Turning municipal solid waste incineration into a cleaner cement production

The incineration of Municipal Solid Wastes (MSW) presents the added advantage of recovering energy from the wastes' residual calorific content. However, the process also generates by-products of ash and carbon emissions. This study evaluates the feasibility of using the outputs of energy, ash, and carbon dioxide in the making of a cementing material through novel steps tailored to allow replicating the process within an incinerator facility. The cementing material was synthesized using more than 85% ash residues and a clinkering temperature of 1000 °C, congruous to the operating conditions of a typical incinerator. Cement so produced is cleaner than traditional Portland cement for not being intensive in resource, energy and carbon footprints. It exhibited no hydraulicity but could be rapidly activated by carbon dioxide. Benched against Portland cement, paste specimens recorded an average compressive strength of 53 MPa and a CO2 sequestering uptake of 6.7 wt. % after undergoing only 2 h of carbonation activation. Mineral analyses identified the active cementing components to be chloro-ellestadite (Ca10(SiO4)3(SO4)3Cl2) and belite (Ca2SiO4), which upon reacting with CO2 rapidly formed a hardened binding matrix. Standardized leaching tests deemed the clinker product stable. This work presents first step of a broader scope to ultimately turn MSW incineration into a cleaner cement production, where locally-sourced heat, ash, and emitted CO2 can be used to generate products for building applications.