The North Sea offers ample opportunities for carbon storage

The Netherlands has enough space available under the North Sea to store around 1.5 gigatonnes of CO₂ in empty gas fields, as well as additional capacity in ‘aquifers’. The first actual CCS projects (Porthos and Aramis) are currently being developed and will be followed by the Delta Rhine Corridor and Delta Schelde CO₂nnection projects.

In 2024, carbon emissions in the Netherlands totalled 144 megatonnes, down 37% on 1990. The target for 2030 is a reduction of 55% compared to 1990. Power generation is rapidly decarbonising as more and more solar panels and wind turbines are installed, and transport-related carbon emissions are declining thanks to the increasing uptake of electric vehicles.

However, industry is finding it a lot harder to go green, especially waste incineration plans, refineries and fertiliser and cement plants. Carbon emissions from industry still totalled 47 megatonnes in 2024. In order to significantly bring down greenhouse gas emissions in hard-to-abate sectors, there is an alternative: capturing and storing CO₂.

The EU Net-Zero Industry Act (NZIA) puts an obligation on EU Member States to develop carbon capture and storage (CCS) projects. By 2030, 50 megatonnes of CO₂ per year must be captured and stored across the EU. Or rather, the Member States must have committed by then to investing in projects that add up to 50 megatonnes of CCS capacity. To put this into perspective, total greenhouse gas emissions in the European Union were just over 2,900 megatonnes in 2023, 37% below the 1990 level.

CO₂ can be stored in empty gas fields under the North Sea. However, not all countries in the EU have such ‘empty’ gas fields. Based on the polluter pays principle, Brussels has imposed obligations on Member States in proportion to their natural gas production over the 2021-2023 period. For the Netherlands, this means that it will have to store a total of 13.3 megatonnes of CO₂ annually by 2030.

Bram Herfkens of state energy company Energie Beheer Nederland (EBN) is closely involved in Dutch CCS projects. ‘There are ample opportunities for CCS in the Netherlands,’ says Herfkens. ‘The geological capacity for storage of CO₂ in depleted gas fields under the North Sea is roughly 1.5 gigatonnes.’ While the geological capacity is considerable, this does not automatically mean that storing CO₂ in these fields is technically and economically feasible. Besides empty gas fields, there are also deep saline aquifers that are suitable for CO₂ storage. ‘We’re currently in the process of assessing that. There is potential there to develop storage projects with capacities upwards of a hundred megatonnes.’

In September, a recent scientific article in Nature caused some confusion. The article put the total storage capacity available on our planet at around 1,460 gigatonnes, which is only a tenth of what was previously estimated. The article’s message is that CCS capacity is limited and should not be used to delay actual industrial decarbonisation.

‘The article makes several assumptions that I have doubts about,’ says Job van der Stoel, geologist at Gasunie. ‘For example, the authors assume that CO₂ cannot be injected into gas fields or aquifers at depths greater than 2.5km, while we here in the Netherlands are already developing projects with injection depths of between 3 and 4 kilometres. With such conservative assumptions, you obviously get a much lower capacity estimate.’

If we want to hit the climate targets, CCS will simply be a necessity over the coming decades. This is also confirmed by the scenarios issued by the International Energy Agency and the UN Climate Change secretariat. ‘CCS is not something you do for the fun of it, but rather because you want to support industry. CCS is part of the transition to the energy system of the future,’ says Marc Naus, reservoir engineer at Gasunie.

This does not mean, however, that decarbonising industry is not a priority. Herfkens of EBN: ‘As a company, your first step is obviously always going to be to improve energy efficiency. Next, you start thinking about using energy from renewable sources, but that can be tricky for sectors such as cement production and waste incineration, making CCS the only option available in the short term to bring down carbon emissions.’

EBN and Gasunie are both involved in the Netherlands’ first major CCS projects: Porthos and Aramis. With an annual injection capacity of 2.5 megatonnes, Porthos is a local project based in the port of Rotterdam. Four industrial customers have already been connected to the Porthos infrastructure: Shell’s and ExxonMobil’s refineries and Air Products’ and Air Liquide’s hydrogen plants. Porthos will store the carbon emissions from the two latter plants, which will be producing blue hydrogen from natural gas. Set to be taken into operation in 2026, Porthos’ total storage capacity of 37.5 megatonnes has already been ‘fully booked’ and accounts for 5% of Dutch industry’s total carbon emissions.

Aramis is a significantly larger-scale project. The Aramis pipeline running from Rotterdam to multiple empty gas fields located approximately 200 kilometres offshore under the North Sea will be able to transport up to 22 megatonnes of CO₂ annually. The first phase will see three storage projects connected to the Aramis infrastructure, with a joint injection capacity of around 10 megatonnes per year. As soon as demand for CCS takes off, additional storage facilities can be connected to increase the total capacity to about 500 megatonnes. According to Herfkens of EBN, there are now sufficient storage projects in the works to reach that figure.

The Delta Rhine Corridor (CO₂ infrastructure connecting Rotterdam to Germany) will be connected to the Aramis infrastructure at the Maasvlakte industrial area. Near the village of Moerdijk, the Delta Schelde CO₂nnection (a pipeline from the Belgian border) will be linked to the Delta Rhine Corridor, creating an integrated CO₂ network for north-western Europe.

‘Porthos and the first three storage projects for Aramis add up to 12.5 megatonnes per year,’ says Herfkens. ‘We’re going to need one more project to meet the EU requirement, but I don’t see that being a problem.’ Preparations for additional storage projects are already underway, which will be filled with CO₂ transported through the Aramis pipeline. If these projects go ahead, the Netherlands will be on course to inject over 25 megatonnes of CO₂ per year by 2040.

As you can see, there is plenty of storage capacity under the North Sea. ‘Capacity is not the limiting factor,’ says Herfkens. ‘The question is whether all stakeholders have sufficient confidence in CCS. The storage capacity is there, and the transport infrastructure will also be in place soon. As soon as demand for CO₂ storage from industry starts to grow, the market can get going.’

When it comes to the safety of CO₂ storage, Van der Stoel is very clear: ‘To get a permit, you have to prove that the CO₂ will be geologically trapped and cannot leak out. Although proving this requires careful work, it is not complicated. After all, these fields have safely held natural gas for 300 million years. The Porthos storage site has an additional safety feature: three thick layers of clay right above it. Other gas fields may have layers of salt instead of clay.’

The safety focus is primarily on the injection wells, because these are the only points where the sealed geological formation is breached. As soon as a gas field has been filled to capacity with CO₂ after fifteen years, the injection wells must be hermetically sealed. ‘The field operator must specify in a “sealing plan” how this will be done. They have to seal the borehole hermetically,’ Naus explains. ‘The Dutch State Supervision of Mines (Staatstoezicht op de Mijnen, or SodM) and the Netherlands Organisation for Applied Scientific Research (TNO) will oversee the inspection and monitoring of sealed fields and wells.’

A comprehensive monitoring plan for Porthos has been submitted to the Dutch Ministry of Climate Policy and Green Growth. ‘Various sensors will be installed in the well to measure any vibrations, pressure and temperature,’ says Naus. ‘If you fail to submit a solid monitoring plan, you won’t get a permit.’ These ‘MMV plans’, whereby MMV stands for measurement, monitoring and verification, require thorough preparation and are mandatory for all CCS projects in Europe. ‘The Northern Lights project is the first commercial project to store large volumes of CO₂ from multiple parties in aquifers. Everyone was looking forward to it being put into operation. It was exciting. However, when the time came, it was actually quite “boring”, because nothing unexpected happened and nothing went wrong.’

The Netherlands is home to substantial geological storage capacity. The first projects are underway, but the success of CCS ultimately hinges on confidence, decisive action, permitting and industry’s willingness to actually invest in it. The challenge lies in the pace of developments and in effective collaborative practices. If these conditions are met, the Netherlands has all the makings to grow into Europe’s carbon transport and storage hub.