Marine carbon removal
Marine CDR (mCDR) includes a range of approaches that remove CO₂ from the atmosphere and store it in oceanic environments. Frontier’s mCDR purchases focus on abiotic pathways that manipulate the inorganic ocean bicarbonate buffer system to either extract CO₂ or enhance its storage capacity for additional uptake of atmospheric CO₂.
- Tons contracted
- 59K
- Dollars contracted
- $30.4M
- Contracted companies
- 6
- Est. total capacity
- Functionally unlimited
- Average offtake price
- —
- Current price range
- $387–1,979/ton
The approach
mCDR covers a broad range of high- and low-tech approaches, each with their own benefits and challenges. The three primary categories of abiotic mCDR are Direct Ocean Removal (DOR), Ocean Alkalinity Enhancement (OAE), and Inland Water Alkalinity Enhancement (IWAE).
| Pathway | Description | Subpathway | Approach |
|---|---|---|---|
| Direct Ocean Removal (DOR) | CO₂ is removed from seawater and stored via geologic injection or mineralization. The CO₂-depleted water is released back to the surface ocean where additional CO₂ is taken up via equilibration with the atmosphere. | – | Electrodialysis |
| Electrolysis | |||
| Photochemical | |||
| Mineral looping | |||
| Ocean Alkalinity Enhancement (OAE) | Alkalinity is added to the ocean to enhance its ability to absorb and neutralize acids such as carbonic acid, enabling the uptake of more atmospheric CO₂. This can be achieved through the addition of alkaline minerals (Mineral OAE) or by splitting seawater into acid and base, removing and neutralizing the acid, and returning the base to the ocean (Electrochemical OAE). | Electrochemical (e-chem) | Electrodialysis |
| Electrolysis | |||
| Mineral | Coastal outfall | ||
| Coastal shelf | |||
| Open ocean | |||
| Inland Water Alkalinity Enhancement (IWAE) | Similar to Mineral OAE, but takes place in inland bodies of water that typically have high biogenic CO₂ concentrations and low carbonate saturation state, which can accelerate mineral dissolution. Alkalinity is added to catalyze the conversion of CO₂ to bicarbonate for storage in the ocean. | Mineral | River and estuary |
| Lake | |||
| Biotic mCDR* | Biotic mCDR leverages biological processes such as phytoplankton growth and macroalgae cultivation to store carbon in biomass, which can be sequestered in deep-sea sediments. | – | – |
* Biotic mCDR is out of scope for our program given the challenge of meeting our scale and durability criteria while minimizing the risk of unintended ecosystem impacts.
mCDR’s role in a CDR portfolio
Abiotic mCDR could scale to large volumes in the future. Abiotic mCDR pathways have the major advantage over other pathways of having functionally unlimited storage potential given the large capacity of the ocean’s dissolved inorganic carbon (DIC) pool.
One of mCDR’s major challenges is operating cost-effectively in the ocean. Relative to terrestrial approaches, deploying in marine environments can introduce additional complexities including the handling of ocean water, siting, measurements for verification, operating within a complex and uncertain regulatory regime, and CO₂ and byproduct handling (for DOR and e-chem OAE). Concerns around ecosystem safety can make permitting and social licensing more difficult, costly and, ultimately, slow mCDR’s path to scale. Given those additional challenges, it only makes sense to pursue mCDR approaches that offer clear cost, scale, or co-benefit advantages over terrestrial alternatives.
Of all mCDR approaches, mineral OAE and IWAE offer the most compelling, low tech path to meeting these criteria and could make up a large portion of the future CDR portfolio. However, the availability and location of suitable mineral feedstocks for ocean application or the low-carbon, low-cost production of CaO and MgO from limestone remain open questions.
DOR and electrochemical OAE present fewer ecosystem and MRV questions. Because they do not introduce any new materials into seawater, these approaches are easier to verify and secure permits for. It’s also easier to mitigate and manage unintended ecosystem impacts compared to mineral OAE. However, they can be expensive and may generate byproducts like HCl acid or CO₂ streams that need to be used, stored, or otherwise managed.
Deploying responsibly is especially critical for projects operating in marine environments. While we need to move quickly to scale CDR, mCDR projects must be carefully designed to limit potential negative impacts and answer questions about their safety and efficacy prior to scaling. It’s essential that projects collect strong data on environmental baselines (e.g., pH, species distribution) prior to deployment, establish robust processes to monitor those baselines throughout deployment, and have clear safety thresholds that if crossed, require projects to pause or suspend operations. Additionally, projects should share project data transparently and engage with local communities and environmental organizations.
Characteristics of great projects
The shape of a great mCDR project will vary depending on the sub-pathway pursued, but all must thoughtfully approach operating cost-effectively and measuring removals in a marine environment, mitigating unintended impacts to coastal environments, and engaging effectively with local communities. These diverse challenges may be best addressed by a strong roster of partnerships with respected local groups and scientific experts. A great mCDR project for Frontier will include:
Compelling evidence of co-benefits. Projects that have the potential to generate co-benefits such as ecosystem restoration, improved oyster and fishery yields, and local, temporary deacidification, along with a strategy to quantify these benefits, will have an easier time developing social acceptance to operate and scale.
Robust, rigorous MRV. Approaches with strong quantification plans that can measure the amount of alkalinity added and credibly model the resulting CO₂ removed (and/or measure the bicarbonate formed) through the intervention will be able to increase MRV certainty and prove that mCDR is a viable pathway.
Integration with existing infrastructure. Rather than starting from scratch, mCDR projects can benefit from existing water handling infrastructure like desalination plants, power plant cooling, and/or wastewater treatment plants. This will allow projects to benefit from existing supply chains and industrial operations and avoid the costly engineering challenges of building new infrastructure in a marine environment.
Robust feedstock sourcing and deployment strategy. For Mineral OAE and IWAE, teams must have a clear feedstock sourcing strategy that can expand to climate-relevant scale, including an analysis of the feedstocks’ CDR capacity, variability, and concentration of contaminants to ensure reliable MRV and ecosystem safety. Teams should also evaluate whether there are more climate-efficient uses for the feedstock outside of CDR.
Robust management of byproducts and contaminants. E-chem OAE developers must have a scalable strategy for acid disposal that renders the by-product permanently inert to the global carbon cycle. Mineral OAE developers using mined feedstocks must have strong ecosystem safety guardrails to screen feedstocks or develop an approach to remove or neutralize potentially harmful contaminants.
Resilience against immature supply chains. Approaches that rely on well-established, scalable supply chains will have a higher likelihood of success and scale faster. Approaches that rely on niche components (e.g., bespoke membrane technology) must be paired with a believable sourcing or manufacturing strategy to deploy this technology at scale.
Frontier’s mCDR portfolio
Frontier has purchased from a number of exciting mCDR projects that match these characteristics. Below are examples from our portfolio.
CarbonRun
- Track
- Offtake - 2024
- Prepurchase - 2023
CarbonRun adds crushed limestone to acidified rivers, raising the pH and enabling carbon removal while simultaneously generating ecosystem benefits like salmon population restoration. Their cheap, widely available feedstock will allow them to scale quickly and keep costs low, and by operating in rivers, they can take direct measurements upstream and downstream of a treatment point, lowering the cost of MRV. CarbonRun’s community engagement approach is best-in-class, and they have secured support from local governments, First Nations groups, and environmental organizations, facilitating faster scaling.
Planetary
- Track
- Prepurchase - 2023
Planetary introduces alkaline materials to existing ocean outfalls like wastewater treatment plants and power station cooling loops. The integration with existing infrastructure lowers deployment costs and speeds up feedstock dissolution through enhanced mixing. Their strong operational execution and multi-pronged approach to sourcing and deploying alkalinity has allowed them to be among the first mineral OAE companies to remove near-term volumes.
Banyu Carbon
- Track
- Prepurchase - 2023
Banyu uses a photoexcitable molecule to generate acid from seawater in a reversible reaction, which is used to cause CO₂ outgassing for capture and removal. Their novel approach using sunlight offers a potential path to very low energy DOR that may even generate excess clean power to return to the grid.
Planeteers
- Track
- Prepurchase - 2024
Planeteers uses a novel pressure-swing process to turn widely available limestone into hydrated carbonate minerals (HCMs), an ultra fast-dissolving feedstock for mineral OAE. They directly integrate with wastewater treatment plants, which enables direct measurements for MRV and dropping capex costs by leveraging existing infrastructure. These integrations will also allow them to prototype and improve their technology rapidly before expanding to open waters.
Purchase targets
Frontier continues to look for new purchases from mCDR companies that complement our existing portfolio and address gaps that accelerate the field more broadly.
Offtake priorities
We are looking for novel projects that meet our criteria for great mCDR projects, meaningfully beat the key performance metrics in our current portfolio, meet the eligibility criteria listed in the Offtake RFP, and:
- Have a believable, steep cost trajectory and can remove large volumes in the near-term
- Have demonstrated the ability to effectively quantify carbon removal from small scale deployments
- Use a low cost, high capacity feedstock for mineral OAE
- Have the potential for large scale removal (with a clear path for acid neutralization at scale, if applicable)
- Offer and quantify valuable ecosystem co-benefits
If you are a carbon removal company that meets Frontier’s offtake eligibility criteria and is addressing at least one of our purchase targets, please take the next step to apply.
Apply for offtake
Prepurchase priorities
We are also looking for earlier-stage companies with novel, potentially breakthrough approaches that are addressing the following innovation areas:
Scalable feedstocks for Mineral OAE
Mineral OAE is one of the most promising approaches to low-cost CDR, but the availability of suitable feedstocks currently limits this pathway. We are looking for stellar teams that have developed feedstock sourcing strategies with gigaton-scale potential. This could include novel ways to enhance dissolution of natural minerals, innovations to remove impurities or extract alkalinity from mixed natural minerals or industrial wastes, or the production of synthetic oxides and hydroxides such as CaO or Mg(OH)₂. Critical properties of promising feedstocks are (1) total availability in relevant geographies to support large scale OAE or IWAE, (2) fast dissolution kinetics, and (3) ecosystem safety. Applicants in this category also need a strong plan for MRV, including methods for effective quantification of feedstock dissolution.
We’re particularly interested in low-cost, carbon-free production methods of calcium oxide (CaO) and magnesium oxide (MgO) from limestone, which could enable outstanding improvements to the efficiency and scale of ocean alkalinity enhancement (i.e., ocean liming). We’re looking for any great approach to generate CO₂-free CaO or MgO at lower energy and cost than conventional methods. This could include novel calciner and CO₂ capture designs or no-heat alternatives.
mCDR approaches with clear co-benefits
Real, measurable co-benefits are a critical accelerant to build project support and give back to communities hosting CDR deployments. Therefore, we are interested in approaches to mCDR that offer clear economic and/or environmental co-benefits such as the restoration of polluted or degraded ecosystems or creating local pH refugia for critically impacted species. It is particularly important for teams in this category to have to have local partners and a sound approach for measuring this co-benefit against a baseline scenario.
If you are a carbon removal company that is pursuing one of these targets and meets our prepurchase eligibility criteria, please apply below.
Apply for prepurchase
Pathway resources
Frontier BiCRS resources
CarbonPlan’s Verification Frameworks