An electrochemical process to help neutralize cement industry CO₂ emissions

Cement manufacturing is the second-largest industrial contributor to world greenhouse fuel emissions, however its carbon footprint might be dramatically diminished with a brand new low-cost, scalable method demonstrated on the College of Michigan.

The method may neutralize essentially the most carbon-heavy step in cement production with out altering the manufacturing course of, in response to a examine lately revealed in Vitality & Environmental Science.

Whereas conventional cement manufacturing will get its needed calcium carbonate from limestone that releases carbon dioxide when heated in a kiln, the U-M researchers could make the calcium carbonate by way of an electrochemical process that captures CO₂ from the air and binds it with ample minerals or recycled concrete.

“Our newly developed electrochemical material manufacturing approach opens a new area in cement production and waste upcycling at scale,” mentioned Jiaqi Li, a College of Michigan assistant professor of civil and environmental engineering, workers scientist on the Lawrence Livermore Nationwide Laboratory and corresponding writer of the examine.

Manufacturing of cement—the world’s most used commodity behind water—at the moment produces 8% of world CO₂ emissions. Demand for the versatile constructing materials, used to make concrete and mortar, is projected to extend by 50% because the world continues to urbanize.

Unusual Portland cement, the commonest kind, is made by heating crushed limestone and clay collectively in a big rotary kiln. Heating the kilns utilizing fossil fuels contributes 40% of the method’s CO₂ emissions. The opposite 60% is the results of warmth breaking down the limestone—a sedimentary rock largely fabricated from calcium carbonate (CaCO₃)—into calcium oxide (CaO) and CO₂.

The proposed method, which replaces naturally occurring limestone with electrochemically produced calcium carbonate, neutralizes the CO₂ launched throughout kiln processing with the CO₂ taken up from the air throughout the electrochemical manufacturing.

If applied at full capability, the brand new technique may scale back world CO₂ emissions by a minimum of three billion metric tons—also referred to as three gigatons—a 12 months. For scale, 37.4 gigatons of energy-related, world CO₂ emissions have been reported in 2023. The 8% of world CO₂ emissions that cement manufacturing contributes at this time might be diminished to three% and even additional, to net-zero with carbon capture.

“The strategy can change the cement industry from a gigaton CO₂ emitter to a gigaton-scale enabler for clean energy and carbon management technologies,” mentioned Wenxin Zhang, a doctoral pupil on the California Institute of Expertise, graduate analysis intern at Lawrence Livermore Nationwide Laboratory and contributing writer of the examine.

The method works by making use of an electrical potential throughout water containing a impartial electrolyte salt in an electrolyzer—a tool with a constructive electrode (anode) positioned at one finish and a unfavourable electrode (cathode) on the different and a cation trade membrane within the center.

As electrical energy flows, water on the anode splits into oxygen fuel (O₂) and positively charged protons (H⁺), whereas water on the cathode produces hydrogen fuel (H₂), releasing negatively charged hydroxide ions (OH^–). This course of creates more and more acidic anodic electrolyte and alkaline cathodic electrolyte that’s harnessed to course of calcium silicates.

Protons break aside the calcium silicate to kind strong silica (SiO2) and calcium ions (Ca²⁺). The calcium ions react with CO₂ from the air and hydroxide ions within the water to kind into strong, carbon-negative calcium carbonate.

Whereas the calcium carbonate is the principle product that can feed cement kilns, the strong silica will be blended into cement as a supplementary materials to enhance concrete or mortar energy and sturdiness. The gases may even be put to make use of, with hydrogen fuel as a inexperienced gasoline and oxy-fuel for facilitating carbon seize and storage from flue fuel.

Going a step additional, the researchers assessed whether or not the know-how is economically viable, taking carbon credit score financial savings into consideration. The electrochemical method proved lower-cost and extra environment friendly in comparison with present strategies.

“As the present strategy requires minimal or no modification to the business-as-usual cement plants, it has low entry barriers to be adopted by the large cement businesses,” mentioned Xiao Kun Lu, a doctoral pupil of chemical engineering at Northwestern College and lead writer of the examine.

This analysis was a collaborative effort between College of Michigan, Lawrence Livermore Nationwide Laboratory, Northwestern College and the California Institute of Expertise.