Applied smouldering for co-waste management: Benefits and trade-offs

Smouldering combustion is emerging as a valuable application for many environmentally beneficial purposes, including waste-to-energy. While many applied smouldering systems rely on small fractions of fuel mixed within inert porous media (IPM) like coarse grain silica sand, there is also an opportunity to pursue co-waste management with much higher fuel loadings. This study explores these co-waste systems by blending non-smoulderable wastes (e.g., sewage sludge) with smoulderable wastes (e.g., construction waste woodchips) to form porous solid fuels (PSFs). Key differences between these IPM and PSF systems were identified by contrasting the temperature profiles in space and time, specific mass loss rates, and emissions profiles across experiments in multiple reactors (with 0.054, 0.080, and 0.300 m radii). For example, the PSF systems exhibited higher throughputs, a more straightforward path towards continuous operation, improved scalability, and higher production of potentially useful by-products (e.g., CH4, H2) than the IPM systems. However, the PSF systems were more sensitive to extinction and exhibited lower fuel moisture content limitations than the IPM systems. Altogether, this study illuminates the benefits and trade-offs of co-waste smouldering.