But wood biomass could soon have a new role in energy production: cleaning up coal-fired power plant emissions.
The technology could enable coal plants to comply with forthcoming EPA mercury rules at a relatively low cost.
The process involves a technique called pyrolysis, in which wood is heated in an oxygen-deprived container. Without oxygen, wood can’t burn. After a sequence of chemical reactions to remove volatile organic compounds, what’s left is a pure material known as activated carbon.
Activated carbon, sometimes called activated charcoal, is a porous material that’s good at absorbing or bonding with other materials. Its most common use is in water filtration, everywhere from municipal water treatment plants to the water pitcher in your refrigerator.
The use of activated carbon at power plants is a relatively new one. A mercury emissions control program at the U.S. Department of Energy’s National Energy Technology Laboratory in Pittsburgh funded activated carbon research for about a decade ending in 2008, when it decided federal support was no longer needed.
“What’s compelling about it is it’s an inexpensive retrofit technology,” says Tom Feeley, a senior technical advisor who managed the DOE mercury control program.
How it works The method doesn’t require any expensive equipment upgrades. Most of the cost is in buying the activated carbon. A fine cloud of carbon is injected into the plant’s exhaust stream, where it bonds with mercury, forming clumps of material big enough to be captured by existing particulate filters.
Feeley estimates that activated carbon controls are now installed or planned to be installed on units accounting for about a quarter of the nation’s coal-fired generation capacity.
The market for activated carbon at power plants is likely to grow with new federal mercury standards on the horizon.
“It’s a half-billion-[dollar]-a-year or more opportunity in the United States alone, and that’s from the base of zero a few years ago,” says Bob McIlvaine, president of The McIlvaine Company, a consulting and technical research firm in suburban Chicago that closely tracks mercury control technologies.
Coal-fired power plant operators spent about $50 million on activated carbon in 2010. By 2015, McIlvaine projects that number will exceed $500 million. That would exceed the current market for water filtration and more than double demand for activated carbon.
The problem, says Biogenic Reagents founder and CEO Jim Mennell, is that most activated carbon is made from coal, through a process that creates mercury emissions itself.
“When you’re making an environmental technology, you can’t just say that when I use it here it reduces emissions,” says Mennell. “Overall, total lifecycle, is it really good for the environment? It’s there that I think we are a factor better than coal-based carbon products.”
Why wood? Biogenic Reagents’ wood-based alternative is far cleaner to produce, says Mennell, and it also costs less and performs better than coal products.
The company hired Stanford University’s Clean Energy Conversions Lab to conduct blind, side-by-side trials that showed it was more effective than two coal-based competitors, he says. It also partnered with a Michigan utility, which he says he can’t name due to a non-disclosure agreement, for a full-scale trial at a coal-burning power plant.
The results: Biogenic Reagents’ activated carbon product was able to reduce mercury emissions by more than 90 percent, hitting levels three times lower than the EPA’s new Mercury and Air Toxics Standards that take effect in early 2015.
Mercury is a neurotoxin that’s linked to learning, growth and development and reproductive issues. A common exposure is through eating fish from waters contaminated by mercury. Coal-burning power plants are the largest human-caused source of mercury pollution.
After about a year of operating in stealth mode, Biogenic Reagents is just now going public with their products. Another variation of the recipe produces a wood-based substitute for metallurgic coke, a coal-based product that’s used in refining metals and a major source of greenhouse emissions.
“We wanted to demonstrate that we could actually scale it up and prove it actually worked on a commercial scale before announcing it to the world,” says Mennell.
The company’s Michigan facility is capable of annually processing 300,000 tons of biomass, all of which will be purchased through suppliers certified by the Forest Stewardship Council or Sustainable Forestry Initiative. The plant will employ about 40 people and will support other area forestry, transportation and construction jobs.
Because activated carbon fetches a far higher price than raw coal or wood fuel, it was able to startup without any direct government support. The company’s founders include Mennell, a Minneapolis environmental attorney who has represented several ethanol and biomass firms, and Dan Despen, owner of Interpoll Laboratories, an environmental sampling and analysis lab north of the Twin Cities.
McIlvaine says there’s opportunity for challengers in the activated coal market. The existing producers, including Calgon Carbon, Cabot, Norit, and Westvaco will be challenged to keep up with new demand if it grows as he expects it will. (Spokespeople for Cabot and Norit didn’t return phone calls for comment)
Mennell says Biogenic Reagents is in discussions with potential large-scale customers, which they hope to announce within a couple of months, with an eye toward expanding the Michigan facility in the next year.
“We’re rolling it out, and our expectation is that we should have a pretty positive reception in the marketplace,” says Mennell.
One that could have a pretty positive impact on the environment, too.