VIDEO SHOWCASE: a new kind of composite decking
The production of the materials used in construction and building emit incredible amounts of carbon dioxide (CO2), a greenhouse gas that exacerbates global warming and climate change, according to the American Chemical Society. But what if building materials could trap and contain CO2?
According to the American Chemical Society, researchers funded by the United States Department of Energy Office of Fossil Energy and Carbon Management and the Southern California Gas Company have designed a composite decking material that stores more CO2 than is required to manufacture it. This material could offer a carbon-neutral alternative that meets building codes and is less expensive than standard composite decking, according to the researchers.
Despite huge, possibly world-changing potential, carbon-negative composites are not yet widely used or available, according to David Heldebrant, an organic chemist helping to lead the project. The composite decking his team has created “is one of the first composite materials to be demonstrably CO2 negative over its life cycle,” he says.
The materials and processes that go into constructing buildings account for 11% of all energy-related carbon emissions, according to the World Green Building Council. However, in many cases, more eco-friendly or “sustainable” alternatives are more expensive than traditional materials or perhaps lack strength or durability.
Composite decking, currently, is usually made from a blend of wood chips or sawdust and plastic like high-density polyethylene (HDPE). Researchers are now trying to use fillers that are waste products or would otherwise be burned.
Per the American Chemical Society, Heldebrant’s colleague, Keerti Kappagantula, had been experimenting with low-quality brown coal and lignin (a wood-derived product left over from papermaking) as filler in decking composites and adding “ester functional groups” to the particles’ surfaces.
Hearing of this technique led Heldebrant and his team to a breakthrough. “Esters are essentially carboxylic acids, which are a captured form of CO2,” says Heldebrant. So, the team wanted to do the same thing and put CO2 onto the surface of the particles in the composite to make the material even more environmentally-friendly—all while improving the composites’ mechanical performance.
Eventually the researchers found that a composite containing 80% filler maximized the amount of CO2 content while still demonstrating strength and durability that meet international building codes for decking materials. The researchers used the material to create 10-foot-long composite boards.
According to the researchers, the new composite boards offer a significant price and sustainability advantage. The new composite boards would be 18% cheaper than standard decking composite boards and also store more CO2 than is released during their manufacture and lifetime, Heldebrant says. If the 3.55 billion feet of decking sold in the U.S. every year were replaced with the researchers’ CO2-negative composite decking, he says, 250,000 tons of CO2 could be sequestered annually, which is equivalent to the yearly emissions from 54,000 cars.
The researchers plan to make additional composite formulations and envision carbon-negative composites being developed for other purposes, such as fencing and siding. For now, the team is keen to commercialize its decking boards, with a hope that carbon-negative decking could be available at building supply retailers as soon as the summer of 2025.
Learn more about this research, which was recently presented at an American Chemical Society gathering, here.