CO2 monitoring

Characteristics of CO2

Carbon dioxide - CO2 for short - is a chemical bond made up of the elements carbon and oxygen. In nature, CO2 occurs as a colorless and unscented gas. It is not explosive, and as a natural component of the air we breathe, at normal concentrations, it is completely harmless. CO2 is used in various ways for everyday applications, for instance as carbonation in drinks, for cooling in air-conditioning systems, and as a solvent for cleaning. It is also used in fire extinguishers. However, too-high concentrations can have a harmful effect on people and animals, in part because of the displacement of oxygen in the air. The CO2 content of air is normally about 380 ppm, or 0.038%. Above a concentration of 1%, CO2 begins to have a physiological effect. A 5% concentration of CO2 in inhaled air can create headaches and dizziness; 8% will result in death within 30 to 60 minutes. This is why accidents frequently occur in wine cellars, wells and feed silos, where increased CO2 concentrations can occur as a result of fermentation processes. However, natural CO2 emissions, for instance in the Eifel region, also show that this does not necessarily pose an increased risk to the environment. When CO2 is emitted at the earth's surface, depending on controlling conditions such as flow rate, landscape, wind speed and wind direction, it can quickly mix with the surrounding air and be reduced to a harmless concentration.

In order to counteract climate change, geological storage would need to prevent CO2 from entering the environment for thousands of years. However, this raises the question of whether such long-term storage is possible without posing a risk to people and the environment. In addition to carefully choosing an appropriate location, this involves making reliable predictions about storage security and the corresponding monitoring options.

The storage sites must be monitored for the following reasons (Kühn, 2011):

  1. Safety and environmental protection reasons: It must be ensured that people, animals and the ecosystem are not endangered or negatively affected, and that the climate-protection goals are met.
  2. Societal reasons: Complete transparency is needed about the details of the safety of the storage operation in order to build the necessary trust within the population.
  3. Financial reasons: The actual amount of CO2 kept in the storage space must be monitored so that it can be written off as "prevented emissions" in the EU's emission trade program.
  4. Operational reasons: For controlling and optimizing the injection process.

The researchers at the GFZ German Research Centre for Geosciences and the project partners are testing a wide variety of monitoring methods on various scales. Models and simulations are also important tools for describing and predicting the processes in the storage system.

Some of the things that are monitored:

Further information about these topics can be found here and at the following links:

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