PORTLAND, Maine — Running Tide, once a venture-backed darling of ocean-based carbon removal, has become a cautionary tale after the startup’s late pivot to sinking wood chips offshore drew scientific and public scrutiny, then ended in a shutdown that still reverberates through the market, Dec. 24, 2025.
carbon removal meets a harder standard
Running Tide launched with an ambition that sounded like science fiction with a climate deadline: use the ocean to lock away atmospheric carbon for centuries. Early coverage described the company’s seaweed-and-buoy concept as a potential breakthrough, and it attracted major buyers willing to pay a premium for “durable” carbon removal. But the company’s trajectory shifted sharply as the challenges of measurement, reporting and verification — the unglamorous plumbing of carbon removal — collided with the speed of venture expectations.
In June 2024, the company publicly said it was winding down, citing weak demand in the voluntary market. Local reporting in Maine detailed how the closure followed controversy over offshore deployments tied to Iceland and questions about how removals were quantified and validated. Running Tide’s collapse also landed as a warning to corporate buyers: the promise of carbon removal is only as credible as the evidence behind it.
From kelp dreams to wood-chip deployments
As the original approach faltered, Running Tide leaned into a different method: releasing treated wood biomass intended to sink and store carbon in the deep ocean. A later investigation described how those deployments became central to fulfilling high-profile deals — and how difficult it was to prove what happened after material entered a dynamic marine environment. In 2025, Wired’s reconstruction of Running Tide’s final chapter reported that monitoring challenges and uncertainty about outcomes undermined confidence in the company’s carbon removal claims.
That reporting fits a broader pattern: carbon removal methods that cannot be independently verified at scale risk becoming reputational liabilities for both sellers and buyers. For a sector trying to mature beyond offsets and into verifiable removals, Running Tide is now shorthand for how quickly credibility can erode when data trails behind marketing.
Why the fallout matters for buyers and regulators
Running Tide’s story arrives at a tense moment for carbon removal. Corporate demand continues, but standards are tightening, and buyers are increasingly sensitive to scrutiny over credit quality. The episode has been cited in industry discussions as a case for slower deployment, clearer guardrails and stronger third-party validation before credits are sold — especially in the ocean, where monitoring is inherently difficult and environmental concerns can escalate quickly.
Even among proponents of marine carbon removal research, the lesson is not that the ocean is off-limits — it’s that ambitious claims require equally ambitious proof. Without that, the next wave of ocean-based carbon removal startups may find the market less forgiving than it looked a few years ago.
Earlier coverage for context: Running Tide’s rise and shift played out publicly over several years, including early optimism about its approach (Reuters, Aug. 9, 2023), mainstream features on its ocean concept (Fast Company, Aug. 9, 2023), reporting on the company’s shutdown in Maine (Maine Public, June 20, 2024), and later investigations into its Iceland-linked wood-chip strategy (Canary Media, Sept. 19, 2024).
More sources: Additional reporting on the shutdown and market impact includes Latitude Media’s account of Running Tide’s final year and scrutiny documented by the Portland Press Herald.
