1. Capture

In addition to CO₂, combustion fumes contain atmospheric nitrogen, which is not a greenhouse gas, and water vapor.
Since storage capacity is finite, the CO₂ has to be separated, which also reduces the amount of energy needed to compress
and transport it. The three options are:

• Recovering the CO₂ diluted in the combustion fumes (postcombustion).
• Separating the nitrogen from the air and using pure oxygen for combustion (oxycombustion).
• Removing the carbon before combustion using a chemical process (precombustion).

2. Transportation

The CO₂ then has to be transported to the storage site:

• By pipeline, at a pressure of more than 74 bar (supercritical state).
• By ship, similar to those used for liquefied petroleum gas (LPG), in liquid form at moderate pressure and low temperature.
  

3. Sequestration
Carbon dioxide can be stored in:

• Deep saline aquifers, with a global capacity estimated at several trillion metric tons.
• Nearly depleted oil and gas fields, where CO₂ flood can facilitate the recovery of additional oil and gas.
• Coal seams that cannot be mined, where injection can be supported by production of marketable methane.