Carbon dioxide (CO2) produced by the combustion of fossil fuels (oil, gas, coal) is one of the most significant contributors to global warming.
One way to minimise the impact of CO2 on the climate is to isolate it from the atmosphere by reinjecting it into deep geological formations. The international community refers to this chain Carbon Capture and Storage (CCS). The Intergovernmental Panel on Climate Change (IPCC) presents CO2 capture, use and storage techniques as a necessity to keep the temperature rise below 1.5°C to 2°C.
CCS is carried out in three stages: the capture of CO2 at its point of emission (mainly from industrial source), its transport to its storage location, and its geological storage in suitable formations.
Capture technologies aim at CO2 separation from the plan exhaust gas instead of releasing it to the atmosphere. They can be classified into three categories, according to the type of changes they induce in the emitting processes:
In these emitting processes, production is associated with CO2 release (e.g. natural gas processing, hydrogen production, bioethanol production). Recovering CO2 for geological storage or any other industrial use thus requires no changes to the emitting process, an example being methane reforming plants in refineries.
This technology is referred to as post-combustion capture. The CO2 is separated from the exhaust gas stream produced either by the combustion of fuels in air or by the process itself (for example, decarbonising in cement production or the reduction of iron oxides in the steel industry). The separation process downstream of the emitting process limits changes to the emitting process.
In pre-combustion capture, the initial carbon-rich fuel is transformed into a carbon-free synthesis gas. Decarbonising the inlet gas generates CO2, which is captured before its used, hence the term “pre-combustion”. The synthesis gas is then used in the industrial process that is being decarbonised. Hydrogen is the gas most often envisaged to play the role of decarbonised fuel.
In oxy-combustion capture, atmospheric air is replaced by pure oxygen, which avoids dilution of the CO2 formed during combustion by the nitrogen in the atmospheric air and facilitates its separation.
For depleted hydrocarbon reservoir storage, the injection strategy can be based on practices established by the oil industry, which has used CO2 injection for many decades to improve reservoir productivity. Enhanced oil recovery mechanisms during CO2 storage may prove economically beneficial.
CO2 storage projects are large-scale ventures requiring investments in excess of €500M, and substantially more for offshore projects. These projects are established in phases:
Geostock offers to its clients recommendations for CO2 capture and separation by studying the emitting process(es) and analysing the applicable technologies. The key sizing parameters to be considered concern the characteristics of the CO2 source and their variation over the lifetime of the facility, and, where applicable, the possibilities of clustering all or part of the capture between sources located on the same industrial site.