Storing CO₂ under the North Sea: how carbon storage projects work—and what critics worry about

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Summary: Denmark’s Greensand Future project plans to inject large volumes of CO₂ into a depleted North Sea oilfield, turning old fossil infrastructure into a storage site for greenhouse gases. Supporters say carbon capture and storage (CCS) is necessary for “hard-to-abate” emissions. Critics warn it can be expensive, divert attention from cutting emissions directly, and create long-term liabilities.

This is the CCS debate in miniature: engineering confidence versus climate-policy risk.

What Greensand Future is trying to do

From the BBC report:

  • The project uses the Siri platform as a hub.
  • It will inject CO₂ into an almost-depleted oilfield in the North Sea.
  • It is backed by a consortium led by Ineos.
  • It aims to store about 400,000 tonnes of CO₂ in the first year, with a stated ambition to reach up to 8 million tonnes annually by 2030.
  • It is described as the EU’s first large-scale offshore CO₂ storage site once commercial operations begin.

Why depleted oilfields are attractive storage targets

Oil and gas fields have two key properties:

  • they have proven geology that trapped hydrocarbons for millions of years
  • they have existing infrastructure and operational expertise

As the BBC notes, decades of production means the geology is well mapped.

In theory, that reduces uncertainty compared to “brand new” storage formations.

The basic CCS mechanism (what it depends on)

A CCS storage site requires:

  • porous reservoir rock to hold CO₂
  • a thick cap rock (seal) to prevent upward migration
  • well integrity so CO₂ doesn’t leak via old boreholes

The BBC report describes pores in rock samples and a thick clay/cap layer that serves as the seal.

This is why supporters argue CCS is a geology problem we already know how to solve.

The economic argument: why critics focus on cost

CCS is often criticised because:

  • it adds cost to industry operations
  • it can become a subsidy sink
  • it competes with cheaper decarbonisation options

Greenpeace Denmark’s view in the BBC piece is representative: CCS is acceptable where emissions are genuinely hard-to-abate, but not as a broad substitute for reductions.

The underlying concern is moral hazard:

  • “we can keep emitting because we’ll store it later.”

The “hard-to-abate” nuance

Some sectors are difficult to decarbonise with today’s tech:

  • cement
  • steel
  • some chemicals

If CCS is targeted at these sectors, the argument strengthens.

If CCS becomes a justification for prolonged fossil fuel extraction and combustion, the argument weakens.

So the critical question is not “CCS good or bad,” but “CCS for what?”

Monitoring and long-term responsibility

Offshore storage raises practical governance questions:

  • who monitors for decades?
  • what happens if leakage occurs?
  • who pays?

These are not purely technical questions. They are legal and political.

The BBC report also quotes concerns about using up seabed storage capacity that future generations might need.

Why the North Sea is becoming a CCS hub

The BBC notes multiple projects across the region:

  • Norway’s Northern Lights is already storing CO₂
  • UK clusters are under development

The North Sea has:

  • suitable geology
  • infrastructure
  • a workforce with relevant skills

That workforce angle is important: CCS can be framed as a “just transition” pathway for offshore workers.

What to watch next

  1. Verification: transparent measurement of how much CO₂ is stored.
  2. Leakage monitoring: credible long-term monitoring plans.
  3. Cost per tonne: whether CCS becomes cost-competitive or remains subsidy-heavy.
  4. Sector targeting: which industries are paying for (or using) the storage.
  5. Policy coupling: CCS shouldn’t replace emissions cuts; it should complement them.

Bottom line

Greensand Future shows how climate policy is colliding with industrial reality.

CCS may be necessary for some emissions. But it’s not a free pass—and the success of projects like this will depend as much on governance, transparency, and economics as on geology.

Sources

n English