Success Story

EPA Research Has Impact on Oregon State Regulations

aerostat with flyer - EPA

Aerostat with Flyer (left) and close-up of Flyer (right). Photo credit: Brian Gullett

To reduce wildfire risk and to improve timber forest productivity and health, woody biomass fuels from selective thinning and timber harvests are mechanically treated and piled for burning. Pile burning mitigates concerns about fire safety and air quality as it allows managers to burn under optimal weather conditions and with reduced staffing levels. To promote pile combustion, the biomass is preferably dry, resulting in faster, hotter, and more efficient burns, presumably with less pollutants. Common practice involves covering these large piles with polyethylene (PE) film to prevent moisture saturation during the rainy season. However, this practice has raised some questions about emissions from the burning plastic film.

In 2015, EPA entered into a Cooperative Research and Development Agreement (CRADA) with the Oregon Department of Forestry to study the effect of covering and burning timber slash piles with PE sheeting. Sampling of the burn piles was conducted using an EPA-developed instrument platform termed the “Flyer” that was lofted into the plume using a tether-controlled, helium-filled aerostat, or balloon. The platform sampled for emissions of pollutants, including carbon monoxide, carbon dioxide, methane, particulate matter, and black carbon to determine emissions factors and the amount of pollutant formed per amount of biomass burned. The aerostat was connected to two winch-equipped all-terrain vehicles (ATVs) with two tethers. The Flyer was maneuvered into the burn pile plume by controlling tether length and the location of the ATV-mounted tether winches. Sampling periods consisted of both active flaming and smoldering emissions.

EPA’s research indicated that burning dry piles, whether covered with PE or not, exhibited statistically significant lower emissions than wet piles due to better combustion efficiency. Variation of PE cover size and thickness showed no statistically significant difference in emissions factor for any of the pollutants, suggesting that the PE was not contributing significantly to any of the measured pollutants. As a result, Oregon modified its state guidelines for covering piles.