Algae Promises Biofuel SolutionsIncreasing investments support microalgae research to solve biofuel process and productivity issues.
by Tim Studt
Researchers at Arizona State Univ. utilize photobioreactors to optimize the lipid output and growth rates of algae-based biofuels. | Second-generation biofuels, like cellulose-based ethanol and biodiesel, have a few problems. First, there’s not enough arable developed land to grow the amount of second-generation feedstocks for the ethanol or diesel biofuels needed to offset imported petroleum (60% of our total use) and meet our gasoline and diesel requirements. Biofuels can and are offsetting some petroleum usage, but the upside scalable volumes are severely limited.
Then there’s the fact that second-generation feedstocks don’t have the high-energy densities of the petroleum-based fuels they’re being asked to replace (76,000 Btu/gal versus 116,000 Btu/gal typically). The total costs of current bioethanol and biodiesel processes are not competitive with petroleum-based processes, and, while progress is being made, they are still substantial sources of greenhouse gases. Finally, these feedstocks offset the food stocks that could be grown in their place.
These issues and the complex processing requirements to convert them into usable biofuels also create a cost structure that’s not competitive with that of traditional fuels.
As such, an alga is being considered as a viable alternative biofuel feedstock. In a recent report by the Wall Street Journal, the editors picked nuclear-, wind- and algae-based biofuels as the most likely alternative energy sources of the future. Numerous supporters believe algae could replace all U.S. liquid fuel requirements in the future while offsetting the carbon dioxide generation of other greenhouse gas sources—when converted into a biofuel and burned, algea emits only the carbon dioxide it absorbed, adding no new CO2 into the atmosphere. All of these are promised, along with the possibility of $1 to $2 per gallon production costs.
The Basics
“The process of sourcing, growing and harvesting clean algae is a complicated procedure,” says Mark Hansen, a principal partner with Stoel, Rives LLP. While the use of algae as a biofuel is a relatively new technology, growing algae is not a new process—it’s been done for nutritional products, nutraceuticals, animal feedstock, wastewater treatment, and CO2 mitigation for a long time.
The primary requirements for growing are sunlight, water and CO2. Algae also require nutrients (nitrates, phosphates, iron and silica) and environmental conditions appropriate to the specific algal species. There are three primary algae cultivation systems being evaluated for biofuel production—open pond-like systems, photobioreactors (PBR), and hybrid systems.
Cultivating microalgae can employ fresh water, but saline or brackish water can also be used. Large waste CO2 sources, like flue gas from a coal-fired or gas-fired power plant, can also be used as a resource for algae biofuel systems.
The vegoil content of algae fuel can be converted in biodiesel, while its carbohydrate content can be fermented into bioethanol. Microalgae (the unicellular algae micro-organisms) have a high lipid (oil) content (~60%) and rapid growth rates (one doubling/day), and produce more lipids per acre than other terrestrial plants (from 10 to 100x). Microalgae also does not compete with food or feed stocks.
While a theoretical maximum value is not yet known for the lipid content of microalgae, some researchers have estimated it to be as high as 85% of their dry cell weight. Higher lipid values in microalgae are, however, also associated with lower growth rates; therefore a biofuel application would not try to maximize lipid content but attempt to develop maximum productivity.
“Making biofuels from algae is all about the economics,” says Nigel Quinn, a water resources engineer at the Lawrence Berkeley National Lab. “In order to cultivate and convert algae into a biofuel, you need huge systems. Right now, algae biofuel can probably be made for a very non-competitive $9 or $10 per gallon.”
The Issues
While developing algae-based biofuels has only recently become relevant to our overall energy-sourcing picture, the failures of ongoing development programs reflect the complexity of this overall process.
One of the largest issues concerning the development of algae into biofuel is the cost of the capital equipment for a pond or PBR process.
Pond systems require vast amounts of land. Harvesting in these systems is done with screens and needs to be automated. Water losses need to be monitoried and controlled, but doing so may adversely affect the systems' economics. Also, the larger the pond, the larger the mixing velocity and mixing power required, the latter of which goes up as a cube of the velocity.
Open pond systems are also prone to contamination, not just from non-biological sources but also from the various algae species that might become invasive. Contaminants could also affect the culture medium (alkalinity and pH).
PBRs are easier to control than pond systems but can cost 10 to 100x more. In a number of cases, organizations over the past 20 years tried PBR systems only to fail due to rising costs.
Gas sources and gas generation also need to be accounted for in the cultivation system developed for algae. For pond systems, a rich source of CO2 needs to be ensured, which reflects on their siting preferences near large power plants. For PBR systems, the generation of O2 from the algae needs to be managed.
Infestations of platyzoan rotifers (near-microscopic animals that eat algae) can also devastate an algae culture, requiring difficult- and expensive-to-clean systems. While a large number of algae species are known to exist, the type most often used in current culturing systems is a wild strain. Little work in the past has been made on selective breeding of algae species, especially for optimal oil yields.
The Industry
Thermo Scientific's Nicolet iS10 FT-IR spectrometer can obtain spectra and lipid content from dried algae. | With all the promises that algae-based biofuels offer, and with economies of scale being one of the barriers to entry, more than 150 industrial companies are looking to create a process that can take advantage of these promises. ExxonMobil R&D Co., for example, announced in 2009 that it was investing $600 million to develop liquid transportation biofuels from algae. Their effort involves a partnership with Synthetic Genomics, the La Jolla, Calif. company founded by genomics pioneer J. Craig Venter. “This agreement represents a comprehensive, long-term R&D exploration into the most efficient and cost-effective organisms to produce next-generation algal biofuel,” says Venter.
Chevron has also partnered with algae biofuel producer Solazyme of South San Francisco and the National Renewable Energy Lab to develop jet fuel and other biofuels from algae. Solazyme’s fermentation process, which is grown in PBRs, is considered to be the closest to maturity.
Sapphire was awarded $104 million as part of the American Recovery and Reinvestment Act (ARRA) of 2009 and the Biorefinery Assistance Program. Sapphire Energy’s Green Crude from algae is a complete drop-in replacement technology for crude oil. The Green Crude can be refined directly into gasoline, diesel and jet fuel. “Sapphire has the largest cultivation of enhanced algal strains, with more than 200 patents in the algal fuel space,” says Brian Goodall, Sapphire’s VP of Downstream Technology.
Melbourne, Fla.-based PetroAlgae licenses commercial micro-crop technologies that enable the cultivation of algae-based biofuels. The PetroAlgae system removes 98% of the water used to grow micro-crops. The process includes large-scale open bioreactors that are harvested via vacuum skimming to stationary screen filters. A screw press dewaters the resulting filtrate, which is then dried and refined into green fuel. PetroAlgae has formed numerous partnerships with U.S. and foreign companies for its large-scale production facilities.
Naples, Fla.-based Algenol Biofuels recently received a $25 million grant from ARRA funds to build a biorefinery in Freeport, Texas. The company is also expanding a plant in Mexico, where it partners with Sonora Fields to commercialize Algenol’s “Direct to Ethanol” process. Their first commercial project is expected this year.
Metrohm's 873 Biodiesel Rancimat analyzer evaluates the fatty acid methyl esters present in oil. | Algenol also stated that it plans to create two new programs: one to create algae-based biofuel from chemical feedstocks and the other in carbon dioxide management. The Algenol process links sugar production to photosynthesis with enzymes within individual algae cells. The naturally occurring enzymes are the same as those used to produce bread, beer, and wine and thus pose no risk to humans.
During a webinar this February, Algenol stated that its prototype production strains were expected to produce ethanol at a rate of 10,000 gal/acre/yr by the end of 2009 and could increase to 20,000 gal/acre/yr.
The Research
A large number of universities are also working on algae biofuels. Milt Sommerfield and Qiang Hu at Arizona State Univ.’s Polytechnic Campus, Phoenix, are developing an algae species that would work well in Arizona’s climate and produce the largest quantities of lipids. They’ve already identified that algae production increases when they’re stressed, which is easily controllable in PBR systems.
Univ. of Arizona, Tucson, researchers are also looking to optimize algae species for hardiness, rapid growth and biofuel capabilities. UA’s Professor Joel Cuello is focusing their research on a PBR they refer to as Accordion, which they use to grow Botryococcus braunii, an oil-rich algae that could be used to produce jet fuel. The device flows water and nutrients through a vertical series of clear polymer panels, allowing the mix to have a controlled flow and steady light gradient.
Martin Spalding, a researcher at Iowa State Univ. (ISU), Ames, is working on stacking traits in the Chlamydomonas algae, similar to the way researchers have developed genetically modified (GM) corn. Working with ARRA funding, Spalding is trying to create algae biofuels similar to their petroleum-based counterparts.
The Instruments
As researchers in industry and academia work to develop and commercialize algae-based biofuel production systems and materials, they’re being aided with specialized instruments.
The Nicolet iS10 FT-IR spectrometer from Thermo Scientific, for example, was originally created for pharmaceutical high-throughput screening systems. It can, however, be applied effectively to the analysis of algae. Researchers are always looking to increase the amount of lipids produced by the algae. To achieve this, FT-IR can be used to characterize the composition of biological samples, including bacteria, single cells, and tissues. FT-IR has been documented as a viable method for determining the protein, carbohydrate, and lipid content in biomass from algae. Configured with a Smart iTR diamond accessory or Smart OMNI-transmission accessory, the iS10 can be used to obtain spectra from dried algae.
Similarly, a Raman-specific 1064-nm spectrometer from BaySpec, Inc. was designed for measuring micro-algae. Using its Nunavut 1064-nm system, researchers are able to overcome characterization issues with fluorescence seen at lower wavelengths.
Metrohm’s 873 Biodiesel Rancimat can be used to evaluate the oxidation stability of fatty acid methyl esters (FAME) present in oil. The amount of water in a biodiesel determines the calorific value and its shelf life. Biodiesel with high water content has a lower oxidation stability.
There also are a number of customized instruments that researchers utilize in the development of algae biofuels. The National Renewable Energy Lab and the Univ. of Colorado, for example, collaborated to purchased a custom BD FaCSAria (Fluorescence Activated Cell Sorter) for high-speed algal cell sorting of populations and individual cells. This keystone system was put into the Colorado Center for Biorefining and Biofuels. Another one of their strategic equipment acquisitions for algae development was a cryopreservation system (MVE Eterne Series) for the long-term maintenance of algal cultures. These cryo systems minimize damage to the algae during low-temperature freezing and storage and thus maintain the long-term cell viability.
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