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Algae species shows promise in reducing power plant pollution and making biofuel

University of Delaware researchers have identified an algae—Heterosigma akashiwo—that grows rapidly on a gas mixture that has the same carbon dioxide and nitric oxide (NO) content as emissions released from a power plant.

The algae, found worldwide in the natural environment, also make large amounts of carbohydrates, which can be converted into bioethanol to fuel vehicles. The findings could have industrial applications as a cost-effective way to cut greenhouse gas pollution when paired with biofuel production.

The majority (90%) of NOx in flue gas is in the form of nitric oxide (NO), a toxic gas that easily crosses cell membranes, diffuses through the cytoplasm, and reacts within the cell to generate a variety of cytotoxic products. The high concentration of NO in flue gas can inhibit the growth of microalgae. However, H. akashiwo is capable of metabolizing gaseous inputs of CO2 and NO.

The algae thrive on the gas. They grow twice as fast and the cells are much larger in size compared to when growing without gas treatment.

—Kathryn Coyne, associate professor of marine biosciences in UD’s College of Earth, Ocean, and Environment“

A year-long laboratory experiment shows that Heterosigma akashiwo not only tolerates flue gas, but flourishes in its presence. The algae also do not need any additional nitrogen sources beyond nitric oxide to grow, which could reduce costs for raising algae for biofuel production.

That alone could save up to 45% of the required energy input to grow algae for biofuels, Coyne said.

Funded by the Delaware Sea Grant College Program, Coyne and her collaborator, Jennifer Stewart, plan to further study how changes in conditions can enhance the growth of Heterosigma akashiwo. So far, they found a large increase in carbohydrates when grown on flue gas compared to air. They also see correlations between the levels of light given to the algae and the quantity of carbohydrates and lipids present in the organisms.

The researchers are exploring opportunities for partnerships with companies to scale up the growth process and more closely examine H. akashiwo as a biofuel producer.

Comments

Engineer-Poet

The problem with these schemes is the cost of the bioreactors on the one hand, and the once-through nature of the cycle on the other.  Unless the carbon comes from the atmosphere, the emissions are not prevented but merely delayed.

Trevor Carlson

Trees, switchgrass, etc are the perfect pathways to capture and convert atmospheric carbon into longer chain molecules. However, unless you sequester that you're again just taking it out of the cycle for a time.
Coal and Oil are the perfect carbon sequestration methods and nature has perfected them already. If too much atmospheric carbon is indeed the greatest problem facing humanity then we need to implement as many capturing methods as possible to keep it out of the atmosphere even if is only for a short time.

It's better to get our carbon from homeland sources above ground than to ship them from underground and overseas. This could also help create another value stream for coal power plants to help them comply with stricter emissions standards. The result is cleaner electricity and a carbon source closer to home for other products.

The only way to reduce sequestered carbon usage is to increase efficiency or reduce productivity and increase the renewable energy contribution to our energy needs.

Engineer-Poet

Nuclear power is an even more effective way than "renewables" (which rely on lots of non-renewable raw materials) to avoid the release of sequestered carbon.

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