Calcium oxide waste-based catalysts for biodiesel production and depollution: a review

Pollution, climate change and waste accumulation are critical societal issues calling for advanced methods to recycle matter and clean polluted ecosystems. Here, we review the use of calcium oxide waste-based catalysts for industrial and environmental applications such as biodiesel production, and pollutant degradation and removal. Catalysts can be produced from mud clam shell, eggshell, spent coffee ground, fish bones waste, marble waste, face mask waste, and snail shell. The preparation of composite catalysts, adsorbents, nanoparticles, and photocatalysts is presented.