The Mississippi River is a transportation powerhouse — especially for agriculture.
Roughly 60% of the U.S. grain exports float down the river by barge, and plenty of soybeans are moved that way.
But barges can move a lot of other goods too.
“Rubber, scrap metal, resin for polymers like paints, varnishes glues,” said Paul Rohde, Midwest region vice president for the Waterways Council, an organization that advocates for barge transportation. “It’s all about capacity.”
It would take more than 1,000 semitrucks to carry the same load as 15 barges and a single tow boat, the standard for this part of the Mississippi River, he said.
That’s significant given that the transportation sector accounts for about 28% of the greenhouse gas emissions in the United States. But only about 2% of that sector is ships and boats, Rohde said.
“We’re a very small part of that carbon footprint the EPA is citing,” he said.
Reducing the emissions from the transportation sector is imperative to meet the country’s climate goals and one reason Rohde advocates for more things to be shipped on the country’s rivers, he said.
“Barges move products with a much lower carbon footprint than rail or certainly trucks,” Rohde said.
A Texas A&M study from 2022 found that the overall carbon footprint of barge shipping is nine times smaller than trucking’s and about half that of rail.
But environmentalists are not sure barges are always a better alternative.
“There’s a lot of assumptions about the fuel economy (of barges) that hasn’t been answered,” said Olivia Dorothy, Mississippi River restoration director with American Rivers.
She points out the study from Texas A&M considers emissions on a system-wide basis, which misses some of the nuances of what it takes to move goods on different waterways.
“Just like cars, you’ve got different fuel economies and emissions when you drive in the city versus when you drive on the highway,” she said. “We believe that’s the same thing for our rivers.”
These are important distinctions because the Mississippi River changes a lot from its headwaters in Minnesota to its mouth in Louisiana, Dorothy said.
For example, going downriver near St. Louis, it’s the first or last place where barges go through a lock and dam
A lock is like an elevator; barges going downstream come in and are lowered to the water level in front of the dam. The process is reversed for barges heading upstream.
It’s a process that takes time, and in terms of carbon emissions, it’s similar to a truck stopping to go through a tollbooth.
There’s not much in specifics on how many emissions come from a barge going through a lock, Dorothy said. The Army Corps of Engineers, the government agency that maintains locks and dams, doesn’t collect data on emissions that come from barges.
“If we’re saying this is the solution to reduce carbon emissions, don’t we need to know the baseline?” Dorothy said. “And we don’t even know the baseline.”
But there’s another reason she questions the environmental advantages.
“These dams that we have to facilitate navigation are themselves emitting large amounts of methane,” Dorothy said.
That’s because they slow down the river flow and everything in it, meaning organic material like leaves, tree limbs, dead fish, algae and other items, settle to the riverbed and begin to break down, she explained.
“If it’s disturbed by wave action, dredging, movement through the dam, that methane then becomes released into the atmosphere,” Dorothy said.
But just how much of the potent greenhouse gas isn’t clear.
“No one has ever done the mass balance,” said Jonathan Remo, a professor at Southern Illinois University Carbondale who studies how humans affect large rivers.
He’s working to build a model of the historical and annual methane that’s emitted from locks and dams that fundamentally altered the Upper Mississippi River. Remo agrees with Rohde, the advocate for barge transportation, that barges and towboats can move goods more efficiently on a per-ton basis.
But there are climate tradeoffs tied to locks and dams that facilitate this kind of transportation, Remo explained, and without details on their emissions there’s not a clear picture of how green barges really are.
“Not having the complete information is like getting a loan and not having what the interest rate is,” he said.
It’s not just the Mississippi River with locks and dams. Other Midwest rivers, like the Illinois and Ohio, have them; even the Columbia and Lower Snake in the Northwest have them.
Many are in dire need of updates or repairs. The federal government is spending billions of dollars on infrastructure for ports and waterways to keep these transportation systems running.
Remo said he hopes his research into the methane that comes from locks and dams can be a tool to help policymakers better manage this country’s rivers and ones around the world.
“That information will potentially guide other countries that may want to develop their rivers like we have here in the United States and have a whole cost accounting of what that could potentially mean for their greenhouse gas footprint,” he said.
It’s a way to know with more certainty if barges are the solid climate solution for the shipping industry they’re made out to be, Remo said.
