Electrochemical Production of Hydrated Lime from Organic Waste: A Feasibility Study

The building and construction industry is a significant source of greenhouse gas emissions. As one of the primary materials used in this sector, hydrated lime, produced from the calcination of limestone, contributes about 3%–4% of global carbon dioxide (CO2) emissions. Recently, electrochemical decarbonization (ED) of calcium carbonate (CaCO3) has been proposed as a favorable method to minimize CO2 emissions associated with CaO manufacturing. This study explores the feasibility of using alternative feedstocks derived from organic waste, namely, eggshells (ESs) and mussel shells (MSs), for hydrated lime production through the electrochemical decarbonization of CaCO3 at room temperature. The benefits of this method include the valorization of waste materials and a reduction in the carbon footprint associated with lime production. The effectiveness of the process was evaluated based on an efficiency metric, reflecting the amount of hydrated lime produced relative to the theoretical amount, as well as its energy consumption and the purity of calcium hydroxide (Ca(OH)2) produced as a precipitate material. This research also compares the electrochemical decarbonization performance of organic CaCO3 with that of a pure CaCO3 source (>99%). The results show that the deposited materials (DMs) consisted mainly of Ca(OH)2 (>88%), and the efficiency of the process ranged between 82% and 86%. The results also show that the deposited material from eggshells and mussel shells complies with the physical and chemical standards for commercial hydrated lime. The results indicate a remarkable potential for direct CO2 emission reduction by approximately 89%. The findings underscore the potential of this innovative approach to contribute to more sustainable hydrated lime manufacturing practices.