Algae: fuel of the future?
PETROALGAE
water to grow, advocates say. algae for biodiesel production in Biofuels produced from algae, Instead, algae can be grown on 1978, but the program was shutrather than from crops, have ennonagricultural land in a fraction of tered in 1996 when the price of oil tered the spotlight lately, and sevthe space and with brackish water dropped so low that growing algae eral companies now say that they for biofuels did not seem economior wastewater. are close to overcoming the technically feasible. NREL researchers In addition, algae are potentially cal hurdles to making algae-derived far more productive than other also ran into difficulties with conbiofuels competitive on a commerleading oil crops such as palm, tamination by non-native algae cial scale. However, experts caution species and with the replithat significant obstacles cation of laboratory condistill need to be dealt with tions in the field. to make algae competitive Companies have spent with energy from fossil the past few years grapfuels. pling with such technical For several years, entrehurdles and now say that preneurs, investors, and they expect to be able to even oil companies have produce algae-based biofubeen quietly looking to turn els on a commercial scale. the photosynthetic powers Harrison Dillon, cofounder of the once lowly and oband president of Solazyme, scure but now coveted Inc., founded in 2003 and green slime, algae, into enone of the first algae comergy. Industry giants such panies to emerge, says that as Dow Chemical Co., Exx- Open-pond bioreactors at the PetroAlgae facility in Fellshis company has used alonMobil Corp., BP p.l.c., mere, Florida. gae to produce more than and Chevron Corp. have canola, and soy. Some companies 10,000 gal of oil at a quality that recently made major investments are reporting that they can produce meets existing fuel standards. Dilin companies seeking to develop up to 6000 gallons of fuel per acre lon believes that the company can renewable fuels from algae, pushper year (gal/ac/yr) from algae, produce oil from algae at a cost ing this group of prolific organisms even though they’re not yet operatthat is competitive with fossil fuels to center stage. ing on a large scale. In comparison, within two and a half years. Other With thousands of strains of alpalm yields 650 gal/ac/yr; canola, companies are focusing on a simigae to choose fromseach possess150 gal; and soy, 50 gal. And belar time frame. Paul Woods, chief ing varying ratios of oils, proteins, cause algae consume CO2, algae executive of the biofuel start-up and starch in their cellssexperts companies plan to link up with Algenol Biofuels, says, “I’m a beare exploring a wide range of possipower plants, cement factories, and liever that we’re one, two, and bilities for harnessing energy from other industrial plants to capture three years away from having this these microbes. For example, the heat-trapping CO2 that would othon a commercial scale.” And Analgae can be indigenous strains or erwise waft into the atmosphere. drew Beck, vice president of public genetically engineered organisms. “There are a lot of opportunities to affairs at PetroAlgae, Inc., an And companies can choose from a address multiple problems that emerging renewable energy comdiverse range of growing techmight make algae all the more atpany, says that his company is niques, from inexpensive open tractive,” says Martha Groom, a commercial-ready today and that ponds to carefully controlled enconservation biologist who is at the they have signed a license deal for closed tanks, to coax algae into seUniversity of Washington Bothell 10 commercial units to be built in creting the desired product, which and studies land and habitat issues China. They hope to begin conmight be ethanol, biodiesel, or associated with energy developstruction later this year and say pump-ready gasoline. ment. that the system will take one to Algae thrive in the presence of Although algae are relative newthree years to be completed. sunlight, CO2, and water. They comers on the alternative-energy Yet some experts warn that, almultiply quickly and can be harscene, researchers have been investhough there is plenty of room for vested year-round. Unlike conventigating the promise of algae as an enthusiasm, significant challenges tional biofuel feedstocks such as energy source for decades. The Naremain. “Just the logistics of bringcorn, soy, palm, and canola, algae tional Renewable Energy Laboraing [this technology] to a large do not require vast and often valutory (NREL) began researching scale are mind-boggling,” says Jerable tracts of land and ample fresh7160 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / October 1, 2009
10.1021/es902509d
2009 American Chemical Society
Published on Web 09/02/2009
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 SOLAZYME
gen 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
Solazyme scientist pours crude algal oil for testing and evaluation.
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.” —AMANDA LEIGH MASCARELLI
October 1, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 7161
