Smoke Management: Techniques to Reduce or Redistribute Emissions

There are two general approaches to managing the effects of wildland fire smoke on air quality:

1. Use techniques that reduce the emissions produced for a given area treated
2. Redistribute the emissions through meteorological scheduling and by sharing the airshed

Although each method can be discussed independently, fire practitioners often choose lighting and fuels manipulation techniques that complement, or are consistent with, meteorological scheduling for maximum smoke dispersion and favorable plume transport.

A land manager’s decision to use a specific burning technique is influenced by many considerations, only one of which is a goal to reduce smoke emissions. Other important considerations include ensuring public and firefighter safety, maintaining control of the fire and keeping it within a given perimeter, complying with numerous environmental regulations, minimizing nuisance and hazard smoke, minimizing operational costs, and maximizing the likelihood of achieving the land management objective of the burn. Often these other considerations preclude the use of techniques that reduce emissions. In some cases, however, smoke emission reductions are of great importance and are achieved by compromising other goals. Emission reduction techniques vary widely in their applicability and effectiveness by vegetation type, burning objective, region of the country, and whether fuels are natural or activity- generated.

Emission reduction techniques (or best available control measures–BACM) are not without potential negatives and must be prescribed and used with careful professional judgment and full awareness of possible tradeoffs. Fire behavior is directly related to both fire effects and fire emissions. Emission reduction techniques alter fire behavior and fire effects and can impair or prevent accomplishment of land management objectives. In addition, emission reduction techniques do not necessarily reduce smoke impacts and some may, under certain circumstances, actually increase the likelihood that smoke will impact the public. Emission reduction techniques can cause negative effects on other valuable resources such as through soil compaction, loss of nutrients, impaired water quality, and increased tree mortality; or they may be dangerous or expensive to implement.

Land managers are concerned about the repeated application of any resource treatment technique that does not replicate the ecological role that fire plays in the environment. Such applications may result in unintended resource damage, which may only be known far in the future. Some examples of resource damage that could occur from the use of emission reduction techniques include the loss of nutrients to the soil if too much woody debris is removed from the site, or the effects of soil compaction associated with mechanical processing (chipping, shredding, or yarding) of fuels. The application of herbicides and other chemicals and/or the effects on soils of the intense heat achieved during mass ignition are also of concern. These issues are difficult to quantify but are of universal importance to land managers, who must weigh the impact of their decisions on long-term ecosystem productivity.

Multiple resource values must be weighted along with air quality benefits before emission reduction techniques are prescribed. Flexibility is key to appropriate application of emission reduction techniques and use of particular techniques should be decided on a case-by-case basis. Emission reduction goals may be targeted but the appropriate mix of emission reduction techniques to achieve those goals will require a careful analysis of the short and long term ecological and social costs and benefits. Air quality managers and land managers should work together to better understand the effectiveness, options, difficulties, applicability, and tradeoffs of emission reduction techniques.

Meteorological scheduling is often the most effective way to prevent direct smoke impacts to the public and some emission reduction techniques may actually increase the likelihood of smoke impacts by decreasing the energy in the plume resulting in more smoke close to the ground. A few of the potential negative consequences of specific emission reduction techniques are mentioned in this chapter although this topic is not addressed comprehensively.

Use of Smoke Management Techniques

The emission reduction and emission redistribution techniques described in this section are a comprehensive compilation of the current state of the knowledge. Much of the information presented was gathered from fire practitioners at three national workshops held during the fall of 1999. Practitioners were asked to describe how (or if) they apply emission reduction techniques in the field, how frequently these methods are used, how effective they are, and what constraints limit their wider use. The information gained at each of the workshops was then synthesized into a draft report that was distributed to the participants for further review and comment. Twenty-nine emission reduction and emission redistribution methods within seven major classifications were identified as currently in use to reduce emissions and impacts from prescribed burning.

For more information see: The Use and Effectiveness of Emission Reduction and Redistribution Techniques

The emission reduction methods described in this document may be used independently or in combination with other methods on any given burn. Any one of these may or may not be applicable in a given situation depending upon specifics of the fire use objectives, project locations, time and cost constraints, weather and fuel conditions, and public and firefighter safety considerations. In addition, a number of different firing methods potentially can be applied to any given parcel of land depending on the objectives and judgments made by the fire manager. As a result, no two burns are the same in terms of pollutant emissions, smoke impacts, fuel consumption, or other parameters.

Significant changes in public land management have occurred since EPA’s release of the first document describing best available control measures (BACM) for prescribed burning (EPA 1992). Some of these changes have dramatically impacted when and how emission reduction methods for prescribed fire can be applied. On federally managed lands, the following constraints apply to many of the emission reduction techniques: National Environmental Policy Act (NEPA), Threatened and Endangered Species (T&E) considerations, water quality and impacts on riparian areas, administrative constraints imposed by Congress (e.g., roadless and wilderness area designations), impacts on archaeological resources, smoke management program requirements, and other state environmental or forestry regulations.