biofuels is betting its future on ethanol. “A lot of algae can make ethanol,” says Algenol’s Woods. “But none of them do it in industrial quantities.” Rather than the usual process of extracting oil by bursting the cells open, Algenol has selected a few strains that “sweat” ethanol through a natural diffusion process, says Woods. And PetroAlgae’s Beck says that its products include a high-carbohydrate lipid mash and a high-value protein. The protein can be sold into the animal-feed market, and eventually, as food supplements for human consumption, he says.
Among the many promising attributes of algae is their ability to harness unwanted CO2 and thrive in less-than-pristine water. Since algae can be grown in brackish and gray water, they do not compete for precious water resources, as agricultural crops do. Solix Biofuels, Inc., has just begun operating a demonstration plant on the Southern Ute Indian Reservation in southwestern Colorado, where it is pumping CO2 and water from a coal-bed methane production plant into its algae growth chambers. The plant is currently producing oil at a rate of 1500 gal/ac/yr, according to Henston, and aims to produce 4000−5000 gal/ac/yr.
If algae were once considered obscure wild cards in the energy field, nobody would say that anymore. In July, ExxonMobil announced that it was investing $600 million to research algae-based biofuels in collaboration with Synthetic Genomics, Inc., a biotechnology company cofounded by genomics pioneer J. Craig Venter. In 2008, Solazyme forged a partnership with Chevron to develop oils for biofuels, and Algenol recently announced a collaboration with Dow Chemical. And in August 2009, BP announced that it is investing more than $10 million in Martek Biosciences Corp., a firm specializing in the development of nutritional supplements from algae, to research biofuels technology.
Dillon notes that when he got into the business in 2003, he never imagined that algae would receive so much attention. “The investment community didn’t know what we were talking about. Back then, they were like, ‘Algae? Fuel? Biology for energy? We don’t get it,” he says. “They know what we’re talking about today.”
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