Greater emphasis has been placed on Life Cycle Assessments in the latest version of LEED, providing a potential boost to carbon capture technologies.
Designers are required to model a base building and intended design to show reduced life cycle impacts. Only the building’s structure and enclosure are included. This means material choices by structural engineers will have a greater impact in this area.
A clean-tech concrete solution developed by Canadian firm CarbonCure Technologies could help meet these credit targets.
By consuming waste CO2 in the production process, the CarbonCure system chemically converts this greenhouse gas into solid limestone within the concrete.
It could potentially revolutionise the building industry, claims the company behind the product.
“With a commitment to continued innovation, this is our first step towards integrating and developing affordable regenerative concrete at scale,” said Robert Niven, founder of CarbonCure Technologies.
The key ingredient in concrete is cement. According to the International Energy Association, the cement industry creates about five per cent of global greenhouse gas emissions. This is largely due to the process required for the production of cement.
It begins with limestone. When limestone is heated, it splits into two components; one part - CaO - is used to make cement, while the other - CO2 gas - is released into the atmosphere.
The CarbonCure system uses the concept of carbon capture and storage (CCS), taking carbon dioxide waste from large emitters like refineries and fertilizer plants, and mixing it into the concrete during the production phase. The chemical reaction that occurs is a reversal of the process used to make cement.
According to the company, 100,000 grey blocks absorb the same amount of CO2 as 92 full grown trees absorb in a year. More carbon dioxide is captured than is emitted during the manufacture and transport of the blocks, reducing emissions by up to 20 per cent.
The new LEED system also now gives points for building products that have issued Environmental Product Declarations (EPDs), which disclose environmental impacts associated with a building products’ life cycle, such as the carbon footprint.
The process to create an EPD is often costly, so CarbonCure has developed a free EPD calculator tool which generates self-declared EPDs for any concrete masonry product made with the CarbonCure technology. This makes it far easier for specifiers to contribute to LEED points.
It is not just the environmental credentials that should appeal to specifiers, however.
Past research has shown that treating concrete with CO2 can improve its strength, reduce water absorption, improve resistance to chloride permeability and improve freeze-thaw performance. Carbonation never compromises quality, colour or texture.
The technology is already being used to good effect.
Concrete masonry units (CMUs) using the CarbonCure technology have been used at UC Davis Jess S. Jackson Sustainable Winery, the first university building to be certified Net Zero Energy under the Living Building Challenge.
Created by the design-build team of Pankow Builders, Siegel & Strain Architects and Guttman & Blaevoet Engineering, the installation used more than 2,500 specially manufactured CMUs, which permanently sequesters CO2 into the units. The CarbonCure blocks were combined with the first use of Central Concrete’s low-CO2 90 per cent cement replacement mix, to make an ultra-low-carbon CMU wall.
Three billion concrete blocks are produced annually in North America alone, with the market projected to increase to 4.3 billion units by the end of 2014. The potential is certainly there for this new concrete to make a difference going forward.