Self-sustaining smouldering combustion of waste: A review on applications, key parameters and potential resource recovery

Smouldering combustion, a phenomenon typically researched from a fire-safety perspective has recently garnered attention for its applications as a soil remediation method and more recently as a treatment process for wastes with high moisture content. This paper aims to review the fuel gas production from thermochemical conversion processes involving self-sustaining smouldering combustion. It also provides an insight into the processes, reactor characteristics, key parameters, applications and gas emissions. Smouldering combustion is a highly energy-efficient, slow, low-temperature, and flameless form of combustion that propagates through a porous fuel. Since smouldering operates under oxygen-limiting conditions, it has the potential to produce gas with fuel characteristics. The production of solid products (such as biochar) also has potential in smouldering combustion due to its characteristically slow heating rate and propagation velocities. However, this same characteristic is not ideal for the production of liquid products. This paper shows that while smouldering combustion was shown to be a robust treatment process for wastes with high moisture content, depending on the feedstock, there are potential for valuable by-products to be produced alongside the treatment process. This research however is still in its infancy, and further research is required particularly for its potential for production of gas products.