The article provides a comprehensive review of carbon dots (CDs), a class of nanomaterials with attractive optical properties, focusing on their sustainability aspects. CDs, which are metal-free and derived from biomass, offer a sustainable alternative to inorganic quantum dots, which contain toxic and precious metals. The review highlights the advantages of CDs, such as their ability to be synthesized using biomass as the sole starting material and their freedom from toxic and critical raw materials. It also discusses the pretreatment, chemical conversion, purification, and processing procedures involved in CD synthesis, emphasizing the environmental and energy efficiency of these processes. The article concludes by recommending that future studies should explicitly consider the environmental impact of the selected starting materials, solvents, and byproducts, and provide quantitative information on the required amounts of solvents, consumables, and energy to enable a more sustainable evaluation of CD synthesis methods.The article provides a comprehensive review of carbon dots (CDs), a class of nanomaterials with attractive optical properties, focusing on their sustainability aspects. CDs, which are metal-free and derived from biomass, offer a sustainable alternative to inorganic quantum dots, which contain toxic and precious metals. The review highlights the advantages of CDs, such as their ability to be synthesized using biomass as the sole starting material and their freedom from toxic and critical raw materials. It also discusses the pretreatment, chemical conversion, purification, and processing procedures involved in CD synthesis, emphasizing the environmental and energy efficiency of these processes. The article concludes by recommending that future studies should explicitly consider the environmental impact of the selected starting materials, solvents, and byproducts, and provide quantitative information on the required amounts of solvents, consumables, and energy to enable a more sustainable evaluation of CD synthesis methods.