Calcining limestone (CaCO3) to produce lime (CaO) is a key industrial process for making cement, steel and chemicals, among other uses. Lime production is a target for CO2-abatement efforts because it generates a great deal of CO2 emissions, not only from fossil fuels burned to achieve the high heat required, but also because the reaction releases CO2 as a byproduct.
A process now being piloted by CarbonBlue Ltd. (Haifa, Israel; www.carbonblue.cc) offers an alternative route to producing lime via calcination. CarbonBlue’s process dramatically reduces CO2 emissions because it doesn’t involve fuel combustion, and utilizes abundant, low-carbonate industrial waste, as source material.
The CarbonBlue process, resulting in a product known as EcoLime, involves two general stages. First, the slag is subjected to a proprietary leaching step that selectively removes the desired CaO from the slag, while leaving behind unwanted components. Then, an electrochemical reactor regenerates the leaching solution for reuse. Because the leaching and electrochemistry occur at ambient temperatures, the process can help bring circularity and low greenhouse-gas emissions to the steel- and cement-making industries, traditionally considered high-emitting processes, says Dr. Dan Deviri, CarbonBlue CEO. In addition, the process lowers the cost of producing lime, a ubiquitous industrial input, compared to incumbent calcination processes, Deviri adds.
Deviri says the first target for the EcoLime product is the steel-making industry. “In steel making, CaO is added to molten iron ore or molten scrap steel to induce a phase separation that helps remove impurities from ending up in steel products. Waste from that process generates large volumes of waste slag, which contains CaO that can serve as a feedstock for our process.”
The 20-kg/d pilot plant for EcoLime is operational at CarbonBlue’s facility in Israel, where the company is in the process of validating the concepts of the process, while producing samples of EcoLime for user testing. The company is also in the engineering stages of a larger 1-m.t./d demonstration plant, to be constructed later in 2026, also in Israel.
Last year, CarbonBlue piloted a carbon dioxide removal (CDR) process for making precipitated calcium carbonate (PCC) as a complement to water desalination (Chem. Eng., September 2025, p. 8).