CO₂GeoNet Network of Excellence was created under the auspices of the European Commission as a group of research institutions capable of maintaining Europe at the forefront of large-scale international research. One of CO₂GeoNet's goals is the communication of clear scientific information on the technical aspects of CO₂ geological storage.

To encourage dialogue on the essential aspects of this vitally important technology, CO₂GeoNet researchers have prepared basic answers to several frequently asked questions. 

Here you can find explanations as to how CO₂ geological storage can be carried out, under what circumstances it is possible, and what the criteria are for its safe and efficient implementation.

It is now accepted that human activities are disturbing the carbon cycle of our planet. Prior to the industrial revolution and extending back some 10,000 years, this finely balanced cycle, involving the natural exchange of carbon between the geosphere, the biosphere, the oceans and the atmosphere, resulted in a low range of CO₂ concentrations in the atmosphere (around 280 ppm, i.e. 0.028%) according to the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (2013-2014).

However, over the past 250 years, our prolific burning of fossil fuels (coal, oil, gas) for power production, heating, industry and transportation, has incessantly raised the amount of CO₂ emitted into the atmosphere (Fig. 1). About half of this human-induced excess has been reabsorbed by vegetation and dissolved in the oceans, the latter causing acidification and its associated potentially negative impacts on marine plants and animals. The remainder has accumulated in the atmosphere where it contributes to climate change, because CO₂ is a greenhouse gas that traps part of the sun’s heat, causing the Earth’s surface to warm.

Immediate radical action is needed to stop today's atmospheric CO₂ concentration of 409.9 ppm (already a +46.4% increase compared to pre-industrial levels).  The last IPCC reports underline what must be our objective: to limit warming to 1.5°C by 2100, that is, global net anthropogenic CO₂ emissions must decline by about 45% from 2010 levels by 2030 and reach net zero emissions around 2050.

According to the International Energy Agency (IEA-GHG), the power generation (electricity and heat) sector contributes the majority of total CO₂ emissions (14 Gt of CO₂ in 2019), followed by the transport sector representing 8.2 Gt of CO₂ emissions. Together they are responsible for approximately two thirds of total emissions and most of the global growth since 2010.

A main source of direct CO₂ emissions results from the burning of fossil fuels to feed the transport and power sectors. An option for the latter is to return the carbon back into the ground by creating a closed loop in the energy production system. In this way, the carbon extracted from the ground originally in the form of gas, oil, and coal, is returned back again in the form of CO₂. But this is not only applicable to CO₂ coming from fossil fuels but also from some industrial process producing clinker by cement industry upon heating mixture obtained from limestone and clay.

Underground storage of CO₂ is not a human invention, but a natural and widespread phenomenon manifested by CO₂ reservoirs that have existed for thousands to millions of years. One example is a series of eight natural CO₂ reservoirs in south-eastern France discovered during oil exploration in the 1960s (Fig. 2). These and many other natural sites throughout the world show that geological formations are able to store CO₂ efficiently and safely for extremely long periods of time.

CO₂ Capture and Storage (CCS)  is one of the crucial measures that needs to be urgently implemented to mitigate climate change and ocean acidification. It will play a decisive role in reaching the net zero CO₂ emissions needed by 2050.

CCS involves:

• capturing CO₂ at coal- or gas-fired power stations and at industrial facilities (steel mills, cement plants, refineries, etc.);
• transporting it by pipeline, train, truck or ship to a storage location;
• injecting it through a well into a suitable geological formation for long-term storage (Fig. 3).

In view of the growing world population and improving economy of developing countries, the rising energy as nogl_well as basic material demand (cement, steel …) is inevitable. Considering the expected use of fossil fuels due to the current lack of large-scale alternative for 'clean' energy sources, and the CO₂ emitted during the production of those basic materials, it is expected an increment of the global CO₂ emissions in the short and midterm. Nevertheless, hand in hand with CCS, Humanity could progress in an environmentally friendly way while creating a bridge to a worldwide economy based on sustainable energy production.

Major research programmes on CCS have been conducted in Europe, the United States, Canada, Australia and Japan since the 1990’s. Much knowledge has already been acquired at the world’s first large-scale demonstration projects, where CO₂ has been injected deep underground for several years: Sleipner in Norway (about 1Mt/year since 1996) (Fig. 4), Weyburn in Canada (about 1.8Mt/year since 2000), and more recently Gorgon in Australia (about 3 Mt/year since 2019).

International collaboration on CO₂ storage research, fostered by IEA-GHG and CSLF, at these and other sites has been particularly important in extending our understanding and developing a worldwide scientific community that is addressing this issue. An excellent example are the IPCC reports, such as its special report on CCS (2005), which describes the state of knowledge and the obstacles that must be overcome to allow the widespread implementation of this technology, and more recently presenting CCS and CCU technologies in several pathways to limit global warming to 1.5ºC (2018).

Robust technical expertise exists, and the world is now confidently moving into the demonstration and commercial phase. In addition to technical developments, legislative, regulatory, economic and political frameworks are being drawn up, and social perception and support being assessed. In Europe, the goal is to have 15 permits for CO₂ storage projects granted or in the advanced stage by 2030.