The figure above shows the sequences of chemical reactions that occur as CO₂ from the atmosphere is converted to minerals such as calcite (DACCM) or the chemical compound bicarbonate (ERW and OAE). The three reaction sequences are nearly identical.

In the reactions, a rock (basalt, for example) supplies positive charged ionsAn ion is an atom or molecule that has a positive or negative electric charge due to the loss or gain of one or more electrons. (called cations) such as Ca²⁺ and Mg²⁺ that balance negative charged ions (called anions) such as bicarbonate (HCO₃^-) and carbonate (CO₃^2-).

The end result is the carbon atoms from CO₂ in the atmosphere end up being permanently stored in calcite (DACCM) or bicarbonate (ERW and OAE).

The balance of charges between cations (+) and anions (-) result in a neutral charged solid (e.g., the mineral calcite) or a solution (e.g., HCO₃^- dissolved in water) — which has long-term stability.

Please note:

• The reactions shown are simplified from actual conditions.
• The reactions occur in groundwater, soil water, or ocean water, depending on the process DACCM, ERW, or OAE.
• Basalt is shown as the injection target for DACCM, but other igneous rock such as peridotite may also be an injection target.
• Basalt is shown as the feedstock for OAE, but other types of rock such as limestone (after heat treatment) may be used as a feedstock to provide positive-charged calcium ions that counterbalance the negative-charged bicarbonate ions .