Composite decking material captures carbon dioxide

Researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory have developed a carbon-negative decking material that traps more carbon dioxide than is released during its production.

A man uses an electric drill and composite materials to create a patio in a garden

Building materials have notoriously high CO2 emissions and significant efforts have been made to develop more sustainable building materials. However, these sustainable alternatives are more expensive or cannot match the strength or durability of traditional materials.

Decking made from wood-plastic composite, rather than wood, is a popular choice among homeowners because of their longevity. Typically, such composite materials consist of a mixture of wood chips or sawdust and plastic such as high-density poly(ethylene), HDPE.

The American scientists’ composite contains low-quality brown coal and lignin, a wood product used in papermaking, fillers instead of the standard wood chips and sawdust. The team modified these fillers by adding waste carbon dioxide to the surface, making them stickier and allowing for stronger composites. The carbon dioxide makes up approximately 4% by weight of the filler. The scientists then mixed these modified fillers with HDPE.

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The team’s testing found that a composite containing 80% of modified filler and 20% HDPE maximized carbon dioxide storage while exhibiting sufficient strength and durability to meet international building codes for decking materials.

More than 230,000 tons of carbon dioxide could be captured annually

The team used this composite to create three-meter-long planks that are similar in look and feel to standard wood composites used for decking or garden furniture. It is also significantly more cost-effective, estimated to be 18% cheaper than typical composite decking.

According to one of the composite’s inventors, David Heldebrant, if all 1.1 billion feet of decking sold annually in the U.S. were replaced with these carbon-negative composite floors, more than 230,000 tons of carbon dioxide could be sequestered annually. That figure is equivalent to the annual emissions of approximately 54,000 cars.

The team is now working on commercializing these decking boards. It is also developing other carbon-negative composite formulations for other types of building materials, including fencing and siding.

Maksud Rahman, a materials scientist at Rice University in Texas who was not involved in this study, is optimistic. “The idea of composite decking is innovative,” he says. The abundance of materials allows production to be scalable and feasible, he adds.

Nina Notman

Reference

Heldebrant D et al, 2024, Ta da – new decking material that is part of the solution to climate change, ACS Spring Meeting: Many Flavors of Chemistry. New Orleans, USA and hybrid

OR

Heldebrant D et al, 2024, New composite decking may reduce the effects of building materials on global warming, ACS Spring Meeting: Many Flavors of Chemistry. New Orleans, USA and hybrid

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Summary slide with questions and the article for context when teaching 14–16 lessons on composites and reducing the carbon footprint: rsc.li/3UvKoGU

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