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NEW BEDFORD - Take a rusting, hulking pile of scrap metal, add a few tons of construction debris, and what do you get?
In the case of Ze-gen Inc., a new source of energy.
Ze-gen, founded four years ago, is using the unappetizing conglomeration to make fuel for power plants.
Borrowing technology from the steel industry, the company turns scrap metal into a 2,800-degree metal bath and injects construction debris deep into the bubbling cauldron. The process produces a clean-burning synthesis gas, or syngas, that can replace natural gas or fuel oil.
Ze-gen has been proving its technology and the quality of syngas over the past year, operating a demonstration plant here that digests about a ton of debris an hour. The company is now considering several sites, primarily in the Northeast, to develop a commercial facility that could eventually process as much as 30 tons an hour and produce enough gas to fuel a plant that could power 20,000 homes.
It expects to begin commercial production at the end of next year.
"We're solving two problems," said Bill Davis, Ze-gen's chief executive. "We're eliminating wastes that would end up in a landfill and reducing fossil fuels."
Ze-gen is one of many companies across the nation using gasification technologies to convert plant, wood, and other organic wastes - known as biomass - into syngas. Some like, Ze-gen, are simply making syngas, which has the same chemical components, carbon and hydrogen, as fossil fuels. Others, like the Massachusetts Institute of Technology spinoff InEnTec LLC, of Bend, Ore., are condensing it into liquid to make ethanol.
InEnTec uses municipal solid waste as feed stock and a technology known as plasma gasification, initially developed at MIT several years ago to destroy hazardous materials. The technology essentially creates an artificial bolt of lightning that vaporizes materials. InEnTec applied the method to solid waste, producing a syngas, then introducing a catalyst to change the gas into liquid, which can be blended with gasoline.
InEnTec and a partner, Fulcrum BioEnergy Inc. of California, recently said they plan to break ground on a $120 million plant near Reno, Nev., by the end of the year, and begin commercial production of ethanol in 2010. The plant will process 90,000 tons of waste annually to produce 10.5 million gallons of ethanol. Including tipping fees (the charge for taking the waste), the company projects making ethanol for about $1 a gallon, said Dan Cohn, a cofounder of InEnTec and senior research scientist at MIT.
"Gasification has a lot of potential because the technology is well established and can process a very wide range of feed stocks," Cohn said. "It has the greatest potential when you can process waste."
Gasification, which uses heat to turn solids into gas, is indeed a well-established technology. Before the invention of the electric light, many cities and towns had plants that converted coal to gas for street lamps. With oil and natural gas prices soaring, coal gasification has gained new interest, but is controversial because coal gas produces high amounts of carbon dioxide, a greenhouse emission that contributes to global warming.
Using biomass as a feed stock is considered more environmentally friendly because plants and trees can be regrown to absorb carbon dioxide created by burning syngas. In addition, keeping waste out of landfills reduces an even more potent greenhouse gas, methane, which is released during decomposition.
Reducing solid waste was a key consideration in the founding of Ze-gen. Davis said more than 300 million tons of waste end up in US landfills every year, about 15 percent of it wood waste from construction. Ze-gen's idea: Tap the waste's energy potential.
The company's engineers determined that channel induction furnaces used in the steel industry provided an energy-efficient way to turn construction debris into a high-quality, clean syngas. The electricity used for the furnace offsets about 15 percent of the energy produced by the syngas, Davis said.
The construction debris is first ground up, then injected deep into the molten metal with ceramic cylinders, much like dipping forks into a fondue pot. The intense heat converts the debris to gas. Heavy metals, such as lead from paint, settle to the bottom of the bath while other contaminants are trapped in crust of silica, known as slag, that forms on top.
Ze-gen raised about $8 million from investors to build the demonstration plant at a New Bedford waste-transfer station. The next step is to find industrial partners to put the gas to work. Syngas is difficult and expensive to transport, so Ze-gen's plan is to build production facilities near users such as power and cogeneration plants at large factories. Cogeneration produces steam as well as electricity.
Several large companies have expressed interest, Davis said. He estimates the company could make syngas for about 75 percent of the current price of natural gas on commodities markets, and less than half that of fuel oil. Tipping fees for taking the waste could further lower the cost, he said.