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Algae-Based Energy Burns With Potential

April 2007
By Henry S. Kenyon

 
Sandia National Laboratories researcher Todd Lane withdraws a sample for analysis from a large culture of microalgae used to produce biodiesel.
Common aquatic plants offer economies of scale without affecting competition for food, land resources.

Scientists are turning humble pond scum into fuel. A research effort seeks to develop techniques to grow algae economically and to convert the oils produced by the tiny plants into biodiesel on an industrial scale.  

This program is one of several alternative energy projects under way at Sandia National Laboratories’ Livermore, California, facilities. One of the promises with algae is that more oil potentially can be extracted on a per-pound basis than from any other type of vegetable-based fuel, says Blake Simmons, the manager of Sandia’s energy systems department.

Sandia’s California laboratory has operated a combustion research facility for some 25 years to investigate, evaluate and optimize engine performance. Simmons explains that since the center was established, it has conducted research into a variety of fuels. “Alternative energy research at Sandia has been going on for quite a long time,” he states.

The combustion research facility recently began studying the flame and ignition characteristics of biodiesel derived from vegetable oil. Simmons notes that in the past two years, Sandia has seen a surge in biofuels research. This work is funded by several million dollars from internal investment efforts such as the Laboratory Directed Research and Development Program that spends discretionary funds on selected technology proposals. 

“The primary motive is to help balance the nation’s transportation fuels supply by putting a renewable element in it,” he says. Of these internal research programs, five or six now are fully established and investigating the creation of alternative fuels such as biodiesel, ethanol and butanol. One of these efforts, which has been underway for the past 15 months, is genetically engineering the metabolism of certain algae to enhance oil production for conversion into biodiesel.

Algae typically build up oils in their bodies when limited nutrients are available in their environment. The challenge is in optimizing the growth environment—the water they are grown in—for nutrient-limited conditions, temperature and the desired rate of oil production and storage. Algae create oil in the form of triglycerides in their cell vacuoles.

But finding the right growth medium is only a small part of the project. To produce oil in industrial quantities, Sandia researchers must genetically alter the algae. And once the algae can be made to produce enough oil, Simmons notes that the last challenge is to extract and process the oil into biodiesel.

Simmons explains that various species of algae have different metabolic functions to survive in specific environments. For example, scientists use green algae to produce hydrogen. Other types of algae are not good hydrogen producers but are adept at producing oil. He adds that up to 60 percent of the weight of some algae is in triglycerides that can be converted into biodiesel products. The challenge is that while algae produce more oil with less nutrients, algae do not grow and reproduce as quickly when fewer nutrients are available. Researchers hope to overcome this impediment by modifying the algae’s genetic structure to maximize both oil production and growth.

Sandia’s research is built on groundbreaking work conducted by the National Renewable Energy Laboratory (NREL), Denver, in the late 1980s and early 1990s. The NREL’s Aquatic Species Program studied algae to determine the best means to produce fuel stock. The program examined how algae made and stored oil and searched for the species that were most suitable for industrial use. Simmons maintains that the knowledge generated by the initiative was essential to all further research. However, the NREL program was unsuccessful because researchers did not have the genetic tools to make viable quantities of algae-derived biodiesel. “The [NREL’s] final report is depressing in the historical sense because they were cut off right as the genomics explosion occurred around the world,” he says.

Sandia scientists now have the genetic sequences of several species of algae that can be engineered to enhance oil production. “That is the power of the genomics age. We have the genomic tool box,” Simmons states. “We can hopefully manipulate these organisms so that we don’t have to achieve such a delicate balance,” he continues, explaining that without this manipulation, scaling up is an unwieldy problem. “This has to be a scalable solution if we’re going to make any kind of a dent on diesel use in the United States. It has to be a massive operation if it is to achieve its promise,” he emphasizes.

Simmons notes that most small commercial biodiesel operations buy feedstock oils from supermarkets or fried fats from restaurants. He explains that this oil already is processed and ready for conversion into fuel. But to make fuel from algae, a completely different system of harvesting, extraction and conversion is needed. And an algae-based fuel system requires a large-scale operation to be efficient. “That is why you need to develop an algae to get the most oil for your buck,” he says.

Algae have several advantages over other types of vegetable-based alternative fuel production systems. The first is that they are not feedstock. This is important because there is no supply and demand balance between competing market forces to use the algae for fuel or food. Simmons notes that vegetable oil is the leading source for biodiesel production, and it usually is derived from feedstock with food applications. “You have two orthogonal market forces there. Once you start increasing the demand for one, you start negatively impacting the supply economics for the other,” he shares.

Industrial algae production also avoids the water usage problems found with intensive agriculture. Algae can use brackish or salty water that is not suitable for agriculture and can grow in ponds on marginal land. Irrigation is not necessary, and the algae can be harvested almost continuously depending on the region that they are grown in.

Simmons notes that water and how agricultural development impacts water resources are major concerns. Sandia has an extensive program under way to understand the energy-water nexus and what the balance of forces is between energy for water and water for energy. Researchers also are using this work to examine the energy-water-agriculture connection. This research will enable them to understand better how biofuels research and biomass research may impact the nation’s water supply. He believes that this effort can serve as a guide for the algae research in terms of selecting strains that are viable and sustainable.

 
Sandia researcher Blake Simmons, manager of the energy systems department, processes algal extracts with a high-throughput robotic fluid handling system for analysis before conversion into biodiesel.
Another advantage of algae as a source of petrochemicals and hydrogen is that they have a much higher oil yield than any other vegetable or feedstock. Simmons observes that algae require less land to produce a significant part of the nation’s transportation fuel supply than if plants or trees were grown for the same purpose. “The energy density, or energy per unit area for algae, is theoretically much higher than for plants or herbaceous materials,” he says.

Sandia scientists currently are establishing the research baselines necessary to understand oil production in a certain kind of algae known as diatoms. “We are just now getting a glimpse of the metabolic pathways that will enable us to engineer them,” Simmons shares.

The laboratory has begun several programs examining industrial-scale algae growth and processing operations. One is a U.S. Defense Advanced Research Projects Agency (DARPA)-sponsored program to develop bio-derived JP8 aviation fuel. Simmons explains that this project has two aspects: creating the industrial process and modifying the algae. Sandia is working with a commercial firm to meet DARPA’s requirements. One of this program’s goals is to produce 100 liters of bio-JP8 as a demonstration, he says.

Sandia also signed a memorandum of understanding with a biofuels firm called LiveFuels Incorporated, Menlo Park, California, to examine the large-scale production of algal biodiesel. The laboratory will help develop the technologies to enable the creation of algal refineries. Because scalability is key to the effort’s success, Simmons notes that Sandia is using its in-house modeling and engineering tools to help design these new processes.

One consideration is the potential implications of industrial-scale use of genetically altered organisms in open ponds. Citing the concerns surrounding genetically modified crops, he observes that this is a sensitive topic that must be approached carefully. “You have to be very aware of some of the legal and public relations requirements to handle the sensitivity. It’s justifiably deserved that people are concerned about it,” he says.

Besides genetic modification and optimizing growth conditions for high oil production from algae, a technique must be developed to remove the water in which they are grown. Simmons explains that algae typically do not grow in dense mats on a pond’s surface. An effective means to dewater the algae, collecting them to a near-solid density and breaking the individual plants open to recover the oil, must be developed. He adds that some indications suggest that modifying the algae will not be the most expensive cost element; instead, it will be processing and dewatering.

Oil currently is removed from algae through several techniques such as solvent extraction and supercritical fluid processing. The GreenFuel Technologies Corporation, Cambridge, Massachusetts, is working on a process to sequester carbon dioxide directly from power plants to use as a feedstock for algae growth. Simmons notes that an added advantage to algae production is that it can be used to help mitigate carbon dioxide emissions. Salt produced by water desalination plants also could be used as a growth medium for algae. “Instead of treating the salt as a waste byproduct, you could use it to aid in the development of a consolidated algal system,” he says.

Besides growing algae in open ponds, researchers and firms are examining methods to grow them in closed systems. Simmons observes that firms such as GreenFuel have developed bioreactors—sealed growth chambers—and that Japan has spent nearly $250 million to optimize bioreactor technology. However, the process still is not mature enough for large-scale commercial use.

One of the challenges of bioreactors is scaling them up. The NREL’s Aquatic Species Program focused on the development of large ponds as a more feasible approach. Simmons adds that most commercial algae producers now grow their crops on open ponds. “There is no economically viable method to growing them [algae] to the scales you need in a photo bioreactor yet,” he says.

Although the Sandia program still is in its initial stages, Simmons sees several paths forward. The challenge will be determining the best one for a chosen mode of production. He notes that this is why it is important to develop relationships with commercial firms to help guide the efforts. “The interest around algal biodiesel is growing, so we think we’re well positioned to take advantage of that. We have a very clear road map. We want to demonstrate that algal biodiesel is economically viable. Until we do that, the rest is kind of moot. Right now we’re developing the tool box for that road map,” he says.

 

Web Resources
Sandia National Laboratories: www.sandia.gov
National Renewable Energy Laboratory: www.nrel.gov
LiveFuels Incorporated: www.livefuels.com
GreenFuel Technologies Corporation:
www.greenfuelonline.com