Techno-economic considerations on cement substitute obtained from waste refining

Abstract

Concrete production is the 3rd most intensive source of anthropogenic pollution, mainly due to its high energy and material demand. Previous struggles to decarbonize the concrete sector have identified that some 88% of the environmental burden is associated with cement production. Efforts to substitute some of the cement with char are of increased interest recently as some chars are considered carbon negative which could turn the entire concrete segment into a carbon-sequestering business. Here we transformed biowaste (fermentation residues) via waste heat (from flue gases at biogas plants) into char that was subsequently activated (by reactants made of scrap metal) to capture phosphorus (at wastewater treatment plant) into phosphates and thus produced novel a cement substitute. Changes in the strength characteristics of the concrete were analyzed and optimized based on robust semi-operational testing. The molecular dynamics simulations performed elucidate the mechanisms by which activation of char (FeCl3 and CaCl2) interacts with phosphorus at wastewater treatment plants (H2PO4−) and generates phosphate-enriched char as a source of crystallization nuclei in concrete.