More than 8,000 landfill fires occur each year, and can range from minor surface fires to massive blazes that can release harmful emissions. The cost of these fires is about $8 million annually in property losses, about 30 firefighters injured each year, and health and environmental dangers the toxic smoke and gases released during the fire.
Fires can begin for a variety of reasons, according to the U.S. Fire Administration. The more obvious causes usually pertain to surface fires and include arson, deposits of hot wastes, and natural causes such as lightening. According to data from the National Fire Incident Reporting System (NFIRS), more than 40 percent of fires with ignition factors are incendiary or suspicious in nature, and another 20 percent are caused by lit or smoldering materials that were discarded. Spontaneous heating makes up about 5 percent of the reported landfill fires.
But fires that start below the surface of the landfill are a bit more complex. Subsurface fires can occur through spontaneous combustion as a result of the decomposition process, or from older, smoldering or ignited items buried within the landfill. Detecting underground fires can be complicated, but can be confirmed by substantial settlement over a short period of time, elevated carbon monoxide levels, combustion residue in wells, temperatures of extracted gas reaching above 140 degrees, subsurface temperatures exceeding 170 degrees, and smoke or smoldering odors in the gas extraction system.
When landfill fires occur—particularly on larger scales—harmful emissions can result, including formaldehyde, hydrogen cyanide, hydrogen sulfide, nitrogen oxides and more. Particulate matter in the smoke created during landfill fires can also exacerbate respiratory and other health complications in those responding to the fire.
There is no one best way to extinguish a landfill fire due to the varying causes and nature of materials within the landfill. Some options for extinguishing landfill fires include excavation, overhauling, burying, injecting nitrogen or carbon dioxide, ground freezing, water injection, and foam-based methods.
Tires can pose additional problems, since they produce copious amounts of oil and smoke that can make a landfill fire even more difficult to extinguish, says the U.S. Fire Administration.
Prevention is key to managing landfill fires, and can be achieved by engineering the landfill site with fire suppression technology, operating in a way that focuses on monitoring potential fire sources, and having tools needed to manage a fire readily available.
Landfill operators should be aware of any odor changes, changes in temperature readings, unexpected changes in the makeup of landfill gases, or changes to the chemistry of leachate. Fires are most common in the spring and summer months, between March and August with the risk peaking in July when temperatures are at their highest in many places.
In addition, meeting with fire departments regularly to keep them apprised of landfill conditions, equipment and the state of facilities can help greatly in the event of a fire, according to Larry Stone, safety director with Waste Pro.
"if you're not preplanning in advance of a fire, it's not going to be a friendly situation when they show up to your scene," Stone said at a panel on fire safety at the annual WasteCon conference late last month.
The Federal Emergency Management Agency (FEMA) and the U.S. Fire Administration recommend the following methods to prevent landfill fires:
- Landfill Management: Prohibit burning and smoldering waste from entering the landfill through thorough inspection of incoming waste. Prohibiting smoking on-site and having good security measures to prevent suspicious fires is also key.
- Methane Gas Detection and Collection: Ensure than gas collection systems are not overdrawn, and that collected gas is either flared or converted into energy.
- Compacting: Adequate compacting of waste ensures there is less air or methane pockets formed that could lead to subsurface fires at landfills.