(Credit: CarbonCure)New York has passed Bill S542A establishing guidelines for the procurement of low embodied carbon concrete.
As I discussed recently about ECOPact and Skansa tests, trends towards reducing embodied carbon in concrete are continuing to build momentum. Concrete remains a critical barrier to climate-friendly buildings. It is responsible for at least 7% of carbon emissions worldwide, according to clean energy research group BloombergNEF.
The new Bill outlines what the Office of General Services will need to examine when crafting the guidelines including incentives for the procurement and usage of low embodied carbon concrete by contractors. Contractors would then need to follow these guidelines and certify that their work and the concrete they are procuring meets these minimum guidelines.
Key companies producing low-carbon concrete products include, but are not limited to, the following:
CarbonCure Technologies has invented a process that involves removing CO2 from the creation of cement and injecting it into concrete during mixing. This takes some of the CO2 out of the air and permanently embeds it in the concrete and strengthens it - reducing the amount of cement needed. So far, CarbonCure concrete achieves a net carbon reduction of about 5 to 7%.
Blue Planet uses carbon dioxide collected from the exhaust stack of power plants to produce synthetic aggregate that can be used to create concrete. The captured CO2 from flue gas does not require purification, which is an energy and capital intensive process. As a result, Blue Planet’s method is extremely efficient, and results in a lower cost than traditional methods of CO2 capture. CO2 from flue gas is converted to carbonate (CO3), which locks up the carbon forever. The result is low carbon, carbon neutral, or carbon negative concrete, with the same structural integrity as conventional concrete.
CarbiCrete uses a process called carbonation activation that eliminates the need for cement in concrete by replacing it in the mix with ground slag, a waste by-product of steel-making. The process can be implemented in any precast concrete manufacturing plant, but is not yet available for poured concrete applications. CarbiCrete’s process eliminates the CO2 emissions associated with cement production and then injects CO2 recovered from other industries into its products. Because more CO2 is consumed than emitted during the process, it is carbon-negative concrete.
U.S. Concrete uses several methods to lower the carbon footprint of its concrete - from using CarbonCure, to using high strength aggregate that lowers the need for cement, to incorporating fly ash from burning coal or steel slag into cement. Incorporating steel slag reduces Portland Cement usage by as much as 50%. It also can produce aggregate from slag. This reduces the amount of slag that becomes landfill waste and reduces the need to mine raw materials.
Solidia Technologies uses a lower temperature, lower energy process, resulting in 30 to 40% less CO2 emissions during cement manufacture. In addition, it cures their concrete with waste CO2 instead of water, permanently trapping CO2. It claims a 70% overall reduction in CO2 emissions compared to standard precast blocks and conserves a great deal of water.
