Marine Carbon Removal Gains Traction as Sargassum Blooms Offer New Offset Pathway

Marine Carbon Removal Gains Traction as Sargassum Blooms Offer New Offset Pathway Persistent Atlantic sargassum could feed ocean-based carbon credits, but the $2 billion voluntary market and compliance schemes remain sceptical of durability. Marine carbon removal projects stand to benefit from persistent sargassum blooms in the Atlantic, according to a new report, as developers look for biological pathways to generate carbon credits from ocean biomass. The approach involves harvesting or sinking sargassum to sequester the carbon it has absorbed, a method that sits outside the established forestry and land-use offset categories that dominate the voluntary carbon market. That market is small. The voluntary carbon offset market has a volume of about $2 billion a year, according to the Economist. Marine-based credits represent a fraction of that total. The challenge for sargassum-derived offsets is demonstrating permanence — how long the carbon stays sequestered after the seaweed sinks — and establishing measurement, reporting, and verification protocols that buyers and registries will accept.³ Compliance markets have been even more resistant. The European Emissions Trading System banned the use of offsets entirely in 2013. Most cap-and-trade systems that allow carbon offsets do so only to a limited degree. Australia's Safeguard Mechanism is a controversial exception, permitting certain nature-based offsets into its compliance framework. Marine carbon removal would need to clear an even higher bar than forestry offsets, which have themselves faced persistent criticism over additionality and permanence.³ The institutional architecture for a net-zero world is still being built. The Colombian carbon tax and similar mechanisms include provisions for nature-based schemes that make use of forestry, coastal mangroves, and similar ecosystems. If well monitored, these provisions could eventually accommodate marine-based carbon removal. But the price of allowances in cap-and-trade markets looks far too low to cover the more durable forms of carbon removal that the scientific community considers necessary.² Carbon capture and storage offers a parallel case study in how slowly new removal technologies gain regulatory acceptance. A Montel report found that a think tank warned the EU against using CCS to decarbonise gas power plants, arguing that the bloc should focus on cheaper alternatives like renewables and stronger grids. The report noted that substantial subsidies would be required to make gas-CCS competitive. Marine carbon removal faces a similar cost-competitiveness challenge against established offset types.¹ The ICAP Status Report tracks how different emissions trading systems around the world treat emerging technologies including CCS. The report explores whether ETSs could play a role in incentivising the development and deployment of carbon capture applications. Marine carbon removal is not yet part of these frameworks, but the policy discussions around CCS inclusion could create precedents that ocean-based approaches eventually follow.⁴ Sargassum blooms have been growing in scale and persistence across the tropical Atlantic in recent years, driven by nutrient runoff and changing ocean temperatures. For Caribbean and West African coastal communities, the blooms are an environmental nuisance. For carbon removal developers, they represent a feedstock that grows without cultivation or irrigation, absorbing CO2 as it proliferates. The commercial question is whether the credits generated from sargassum removal can command a price high enough to cover the cost of harvesting, processing, and sinking the biomass. Voluntary market credits from forestry projects trade at wide price ranges depending on quality and vintage. Marine credits would need to establish their own price discovery, likely at a premium given the novelty and the verification costs. For energy market participants, the relevance is indirect but growing. If marine carbon removal credits gain acceptance in compliance schemes, they would increase the total supply of offsets available to emitters, potentially putting downward pressure on allowance prices in systems that permit offset use. Conversely, if compliance markets continue to restrict offsets, the credits would remain confined to the voluntary market where their impact on energy sector pricing is negligible. The signal to watch is whether any major carbon registry — Verra, Gold Standard, or a compliance-linked body — publishes a methodology for sargassum-based carbon removal credits. Without a methodology, the projects cannot generate tradeable credits regardless of how much sargassum they harvest. The gap between biological opportunity and market infrastructure is where this story sits.^3,2