Producing Forest Products From Birch Trees

By Chantal Hunter

New technology will allow a pulp mill in Quebec to produce and commercialize dissolving pulp from birch trees, a currently underutilized species.

At its Thurso, Quebec mill, Fortress Specialty Cellulose recently launched a new project that will use wood from birch trees to produce dissolving pulp, an ingredient that can be used in many everyday products including clothing, car parts and medical equipment.

Once operational, Fortress Specialty Cellulose will be the first mill in North America to produce dissolving pulp from birch wood on a continuous basis.

Dissolving Pulp From Birch Wood

Birch, a tree species that grows abundantly in Canada, has been largely underutilized by the pulp and paper industry mainly because it tends to have a high sugar content, making it difficult to convert into dissolving pulp.

With funding from Natural Resources Canada’s (NRCan) Investments in Forest Industry Transformation (IFIT) program and the Government of Quebec, Fortress Specialty Cellulose is installing new equipment, including a super-batch digester. The new digester will support a specific cooking cycle for birch wood, which will allow the mill to produce dissolving pulp using birch.

Creating Dissolving Wood

Though both dissolving pulp and “regular” pulp are derived from wood, they are different products.

Regular pulp is produced by cooking wood biomass with chemical products at temperatures between 130 and 180°C. The resulting sludge-like substance is then pressurized and put through a screening and bleaching process to remove any debris, leaving only the pulp.

To create dissolving pulp, a pre-hydrolysis step is introduced in the process that removes hemicellulose, a weaker component, from the wood. The resulting pulp has a cellulose content of about 95 percent, which is much higher than regular pulp. Regarded as “specialty cellulose” by the pulp and paper industry, dissolving pulp, with its higher cellulose content, is used for a variety of products from textiles to food additives.

Reducing Greenhouse Gases

In addition to the economic benefits of producing dissolving pulp, one of the by-products of chemical production – black liquor – will also be converted into green energy in the process.

Mills typically dispose of their black liquor by using oil-based burners to recycle the cooking chemicals and generate renewable heat and power for their energy needs. The new dissolving pulp process will allow Fortress Specialty Cellulose to scale-down part of its oil-based boiler and, as a result, reduce greenhouse gas emissions by about 11,000 tonnes a year.

“This technology has the potential for replication across other dissolving pulp facilities in Canada with access to significant quantities of birch wood, thus benefiting the industry as a whole and helping wood product producers to stay competitive,” stated Glenn Mason, Assistant Deputy Minister, Canadian Forest Service. “It also supports Canada’s forest products sector in becoming more environmentally sustainable.”

“This investment highlights the innovative and transformative potential of producing dissolving pulp using birch and demonstrates our commitment to pursuing environmentally sustainable strategic projects,” stated Yvon Pelletier, Chief Executive Officer of Fortress Specialty Cellulose.

For more information, visit the NRCan Web site.