Since more companies than ever before are gaining permits to accept creosoted wood to recycle for biomass, opponents and environmentalists want to know what is being done to ensure the toxins are being properly removed—and if it is really environmentally safe. Enerkem, a leading producer of cellulosic biofuels, has developed a new technology to remove contaminates such as creosote from wood using a gasification and catalysis process.

Enerkem Emerges
Enerkem, founded in 2000, is headquartered in Montreal. The company has operated a pilot plant in Sherbrooke, Québec, since 2003—testing a new gasification and catalytic synthesis technology.

The unique factor Enerkem possesses is the ability to process certain types of demolition wood—such as decommissioned power poles and creosote treated wood—that most corporations cannot, because of permit limitations preserving air quality and the environment. Enerkem has recently partnered with GreenField Ethanol, Canada’s leading ethanol producer, and is in the midst of constructing the company’s first commercial-scale plant in Westbury, Québec, along with a series of other projects in Canada.

Enerkem is colocated with a saw mill that recycles the middle part of the decommissioned power poles into construction wood, such as 2x4s. The remaining treated portions containing impurities cannot be recycled into construction wood. These pole residues are transformed into wood chips by the saw mill and transferred to Enerkem to be converted into ethanol.

In the first step, the wood chips or other feedstocks are dried, sorted and shredded to be stored in a container that is connected to the gasifier by a front-end feeding system capable of handling fluffy material, without the need to pelletize. Slurries or liquids may also be fed into the gasifier through appropriately designed injectors. The carbonaceous materials, such as biomass treated with creosote, are converted into a synthetic gas—consisting mostly of carbon monoxide and hydrogen—through a chemical gasification process.

The gasification process is carried out using air as a partial oxidation agent or using oxygen-enriched air, with the oxygen level tailored to the desired composition of the synthetic gas. The presence of steam at a specific partial pressure is also necessary. The gasifier operates at low severities, temperatures of approximately 700 degrees Celsius (1,292 degrees Fahrenheit) and below 10 units of atmospheric pressure. During the gasification process, part of the creosote is broken down, forming a portion of the product syngas.

Other traces of impurities are captured as residues in the form of a neutralized ash, or through a wastewater treatment system for effective disposal through the syngas cleaning system. At this stage, the gas is effectively cleaned and conditioned for use with existing catalysts. This is accomplished through a sequential conditioning system, which includes cyclonic removal of inerts, secondary carbon and tar conversion, heat recovery units, and reinjection of tar/fines into the reactor. The gas that is produced at the end of the cleaning process is ready for conversion into liquid fuel and end products which Enerkem says meet all requirements as either industrial grade products or fuel additives.

The Westbury plant is scheduled to begin production in the fall of 2008, and will have the capacity to produce more than 1.3 MMgy. The company is currently negotiating with other facilities to take their treated wood, Enerkem tells Biomass Magazine.

The number of companies that are striving to develop new technologies to utilize less commonly used but accumulating wastes, such as creosote treated wood, is on the rise. As the renewable fuels race continues—so does the recycling race.

Anna Austin is a Biomass Magazine staff writer. Reach her at aaustin@bbiinternational.com or (701) 738-4968.

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