Greg Goddard, Los Alamos National Laboratory bioscience division, concentrates algae using innovative ultrasound technologies he invented for this purpose.
A Biofuels Consortium
December 2009 / January 2010
Volume 7 Number 6
For decades, researchers have recognized the potential for abundant, renewable fuels produced from photosynthetic organisms such as plants and algae. However, certain breakthroughs are necessary to produce enough biomass and to efficiently release the energy stored in these organisms' cells in order to create cost-effective fuels that could be competitive. A consortium of 28 partners from national laboratories, industry, and academia—€”the National Alliance for Advanced Biofuels and Bioproducts (NAABB)—€”has brought together unique ideas and long-standing expertise that, combined, stand to revolutionize the production of biofuels.
Similar to other photosynthetic organisms, algae converts solar energy, CO2, and water to chemical energy. The chemical energy is then stored as lipid oil that can be converted to fully fungible biofuels; these fuels have a higher energy content than alcohols (such as sugar-based fuels from corn) and are compatible with the existing petroleum refining infrastructure, making them more desirable. Other advantages of algae are that they do not require vast amounts of rich agricultural soil to grow, or need large amounts of clean water. Despite these advantages, the costs for industrial-scale production of algae are high and the harvesting and extraction methods currently used require expensive, hazardous chemicals, or are energy inefficient. To overcome these obstacles, NAABB scientists are addressing problems at multiple steps of the production process to achieve the most overall efficiencies and cost savings.
Although initial projects and efforts are focused on algae as a feedstock, many of the techniques could also be applied to other types of biomass; the partners are actively investigating all options.
"The transportation problem is so big that we should take advantage of lignocellulose from arid lands, and algal lipids from coastal, non-arid lands, plus the most efficient extraction methods to meet the energy needs of the country," said Cliff Unkefer, group leader for the bioenergy and environmental science group at the Los Alamos National Laboratory.
Key to making biofuels viable is increased algal growth and lipid production. Based on research in the stable isotope-based metabolomics lab, one NAABB partner already has several licensed patents for methods of enhancing biomass. One such product, Take-off—„, is currently being marketed worldwide has now been shown to improve both growth rate and lipid production in algae. Furthermore, NAABB scientists have made breakthroughs in the advanced management of key nutrients such as Nitrogen and Carbon Dioxide to reduce cycle times and effectively optimize algae biomass and lipid production.
Another approach taken by NAABB scientists is to engineer algae to have reduced harvesting antennae. This is important because the extensive light harvesting antennae required for survival in the wild limit productivity by algae under the high light conditions of industrial ponds or bioreactors. In deeper ponds and under high light conditions, algae engineered—€”by NAABB scientists—€” to have reduced light harvesting antennae accumulated 40 percent more biomass than did wild-type algae.
Overall, NAABB partners use a "systems biology" approach for fundamental characterization of the gene regulation and metabolic flux in lipid and hydrocarbon biosynthesis pathways. For instance, genomes from various algae strains are sequenced and analyzed and proteomic analysis is then used to determine protein levels during lipid production.
For algal biofuels to be economically viable, two to five grams or more of dry weight algae per liter would be required. This equates to nearly 200-500 grams of water having to be removed for each gram of algae; most current methods of doing so are not cost-effective and create many waste streams. Research has led to a novel technology using acoustic focusing to concentrate and separate algae for lipid extraction.
Acoustic focusing works by exposing suspended particles to an acoustic standing wave, through which they experience a time-averaged drift force. The force exerted on the particles depends upon frequency of excitation, pressure amplitude within the medium, and the relative density/ compressibility contrast between the particle and the host medium. By changing the geometry of the field, it is possible to spatially separate particles to the node and anti-node of the standing wave fields, depending on differences in fluid and particle density. This technology offers a very efficient way of removing the water from algal biomass.
Oil extraction—€”the next step—€”is one of the more costly processes and can alone determine the viability of algae-based fuels. Again, research in acoustics has produced a viable solution. This strategy uses ultrasonic lysis, which can proceed by two different nonlinear acoustic phenomena: shear forces due to streaming and acoustic bubble nucleation. Once the lipids are released from the cells, the technique takes advantage of the physical property differences of oils, water and cell debris to purify and fractionate the lipid and protein components from the lysed sample.
To be competitive with fossil fuels, it is essential that biofuels take advantage of existing fuel production infrastructure, and existing vehicles. To this end, the NAABB has industry and academic partners that are investigating ways to modify algal oil to "drop in" fuels.
Additional efficiencies and cost savings for biofuels can be made in the areas of resource management and byproduct development. For instance, after lipid extraction, the left-over algal biomass can be readily transformed into a high-protein livestock feed. NAABB partners have extensive experience in agricultural studies and are leading the effort to develop methods to convert the lipid extracted algae to healthy livestock feed. This not only creates an additional revenue stream to offset the cost of making fuel, but also is an opportunity for nutrient cycling making the overall process more efficient and CO2-neutral.
In fact, because in some algal species lipid production is induced by nitrogen limitation, essentially all of the nitrogen used for growth is captured in the protein fraction of the algae. Thus, animal feed derived from algal cultures is produced with three times the nitrogen efficiency of traditional agricultural methods.
"As a strategic partnership, the NAABB is able to coordinate the most promising research from institutions and industry from across the country, to test technologies, and maintain the dynamic ability to modify and redirect efforts to reach the best possible outcomes for a viable biofuels industry," said José A. Olivares, NAABB executive director and bioscience division deputy division leader at LANL.
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