Running Tide’s office in the Marine Trade Center on Portland’s waterfront. The carbon-capturing company went out of business Friday because of a collapse in the market for carbon credits, its CEO said. Scientists have raised questions about the ecological impacts and efficacy of the company’s technology. Gregory Rec/Staff Photographer

The Portland-based carbon-capture startup that shut down suddenly on Friday after gaining international praise is being criticized for dubious scientific claims and practices.

Running Tide purported to deploy chunks of wood waste coated in limestone and kelp spores into the ocean near Iceland, where they would absorb carbon and sink to the seabed or be eaten by marine animals. The startup would then sell carbon credits to big companies such as Microsoft and the ecommerce platform Shopify to offset their emissions.

CEO Marty Odlin said Running Tide, which had over 120 employees at its peak and raised more than $50 million from private investors, closed because it could no longer sell enough carbon credits to survive after the market collapsed last fall. Analysts attributed the collapse to questions about the environmental impact of carbon credits and the integrity of projects claiming to offset carbon emissions.

A three-month investigation published Friday by the Icelandic newspaper Heimildin (The Source) found that Running Tide didn’t deploy basketball-size buoys of wood and kelp, as promised, to absorb carbon.

Instead, the company dumped about 19,000 tons, or 15 full barges, of Canadian wood pellets or chips into prime fishing territory off the coast of Iceland, which allowed the project under a research license that was granted by top officials but came with little actual government oversight, the investigative weekly reported.

The article raised questions about the safety and effectiveness of the project, saying that ocean carbon capture technology remains unproven and impossible to measure, and that the wood pellets could have a negative effect on the ocean environment whether they sank off Iceland or floated into European waters.


“They were doing this last summer without anybody watching and without doing any real research,” said Bjartmar Alexandersson, one of two journalists who worked on the story. “We have really strict laws in Iceland about what you can put in the ocean because we live on the ocean and fishing is a huge industry for us.”

Heimildin’s report, which included photos of a massive pile of wood chips, featured interviews with several top scientists around the globe who questioned or debunked the technology.

“The methods used by Running Tide do not sequester any carbon dioxide from the atmosphere. Zero,” said Jón Ólafsson, oceanographer and professor emeritus of the University of Iceland. “All this nonsense is for nothing.”

Ólafsson and other scientists also questioned whether ocean carbon sequestration could ever be an environmentally sound alternative to actually reducing fossil fuel emissions.

Scientists previously flagged potential ecological risks of using Running Tide’s technology on a large scale in a 2022 MIT Technology Review article. The publication found that the startup had “lost a string of scientists in recent months,” who were concerned that company leaders had disregarded possible environmental impacts and were “discussing more controversial practices, including adding nutrients to the ocean to stimulate macroalgae growth.”

Reached by phone on Monday, Odlin called the Icelandic newspaper article “absurd” and defended Running Tide’s technology and approach as “basic best practices in research and engineering.”


He said mineral-coated wood pellets deposited off the coast of Iceland last summer were the first phase of a four-year research license that started small and would have led to basketball-size floats made of wood chips in the future.

“The idea was you can manipulate ocean chemistry positively to increase the (alkalinity),” Odlin said. “They’re trying to make a controversy out of us approaching this as professional engineers.”

Odlin said the company never applied for a permit in Maine waters because they weren’t deep enough, but it had acquired a permit for a similar project in Canadian waters that was never used.

Odlin referred additional questions to one of Running Tide’s scientific advisers, Justin Ries, Ph.D., head of the Ries Lab at the Marine Science Center at Northeastern University. Ries was unavailable to be interviewed Monday, but later said he wasn’t involved in day-to-day operations, and defended the company’s long-term research goals and the science behind its technology.

“This was small, pilot-scale research,” Ries said in an interview Tuesday. “They did countless experiments that resulted in important breakthroughs for the industry. It would have taken a lot more research to be able to release buoys to grow algae.”

Ries said Running Tide’s limestone-coated wood pellets wouldn’t harm the world’s oceans, which already absorb nearly 1 billion tons of woody plant debris washed from their shores each year. Many carbon-capture ventures struggle to stay afloat, he said, because the industry wants immediate results with positive cash flow for what should be considered research.



Heimildin’s report delved into questions about Running Tide’s project.

The Icelandic Environmental Agency sent a report to the Ministry of the Environment saying there was “significant uncertainty” about the project, whether it would work as expected and what its environmental impact might be, Heimildin reported. The agency also said it would be a significant change from Running Tide’s plans as stated in the research permit, which remained in effect despite any concerns raised.

“It is clear that a significant amount of materials will be thrown into the sea and it is difficult to assess whether it conflicts with the objectives of the Act on the Protection of Seas and Coasts,” the agency concluded. “The main goal is not to grow kelp and sink it into the deep sea, but to throw wood pellets mixed with alkaline substances into the sea.”

David Ho, a University of Hawaii professor who co-founded [C]Worthy, a nonprofit that researches safe ocean carbon sequestration, said the success of ocean carbon capture technology hasn’t been proven and currently can’t be measured, Heimildin reported.

Alexandersson, the journalist, said an unfortunate result of Running Tide’s project is the impact it could have on the wider effort to fight climate change, providing fodder to climate deniers.


“This company is a good example of the problems with carbon sequestration and why startups can’t be trusted,” Jean-Pierre Gattuso, an oceanography research professor at Sorbonne University in France, told Heimildin.

Despite previous scrutiny, Running Tide claims to have removed the equivalent of 25,000 tons of carbon dioxide and delivered 21,000 credits since its founding, becoming the largest company in the world to trap carbon without taking it directly from the air or point of emission, according to its website. It had 30 academic and commercial partners, 25 enterprise customers and 12,000 total purchasers.

Just this year, Time magazine and Statista ranked Running Tide No. 37 among America’s top 250 green tech companies and a Musk Foundation initiative named it one of the top 100 most promising carbon removal innovators.

Running Tide laid off its remaining 32 U.S. employees on Friday, most of whom were based in Portland, Odlin said. Fifteen workers in Iceland also lost their jobs.

The company had been operating for seven years, after Odlin’s family sold its groundfishing fleet.

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