Open-pond growing and closed-tank bioreactor plants for algae

Oil giant Exxon has partnered with Synthetic Genomics Inc. to create and develop algae biofuel.

The tremendous industrialization of the 20th and 21st centuries, with its corresponding increases in fuel consumption and greenhouse gas emissions, has posed a unique and challenging problem for the United States namely, that of safe and reliable energy. The solution to this dilemma may lie within algae, certain types of which can be harvested and refined into a biofuel replacement for oil. One company at the forefront of research and development for algal fuel is Synthetic Genomes Incorporated, which has entered into a $300 million partnership with oil giant ExxonMobil to find new ways to tackle problems such as the efficiency, practicality, and implementation of the biofuel.

Algae can be used as a fuel due to its innate chemical properties. It uses carbon dioxide, nutrients and solar energy to create an oil compound stored within itself. The oil is extracted using one of three methods, each of varying efficiency. The first method is simply using an oil press, similar to an olive press in function, to remove up to 75% of the contained oil. When this process is followed up by the usage of hexane, a liquid solvent derived from petroleum, that number goes up to 95%. The hexane is mixed in with the leftover algae and then put through a filter, which causes most of the remaining oil contained within the algae to separate. The third method is known as the supercritical fluids method, which involves extremely pressurized and heated carbon dioxide – the supercritical fluid – being mixed with the algae to completely turn the algae into oil. While this yields 100% of the algae’s usable oil, it is relatively impractical due to the equipment necessary to fulfill the reaction. Because of these problems, SGI seeks to bioengineer a new type of algae that constantly secretes oil from its cell walls, removing the need to continuously harvest and replenish the algae stores. This could potentially be the most efficient of all of the methods, though it is still in the early stages of development.

The extracted oil is then refined using fatty acid chains in transesterification, which involves mixing an ester and alcohol compound. A catalyst is mixed with an alcohol, creating a biodiesel fuel combined with a glycerol which is then further refined to remove the glycerol and create the final fuel product. On the molecular level, this is a feasible and universal process; the real question with algae biofuels is how they can effectively be produced on a large-scale basis.

This production method is precisely what SGI and Exxon seek to discover. There are two specific techniques being researched by the companies as of now: open-pond growing and closed-tank bioreactor plants. The former is akin to farming the algae, and involves growing algae in ponds. The problems faced with this process are primarily natural, as the algae must be kept in hot, sunny areas with water at a constant temperature. For better regulation of algae production, indoor facilities can be used to grow algae at optimum conditions inside large, round drums. Nutrients, carbon dioxide, and water are pumped into the containers and oil is continuously extracted.

Despite these difficulties, Exxon and SGI claim that the potential benefits of algae are worth taking a look at. Algae is a non-food product and can be grown in areas unused for farming, unlike other biofuels such as corn. It is the most efficient of all biofuels, and an acre devoted to the growth of algae is estimated to produce 2,000 gallons of fuel per year. When that is compared to palm (650 gallons) and corn (250 gallons), it is easy to see why algae is so promising. Algae biofuel can easily be incorporated with current fuel infrastructure, and modern car engines can run on it without any modifications. If SGI and Exxon are successful in their endeavors, algae will likely become commercially viable within five to ten years as the price of oil rises and demand for new fuel grows.

Veronica Cassandra