Manufactured Wood Fuels Pilot Project

The Missoula City-County Health Department continues to look for strategies to address the high wood stove smoke levels that occur in some Seeley Lake neighborhoods. This past winter we launched a pilot project to look at an alternative wood-based fuel source (manufactured wood fuel logs) to see if it would be effective at reducing smoke emissions and if it would fit the home heating needs of Seeley Lake residents.

Manufactured wood fuel logs are made of compressed sawdust or wood chips with or without binder additives. These logs, with a moisture content between two-eight percent, can drastically reduce smoke emissions from a wood stove when compared to firewood (which typically has a moisture content above 20 percent).

Other benefits of manufactured logs are that they produce less ash in the hearth and reduce creosote buildup in the chimney when compared to regular firewood. For the pilot project, three Seeley Lake residents accepted two pallets of manufactured logs each and then gave feedback on how the fuel performed for home heating. One pallet of manufactured logs has a heating capacity roughly equivalent to one and half cords of firewood. The manufactured logs used in the pilot project were made of 100 percent compressed wood with no wax or other binders added.

The three devices involved in the pilot project included a small wood stove, a wood-fired furnace and a fireplace. All three devices were the primary source of heat for the residences.

For the wood stove, the manufactured logs burned hot and lasted a long time. The logs would eventually turn into red hot coals. One of the people living at this residence loved the wood and how hot it burned, while the other participant thought the logs burned a bit too hot. Both said they would use the manufactured logs again if they ever became available.

To moderate the heat from the manufactured logs, one of the operators at times mixed firewood (larch or lodge pole) in with the fuel loads. This operator felt that the manufactured logs produced more ash than regular firewood and the manufactured logs were a bit trickier to ignite than normal firewood.

The wood-fired furnace operator rarely mixed fuels and found that two pallets of manufactured wood lasted 60 days from the end of December into February. Less ash was generated with the manufactured wood compared to firewood, and the stove pipe stayed clean.

The operator stated that it takes a good kindling fire to get the manufactured logs started but once going, the manufactured wood works great. Another big benefit that the operator found was that less smoke entered the home when reloading the furnace with manufactured wood. If the price was comparable to regular firewood, the operator would consider using manufactured wood in the future.

When used in a fireplace, the manufactured wood worked great. The logs burned hot and looked like red coals once the fire was fully active. As with the furnace, ash generated by the manufactured wood was considerably less than the ash generated by regular firewood.

Smoke emissions from each device were typically minimal when the manufactured logs were burning, and frequently only heat waves were visible exiting the chimney.

If an affordable local supply of manufactured logs ever becomes available, this pilot project demonstrates that manufactured wood logs, with their low moisture content and reduced smoke emissions, are a viable fuel for home heating. Unfortunately, a pallet of manufactured logs costs more than $300.00, which is not cost competitive with the firewood easily available in Seeley Lake.

Strategies to further reduce wood stove smoke emissions include reducing fuel moisture content, installing a centralized district heating system, or replacing standard wood stoves with fully automated wood stoves. Two ways to reduce moisture content in wood are to use manufactured fuels (such as the compressed wood used in the pilot project), or to set up a wood storage shelter where wood is collected, split and seasoned until the moisture content is below 20 percent before the fuel is distributed.

A district heating system is a wood boiler that circulates hot water to local residences and business. A community wood boiler can be a clean source of heat and the technology has worked well in other communities around the country. However, there are large upfront costs for the initial boiler and hot water line installation.

Automated stoves are relatively new and they use temperature and other sensors to control air flow into the stove at startup and throughout the burn cycle. The cleaner burning automated stoves use a hybrid design that incorporates a secondary burn chamber with a catalyst. One of the benefits of the catalyst is more of the heat stays in the home and a load of fuel can last considerably longer than in a non-catalytic stove. Some recently designed automated stoves can be controlled by a thermostat and be set to maintain room temperatures near a set point. This load it, light it and set the temperature design is convenient, burns cleaner and puts more wood heat into the home instead of out the chimney.

While the wood stove change-out program greatly improved winter air quality in Seeley Lake, there are still a couple neighborhoods around the elementary school where further progress reducing wood stove smoke is needed. Fortunately, most of the Seeley Lake Valley appears to meet the National Ambient Air Quality Standard for fine particulate matter and so most of the available resources and attention can be focused on the elementary school neighborhoods.

The Missoula City-County Health Department is committed to working with Seeley Lake residents to find solutions that work for the neighborhoods to ensure everyone can heat their homes and breathe the air.

Benjamin Schmidt is the Air Quality Specialist with the Missoula City-County Health Department.