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Fully instrumented bioreactor makes major contribution to bioenergy conversion

Bill Scanlon of Renewable Energy World released an article on March 5, 2014 entitled Unique Bioreactor Finds Algae's Sweet Spot. The National Renewable Energy Lab (NREL) has developed a large bioreactor that has added significant instrumentation and controls to optimize the conversion of algae into various hydrocarbons.

The Simulated Algal Growth Environment (SAGE) has the capability to duplicate conditions for growing algae in any state in the US or around the world. SAGE has instrumentation and controls that precisely regulate the amount of simulated sunlight, carbon dioxide, nitrogen and temperature in the algae growth process. The reactor is located at the NREL's field test laboratory in Golden, CO.

The research done at NREL has documented different process conditions for different algae strains to optimize the production of various length hydrocarbons for use in fuels. By aerating the algae and controlling the nitrogen and carbon dioxide content at different phases of the growth cycle, the algae can optimize production of proteins, lipids (fats) and carbohydrates.

NREL senior scientist Lieve Laurens discussed the major outcomes of the new process capability.

"We've almost doubled the fuel we can get out of the same amount of biomass by using these additional components. We can model how a particular strain would grow in different locations around the United States, and how this impacts the oil productivity, as well as the general biochemical composition of the biomass.”

The developments in the algae strains and the improved process knowledge allow wider application of the conversion of algae into different hydrocarbon components to meet market demands. With abundant nitrogen and carbon dioxide, and the right temperature and amount of light, the algae grow quickly and produce a large volume of algae.

When the nitrogen is reduced, the algae change their activity from rapid growth to building more complex organic compounds that will convert into more complex carbohydrates and lipids. The end result of the cycling between feeding the algae and then starving it allows control of the chain length of the hydrocarbons being produced.

Proteins mainly produce butyl alcohol. Carbohydrates mainly produce ethanol. Lipids mainly produce oils used to form light diesel fuel. These compounds can be separated through distillation. The NREL reactor has shown that the process can be optimized to yield the most desirable output components at the time.

NREL is funded by the Energy Department's Bioenergy Technologies Office. Other companies such as Exxon-Mobil have made substantial investments in biomass conversion. There are competing processes in the algae to oil conversion from other research locations. The US is a leading technology developer and there are many companies focused on biomass as an alternative energy source.

NREL is one technology provider. Pacific Northwest National Labs is another contributor for biomass conversion. Commercialization of this technology is increasingly important on a global basis. It is estimated that 10 to 15% of the global energy output is currently fueled by biomass. The largest amount of this bioenergy is being acquired from wood and wood byproducts. Algae are a potential energy source that utilizes carbon dioxide while producing hydrocarbons.

Much of the technology used in algae to bioenergy production can be utilized to convert other forms of biomass to bioenergy. As the world population grows, major sources of biomass are automatically generated. The largest available non-wood sources of biomass are animal and human waste, and byproducts of food processing and processing byproducts. The conversion of biomass to bioenergy is a necessary component of meeting growing energy demands to support an increasingly growing global population.

This work by NREL is another step forward in reducing reliance on coal and oil while reducing carbon dioxide and solving waste disposal problems generated by an ever increasing global population.

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