By Megan Tseng
What happens when a forest goes up in flames? Firefighters drive in to control the fire, helicopters rain buckets of water, and reporters fly in for their next breaking news headlines. By the time the media coverage is over, the fire has died down.
But for peat fires, it doesn’t end there.
Commonly dubbed “zombie fires,” peat fires are caused by a type of soil constituting the partially decayed remains of plants. As the formation of peat results from a lack of drainage and oversaturated water, peat is found in swamps and bogs, often forming entire “peatlands.” Typically, peat is able to hold quantities of water up to 12 times its own weight, but its permeability, or ability to absorb, fluctuates with its moisture content; as a result, it resembles dry wood and becomes highly flammable during dry seasons.
The self-ignition of organic matter like leaves and wood are due to heat from oxidation reactions increasing the temperature of the matter when it cannot be released into the environment. A similar process causes the temperature of underground peat to spiral out of control, as its heat cannot escape into the atmosphere. Because of this, peat is able to reach temperatures up to 500 degrees Celsius, and the probability of self-ignition skyrockets. Due to the peat’s low moisture and high carbon content, it is able to sustain fires for extremely long periods of time.
These fires, commonly seen in peatlands and areas of low rainfall like Southeast Asia, are notoriously difficult to put out because of peat’s tendency to direct water into several large channels, allowing the rest of the peat to continue smouldering underground and reignite even after its flames are extinguished, hence its nickname: “zombie fires.” In this way, a single peat fire can consume up to billions of litres of water.
Recently, scientists at the Imperial College of London tested a type of surfactant commonly used in fighting wildfires, on suppressing peat fires. They mixed the surfactant with water in varying concentrations, 0%, 3%, and 5%, and measured the amount of time each took to suppress a laboratory-controlled peat fire. Their data showed that the medium concentration of surfactant was able to reduce fire suppression time by 39%.
So how did this happen? The surfactant reduced the surface tension of the water, allowing it to penetrate the pores of the peat much more quickly and increase its moisture throughout. This eliminated the smouldering that allows peat fires to reignite from within.
Think of that one science experiment with milk, soap, and food coloring. You drop food coloring into a plate of milk, and touch a bit of soap to the food coloring. As soon as the soap comes into contact with the food coloring, the colors swirl out and mix into the milk. Just like the one used in the research study, soap is a surfactant; it reduces the surface tension of the surrounding substances -- milk and food coloring -- and allows them to mix. Similarly, the surfactant used in the peat fire experiments allowed the water to spread through the peat easily.
With this type of surfactant, peat fires will become much less difficult to suppress. One of the current methods of controlling peat fires is flooding. Yes, it’s exactly what it sounds like: the entire area of peat is flooded with water, which gradually sinks into the peat and eliminates the smouldering. While effective, this method consumes billions of litres of water. Using findings from this study, the amount of water it takes to control a fire would reduce by over one-third, and flooding techniques would not be necessary when considering the water-surfactant solution. In addition, the surfactant is plant-based and biodegradable; after being absorbed into the peat, it will not cause any harm to the environment and can decay naturally.
In the future, scientists plan on further studies by starting controlled fires in peatlands. Not only would such research reform firefighting strategies, it would also help to prevent the burning of peat, a large producer of atmospheric carbon pollutants. Through the implementation of this new peat firefighting method, we can expect to see positive changes in the environment and less damage from fires.
A Taufik, Arief, et al. “Self-Ignition Temperature of Peat.” IOP Science, IOP Publishing Ltd, 2019, iopscience.iop.org/article/10.1088/1742-6596/1198/4/042021.
Brogan, Caroline. “‘Magical’ fire suppressant kills zombie fires 40% faster than water alone.” Imperial College of London, 12 Mar. 2021, imperial.ac.uk/news/217233/magical-fire-suppressant-kills-zombie-fires/.
“Peat Wildfires.” University of Leicester, le.ac.uk/departments/geography/research/projects/tropical-peatland/peat-fires.
Rein, Guillermo. “The long slow burn of smouldering peat mega-fires.” International Association of Wildland Fire, 2021, iawfonline.org/article/the-long-slow-burn-of-smouldering-peat-mega-fires/.
Santoso, Muhammad A., et al. “Laboratory study on the suppression of smouldering peat wildfires: effects of flow rate and wetting agent.” International Journal of Wildland Fire, CSIRO Publishing, 2021, publish.csiro.au/WF/WF20117.