Chapter 7: Applied Smouldering Combustion for Supporting a Circular Economy

Sustainable waste management requires significant increases in the proportion of waste and its components being reused, repurposed, and recycled instead of landfilled. Recent research and regulations have supported growing interest in circular economies, with a significant focus on making waste management processes more cyclic, increasing reuse, and reducing disposal. Resource recovery of nutrients and metals from municipal and industrial wastewater treatment plants and other sources of sludges may relieve the depletion of essential elements and have significant environmental and economic benefits. Thermal technologies offer strong promise for combining resource recovery with the robust destruction of hazardous compounds that must be removed from a circular economy. Applied smouldering is an emerging thermal technology that has demonstrated unique benefits in managing challenging wastes, such as high-moisture-content biomass, in a self-sustaining manner with minimal energy footprint and limited pre-processing infrastructure. Therefore, smouldering can support the inclusion of challenging wastes into circular economies. Most relevant applied smouldering studies to date have focused on municipal wastewater treatment sludge (i.e., sewage sludge). Therefore, this chapter will focus largely on the application of smouldering as a circular economy solution for sewage sludge; however, its applicability can be extended to a wide range of carbon-rich waste materials.