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​The Plan to Turn Toxic Algal Blooms into Energy

How researchers want to turn one of our worst environmental problems into fuel for the future.

by Maddie Stone
Mar 25 2015, 3:20pm

​Satellite image of the 2011 Lake Erie algal bloom, one of the most severe in decades. Image: MERIS/NASA; processed by NOAA/NOS/NCCOS

Every year, nutrient-rich runoff from the Midwestern corn belt makes its way down the Mississippi river and into the Gulf of Mexico. The result? ​Algal blooms, which, over time, have triggered ecological collapse, and now maintain a "dead zone" nearly the size of Con​necticut. It's a dramatic example of a common tragedy: there are over ​400 such coastal wastelands worldwide.

But what if we could flip this problem on its head and turn toxic blooms into something useful? Algae happen to be one of the most promising sources of biofuel we've got. If we could harvest deadly blooms and juice them for fuel, we'd be cleaning up the environment and our energy profile in one fell swoop.

That's exactly what John Miller, a professor of chemistry at Western Michigan University, now hopes to do. At a press conference held today at the annual meeting of the American Chemica​l Society, Miller will discuss his idea for transforming algae—the same ones responsible for deadly blooms—into bioremediation agents and an additional revenue stream for small farmers.

Synthetic nutrient fertilizers are a mainstay of modern agriculture, and have boosted yields many times over. They're also a serious environmental problem, leaching into waterways and causing nutrient-loving algae to blossom. These algae live hard and die young—they grow fast, run out of resources quickly, and sink en masse to the ocean floor. Here, their dead bodies become a feast for bacteria, which, in turn, eat up all the oxygen in the water column and choke out everything else.

Algae may be ​harbingers of ecological destruction, but while they're alive, these microscopic plants actually provide an important ecosystem service by soaking up nutrient pollution. Algae are also an attractive source of ethanol-​based biofuels, growing up to ten times faster than land-based feedstocks such as corn and soy. And, it so happens, these two benefits of algae can be combined. "Turf scrubbers"—large, outdoor algal farms—are systems in which thick mats of algae filter wastewater and are periodically harvested for biofuel.

"There's a very good synergy here, between environmental remediation and biofuel production," Miller told me when I spoke with him over the phone.

Thick mats of overgrown algae choke out coastal ecosystems. Image: Eutrophication & Hypoxia / Flickr

Building off the turf scrubber approach, Miller's team is now developing small-scale algae processing systems that can be deployed in water bodies near individual farms. If algae can be grown and collected at the pollution source—the farms themselves—then a distributed network of small scale systems could reduce the amount of nutrient runoff into large water bodies in the first place.

"My focus is to look at small scale, distributed production of algae to clean up eutrophic [nutrient-rich] water at the source," said Miller. "If we can do that, we wouldn't need to scrub the entire flow of the Mississippi where it enters the Gulf of Mexico—we'd have already done it upstream."

To make small-scale algal production appealing to farmers, it needs to be easy to operate and inexpensive to maintain. "If you look at the large-scale turf scrubbers, these systems need a lot of power to run," Miller told me. He explained how he's trying to make his systems energy efficient by growing algal remediators in natural water bodies, rather than pumping water into artificial pools for treatment. He envisions deploying supports that will promote benthic (bottom-growing) algal growth and that can be harvested without additional filtration steps.

"Floating algae have spent millions of years figuring out how not to be filtered out of the water column," Miller said. "When we deploy a substrate that benthic algae will attach themselves to, that makes harvesting it a whole lot easier."

Miller's approach is a stark contrast to industrial algal production, in which a monoculture is grown within an environmentally controlled tank, or bioreactor. His systems will promote the growth of native algal communities best suited for their environment.

"We're not introducing any species and there's no genetic modification involved," he said. "At this point, we're not even trying to optimize growth for a particular organism, just for all attached algae, to maximize the overall biomass production."

Once farmers harvest the algae, they'll be able to sell the feedstock to fermentors, which can convert it into fuel. According to Miller, a nutrient-rich waste is left over after the fermentation and distillation process. This waste could be sold as an organic fertilizer and re-applied to fields, helping to close the nutrient loop entirely. In the long term, it could even be possible that some farmers could reduce their reliance on mineral nutrients, instead recycling their new algae-based fertilizer over and over.

Miller, who is pilot testing his remediation systems at several farms this spring, is hopeful that the combined economic and environmental benefits of growing and harvesting algae will encourage farmers to buy in. If the approach catches on, we may soon see these little green microbes transformed, from agents destruction into an environmental solution.

Sure, extracting precious metals fro​m human poop may prove more lucrative in the short term, but if we take a longer view, mopping up this particular environmental catastrophe will pay for itself many times over.