Carbon capture and storage (CCS) is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually the CO2 is captured from large point sources, such as a chemical plant or biomass power plant, and then stored in an underground geological formation.
The capture and utilization of carbon dioxide (CO2) to produce economically viable products offers the twin benefit of mitigating climate change and generating economically viable products such as concrete. Multiple emerging approaches such as carbonation of recycled concrete aggregates, CO2 sequestration in alternative MgO based binder, CO2 mineralization in industrial waste-derived aggregates and filler, and CO2 dissolution in mixing water have been investigated for CO2 utilization in concrete. The CO2 produced during the calcination reaction can be captured at point-source to be either stored safely underground (carbon storage) or used for a range of industrial applications (carbon utilization), including concrete manufacturing. These carbon capture, utilization, and storage (CCUS) technologies are likely to play a key role in the fight against climate change. Carbon capture means capturing CO2 from sources such as industrial processes or power generation and preventing it from entering the atmosphere, either by storing it or consuming it. There are natural ways to capture and store carbon.
Carbon Capture in Concrete Manufacturing
Carbon capture is still in its infancy – there are only about 20 projects in commercial use worldwide, according to the IEA – but billions of dollars in investment is flowing into the sector. Microsoft has announced a “moonshot” climate plan that will involve direct air capture of CO2 and biomass energy carbon capture and storage, where wood chips are burned and the resulting carbon is injected into rock formations. Norway is launching a full-scale carbon capture and storage project, named Longship after the Viking vessels, while a direct air capture project for the Permian Basin in the south-western US is doubling in size and aims to suck up 1m tons of CO2 a year. The US government is pitching in, recently awarding $72m to two dozen different carbon capture initiatives.
Several companies across the globe have taken the initiation on decarbonizing concrete, few of them are discussed below.
- The Montreal-based cleantech CarbiCrete uses this CO2-curing method to produce carbon negative precast concrete blocks. The negative emissions are achieved not only by utilizing CO2, but also by using an industrial waste as raw material, steel slag, eliminating the need for cement altogether. A more modest carbon footprint reduction of around 5% is promised by CarbonCure, although its technology has a broader market penetration, spanning both precast and ready-mix concrete. The company is also using captured CO2 to strengthen recycled concrete aggregate (RCA) and to treat concrete wash water to allow for its reuse.
- Canadian startup, Carbon Upcycling Technologies (CUT), makes additives for concrete by incorporating CO2 into industrial waste powder by-products such as fly ash. CUT’s resulting CO2-enhanced fly ash promises to improve concrete strength whilst reducing its carbon footprint by up to 25% through both sequestering CO2 and decreasing the demand for cement as a raw material by 10%.
- The UCLA CarbonBuilt approach captures CO2 generated during production and then infuses it into the concrete, using hydrated lime. The process uses 60 to 90 percent less ordinary portland cement (aka calcium silicate cement), and it doesn’t require as much heat, which has an energy efficiency benefit. CarbonBuilt’s Reversa™ process includes CO2 emission-reducing innovations to both the concrete mixture design and its manufacturing process. On the formulation side, we introduce portlandite (also known as calcium hydroxide, a commodity chemical), reduce the usage of traditional cement and increase the use of waste materials like fly ash. The concrete is then formed using the same processes and equipment that are used today. After forming, we cure the concrete with waste CO2 emissions using a process that does not require expensive capture, compression or purification of the CO2. In 2020, with support for UCLA from the U.S. Department of Energy and the NRG COSIA Carbon XPRIZE, the technology was used to produce over 10,000 concrete blocks using a full-scale curing chamber and flue gas CO2 sourced directly from a coal power plant in Wyoming.
- CarbonCure Technologies, a Canadian firm seeking to slash the carbon dioxide emissions of concrete. Producing cement, the key ingredient in concrete, creates so much CO2 that if the industry were a country only China and the US would emit more over the course of a year. CarbonCure works with nearly 300 concrete producers to inject captured CO2 into their product. The injected gas chemically transforms into limestone, reinforcing the concrete. Amazon will use the concrete in its buildings, including its vast new headquarters in Virginia. Currently, CarbonCure is injecting CO2 normally used in products such as carbonated drinks but hopes to “close the loop” by capturing it from cement production in order to reduce global concrete emissions by 500m metric tonnes by the end of the decade.
Concrete manufacturers are facing a growing pressure to abate their emissions, even though the economic advantages of doing so are still uncertain. To capitalize from carbon capturing technologies, the manufacturers will need to commit to fundamental changes in their well-established manufacturing methods. Forward-thinking players are likely to future-proof their business, as they would like to focus on both manufacturing with sustainability.