Carbon Capture & Storage at Sea: Integrating CCS with Onboard Fuel Systems

Introduction

As the maritime industry accelerates its shift toward sustainability, it faces the challenge of reducing greenhouse gas (GHG) emissions without compromising global trade efficiency. While alternative fuels such as biofuels, methanol, and ammonia are gaining traction, their widespread adoption remains uneven and limited by infrastructure, cost, and technological readiness. In this context, Carbon Capture and Storage (CCS) presents an innovative approach to mitigating shipboard emissions—especially for vessels running on conventional or transitional fuels.

This article explores the potential of integrating CCS systems directly into ship fuel systems, analyzes current technological progress, and discusses operational, economic, and regulatory implications of deploying CCS at sea.

1. The Case for CCS in Maritime Applications

1.1 The Emission Burden of Shipping

Shipping accounts for nearly 3% of global CO₂ emissions, with most vessels still operating on fossil-based fuels. Although improvements in efficiency and the gradual introduction of low-carbon fuels have yielded some progress, many ocean-going vessels—particularly in deep-sea freight—continue to emit large volumes of CO₂. Given the longevity of ships and the lag in fuel transition, CCS offers a near-term, scalable way to address emissions onboard.

1.2 Why CCS Makes Sense at Sea

Unlike power plants or industrial facilities, ships cannot be easily connected to national carbon pipelines or grids. However, they present a closed combustion environment, which means CO₂ emissions can be concentrated and captured at the point of origin. This makes CCS technically feasible—though operationally complex—for onboard use. Moreover, CCS enables vessels to continue using current fuel systems (e.g., LNG, marine gas oil) while complying with tightening emissions regulations.

2. Carbon Capture Technologies for Marine Use

2.1 Overview of CCS Methods

There are three primary types of carbon capture technology that can be adapted for marine use:

Post-combustion Capture: Extracts CO₂ from exhaust gases after fuel combustion, typically using chemical solvents like amines.
Pre-combustion Capture: Involves converting fuels (e.g., via gasification) into hydrogen and CO₂ before combustion. Not commonly used in maritime settings due to complexity.
Oxy-fuel Combustion: Burns fuel in pure oxygen, creating a CO₂-rich exhaust that’s easier to separate.

Among these, post-combustion capture is the most practical for shipboard integration due to its adaptability to existing engine configurations.

2.2 Marine-Ready CCS Systems

Early prototypes and pilot projects are proving the concept. Companies like Wärtsilä, Mitsubishi Heavy Industries, and Carbon Clean are developing compact CCS systems designed to fit within a ship’s existing engine room footprint. These systems rely on absorption towers, gas coolers, and CO₂ compressors to separate and liquefy CO₂ for onboard storage.

Key features of marine CCS systems:

Designed for space efficiency
Modular and retrofittable
CO₂ liquefaction at around -50°C and 6–7 bar pressure for storage
Storage tanks similar to those used for LNG or LPG

3. Integrating CCS with Onboard Fuel Systems

3.1 Compatibility with Current Fuels

Carbon capture systems are inherently flexible and can be paired with a variety of onboard fuel types:

Heavy Fuel Oil (HFO): High emissions; CCS can significantly reduce CO₂ output.
LNG: Lower CO₂ per unit of energy but still emits methane and CO₂; CCS improves overall lifecycle emissions.
Methanol & Biofuels: When used with CCS, these can potentially lead to net-zero or even carbon-negative emissions, depending on feedstock.

3.2 Engineering Integration

Integrating CCS with fuel systems involves several technical challenges:

Exhaust Gas Routing: Ship exhaust must be diverted to scrubbers or absorber columns.
Energy Demand: CCS processes require auxiliary power (approximately 5–15% of engine output), increasing overall fuel consumption unless energy efficiency is improved elsewhere.
Cooling & Compression: CO₂ must be cooled and compressed for storage, necessitating heat exchangers and compressors.

These systems must be optimized for:

Space limitations
Motion and vibration at sea
Maintenance access
Safety protocols, particularly for high-pressure gas storage

4. Storage and Offloading of Captured CO₂

Captured CO₂ needs to be safely stored until it can be offloaded at port. Storage options include:

Onboard Liquefied CO₂ Tanks: Similar in design to LNG tanks, sized based on voyage length and capture rate.
Reinforced CO₂ Cylinders: Used for smaller vessels or shorter trips.

Once in port, the CO₂ can be:

Offloaded to shore-based pipelines for permanent storage (e.g., in geological formations)
Delivered to carbon utilization facilities (e.g., synthetic fuel production, building materials)

Key consideration: Ports will need dedicated CO₂ handling and storage infrastructure—a major logistical hurdle.

5. Operational Challenges and Risks

5.1 Added Complexity

CCS adds a new layer of technical complexity to marine operations. Ship crews must be trained in system operation, safety procedures, and emergency protocols related to pressurized gases and chemical solvents.

5.2 Energy Penalty

Running CCS systems requires additional fuel or energy, which could reduce voyage efficiency. Unless ships offset this with better hull design, renewable-assisted propulsion (e.g., wind or solar), or fuel-saving tactics, operational costs could rise.

5.3 System Reliability

Marine environments are harsh. Saltwater corrosion, ship motion, and varying engine loads may affect system reliability. Maintenance requirements for CO₂ absorbers and compressors must be carefully managed.

6. Economic and Policy Considerations

6.1 Cost of Onboard CCS

The upfront capital expenditure for onboard CCS is significant, often exceeding $10 million per system depending on ship size. However, these costs are expected to decline with scaling and standardization.

Operating expenses include:

Solvent replacement
Additional fuel usage
Periodic maintenance
CO₂ transport and storage fees

Incentives such as carbon credits, tax breaks, or emission trading schemes could help offset these costs.

6.2 Regulatory Framework

Currently, there are no standardized international rules for CCS-equipped ships, though IMO is exploring how CCS fits within its GHG reduction strategy. Regional schemes like the EU Emissions Trading System may eventually recognize onboard capture, providing carbon credits for verified reductions.

Inclusion of CCS in fuel lifecycle assessments and emissions reporting frameworks (e.g., IMO DCS, CII ratings) will be critical to its adoption.

7. Pilot Projects and Real-World Applications

Several pilot projects are underway to demonstrate CCS at sea:

Norway’s Northern Lights Project aims to use CCS in maritime transport of CO₂ to permanent storage sites.
Mitsubishi and NYK Line are testing a small-scale shipboard carbon capture system on a coal carrier.
Wärtsilä has announced R&D projects targeting scalable marine CCS solutions by 2030.

These early projects are essential for ironing out technical bottlenecks and proving commercial viability.

8. Long-Term Role of CCS in Maritime Decarbonization

Carbon capture is not a silver bullet but can serve as a critical bridge solution, particularly for:

Long-haul vessels where fuel switching is less feasible
Fleet retrofits where engine replacement is cost-prohibitive
Hybrid systems combining CCS with low-carbon fuels

As fuel prices, carbon taxes, and regulatory pressures evolve, CCS could become a strategic decarbonization tool, especially when paired with renewable fuels or used to reduce residual emissions in otherwise low-carbon operations.

Conclusion

Integrating carbon capture and storage technology into shipboard fuel systems offers a compelling path to lower emissions in a sector that has few easy options. While challenges remain—ranging from cost and complexity to port infrastructure needs—the potential for near-term emission reductions makes onboard CCS a viable part of the maritime decarbonization toolkit.

Its success will depend on continued innovation, supportive regulation, and collaboration between shipowners, equipment providers, fuel suppliers, and port authorities. As the industry moves toward a net-zero future, CCS at sea could shift from experimental to essential.

Technology