What are the carbon reduction benefits of regenerating ceramsite from solid waste? A new perspective on carbon footprint

The ceramsite industry is experiencing the demand for low-carbon transformations; therefore, solid waste is gradually being used for raw materials. However, the carbon footprint of ceramsite products produced from solid waste and the extent of future carbon-reduction benefits remain unclear. Therefore, this study evaluated the carbon footprints of sludge, fly ash, and aluminum ash, common hazardous waste ceramsite products that are difficult to recycle. The carbon reduction potential of the three solid-waste ceramsite products were predicted and evaluated based on scenario analysis. The simultaneous addition of sludge and aluminum ash to produce ceramsite was sustainable and improved its carbon performance. Sludge‑aluminum ash ceramsite from Zhejiang Province, China, achieved carbon reduction benefits of approximately 29 % and 5 % compared to the sludge ceramsite in Zhejiang Province and fly ash ceramsite in Shandong Province, respectively. The three single factor low-carbon scenarios optimized the raw material (RMO), transportation (TO), and power (EO) structures. Under the TO and EO scenarios, a single solid-waste ceramsite product achieved maximum carbon reductions of 0.08 kg, which was lower than that of the RMO scenario (0.40 kg). In the other three collaborative low-carbon optimization scenarios, the carbon reduction potential of scenario RM-TO (simultaneously optimizing raw material and transportation structures, 12–68 %) was higher than that of scenario T-EO (simultaneously optimizing transportation and power structures). The emission reduction potential of simultaneously optimizing the three factors was the highest (∼70 %). Considering economic and time constraints, the joint optimization of transportation and raw material structure is preferred for Chinese ceramsite products.