Suppressing underground peat fire and smoldering spread via water, ice, dry ice, and liquid nitrogen

Abstract

Smoldering peat fires are a persistent and globally significant environmental hazard, releasing substantial greenhouse gases and driving long-term ecosystem degradation. Conventional suppression methods, particularly water application, often fail to fully extinguish smoldering fronts due to limited cooling persistence and uneven infiltration within porous peat layers. In this study, we experimentally evaluated the suppression performance of four extinguishing agents (dry ice, ice, liquid nitrogen, and water) under controlled laboratory conditions across a wide range of peat moisture contents (up to 100%). Suppression performance was assessed using three metrics: extinguishment probability, required quantity, and effective cooling duration. We found that dry ice achieved the highest extinguishment probability through sustained sublimation and oxygen displacement, requiring a minimum mass of 41 kg/m2 for air-dried peat (MC∼10%) while providing the longest effective cooling duration (up to 175 min) under current experimental conditions. Liquid nitrogen exhibited rapid and intense cooling, instantaneously reducing soil temperature to around −175 °C; however, its short residence time frequently resulted in rapid temperature rebound. Ice exhibited moderate suppression performance, whereas water required approximately 90 kg/m2 for air-dried peat (more than twice the mass of dry ice) to achieve comparable suppression. Even in unsuccessful cases, solid suppressants, especially dry ice, slowed fire spread more effectively than liquids by maintaining subcritical fuel temperatures for extended periods. These findings provide new insights into the selection of suppression agents for smoldering peat fires, informing more effective and environmentally conscious fire management strategies for peatland ecosystems.