CO₂ Transport & Storage: What Do We Do With All This CO₂?
23 minute read
Updated on Fri Aug 13 2021
Transporting CO₂ is difficult because CO₂ is a gas at room temperature and pressure, meaning it takes up a lot of space!
Pipes and ships are the best methods we know for transporting this space-hungry gas, so let’s look at how these work...
How can CO₂ be transported in pipelines?
Pipelines can be onshore (on land) or offshore (underwater). Onshore pipelines are currently the cheapest option for short-distance transport (less than 1000km), with shipping becoming the cheapest method over longer distances (especially for smaller amounts of CO₂).
Where can pipelines be built?
Onshore pipelines can be built through deserts, mountain ranges, cities, and farmland. These different places come with different challenges, costs, and obstacles. These depend on whether roads, railways, or rivers are in the way, what the ground type is like, and how many people live in the area. A big network of pipes can be disruptive, whether that’s to people’s property or to wildlife.
What happens if a pipeline leaks?
Luckily, a CO₂ leak is less likely to cause environmental damage than an oil spill or natural gas leak, because CO₂ is not very reactive. All in all, CO₂ transportation pipelines should be fairly easy to build and safe to operate.
How can CO₂ be transported on ships?
Just like with pipelines, we first have to compress the CO₂ into a liquid so that it’s easier to transport.
How can we store CO₂?
In order to permanently remove CO₂ from the atmosphere, we need to store it somewhere where it will stay, ideally for thousands of years or longer, without causing problems.
What is Geological storage?
Will the CO₂ stay underground?
Depending on the type of leakage, this could have very serious consequences: local water supplies could be contaminated and people or animals could be killed if CO₂ reaches particularly high concentrations.
How much will it cost?
Can it work at the scale required?
We know of about 2,000 GtCO₂ of storage capacity in geological formations today, and we will probably find more if we look harder. We can also use many technologies from the oil and gas industry for CO₂ injection too.
However, large‐scale injections involving tens of megatonnes of CO₂ per year in the same reservoir haven’t yet been demonstrated.
What is mineral carbonation?
We need between 1.6 - 3.7 tonnes of rock to react with each tonne of CO₂ in order to lock it up. So it’s a good thing that magnesium and calcium oxides are found in large amounts in silicate rocks, as well as smaller amounts in some industrial wastes. What’s more, the resulting carbonates don’t need to be monitored because they are stable for a very long time and will not release CO₂ into the atmosphere.
Underground, on the other hand, pure CO₂ is mixed with hot water and pumped into volcanic rock called basalt. Within 2 years, the CO₂ reacts with the rock and turns into stone (more specifically, limestone in pores in the basalt)!
Will it have environmental impacts?
- Land clearing
- Worse local air quality
- Affected plants and water due to drilling
- Polluted soil, water, and air as a result of moving earth
- Grading and leaching of metals from mining residues
How much will it cost?
How much CO₂ can be stored?
A lot! The quantity of metal oxides in the silicate rocks that can be found in the Earth’s crust is actually more than the amount needed to fix all the CO₂ that would be produced if we burned all available fossil fuel reserves today! It’s the costs and environmental impacts that limit us from doing this.
CO₂ transport is a well-established technology that we know how to do safely and cheaply, as long as it is carefully planned.
Storing CO₂ in geological formations then seems like a safe and cheap(ish) option to almost permanently take CO₂ out of the atmosphere. Mineral carbonation could provide an even more permanent solution, but it still costs too much to be done on a large scale.
Whatever we do, it should be done carefully to minimise health risks and to ensure that the CO₂ stays put!Next Chapter