MDU says the limestone would be produced using sequestered carbon dioxide.
The companies are working together to develop construction-grade rock and concrete that would have a net-zero or net-negative carbon footprint – while maintaining the strength of concrete.
Blue Planet founder Brent Constantz says: "Bringing Knife River's aggregate knowledge to our team will help us fully understand how our products will need to perform in the construction world, particularly as a component of concrete. As we scale our technology, we are going to be running our aggregate products through industrial-level crushing, screening, filtering and placement processes, each of which Knife River knows well. Blue Planet's aggregates are created using carbon-sequestration technology, and we will be able to see how they perform at this industrial level. We'll be able to compare our products to traditional geological materials. And we'll be able to see the effects of our products in concrete, which can be a highly impactful method of permanent sequestration of carbon dioxide."
According to MDU, concrete can be produced by capturing CO2 from existing sources to create synthetic limestone while preventing that CO2 from entering the atmosphere.
Using synthetic limestone would prolong the life of natural aggregate sources, the company adds.
As part of the deal, Knife River CEO David C. Barney has joined the five-member board of directors at Blue Planet.
Barney says: "Concrete is the foundation of the world's infrastructure. We want to be proactive in finding ways to minimise our carbon footprint while continuing to build the strong roads, bridges, runways and driveways our nation uses every day."