BURIED GREEN: Researchers devise new ways to grow algae for biofuel, using underground mines instead of outdoor ponds.
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Backers of algae-based biofuels tout the simplicity of their feedstock. Sunlight and water are all that's needed to convert carbon dioxide into fuel.
Now, some scientists are testing the notion that sunlight might be optional.
Researchers at the Missouri University of Science and Technology are planning to grow algae for fuel in abandoned mines using light-emitting diodes, or LEDs.
"About this time in the conversation, someone usually raises their hand and says, 'But it's dark,'" said David Summers, a mining engineering professor. "That's not necessarily a disadvantage."
Algae need light to produce lipids, or oil, but they work best when they use only the red and blue parts of the light spectrum and when they are given time in the dark to process the photons, Summers said.
That is where LEDs come in, Summers said. They can be tailored to emit only the needed light frequencies, and they can be set to pulse several times a second at a rate that gives the algae time to absorb and process the light energy without wasting it.
"When it's sunny, plants are totally saturated pretty early on in the day," said D.J. Vidt, a graduate student. "Unless they get shade to process the photons, it's basically wasted energy. We're just shortening ours from hours to milliseconds ... for efficiency."
Using LEDs to grow algae is not a new idea. Researchers have been working on the concept for years, and some startup companies are using the idea as the basis for their business models.
"We like LEDs because they're so efficient," said Riggs Eckelberry, president and CEO of OriginOil Inc., a California-based company using LEDs to grow algae.
But Summers wants to take the concept a step further by placing the photobioreactors, which house the algae, underground in abandoned mines. Using mines allows algae growers to address three problems of open, outdoor ponds: evaporation, contamination and fluctuating temperatures.
"The one thing that underground mines have is constant temperatures," Summers said.
Plus, mines can be inexpensive, since mining companies have already done the most expensive site preparations.
"Something like 47 percent of the capital costs of surface algae ponds are infrastructure," Vidt said. "We're just shifting it from investing in pavements to investing in lighting systems."
Growing the photosynthetic algae underground also addresses concerns about invasive species of algae escaping, Vidt said. Even if the species escape containment from the photobioreactors, they pose little threat as invasive species because they could not survive for long in the dark.
The setup also provides a perk for mining companies faced with the task of cleaning up in the wake of excavation.
"Algae are exceptional at sequestering metals," Vidt said, adding that the biodiesel produced on site could be used in additional mining operations. "This is a [public relations] boon for these guys: It works for them, they get some fuel, and on the flip side, they don't have to pay reclamation."
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12 Comments
Add CommentAnother use for abandoned mines that occurred to me is to use them as the lower reservoir for a pumped storage system working in combination with a renewable energy generation system.
Reply | Report Abuse | Link to thisAnother use for abandoned mines that occurred to me is to use them as the lower reservoir for a pumped storage system working in combination with a renewable energy generation system.
Reply | Report Abuse | Link to thisA novel idea but if you want to use the resources you already have available, wouldn't light (the sun) be the most obvious?
Reply | Report Abuse | Link to thisIt seems the lighting is a very expensive part of this process.
The sun is free.
what an idiotic idea, use LED's that use coal produced electricity? the conversion rate from coal to electricity to algae would be about 0.33 x .0.95 x 0.2 x0.4 x 0.6 = 0.015.
Reply | Report Abuse | Link to thisif the coal is converted to high performance synthetic fuels the conversion rate would be 60 to 80%
Ripplinger is right.
Reply | Report Abuse | Link to thisMy initial reaction to this article was to think of perpetual motion machines. I trust that the researchers have other legitimate goals with their research, since the energy production motive is energetically preposterous.
@rickrow. I've been thinking about that for a while. We (South Africa) have one pumped water scheme, in the Drakensberg mountains, about 200km from any real industry. However, Johanesburg is the industrial capital and has the worlds deepest mines (8000m). The mines have to be continuaously pumped out, whether functional or not, due to water table pressure. The pruduct is usually toxic to some degree. The advantages, beside power storage, are 1) by filling the mine with water for half the day, the water table pressure would be equilized, reducing toxic inflow. 2) the water could be treated and "reused", instead of dumpin it into the surface water system, as is now the practice. Two comments on the article. If the algea picks up heavy metals, and they are not fully recovered when processed, will the biofuel be toxic? Secondly, I never considered the benifits for leaves of a plant, shaded by the outer leaves in full sun light, especially in wind, affording the lower leaves time to process photons. Are the lower leaves more productive?
Reply | Report Abuse | Link to thisEthanol uses far more coal to produce than the light these mines would require. They said too much light inhibits maximum oil production from the algae and surmise the led's would be more efficient. I guess tests will tell.
Reply | Report Abuse | Link to thisIf, however, you are deriving your LED energy source from solar arrays, then you are simply converting the solar energy into a more efficient spectrum for producing algea. There is loss in this due to the sun - to - energy conversion, but the increased production of the algae may compensate for that.
Reply | Report Abuse | Link to thisThe missing point is producing and/or getting electricity to these sites to power the LEDs. The "sweet spot" for algae-to-oil production sites are anywhere electricity is cheap--which usually means in hydroelectric or nuclear power regions. If those areas are also areas of high oil costs, then the spot becomes even sweeter.
Reply | Report Abuse | Link to thisAnother question for the researchers is about how much carbon does the algae absorb and how much oxygen does it give off. in a productive mine you have lots of heavy machinery giving off CO2, Will the algae oxygenate the air and cut down on forced air circulation? If the mine is not productive, how long before the increased oxygen levels make the mine explosive?? As the article says, the main cost is in buying the LED arrays, solar cells and batteries can easily provide free power for isolated underground mines, so while you've got high setup/startup costs, you've got years of free oil production in land that would otherwise be toxic to use.
Reply | Report Abuse | Link to thisERRATA. In my comment on 11/11/09 I said the worlds deepest mines were 8000m deep. The deepest is 3900m deep (TauTona). I was vastly WRONG!
Reply | Report Abuse | Link to thisIn my comment on 11/11/09 I said the worlds deepest mines were 8000m deep. The deepest is 3900m deep (TauTona). I WAS VASTLY WRONG.
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