Do fires produce more emissions than cars?

Traffic Bejing
Traffic in Bejing

During a speech in Sacramento on August 15, 2008 California Representative Kevin McCarthy claimed that fires produce more emissions than cars:

“What I have found”, Rep. McCarthy said, “because of these fires, there are studies that are showing they are producing more emissions than all of our cars are doing.”

Politifact looked into Rep. McCarthy’s statement. Here is an excerpt from their article:

Bill Stewart, a researcher at the UC Berkeley Center for Forestry, said there’s a key point missing from McCarthy’s statement. While fires emit more particulate matter, cars produce far more greenhouse gas emissions, particularly carbon dioxide, he said.

“Those are two important but different issues,” Stewart said.

Mike Kleeman, a UC Davis professor of environmental engineering, added that wildfires also emit some greenhouse gases.

“But burned areas also regrow during which time they act as a net carbon sink.  Assuming a burned area regrows completely over a time of decades, the net CO2 emissions should be low,” Kleeman wrote in an email.

“Wildfires are a problem,” he added, “and we should be taking steps to reduce their frequency and intensity. But it isn’t an ‘apples to apples’ comparison to an every-day source like cars.”

Earlier this month, the Trump administration proposed rules that would ease vehicle emissions standards nationwide.

s2t airtanker holy fire
An S-2T air tanker comes out of the smoke to drop retardant near the communication towers on Santiago Peak August 8,2018 as the Holy Fire approaches. HPWREN image.

Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire. Google+

4 thoughts on “Do fires produce more emissions than cars?”

  1. In the last several years, it seems far more likely to have an air quality alert for wildfire smoke than automobile exhaust.

    Simply comparing CO2 emissions to projected or assumed CO2 consumption in long-term plant growth (I assume Kleeman is referring to photosynthesis) does not negate McCarthy’s claim, simply because the plants that burned were consuming CO2 before the fire. That process is stopped by the fire, and as Kleeman hinted, it could take decades to achieve the full absorption of CO2 that a mature ecosystem would have provided before the burn.

    If you consider the unburned hydrocarbons, the effects of alkaline ash, plus the additional toxic pollution created when synthetic materials now used construction are burned rapidly (and incompletely) by a wildfire, Mr. McCarthy’s claim is much more legitimate.

  2. There are many types of emissions which are monitored, including ozone, PM10 and PM2.5, nitrogen oxides, sulfur oxides, hydrocarbons, and carbon monoxide. Air Quality agencies develop emission inventories to document the sources of these pollutants, which are especially important if the area is found to be in a nonattainment status under the Clean Air Act for one or more criteria pollutants, such as ozone, and regulatory rules must be developed to bring the area into attainment. It is true that for short periods, fires can contribute substantial amounts of particulate matter. So, the statement may or may not be true, depending on the pollutant and the period of time. But I doubt any air quality regulatory unit has been classified as a nonattainment area because of smoke from wildfires, while they certainly have been classified as such due to cars and various other human-caused sources. Interestingly, President Reagan in 1981 claimed that trees produce more air pollution than automobiles, which set off a round of jokes about killer trees.

    1. One of the main reasons this issue continues to go round and round is grounded in the fact that the majority of those who become critical of climate policy are outcasted and made fun of. The biggest failure in today’s climate lab is the mantra of so-called
      ‚Political´ knowns. Maybe Reagan was on to something. “Plant species release appreciable quantities of volatile organic substances to the atmosphere. The major compounds emitted are monoterpenes (C10) like α-pinene, β-pinene, and limonene and the hemiterpene (C5) isoprene. The rate of emission of isoprene is light dependent and ranges between 0.04 to 2.4 ppb/cm2/min/l for oak, cottonwood, and eucalyptus foliage. The rate of emission of a- and/3-pinene and limonene is dependent on the rate of transpiration, structural integrity of the oil cells and resin glands, and temperature of the foliage. Rates of emission for conifer foliage range from 0.4 to 3.5 ppb/g/min/l. An inventory of North American forest regions for the frequency of occurrence of these chemicals released by different tree species showed that 15% was the lowest value for a specific forest-type that emitted terpenes to the atmosphere. More commonly 100% of the trees of a given forest-type emitted terpenes to the atmosphere. An average of 70% is typical of the United States forested regions as a whole. The annual contribution of forest hydrocarbon emissions to the air pollution problem on a global basis is reflected in the 175 × 106 tons of reactive hydrocarbons from tree foliage sources compared to the 27 × 106 tons from man’s activities; in other words, there is a 6.2-fold greater emission level from natural sources than from man made sources. The fate of these gaseous olefins in the atmosphere is
      undetermined“. https://www.tandfonline.com/doi/pdf/10.1080/00022470.1972.10469676?needAccess=true

  3. Perhaps we should look at the potential policy implications of the statements made….“Wildfires are a problem,” he added, “and we should be taking steps to reduce their frequency and intensity.” Does reduced wildfire frequency not equate to increased intensity in most cases over the long term? I’m just wondering if the general public have concerns that extend beyond the end of our noses? Is the immediate benefit of wildfire suppression not contributing to the increased intensity of future wildfires and costing more in the long run? As a culture, we really need to consider becoming more ardent fire MANAGERS. We’ve gotten pretty darn good and spending money, exerting energy, and sacrificing the lives of our firefighters in an attempt to squash most new starts as quickly as possible. Have our suppressive actions over the last 120 years not at least contributed to the increased volatility our fire environment today? We have to at least consider it…There has always been wildfire producing smoke. There always will be. Let’s get real about management.

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