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Environmental engineers use algae to  capture carbon dioxide

Global warming's effects can be seen worldwide, and many experts believe only going to get worse still. What's coming from power plants, traffic jams and industrial smog is causing our ozone to disappear, ice caps to melt, and temperatures to rise. The latest international report says carbon dioxide is responsible for 60 percent of the greenhouse gases.

Engineers have designed a simple, sustainable and natural carbon sequestration solution using algae. Along with a team, David Bayless Professor of Mechanical Engineering at Ohio University in Athens, created a photo bioreactor that uses photosynthesis to grow algae, passing carbon dioxide over large membranes, placed vertically to save space. The carbon dioxide produced by the algae is harvested by dissolving into the surrounding water. The algae can be harvested and made into biodiesel fuel and feed for animals. A reactor with 1.25 million square meters of algae screens could be up and running by 2010.

Bayless, says," If this sort of technology can be developed, it can be deployed anywhere there is sunlight". He has developed a bioreactor that cleans up carbon dioxide emissions from fossil fuel exhaust with the help of heat-loving algae and hybrid solar lighting. He introduced the easiest way to eliminate C02 from coal-burning power plants to use the natural process of photosynthesis.

Bayless designed a box packed with blue-green algae spread onto vertical membrane screens. Ben Stuart, an Ohio University environmental engineer, adds. "These membranes are fabric just like shirt. It is a woven material, and as the carbon dioxide passes by them, that carbon dioxide dissolves into the water." That carbon dioxide is broken down by the algae. Nitrogen and clean oxygen are released back into the atmosphere. The algae use the C02 and water from the power plant to grow new algae, giving off oxygen and water vapor in the process. The organisms also absorb components of acid rain, such as nitrogen oxide and sulfur oxide.

Building a workable prototype had its share of challenges. For instance, there was a problem of limited space, it just wasn't possible to cover an area of around 100,000 acres with algae. So Bayless instead placed screens of woven fiber with algae vertically. Since algae need sunlight to thrive he brought in hybrid solar lights that collect sunlight with curved mirrors and then channel it through the reactor via optical fibers and instead of trying to genetically modify any kind of algae, he found a species that naturally thrives in the hot springs of Yellowstone National Park, and does equally well in the exhaust of a power plant. A remaining challenge is how to dispose of the large quantities of algae produced by the bioreactor; one option is to collect it and use it as a biologically derived fuel.

All about algae

Algae are relatively simple organisms that capture light energy through photosynthesis and use it to convert inorganic substances into organic matter. Photosynthesis is the process of producing sugar from sunlight, carbon dioxide and water, with oxygen as a waste product. Nearly all life depends on this complex biochemical process, which occurs most famously in plants, but also in phytoplankton, algae, and some bacteria, among other organisms. They are usually found in damp places or bodies of water. They vary from single-celled forms to complex forms made of many cells, such as giant kelps, which can grow as much as 65 meters in length. It is estimated that algae produce between 73% to 87% of the net global production of oxygen.

Source: www.sciencedaily.com

ENVIS CENTRE Newsletter Vol.7,Issue 2 April 2009 Back
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