Emission Reduction Techniques

The use of emission reduction techniques (ERTs)

Several methods for reducing emissions are available to burners. The overall approaches include reducing the fuel load, reducing the fuel burned, increasing burning efficiency, and increasing burn frequency. When choosing an ERT, be sure to keep the following considerations in mind:

  • Effectiveness over time: Ensure the methods chosen actually reduce the amount of total emissions over time, not just delay them.
  • Emissions transport: Some ERTs can also reduce plume rise and could increase surface smoke concentrations.
  • Documentation: It is recommended that documentation be kept on the use of ERTs and emissions averted if needed.
  • Fire personnel exposure: If mop-up is considered as an ERT, be aware of the potential smoke impacts to fire personnel carrying out the mop-up operations. Are the risks associated with smoke being eliminated, or just transferred from the public to the fire personnel?

Each of the following methods, and some of the considerations that accompany them, are described below:

Reducing the fuel load

Fuel loading can be reduced either mechanically, or by grazing.  Mechanical treatment can include onsite chipping of debris, firewood collection, thinning, piling, mastication, mechanical removal of logging debris, or whole tree harvesting. Sometimes these fuel reduction techniques may be effective enough to eliminate the immediate need for prescribed burning. Grazing is another option for reducing fuel loading. Grazing may be economical, however animals are selective in what they eat, and may cause changes in the plant community over time. Grazing on steep slopes may also cause erosion.

Reducing fuel burned

Reducing the quantities of fuel burned in another method of reducing emissions. This can be accomplished by burning in high moisture conditions, implementing mop up quickly after a burn, or by burning before new fuels emerge.

Reducing the quantity of fuel consumed by fire may be achieved by burning in high moisture conditions when less fuel will be consumed than in dry conditions. Generally, conditions that facilitate this strategy occur a few days after a soaking rain, or following snowmelt. Burning in high moisture conditions creates the possibility of longer smoldering times and increased emissions if burning material does not extinguish soon after the burn. Rapid mop up is another strategy to reduce the amount of fuels consumed by not allowing them to smolder for long periods of time. Burning before new fuels emerge is another method of reducing the quantity of fuel consumed, thereby reducing emissions.

Increasing burning efficiency

Pile burning, back fires, and burning in dry conditions are all methods which generate greater heat allowing the materials to be consumed by fire more completely. These methods cause more fuel to be burned in the flaming phase of combustion, creating less emissions than if the fuel were allowed to smolder. This method should be chosen with care, due to the risk that a hotter fire may burn more fuels than would have otherwise consumed, reducing its usefulness in decreasing emissions. Soil heating should also be taken into account when using this strategy. High heat for long durations of time can destroy soil organic matter and greatly alter soil structural properties, which may result in increased post-burn erosion.

Burning more frequently

Burning more frequently reduces fuel accumulation, resulting in less biomass being burned. This approach of frequent low intensity burns may also prevent unwanted species from establishing.

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Sources:

Ottmar R.D. Techniques to Reduce Emissions from Prescribed Fire. Chapter in: Peterson, Janice; Lahm, Peter; Fitch, Mark; George, Michael; Haddow, Dennis; Melvin, Mark; Hyde, Josh; Eberhardt, Ellen. 2020. NWCG Smoke Management Guide for Prescribed Fire PMS 420-3. https://www.nwcg.gov/publications/420-3

Whalen, et al. 2003. Smoke Management Techniques RX-410. A publication of the National Wildfire Coordinating Group.

USDA Forest Service and Natural Resources Conservation Service. 2011. Basic Smoke Management Practices. Basic Smoke Management Practices Tech Note, October 2011. Accessed 3 January 2017. Available at: https://www.frames.gov/catalog/20307