The Cutting Edge

The city of Edmonton in Alberta, Canada has taken a large step forward in liquid fuel production. But it has nothing to do with the famous tar sands deposit of the province—it has to do with trash.

Prior to mastering the drilling and piping of natural gas in the 1940s, lighting and cooking in cities used what was called "town gas" or producer gas. Coal was heated in a low oxygen atmosphere (sometimes with water) and a mix of hydrogen, carbon monoxide, methane, and carbon dioxide was emitted. Carbon monoxide was the key. Although even in low concentrations it is dangerous as it binds very tightly to the oxygen-carrying part of our blood, carbon monoxide is a fine fuel, burning just as natural gas does.

Fast-forward to 2008, and Edmonton is reviving this process with a 21st century twist.

Edmonton has an aggressive trash reduction program with 60 percent of all solid waste being recycled or composted. What’s new is that they intend to improve that figure by taking an additional 30 percent of their waste stream and making ethanol.

The process involves four distinct phases. The carbon based portion of the city's trash stream that can't be recycled or composted is shredded and dried. This material is then passed into a fluidized bed gasifier and a dirty syngas is created. The syngas conditioning step is next, followed by feeding the pure gas into a catalytic reactor to produce ethanol.

This process is flexible on the front end, being able to take any solid material without pelletization, and liquids or slurries with appropriate injectors. The gasification phase can be tuned to produce differing mixes of hydrogen and carbon monoxide, by varying temperature, pressure, available oxygen, or the injection of steam. Even the fly ash is put to use – it ends up as a slag suitable for inclusion in cement or asphalt.

The hands-on players in this new system are the forward-looking city of Edmonton, Greenfield Ethanol, Canada's largest ethanol producer, and Enerkem, the biofuels plant developer who created the process. Edmonton and the province of Alberta via the Alberta Energy Research Institute are the funding sources. Edmonton is providing $50 million and the balance of the $70 million plant is covered by AERI dollars.

The city expects to put 75,000 tons of waste into the process annually and get back nearly seven and a half million gallons of ethanol. The payback on the $70 million investment should come very quickly, even with the currently depressed oil prices—perhaps in as little as seven to ten years.

Neal Rauhauser is an analyst and consultant on energy and telecommunications. He is a member of the Stranded Wind Initiative and can be found at www.strandedwind.org.