Ze-gen: Waste Is A Terrible Thing to Waste

8/6/07Follow @wroush

As a Web journalist, I’ve been writing and thinking about intangibles like software and the Internet for so long that my idea of “hardware” is an Apple iPhone, and I’d almost forgotten that a “router” used to be something you use to cut grooves in wood. So it was a welcome kick in the pants last week to get a look at a seriously manly piece of industrial equipment—a gigantic steel pot that will soon hold 25 tons of molten iron. Cool!

The pot in question is the centerpiece of a new “waste gasification” demonstration plant approaching completion in New Bedford, MA. My guide, project manager Megan Feldt of Boston energy startup Ze-gen, gave me a close-up view of the belts, towers, elevators, and tubes that will convey shredded wood and other organic waste directly into the 2,600°F liquid metal, where it will instantly dissociate into hydrogen, carbon, and oxygen and bubble to the surface as a mixture of hydrogen and carbon monoxide gases. Ze-gen wants to show that this clean-burning “syngas” can be generated and harvested reliably enough to fuel the turbines of a 30-megawatt electric power station.

Feed tubes for Ze-gen reactorAccording to Ze-gen president and CEO Bill Davis, the United States produces 300 million tons of solid waste every year. About two-thirds of that is municipal household waste, and one-third is construction-and-demolition or “C&D” waste. Today, almost all of New England’s solid waste is trucked to far-away landfills and incinerators in places like Ohio and southern Virginia where it’s easier to get the necessary permits. “You use a lot of energy just moving the waste around,” Davis points out.

It would make a lot more sense, Davis says, to get rid of this waste at gasification plants near local waste-transfer stations—and Ze-gen hopes to build them. In fact, the Ze-gen demonstration plant, built using a $2.25 million investment from the Massachusetts Technology Development Corporation and several other organizations, sits on the grounds of a bustling waste sorting facility owned by New Bedford Waste Services. As Feldt and I talked, big trucks rumbled by carrying everything from torn-apart two-by-fours to concrete and chickenwire; once separated and sifted, the C&D portion of that waste will go into Ze-gen’s specially designed hoppers and dryers, then on to the reactor. “We’re going to take anything that can’t be recycled and use that as fuel,” says Davis. (Metal, sand, and other inorganic materials that don’t get sifted out before they reach the reactor will simply collect atop the molten iron as slag, and will periodically be tipped off.)

Unfinished lid of Ze-gen reactor potGasification isn’t a new technology—Germany used it to turn coal into gasoline during World War II. But gasifying waste is a tricky proposition, says Davis. The process hasn’t been successfully commercialized in the past because the quality of the syngas varies tremendously depending on the mix of waste materials dumped into the smelting pot.

“A unique challenge is ending up with a gas that is homogeneous even though the source isn’t,” Davis says. “We think we have figured out a way to smooth out the variability in energy levels.” Specifically, the company has patented an automated system that blends whatever waste materials are available, such as shredded wood and tires, to create a mix with a constant energy density per volume.

There’s no generator attached to Ze-gen’s plant, so the gas it produces will simply be flared into the sky, rather than burned for electricity. But if the company can prove its new gasification procedure works, it will become much easier for it to raise the $60 million needed to build its next facility, a production plant with three 40-ton reactor pots. A positive result for the demonstration plant would be “a constant supply of 300-BTU or higher syngas,” says Feldt, referring to the amount of combustion heat released by one cubic foot of the gas.

Feed Tower at Ze-gen plantCoal and natural gas are much better heat sources than syngas, producing in the neighborhood of 1,000 BTUs per cubic foot. But the big advantage of syngas collected from C&D waste, Feldt explains, is that has a minimal carbon footprint, since the waste is mostly wood—a resource that’s largely replaced through the planting of new trees, which soak up carbon dioxide from the atmosphere. At a Ze-gen-style plant, about 30 percent of the power produced would go back into running the plant, since it takes a lot of energy to melt the iron in the reactor and keep it molten. But the plants would still churn out many megawatts of electricity that wouldn’t have to come from burning fossil fuels. And keeping the waste out of landfills would prevent the release of millions of tons of methane—which traps heat in the atmosphere 22 times more efficiently than carbon dioxide.

Ze-gen has raised about $8.9 million altogether, including a $4.5 million Series A round from Cambridge investment firm Flagship Ventures and San Bruno, CA, firm VantagePoint Venture Partners. The company has spent about $3 million on the demonstration plant so far, according to Feldt, and the remaining funds should be enough to get the company through the testing phase. But the company will have to hit the fundraising trail again as soon as this winter.

Recycling Trucks at New Bedford Waste ServicesDavis will try to convince investors that now is the time to scale up waste gasification technology. “We’ve got high energy prices, the desire to reduce dependence on fossil fuels, and increased awareness of the detrimental effects of landfilling,” he says. “It’s a perfect storm of need and opportunity.”

Photos by Wade Roush

Wade Roush is a contributing editor at Xconomy. Follow @wroush

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  • http://www.waghormley.com bill ghormley

    This is GREAT technology, Wade!

    Is there an equation to show the inputs to outputs on this process?

    BG

  • Vivek R Dave

    Wow- wonderful stuff!

    Finally we can potentially take advantage of the 10% of US oil consumption annually that ends up as clear plastic bottles in landfills and never gets recycled or otherwise converted into useful energy.

  • jamie

    No mention of the high levels of mercury and other toxins which are emitted from projects like these. Also if you are burning your waste you are not recycling it. These issues have to be considered before you can say this tech is GREAT. If this tech was so GREAT then it would probably already be in use as the article says gasification has been around for years. Unfortunately no silver bullet yet…

  • Anne Logan

    Cool! I saw the show Invention Nation on the Science Channel, where they showed the plant in New Bedford. I looked up Ze-gen online. Very hopeful development. We have to do something better with our waste, not create more toxic methane. Congratulations on this clever use of construction waste.

  • http://www.sos.org Roberta Murphy

    Is there any possibility that this could be the answer for that continent of trash in the Pacific Ocean. Can you imagine how much energy that would produce. The entire mass is larger than the entire U.S. Bill, if you need any help, call me!

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