Reducing energy consumption and conserving resources are integral to our success. Energy consumption has accompanying financial and environmental costs that vary depending on the type of energy used. We continually evaluate our operations and planned projects to minimize these costs by emphasizing conservation and the use of renewable energy.
Energy needs at our wood products facilities are principally supplied by residual wood-fired boilers, purchased electricity, and some fossil fuels. Residual wood from lumber production is utilized in boilers to produce steam energy to dry wood in the kilns and to provide comfort heating. Purchased electricity is used to run process equipment and for heating and cooling. Other fossil fuels (mostly diesel) are predominantly used in mobile equipment with one facility also having a supplemental natural gas-fired boiler and direct-fired kiln.
Another energy consuming piece of equipment is our regenerative catalytic oxidizer (RCO), which is an air pollution control device at our plywood mill. The RCO uses propane to maintain a sufficient temperature to destroy air pollutants before they’re released. The catalyst in the RCO allows for a lower temperature, therefore reducing propane usage.
Residual wood-fired boilers represent the heart of our wood products facilities. These boilers create steam that provides heat to our operations and power to our kilns where lumber is dried. At St. Maries, the boilers also provide efficient and economical steam heat to the veneer dryers. The boiler energy is provided by renewable wood residuals in the form of hogged fuel. Hogged fuel is a mixture of bark, wood, and sawdust residuals from the manufacturing process that are ground up or “hogged” for better consistency.
The sources of energy consumed at each mill vary depending on equipment configuration. The goal is to optimize the use of renewable fuels such as our wood residuals, within the physical equipment constraints while minimizing other environmental impacts. Our Warren and Bemidji wood products facilities obtain approximately half of their energy requirements from wood residuals. The Gwinn facility utilizes natural gas and other fossil fuels to meet about 20% of total energy needs. The natural gas fired boiler and kiln at Gwinn minimize emissions of criteria air pollutants such as particulate matter, carbon monoxide, and oxides of nitrogen compared to emissions from a biomass boiler. The regenerative catalytic oxidizer used to meet the NESHAP Rules at our St. Maries plywood facility also uses propane to destroy the hazardous air pollutants from the veneer dryers.
The greenhouse gas emissions from the boilers burning wood residuals produce biogenic emissions. Even though the wood residuals emit CO2 when burned, the carbon emitted is part of the biogenic cycle rather than an increase in total carbon in the atmosphere from burning fossil fuels. Using residuals for energy sourced from sustainably managed forests reduces wood waste and has the additional benefit of avoiding carbon emissions from fossil fuels.