Systematic life cycle assessment of cobalt-based blue ceramic pigments: evaluating CoAl2O4 and lower-cobalt alternatives

To enable a sustainable transition of the ceramic industry towards digital decoration via inkjet printing, it is imperative to promote the production of more environmentally friendly pigments. Despite its widespread use as a blue pigment, the environmental profile of cobalt–aluminium spinel (CoAl2O4) has never been assessed by Life Cycle Assessment (LCA), therefore potentially overlooking opportunities for less impactful alternatives. This work presents the first comparative environmental LCA of four distinct synthetic strategies for producing CoAl2O4 and several lower-cobalt alternatives. The study also accounts for two hybrid pigments, three M2+-doped spinels (M1−xCoxAl2O4, M = Zn2+, Mg2+), cobalt olivine (Co2SiO4) and its lower-cobalt variants, including Co2+-doped willemite (Zn2SiO4). The results throw light on the main substances and processes contributing to the environmental burdens of cobalt-based blue ceramic pigments and identify strategies to reduce their potential impacts. The study revealed that hybrid pigments are promising candidates with intense blue hues and lower environmental impacts than the traditional CoAl2O4, with Co0.05Zn1.95SiO4 delivering the lowest environmental impacts among all the analysed pigments. The reliability of these findings was validated through Monte Carlo (MC) simulations. Potential environmental impacts were plotted against CIELAB colour parameters to identify pigments that exhibit desirable blue hues while being environmentally sustainable, thereby supporting their practical application.