Combating Challenges of Elevated Temperature Landfills

Concern over elevated temperature landfills (ETLFs) has led to a spike in requests for proposals to study and understand the costly phenomenon. This decade has seen landfills with elevated temperatures exceeding 300°F. Fires are not the cause of these elevated temperatures; but abnormal biological and chemical reactions within the landfill. The result is increased difficulty and capital expense in managing both leachate and gas production.

While the exact nature and cause of ETLFs is unknown and needs further research, observations over the years have led to characterizations that can help find early onset ETLFs. In this article, we will discuss known symptoms and risk factors of a landfill transitioning into an ETLF and describe countermeasures including a temporary exposed geomembrane landfill cover.

Known symptoms of an elevated temperature landfill

The first symptoms of ETLF are usually chemical in nature with unusual changes in temperature of gas emitted at wellheads or in header pipes. Changes in gas composition is also a known indicator. Increased liquid and leachate production with changes in the chemical composition of these excretions are other symptoms. Physical symptoms present as large, rapid sinkholes at the waste surface.

ETLFs inhibit the methane-producing microbes that are present in normal landfill conditions. Reduced methane content in the gas causes the gas collection and control system to fail. Additionally, without these methane-producing microbes in place, the chemical reactions that normally consume excess hydrogen does not take place, leading to corrosion. It may be difficult to detect elevated levels of hydrogen in the gas as typical handheld equipment often misclassifies the gas as carbon monoxide. Upon dedicating changes in gas temperatures, consider performing more rigorous sampling and testing.

An untreated ETLF will continue to progress, first with an increased quantity of liquid. Without methane-producing microbes, the landfill will keep more water moisture. The water will then transition into leachate seeps or wet sloppy conditions at the waste surface. Such conditions are problematic for slope stability.

Late-stage ETLF begins to manifest with physical changes in the landfill structure. Whereas a normal landfill will decompose in a uniform manner, ETLFs present pockets of extreme decomposition in a brief period. In a matter of days or hours, large sinkholes can develop with a depth and temperature that poses safety risk to equipment, personnel, and infrastructure.

The rapid propagation of damage by an ETLF necessitates prudent means to slow or counter further development.

ETLF countermeasures

Each ETLF is unique. Regardless of what we know, it is unwise to generalize these landfills. Each ETLF will pose site-specific hazards. That said, current research suggests controlling ETLFs by increasing gas flow from elevated temperature areas to remove heat and reduce worsening conditions. This strategy works after sealing off the waste area to prevent air from flowing back into the elevated temperature region. Other mitigating techniques involve cooling the region by removing liquid from the waste while improving the effectiveness of the gas system.

Regardless of which approach you take at your site, the interim phase needs several controls to improve the safety standard for on-site workers. A temporary exposed geomembrane landfill cover can be useful to control some risk such as the spread of gas and foul odors. However, keep in mind that these exposed landfill covers will create more obstacles for workers. Choosing the right kind of landfill cover system and approach is essential to drawing on the benefits of a temporary cover without increasing risk for on-site workers.