Heat generation in landfills is a natural phenomenon. It happens in every landfill to a degree. Heat generation in landfills accepting organic matter occurs to a higher degree due to organic material biological degradation. Subtitle D landfills accepting organic matter also accept other types of materials that can chemically react under specific conditions to generate additional heat through exothermic reactions.
Recent experience has shown that deep landfills with high levels of organic matter and high levels of moisture in the waste column can potentially create conditions deep within the landfill so that the heat generated cannot escape from the landfill boundaries fast enough. As a result, heat accumulates in the landfill and creates the condition known as elevated temperature landfill or ETLF.
The accumulation of heat causes rising temperatures within the landfill that can adversely affect the beneficial biological degradation of organic waste. Beneficial degradation of organic matter generates methane that is captured by the landfill gas control and collection system (GCCS) and in many instances converted to energy through highly technologically sophisticated systems.
Adversely affected biological degradation of organic waste under high-temperature conditions causes significant increases in the generation of carbon dioxide, hydrogen, and other gasses that have no economic value and can cause other environmental challenges, including regulatory compliance and increased public scrutiny. Additionally, control systems placed in service to address conditions resulting from elevated temperatures can be costly.
If you manage a deep and wet landfill with significant organic matter in your waste stream, you should consider design and operational steps to mitigate future operational and compliance challenges. These might include new engineered features to enhance liquids, gas, and heat removal from the deeper parts of the landfill. Many of the major landfill companies are currently designing and constructing systems to expedite the movement of water and gas through the waste column, which is a great help to potentially minimizing heat accumulations in the landfill.
Significant research work is currently underway to find out causes of heat accumulation in landfills, but it may take years before accurate cause and effect of such complex and inter-relating processes are more clearly determined, and solutions developed. Heat removal by landfill gas and leachate takes place on a regular basis, but the quantities are insignificant to affect a major reduction in accumulated heat in the landfill.
SCS is an expert in the management of elevated temperature landfills and has been promoting the development of heat management systems over the past several years. As a result, we are highly qualified to address heat accumulation in landfills and development of heat removal systems to control temperatures below the landfill surface. If you have an elevated temperature landfill at your facility or a landfill that seems to be progressing in the direction of becoming an elevated temperature landfill in the future, contact us and let us review field data from your facility and develop means to control temperatures below the landfill surface.
Author: Ali Khatami, PhD, PE, LEP, CGC, is a project director and a vice president of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.