Decarbonisation of Earthenware Ceramic Production Using Bivalve Shell Waste

To mitigate CO2 emissions from raw material decomposition and reduce the consumption of natural resources, this study investigated the use of mussel and oyster shell waste as secondary raw materials in earthenware production. Mineralogical, chemical and thermal analyses confirmed their suitability as sources of bio-calcite. Specimens incorporating various replacement levels (0–100%) showed no significant differences in key properties. Plates produced with mussel-derived bio-calcite in a pilot plant exhibited comparable properties to standard ceramics, demonstrating their industrial viability. CO2 emissions were reduced by 14% and 10% in mussel and oyster shell-based ceramics, respectively, potentially saving up to 53 kgCO2eq/t under the European Emissions Trading System, if the shells are classified as by-products. These findings demonstrated that bivalve shell waste can effectively replace mineral calcite in earthenware products, reducing CO2 emissions and virgin raw material consumption, diverting waste from landfills and promoting sustainability in the ceramic industry.