Enerkem commercial-scale biogas plant starts up

By Anna Austin
Implementing a unique technology that has been in the works over the past six years, Quebec-based Enerkem Inc. began the start-up phase of its commercial-scale biogas plant in Westbury, Quebec. After a 14-month construction period, it will process biomass into synthesis gas, ethanol and methanol.

Since 2003, the company has operated a pilot plant in Sherbrooke, Quebec. Enerkem President and Chief Executive Officer Vincent Chornet said he expects the commercial-scale facility to become fully operational within a few months after the alcohol modules are bolted to the syngas island.

The company's sequential gas conditioning and catalysis technology uniquely allows for the processing of certain types of demolition wood, such as decommissioned power poles and creosote-treated wood that most companies can't process due to air or environmental permit limitations. The 1.3 MMgy facility in Westbury is collocated with a sawmill and will utilize waste materials to produce 365 liters (95 gallons) of ethanol per ton.

Besides treated wood waste, the plant is also capable of processing sorted municipal solid waste. "Forestry biomass is like butter for us, although the plant is designed to be flexible," Chornet said.

After the wood chips and other wastes are dried, sorted and shredded, they are stored in a container connected to the gasifier by a front-end feeding system. Slurries or liquids may also be fed into the gasifier through injectors. The carbonaceous materials, such as biomass treated with creosote, are converted into a syngas consisting mostly of carbon monoxide and hydrogen through a chemical gasification process.

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 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. The gas is cleaned and conditioned for use with existing catalysts through a sequential conditioning system that includes the cyclonic removal of inerts, secondary carbon and tar conversion, heat recovery units, and the reinjection of tar and 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.

The ethanol produced at Enerkem's facility will be marketed and sold within Canada to refineries. Chornet said the company is currently in talks with refineries in the greater Montreal area.