Cement kiln carbon negative future mapped in ETH Zurich life-cycle study. August 20, 2026 A cement kiln carbon negative outcome is achievable, but only under specific conditions, according to new research from ETH Zurich. The study finds that combining cement production with calcium looping direct air capture (DAC) technology could allow plants to remove more CO2 over their full lifecycle than they produce, provided the kilns run on clean electricity rather than fossil fuels. How cement kilns could turn carbon negative. Cement manufacturing currently generates around 4 billion metric tons of CO2 per year, making it one of the largest industrial sources of the greenhouse gas. Much of that comes from calcination: the thermal decomposition of limestone into quicklime and CO2, a chemical process that cannot simply be engineered away. What the ETH Zurich research team argues is that the chemistry driving those emissions can also be turned to carbon removal. The mechanism works like this. When water is added to quicklime, it becomes slaked lime, which then absorbs CO2 from the surrounding air and converts back into limestone. That regenerated limestone can be fed back into the kiln as raw material. Each time calcium completes this cycle before being processed into cement, the plant draws more CO2 out of the atmosphere. The CO2 captured this way is not locked into the final cement product; instead, it is compressed and transported to underground storage sites. Running the kiln on fossil fuels breaks the loop. Burning oil, coal, or gas introduces heavier compounds into the emissions stream that interfere with reabsorption into the limestone. The ETH Zurich team, led by PhD student Vittoria Bolognaro, determined that switching to electric kilns could cancel out 78% of a cement kiln's carbon emissions. Heirloom's California plant and the scale-up challenge. The research was conducted in collaboration with Heirloom Carbon Technologies, which already operates a commercial calcium looping DAC facility in Tracy, San Joaquin County, California. The plant has been running since 2023 with an annual nominal capacity of 1,000 tonnes of CO2, making it the first calcium looping DAC system operating at commercial scale. Heirloom has secured CO2 removal agreements with Microsoft, Meta, Shopify, JPMorgan, H&M, and Autodesk, according to Louisiana Economic Development. A second, much larger facility is planned for Northwest Louisiana at the Port of Caddo-Bossier near Shreveport, with a 17,000-tonne capacity targeted to come online in 2026. That scale-up matters to the ETH Zurich findings: the study is the first prospective life-cycle analysis of calcium looping DAC at industrial scale, and its conclusions are built around plants substantially larger than the California site. 'Heirloom was an ideal partner for us because the company is already operating the first calcium looping DAC systems on a commercial scale,' Bolognaro said. 'From a climate perspective, the combination of DAC and cement production is very promising.' Energy mix is the deciding variable. The study tested three energy scenarios: operating on the current US electricity mix, drawing on a heavily decarbonised grid of wind and solar, and running a fully autonomous system powered by photovoltaics and battery storage. The results shifted considerably depending on which scenario was used. 'We were able to show that the technology has a net-negative carbon footprint; in other words, commercial calcium looping DAC plants with CO2 storage remove more CO2 than they generate over their entire lifecycle,' Bolognaro said. 'Depending on the energy mix used in our projections, the efficiency of CO2 removal by 2050 ranges between 85 and 96%.' By far the largest share of the environmental footprint is attributable to the energy required. Capturing CO2 from ambient air is energy-intensive, and that characteristic applies to all DAC processes, not only calcium looping. Water and land use were examined as secondary environmental factors; neither dominated the footprint in the way energy did. Real obstacles still to resolve. The caveats are genuine. The study's key calculations are based on scenarios projecting to 2050 and assume material progress in electricity decarbonisation that may not materialise. Some plant components, including the electric calcining kilns themselves, are not yet in large-scale industrial use. A detailed cost analysis was not part of the current work, so whether the system can be operated economically remains an open question. Bolognaro frames the findings as an important starting point rather than a blueprint ready to deploy. The Louisiana facility, targeted for 2026, will be one of the first tests of whether calcium looping can deliver at a scale that begins to validate the life-cycle projections the ETH Zurich study sets out.

Heirloom, TKMS and thyssenkrupp Calvion partner on large scale DAC in Canada. June 12, 2026 TKMS, Heirloom Carbon Technologies, and thyssenkrupp Calvion have joined forces on large-scale direct air capture (DAC) development in the Canadian province of Alberta. The three partners will unite on developing a DAC hub aligned with Canada's Industrial and Technological Benefits (ITB) policy. As shared in the announcement, the companies have signed two Memorandums of Understanding (MOUs), agreeing to build a large-scale DAC site that will create long-term job opportunities in the region, significantly impacting the GDP. With the signed MOUs, the companies have created a framework that will enable research, technology transfer, and DAC commercialization on the Canadian market. The ambitious project will be developed with a substantial investment by TKMS, combining Heirloom's carbon dioxide removal (CDR) expertise with thyssenkrupp Calvion's professional skills in engineering and scale-up, large-scale materials handling, systems integration, and complex plant delivery. Heirloom Carbon Technologies will leverage its know-how on accelerated mineral carbonation, a process that dramatically speeds up the natural rate at which rocks absorb atmospheric CO2, to support the DAC development and contribute to the creation of a low-cost, scalable CDR supply chain in Alberta. Rich in natural resources, skilled professionals, and advanced technologies, Alberta has emerged as an attractive location for the development of climate solutions. The DAC collaboration aims to position Canada as a globally competitive producer and exporter of CDR credits and low-carbon products, such as low-carbon fuels. This partnership will also directly support Canada's ITB policy by making sure that Canadian companies receive technology, knowledge, intellectual property rights, and capital while generating high-value economic activity in the clean tech sector. "Alberta's natural resource base, workforce, and technical capacity are a compelling foundation for carbon removal research, development, and large-scale deployment," said Max Scholten, Head of Commercialization at Heirloom Carbon Technologies. "Our partnership with TKMS and thyssenkrupp Calvion lays the foundation for investments that remove carbon, produce low-carbon fuels, create durable jobs, and cement Canada's place in a decarbonizing global marketplace," he added.