The blistering heatwave sweeping across Europe has brought climate change, and the challenges of tackling it, to the forefront of public discussion. It is clear that a range of urgent solutions are needed, and quickly, if we are to avoid increasingly uncomfortable summer weather.

One such solution could be carbon capture and storage (CCS). Recent months have seen a number of CCS projects being given the go-ahead, with enthusiasm across multiple sectors. SSE Thermal and Equinor are pushing ahead with a power station at Peterhead which has the potential to become Scotland's first power station with carbon capture technology. Elsewhere, Tata Chemicals Europe plan to capture 40,000 tonnes of carbon dioxide (CO2) per year and turn it into baking soda. The first CCS project opened in the United States in 1972, so the concept has been around for a while.

What is CCS?

Carbon capture and storage (CCS), or CCUS (with the 'U' denoting 'usage', where some of the captured carbon is used to manufacture physical products, such as cement), is the process of capturing CO2 emissions before release into the atmosphere, and burying these emissions in deep, underground locations. CO2 can be captured from large emitters, such as power plants and heavy industries. At present, it is thought that CCS technology can capture up to 90% of CO2 released through the burning of fossil fuels and industrial processes.

It is envisaged that CCS can occur by one of three processes:

  1. post-combustion CCS captures exhaust gases from burning fossil fuels, and can be retrofitted to existing plants and factories;
  2. pre-combustion CCS involves partial burning of the fossil fuel in a gasifier to form synthetic gas. CO2 can then be captured from this synthetic gas, which also results in the formation of hydrogen which can be separated and used as fuel. Pre-combustion CCS cannot be retrofitted to older plants, but can be cheaper than post-combustion CCS; and
  3. oxyfuel, involves burning the fossil fuel in oxygen rather than in air. The resulting flue gas is composed of mainly CO2 and water vapour, the latter condenses into water and leaves almost pure CO2. Oxyfuel technologies are yet to be widely commercialised.

At present, post-combustion CCS is the most commonly deployed method. Once the CO2 has been captured by one of these methods, it is compressed and transported, before being sequestered in underground rock formations. Past examples of storage sites include saline aquifers, or depleted oil and gas reservoirs.

Can CCS contribute to net-zero ambitions?

It is safe to say that CCS is a technology that has attracted significant scepticism over the years. Since the opening of the first CCS facility in 1972, investor confidence has been low, hindering progress. Critics argue that CCS is expensive, and that a plant with CCS technology uses more fuel than one without. Furthermore, CO2 at high concentrations can act as an asphyxiant, so leakage from storage facilities could be a hazard to human health, as well as failing in its original purpose.

However, there is now an emerging policy consensus around investment in CCS. The UN's Intergovernmental Panel on Climate Change (IPCC) has stated that in order to keep global warming below 1.5°C, a range of mitigations, including CCS, will be required and emissions reductions alone will not be sufficient. The UK Government's 2017 Clean Growth Strategy aimed to "demonstrate international leadership" in CCS, and in November 2020 the CCS Infrastructure Fund was allocated £1 billion in the Government's spending review. In January 2022, the Scottish Government's Emerging Energy Technologies Fund provided backing of up to £80 million for the Scottish Cluster carbon capture project. Beyond power production, CCS is seen as crucial for reducing emissions from industries such as cement and steel, as well as from Energy from Waste (EfW). Indeed, in its push to become the world's first carbon-neutral city, Copenhagen is to equip one of its EfW plants with CCUS technology.

As with many emerging technologies, CCS attracts both spirited support and fervent criticism. However, since its inception in the 1970s, CCS projects are now operating or under development in 25 countries around the world and over 100 new CCUS facilities were announced in 2021. As the world searches for ways to meet net-zero ambitions and keep global temperatures at agreed levels, it may be that CCS is an idea whose time has come.