- The Hawaii Department of Transportation (DOT) plans to use carbon-injected concrete in all construction as part of its climate change solution. The material is now approved for all flat work, like roads and sidewalks, and is being tested for use in vertical projects.
- In an interview with Smart Cities Dive, Edwin Sniffen, deputy director of highways for the Hawaii DOT, said the carbon-injected material has turned out to be stronger and more workable, with no increase in cost over traditional concrete.
- Green concrete can reduce embodied carbon by 25 pounds per cubic yard, according to the state. A demonstration project that poured 150 cubic yards saved an estimated 1,500 pounds of carbon dioxide (CO2), the equivalent of 1,600 miles of highway driving.
Transportation is the largest source of greenhouse gas emissions, but reducing its impact largely requires turning over fleets of gas-powered vehicles to hybrid or electric cars. Focusing on infrastructure was an area where Hawaii felt it could make an impact, Sniffen said, since the government can control what cement is used for publicly-funded projects.
According to the think tank Chatham House, cement production produces about 8% of the world’s greenhouse gas emissions, and even though production has grown more efficient, higher demand means the industry has not lowered its overall emissions.
“Definitely we’d like everyone to convert to clean vehicles,” Sniffen said. “But while we work towards electrification, this is a step we can take now.”
The state is using technology from Canadian startup Carbon Cure, which sources CO2 from industrial facilities and converts it into a mineral that is injected into concrete, replacing some of the cement mix. A field test in May showed that the technology was workable for flat surfaces — in fact, Sniffen said contractors found it easier to work with than traditional concrete. Now it is being tested to see if it will work for more intense projects, including a rockfall protection wall and bridges.
The goal is not just to have it be used by the DOT, but by other state agencies for vertical structures such as public multifamily residential buildings. The Honolulu city council in April passed a resolution calling on the city to consider CO2-injected concrete wherever applicable. (The DOT tests had been in the works before the resolution was passed.)
Other states are also exploring mandates for greener concrete; Reuters reports that both New York and New Jersey are exploring legislation, and Austin, TX has been weighing how green concrete could be used. Cost remains a concern for some governments and private companies, but CO2-injected cement could provide a path forward for states like New York that have set goals to offset greenhouse gas emissions by capturing some carbon dioxide.