Greentech Media

Mark Mentemurro, CEO of Calgary-based Alter NRG, a supplier of plasma-gasification systems that produce syngas from waste, said he doesn't want to tie his company to any particular type of energy output.

But he conceded that burning syngas for power is a waste of waste. "The syngas produced from gasification, it would be 40 to 50 percent efficient to burn for electricity. If it's for ethanol, the energy conversion is much higher - upwards of 80 percent."

In 2009, Coskata - which claims it can produce ethanol for less than $1 a gallon -- plans to start producing cellulosic ethanol using syngas from an Alter NRG gasifier plant near Pittsburgh. General Motors (NYSE: GM), a strategic investor in Coskata, will test the ethanol in its flex-fuel vehicles.

Mentemurro cautioned that not all technologies are created equal, and that economics are also shaped by geography and logistics. Fluid-bed gasification technology from Enerkem, for example, may be cheaper to operate because it uses lower temperatures than the plasma system from Alter NRG. But higher temperatures may make it easier to handle a variety of waste, which saves on the cost required to handle and separate feedstock.

That's why a 25-year feedstock supply agreement with Edmonton was so attractive, said Pierce, pointing out that the city has a world-class sorting system. It means Greenfield and Enerkem don't have to absorb that sorting cost into their own plans.

Enerkem is building at the sorting site, which also is about five minutes away from where the ash resulting from Enerkem's process will also be used to help manufacture bricks. "The logistics are ideal," he said.

Chornet disputed the suggestion that Enerkem's process, because it uses lower temperatures and is less energy-intensive, can't handle diverse materials. Still, sorting has other benefits as well: it separates low- from high-calorific waste. The economics of a plant that gets mostly plastics can be wildly different than a plant using low-energy materials with high water content.

"What they will make energy from in Edmonton is 100 percent inorganic," mostly plastics, argued Rod Bryden, CEO of Ottawa-based Plasco Energy Group, one of a few companies getting traction with the idea of turning syngas to electricity.

Plasco has a small gasification demonstration plant at an Ottawa-area landfill site that processes up to 85 tons of municipal solid waste daily. Last month the city gave a conditional go-ahead for a 150,000 ton-a-year facility under a 20-year waste supply contract. Plasco would get a $60 tipping fee for every ton received and also, under a new Ontario feed-in tariff program, would be able to sell electricity to the grid for 11 cents a kilowatt-hour. The plant is expected to have a baseload capacity of about 21 megawatts.

"We're taking garbage right off the back of a garbage truck," said Bryden, explaining that the mixed and moisture-heavy waste that Plasco is processing probably has a third of the energy content as the waste that Enerkem will process.

The advantage is that little sorting is required, making the process appealing to smaller communities that lack the sorting infrastructure. Plasco prefers to keep its plants under 400 tonnes a day. Beyond that, transportation costs and associated emissions go up, offsetting the environmental advantages a gasification facility offers.

Bryden also argued that the efficiency of Plasco's process allows it to extract 78 percent of the energy from the waste that it converts, resulting in the production of more electricity than competing gasification systems. He's not against producing ethanol from the syngas - some day - but said "our analysis tells us we're still better to use it for electricity."

Plasco is in advanced talks with four cities in California - two expected to result in signed contracts by the end of this year. Chile's capital, Santiago, is also interested and serious talks are taking place with communities in France.

In Canada, two small towns - one in Alberta, the other in British Columbia - are also ready to sign up. Bryden said the pitch is simple: We'll pay for and build it, you pay us $70 a ton and give us 11 cents per kilowatt-hour for the electricity.

"Under such a case, they don't care if we're making ethanol or beach sands, as long as it's clean," he said.

Columbia University's Castaldi said modern gasification systems can be more environmentally sound than older incineration technologies or so-called "mass burn" systems. But as far as the public is concerned, they're still burning garbage, and this conjures up images of big industrial stacks spewing black smoke in the air.

Ethanol, he said, is newer and closer to home. "We all buy gasoline every day." For this reason, it's likely to face less community resistance, he said.

Chornet said communities are more embracing of approaches that can be sold as recycling. Electricity simply doesn't fit that bill - ethanol does. "It's a true chemical recycling of our wastes."

And, by relying on garbage, it won't cause tortilla riots in Mexico.