1. What is carbon dioxide (CO2)?

Carbon dioxide, or CO2, is a very common, naturally occurring molecule that contains two oxygen atoms and one carbon atom. In everyday conditions on Earth, carbon dioxide is a commonly occurring gas that is all around us. It is colourless, odourless, is naturally present in Earth's atmosphere and is an important part of Earth's carbon cycle. All humans and animals exhale carbon dioxide when they breathe, and plants absorb it during a process called photosynthesis in order to grow.

CO2 is called a greenhouse gas (GHG) because as part of Earth's atmosphere CO2 traps the energy from the sun and keeps the world at a livable temperature. But increases in atmospheric CO2 associated with human actvites can pose problems. For example, on the one hand, burning of fossil fuels releases extra CO2 into the atmosphere (along with other greenhouse gases), and, on the other, destruction of forested areas causes less CO2 to be absorbed by trees, etc. Both cases lead to too much energy or heat being trapped in our atmosphere. This extra energy causes increasing climatic instability, which results in major changes in weather patterns.

The CO2 injected into the Weyburn and Midale oilfields is produced by the conversion of coal into methane from a coal gasification plant in the United States and transported to southeastern Saskatchewan (Canada) by pipeline. The methane produced in the plant is used to heat homes and businesses. As part of this process for turning coal into methane, CO2 is produced as a by-product. The carbon dioxide provider – Dakota Gasification Company in Beulah, North Dakota – captures the CO2 produced during this gasification process and compresses it (puts it under great pressure) using large compressors until it is liquid-like. It is then sent by pipeline to southeastern Saskatchewan for injection into Weyburn and Midale oilfields, where it helps to produce more oil from the ground. For the two oil companies operating in those fields, CO2 is, therefore, a valuable commodity used to increase the production of oil.