Researchers study how to reduce soot produced by agricultural fires

agricultural burning smoke
Smoke plume from the burning of wheat residue on the Nez Perce Reservation. The field was burned using a head fire. The dark color of the smoke plume indicates high soot content. Photo by Emily Lincoln.

The production cycle of cereal crops and grasses in many areas of the United States includes burning fields of post-harvest residue such as wheat stubble. Like smoke from forest fires, smoke produced by agricultural burning can have harmful effects on public health.

The U.S. Forest Service and the Washington State Department of Ecology conducted a study to determine the effects different ignition tactics had on the smoke produced by agricultural burning of wheat residue.

agricultural burning smoke
Smoke plume from the burning of wheat residue north of Walla Walla, Washington. The field was burned using a backing fire. The light color of the smoke plume indicates low soot content. Photo by Emily Lincoln.

They found that smoke plumes produced from burning wheat residue using head fires contained more soot than plumes produced using backing fires.

Soot particles are black aerosols composed primarily of elemental carbon. The World Health Organization reports that soot particles may have significantly greater negative health impacts than other particle types found in smoke and air pollution since these particles can act as a carrier for toxic combustion-derived chemicals.

NIST seeks help studying embers

The National Institute of Standards and Technology (NIST) is beginning a study to help determine how wildfires spread through a Wildland-Urban Interface (WUI). Many studies have found that structures are primarily ignited during a wildfire by burning embers that are lofted into the air and then land on or near buildings.

Without research, NIST says, building codes and standards do not provide adequate protection to structures within the WUI. More specifically, codes and standards do not adequately address the range of exposures during a WUI fire – especially firebrand or ember exposures.


NIST intends to develop a device which will help them learn more about burning embers. They are calling this instrument a “emberometer”. During the next two years, the researchers plan to fabricate and test an “emberometer” design developed for laboratory settings. Once initial testing is complete, a new design will be developed for an “emberometer” that can be used in controlled field experiments and actual WUI fire events (i.e., outside of the laboratory setting). Once fabrication for the “outdoor emberometer” is completed, NIST will identify field teams that can employ the instrument to collect exposure information on firebrands (embers) during field studies, and initial data collection to characterize firebrand (ember) exposure can begin.

How you can help

Fire photographers who have taken photographs of WUI fires with significant firebrand activity are encouraged to share their pictures and videos for analysis. If you are interested, contact Erica Kuligowski at or 301-975-2309 for guidelines.

Impressive convection column on Pioneer Fire is being studied by researchers

Above: The photo above was taken from the research aircraft August 30 by Nick Guy of the University of Wyoming’s Atmospheric Science department.

The Fire Weather Research Laboratory from San Jose State University is conducting research from an aircraft flying over the Pioneer Fire in central Idaho. Today using N2UW, a twin engine 1977 Beech 200T King Air, they flew for over three hours at 27,000 feet studying the fire for the RaDFire project.

The aircraft is outfitted with a ton of instruments including Doppler radar. Craig Clements, Associate Professor in the Meteorology Dept. at SJSU, described it for us:

The radar is called the Wyoming Cloud Radar (WCR). It’s on the aircraft, points up, down, and down-forward to get horizontal winds and vertical winds. The goal of the RadFIRE (Rapid Deployments to Wildfires Campaign) is to get data on plume dynamics from ground based mobile Doppler Lidar. But we were awarded 10 flight hours to test the WCR to see if it works in smoke plumes. And it does so well, more than we can imagine!

The group has been known to fly through the convection column. I’ve done that a few times and it’s an interesting experience — it can get a little turbulent, as you might expect.

On Monday they said the top of the pyrocumulus cloud over the fire topped out above 30,000 feet. In Tuesday’s photos it was at about 25,000 feet but toward the end of the day the top got up to at least 32,000 feet, Mr. Clements said.

The project is sponsored by the National Science Foundation and it’s being led by San Jose State University. Other collaborators on the project are David Kingsmill at the University of Colorado Boulder, and the University of Wyoming King Air team.

Since it started on July 18 the Pioneer Fire has burned over 140,000 acres.

This last photo of the convection column was not taken by the researchers. It was shot by Steve Botti in Stanley on August 29, more than 20 miles away from the fire.

Pioneer Fire
Pioneer Fire, as seen from Stanley August 29, 2016. Via Mike Warren.

Researchers predict impacts of wildfire smoke after climate change

Above: Illustration from Harvard/Yale paper about the impacts of wildfire smoke following climate change. The colors indicate the number of smoke waves based on the primary smoke wave definition (cutoff= 6 μg/m3). The map on the left represents the present day (based on 2004-2009 data). The map on the right represents the future under climate change (based on projected data for the years 2046-2051). 

(Originally published at 11:39 a.m. MDT August 16, 2016; edited at 6 p.m. MDT August 17 to include this link to the research paper.)

Researchers at Harvard and Yale Universities have written a paper predicting the quantities of wildfire smoke that will be impacting residents of the United States in the years 2046 through 2051. Unfortunately it will cost you $40 to get a copy of the complete results of their research. Open Access to publically funded research is apparently not a priority at Harvard and Yale. (UPDATE: on August 17 we obtained a copy of the paper from one of the authors. But it would still cost $40 to buy it from the journal.)

The information here is obtained from the abstract and one document with supplementary material that was available.

To identify the highest-risk areas, the team used a fire prediction model and advanced atmospheric modeling to separate pollution caused by wildfires from other pollution sources and track the likely movement of smoke. The authors estimate that under future climate change, more than 82 million individuals will experience a 57 percent and 31 percent increase in the frequency and intensity, respectively, of Smoke Waves, which they define as ≥2 consecutive days with high wildfire-specific PM2.5.

Northern California, Western Oregon and the Great Plains are likely to suffer the highest exposure to wildfire smoke in the future. Results point to the potential health impacts of increasing wildfire activity on large numbers of people in a warming climate and the need to establish or modify U.S. wildfire management and evacuation programs in high-risk regions. The study also adds to the growing literature arguing that extreme events in a changing climate could have significant consequences for human health.

A call to Loretta J. Mickley, one of the authors, to ask about access to the publically funded research, was not immediately returned. UPDATE, August 17, 2016: Ms. Mickley did call the following day, and said she was disappointed that Harvard chose a non-Open Access journal in which to place the paper. She said she will send us a copy of the paper and it will also be posted on her web site in the next day or two. We will link to it later. The research was funded, she said, by the Environmental Protection Agency and the National Institutes of Health. In our opinion government agencies that fund research should only do so if the findings are made public at no additional charge.

The paper’s authors are J.C. Liu, L.J. Mickley, M.P Sulprizio, et al.

Scientists discover a new kind of fire whirl

The “blue whirl” can greatly reduce pollution

Above: A “blue whirl”.

Scientists attempting to develop a new method for mitigating oil spills by burning the oil were hoping to find a way to reduce the air pollution as the petroleum product burns. We’ve all see the thick, black smoke at an oil fire. They may be a step closer to their goal with the discovery of a new type of fire behavior — a previously unseen type of flame. They call it a “blue whirl”.

A paper published online August 4, 2016, in the peer-reviewed journal Proceedings of the National Academy of Sciences describes this previously unobserved flame phenomenon.

A yellow flame is a sign of very incomplete combustion and produces more particulates and air pollution than a blue flame like you see on a gas fueled stove.

So far they have only created the blue whirl in a chamber which has slits in the side that cause the air to rotate as it enters. Over a layer of water they injected a liquid fuel, n-heptane, and then ignited it. The flame at first is yellow but eventually transitions to a small, swirling blue flame.

“Blue whirls evolve from traditional yellow fire whirls. The yellow color is due to radiating soot particles, which form when there is not enough oxygen to burn the fuel completely,” said Elaine Oran, Glenn L. Martin Institute Professor of Engineering and co-author of the paper. “Blue in the whirl indicates there is enough oxygen for complete combustion, which means less or no soot, and is therefore a cleaner burn.”

“This is the first time fire whirls have been studied for their practical applications,” said Michael Gollner,  co-author of the paper and assistant professor of fire protection engineering at the A. James Clark School of Engineering at the University of Maryland.

One of the principles that reduces the pollution in the blue whirl is that plenty of oxygen is available for the fuel, helping it to burn more completely. Another is that the partially burned fuel remains in the flame longer, burning more completely.

An air curtain used near Custer, SD in 2013 produced very little visible smoke. Photo by Bill Gabbert.

Land managers sometimes use an “air curtain” to burn woody debris from fuel reduction operations. We wrote about this in 2013 after visiting one near Custer, South Dakota. The one we saw was trailer-mounted. The key to the system is pumping large amounts of compressed air into the fire box or open trench. Some of the devices create a vortex which traps the particulates keeping them in the burn zone longer, causing them to more completely burn while reducing their size and the visible smoke.

air curtain
Air Burner Inc.

Some oil spill remediation techniques include corralling the crude oil to create a thick layer on the water surface that can be burned in place, but the resulting combustion is smoky, inefficient, and incomplete. However, the Clark School researchers say blue whirls could improve remediation-by-combustion approaches by burning the oil layer with increased efficiency, reducing harmful emissions into the atmosphere around it and the ocean beneath it.

“Fire whirls are more efficient than other forms of combustion because they produce drastically increased heating to the surface of fuels, allowing them to burn faster and more completely. In our experiments over water, we’ve seen how the circulation fire whirls generate also helps to pull in fuels. If we can achieve a state akin to the blue whirl at larger scale, we can further reduce airborne emissions for a much cleaner means of spill cleanup,” explained Gollner.

Beyond improvements to fuel efficiency and oil spill remediation, there are currently few easy methods to generate a stable vortex in the lab, so the team hopes their discovery of the ‘blue swirl’ can serve as a natural research platform for the future study of vortices and vortex breakdown in fluid mechanics.

“A fire whirl is usually turbulent, but this blue whirl is very quiet and stable without visible or audible signs of turbulence,” said Huahua Xiao, assistant research scientist in the Clark School’s Department of Aerospace Engineering and corresponding author of the paper. “It’s really a very exciting discovery that offers important possibilities both within and outside of the research lab.”

NOAA experiments with forecasts for wildfire smoke

Wildfire smoke forecast
Wildfire smoke forecast for 6 p.m. MDT August 4, 2016

The National Oceanic and Atmospheric Administration is experimenting with a system that produces forecasts for the distribution of smoke from wildfires.

The examples of their products created at 6 a.m. MDT August 4 for near-surface smoke are included here — predicting conditions for 6 p.m. MDT August 4 (above) and 6 p.m. August 5 (below). Click the images to see larger versions.

Developers are collecting feedback from users to improve the model before it is considered for transfer into operations.

The HRRR-Smoke air quality modeling system simulates the emissions and transport of smoke from wildfires detected by the VIIRS/JPSS satellite fire product in high spatial resolution (3km) over the CONUS domain. Currently the model is run every 6 hours (00, 06, 12 and 18 UTC) to produce smoke forecasts for next 36 hours. The forecast products of near-surface and vertically integrated smoke concentrations are visualized on a GSD web-site in real time:

Wildfire smoke forecast
Wildfire smoke forecast for 6 p.m. MDT August 5, 2016