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MSU biologist: Planting along roadways can capture carbon emissions




BOZEMAN – The nation’s roadside landscaping could capture and store millions of tons of carbon dioxide, according to new research from Montana State University’s Western Transportation Institute.

At the annual meeting of the North American Congress for Conservation Biology held this summer in Missoula, WTI researcher Rob Ament described how federal roadways currently absorb the emissions of approximately 7.6 million cars and could be managed to absorb the emissions of millions more.

“There is a lot of potential there, given that our study only accounted for those roads and highways that are managed by federal land management agencies, such as the Forest Service or Bureau of Land Management,” Ament said.

Since plants absorb carbon dioxide and give off oxygen, shrubs and grasses combat carbon emissions. With more active management, the landscape along our roadways could become a significant carbon sequestration source, Ament said.

Carbon sequestration is a process of removing and storing carbon that might otherwise get released into the atmosphere. Engineers and scientists have proposed pumping carbon emissions from coal-fired power plants underground where it can be stored in certain geological formations. Plants naturally sequester carbon when they convert carbon dioxide into carbon during photosynthesis.

Ament’s study, performed for the Federal Highway Administration, showed roadside plants on federal lands – national parks, wildlife refuges, forests and other areas – currently capture some 7 million metric tons of carbon each year, the carbon equivalent of the average annual emissions from 5 million cars, Ament said.

“From plants growing in the right of way of the national highway system alone, we are absorbing enough carbon to neutralize the annual emissions of 2.6 million cars,” he said. “And if we can adjust how we plant and manage roadside landscapes across the nation, I think we can significantly increase the capacity of those areas.”

Roads traversing federally owned lands, which amount to about 10.5 percent of the nation’s public roads, are already growing plants that capture nearly 2 percent of total U.S. transportation carbon emissions. The FHWA could increase carbon storage by using the optimal mix of plantings, maintaining grass up to 6 inches, rather than at the “golf course” profile of 2 inches.

“There is a significant amount of [carbon capture and sequestration] going on right now, passively,” Ament said. “So the next step is to research active management techniques and take a good hard look at what’s possible.”

The Western Transportation Institute at MSU was established in 1994 to provide innovative solutions to transportation problems at all levels, from local to international. More information about the WTI is available at

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