Every year at GreenBuild (the US green building conference and expo), green building guru Alex Wilson reveals his top ten favourite new green products. These products are carefully thought out and vetted, and are considered the best of the best. If you’re not familiar with the BuildingGreen website, take some time to look around — it is the authoritative source for green building materials and services for professionals involved in the green building sector. This year, one of the products that made his list was CarbonCure, which is a technology developed by a Canadian company, based in Nova Scotia. CarbonCure seeks to solve the problem of the greenhouse gas emissions produced during concrete production.
The manufacturing of concrete is the second most energy and CO2 intensive industry in the world. It is only topped by the emissions output of power generation, particularly from plants that burn coal and gas for power production. Since concrete is a key material in the building sector and will likely remain so in the near future, aspiring to reduce its overall carbon dioxide footprint is an essential strategy for lowering global carbon emissions. According to the CarbonCure website, the reason that concrete is such a carbon dioxide intensive product is partly due to the high kiln temperatures needed to make cement (the key ingredient in concrete), and partly due to “liberating the CO2 from its chemically stable form as CaCO3(limestone)” during the cement making process.
The technology developed by CarbonCure captures carbon dioxide emitted by heavy sources and adds it back into concrete, where a chemical reaction converts the CO2 into limestone. One of the side benefits of adding carbon dioxide (CO2) to concrete is that it makes the concrete stronger, enabling manufacturers to use less cement, the most CO2-intensive part of concrete production.
I had several questions about the technology, so I contacted Jennifer Wagner, Vice President of Marketing for CarbonCure.
On their website I read that for every tonne of cement produced about 0.8 tonnes of CO2 are emitted into the atmosphere. Their website notes that Atlas Block, a concrete manufacturer in Ontario, is able to sequester 50 grams of CO2 per concrete block. Jennifer noted that the percentage of CO2 sequestered varies depending on the concrete manufacturing plant that’s using it. Plants have different equipment, raw materials, and processes, so the potential CO2 reduction can differ from plant to plant. One of the operations using their technology has reduced its CO2 emissions by 20%. Their eventual goal is to produce carbon-neutral oreven carbon negative concrete. In other words, concrete production would sequester more CO2 than is emitted. While they are not close to that number yet, just having that goal is encouraging.
Jennifer pointed out that over time concrete naturally sequesters CO2 but only the exposed surfaces of concrete absorbs the CO2. Their technology mixes concrete with CO2 while it’s still in its looseform (its texture is similar to a sandcastle) in order to maximize the absorption of CO2. Further, calcium carbonate increases the strength of the concrete and permits the use of less cement.
Carbon dioxide is collected from the nearest CO2 emitting plant to keep transportation emissions and costs down. When CarbonCure calculates the carbon footprint sequestration of their product, they do take into account the amount of emissions produced in the production of cement, as well as the transportation emissions to get the CO2 to the cement plant.
The technology is constantly improving. Right now they are working on developing it for ready mix concrete – that’s the concrete used to pour sidewalks and foundations. That means the machinery would have to be portable and attach to concrete mixing trucks. It’s an important area on which to focus because the majority of concrete produced is ready mix concrete, so solving that problem would significantly increase the potential greenhouse gas reductions of the technology.
CarbonCure is currently working with three concrete producers, a local Nova Scotian company (Shaw Group), an Ontario company (Atlas Block), and a company in California (Basalite Concrete Products). Atlas Block currently offers three products that include sequestered carbon: concrete blocks, pavers and segmented retaining walls (SRWs). Currently, each concrete block contains 50 grams of sequestered CO2.
Cost: according to the website, the up-charge of using their technology should be minimal because less cement is needed to make concrete which offsets the cost of adding the technology.
CarbonCure presents a new and exciting technology in the process of reducing carbon dioxide emissions from concrete. If the technology continues to progress towards making carbon neutral or carbon negative concrete a reality, it could become a significant factor in reducing overall CO2 emissions from the building sector.
Feature photo courtesy of CarbonCure