Transforming biowaste into sustainable supplementary cementitious materials

The construction industry considerably contributes to global CO2 emissions, primarily by preparing raw materials for cement production, which necessitates sustainable alternatives. Incorporating biowaste-based constituents into construction materials can help to reduce carbon footprint of the cement production. Various kinds of biowaste (organic and inorganic) can be converted to supplementary cementitious materials (SCMs). Organic waste (e.g., agricultural and forestry waste) are used as SCMs in the form of biochar and ash composed of carbon and mineral species like SiO2 and CaO, made by thermochemical conversion process such as pyrolysis and combustion, respectively. Inorganic waste (e.g., eggshells and seashells) has compositions similar to ordinary cement (e.g., a high CaO content); thus, it can be employed as SCMs after grinding. The results thus far have reported that biowaste-derived SCMs can enhance the mechanical, physical, and environmental properties of the final product. Nevertheless, despite the positive aspects of using biowaste as SCMs, it may negatively affect cement reaction and structural performance. It is hoped that a balanced overview of the utilization of biowaste-derived SCMs provided in this review will foster more extensive research on environmentally friendlier construction materials.