Experimental study of the ignition conditions for self-sustained smouldering in peat

Tackling peatland wildfires, the largest fires on Earth in terms of fuel consumption, is an emerging combustion topic in the context of climate change and environmental protection. The understanding of the basic mechanisms of ignition of peat to initiate self-sustained smouldering is essential in the development of mitigation technologies, but it is not well studied yet in the literature. In this research, laboratory experiments were conducted to improve the understanding of how peat conditions (moisture content and bulk density) and the ignition protocol influence the ignition probability. A new ignition protocol was developed by stopping the heat source when 10% mass of the sample is lost. This mass-based ignition protocol was found to be robust to initiate self-sustained smouldering in peat samples for a wide range of soil conditions. By using the new ignition protocol, experiments using peat samples of moisture content from 100% to 180% with a range of bulk densities were conducted to investigate how these properties together influence the critical ignition conditions. Results show that although the moisture content plays a major role in the ignition probability, bulk density is also important. Increasing peat density increases the mass of water in a unit volume. This increase of heat sink makes the ignition more difficult. These findings contribute to studying smouldering peat fires and improve the understanding of ignition.