Toward a more reliable evaluation of CO2 emissions from the firing stage of ceramic tiles within the life cycle assessment (LCA) methodology

The need for a more realistic evaluation of the environmental impacts caused by hard-to-abate industrial sectors, such as ceramic tiles production, is essential in order to meet the European Union (EU) target for carbon neutrality by 2050. This implies that the environmental impact assessment of ceramic processes must also account for the emissions of CO2 arising from sources different from the natural gas combustion upon firing, with the latter being typically the only CO2 considered according to the stoichiometry of the combustion reaction. The current study proposes a method for determining the CO2 emissions associated with the physicochemical transformations occurring while firing the ceramic body. By integrating chemical and mineralogical composition, structural water loss estimation, and loss on ignition data, this approach enables the inclusion of these emissions in the Life Cycle Inventory (LCI) phase of Life Cycle Assessment (LCA). A comparative LCA, based on a reference flow of 1 m2 of porcelain stoneware tile, average thickness of 9.5 mm, corresponding to a mass of 24.5 kg, showed that including these additional emissions results in an 8.4 % increase in climate change compared to conventional assessments that only consider CO2 from natural gas combustion. Furthermore, the study challenges the conventional climate-neutrality assumption applied to biogenic CO2 by assigning a Global Warming Potential (GWP) of 1 to emissions from organic matter in clay minerals—an application not previously addressed in LCA literature. This novel framework not only enhances the accuracy of carbon accounting in ceramic tile manufacturing but also provides a versatile methodology that can be applied across various ceramic products. By addressing previously overlooked emission sources, the study contributes to more realistic environmental impact assessments, supporting the EU's carbon neutrality goals and informing policy, industry practices, and future LCA standards.