Carbon capture has been in the news a lot recently, but what exactly is it? Never fear, we're here to help explain this technical topic (using chocolate!).

Chocolate: the tastiest way to explain a complex process

We’re researching a broad portfolio of energy technologies to ensure we can keep the lights on, remain economically competitive and importantly, lower emissions. Carbon capture and storage (CCS) is one key solution, and our researchers are on the case.

But what exactly is CCS? How does it work? What can it achieve? How can I sound super-smart when I’m with my friends and the topic comes up?  Never fear, we gentle science folk are here to help give you the scoop on this technical topic (including the best kind of analogy: a chocolate-based one).

How does it work?

CCS is a process used to capture carbon dioxide (CO2) gas emitted while producing power or making materials such as steel, cement or fertiliser. Broadly speaking, the gas is captured, transported, and then safely stored underground – permanently. By doing this, we can typically capture 90 per cent of the CO2 that would otherwise be emitted from power stations and industrial facilities.

Capture

Energy from fossil fuels such as coal, oil and natural gas is released in the combustion (burning) and conversion process, which also results in the emission of CO2 as a by-product. It’s possible to capture the gas before it is emitted, and we’re working at Victoria’s AGL Loy Yang Power Station to make the capture process more efficient.

Transport 

CO2 is transported by pipeline, truck, rail or ship. In fact, there are already many pipelines around the world that safely transport large amounts of CO2 every day.

Uses

The gas also has many uses in the food and beverage industry (like creating the bubbles in your soft drink!) and it can assist with industrial processes such as the recovery of oil from underground. Of course, there’s only so much soft drink we can consume, so we also need to think about what to do with the remaining CO2.

Storing CO2 

Once CO2 has been captured and transported, it is injected deep underground, usually at depths of over 1 km. This process is sometimes called ‘geosequestration’. Generally, the rock needs three features to be suitable:

  1. Sufficient pore spaces in which CO2can be contained (porosity)
  2. Pathways connecting the pore spaces for the CO2to move through (permeability)
  3. A solid, sealing layer of rock on top of the porous, permeable layer, to stop the CO2moving outside the target area (seal or ‘cap rock’).

Here’s a delicious example of why these geological features are important.

A Tim Tam and an aerobar

The humble Tim Tam is a lot like a reservoir rock, while the Aero Bar, although seriously delicious, has no chance of holding your milk. Images: seriouseats.com and foodproductiondaily.com

Let’s consider a Tim Tam and an Aero Bar as two possible types of reservoir rock and milk as our CO2. Both chocolate bars have plenty of porous space in them, yet if you bite an end off each and try to use them as a straw through which to draw milk, the permeability of the Tim Tam will allow the milk to be pulled through the porous spaces into your mouth, but the Aero bar won’t.

This is because the Aero Bar, although porous, does not have any channels connecting the spaces and therefore the milk cannot move through the chocolate. The principle is the same for the reservoir rock needed to store CO2. The CO2 needs to be able to move through the rock and fill all the porous spaces.

Storage of CO2 has safely happened around the world for many years, and we’re finessing the finer points at our National Geosequestration Laboratory.

Serious potential

In addition to limiting the emissions expended to power our homes, CCS can play a vital role in decarbonising energy-intensive industries (such as steel production) which involve the continued use of fossil fuels. If fossil fuel is replaced by biomass, applying CCS will actually start to directly reduce the CO2 levels in the atmosphere, demonstrating its large potential for climate change mitigation.

While we’re working on making these technologies more efficient and cost effective, a number of major CCS projects are already operating or being built, capturing and storing many million tonnes of CO2 per year.

Achieving a low-emission economy for Australia

31 comments

  1. CCS? How about dehydrated water? Comes in an empty bottle, just add water. Makes as much sense to me.

  2. The geological instability and porosity of underground storage does not support this pollution storage application. Forests are the best and cheapest carbon capture and storage facilities, are largely self managing, and the resultant carbon storage identifiable, and provide oxygen (which may be critically needed if the increased warming and acidification of oceans adversely affect the oceans production of half of the oxygen that we are currently breathing). As with all industrial pollution, the best scenario is alternative production that does not incur pollution. Coal resources need to be preserved for the reduced oil production future, where, with great pressure coal can be turned to oil and its valuable side products (stuffing around with catching carbon from pollution is likely to be of only some value and is likely to lead to no future, or more accurately peripheral fiddling while collapsing global civilizations take us back to the stone age). In terms of coal, why spend time and money on attempting to retrofit last centuries technology when this centuries progress identifies a cleaner, cheaper and sustainable product.

  3. Chocolate wind farms …. Could be a new energy

  4. Isn’t burying our waste just creating a Pandora’s box for sometime in the future? I would much prefer coal to be left in the ground and not used at all, asap.
    Even so, isn’t the reason we started using coal over biomass (like wood and peat) because it was by far a much more efficient combustion material?

  5. Sounds great. How much CO2 can we store in the ground? Is it just building a giant pressure bubble that will result in geological issues and contamination issues?? What is the carbon footprint of transporting these mega volumes of CO2. Can imagine all the bore water one day being nice and fizzy. Someone smarter than me is hopefully considering these things.

    1. Hi Graham,
      The key to a successful CCS project is finding the right CO2 storage site. Each geological storage site will have a different capacity. For example, the Gorgon Carbon Dioxide Injection Project in Western Australia has a capacity volume of 3.4-4 million tonnes of CO2 per year. While the CO2 is pressurised in order to be injected for storage, the vast depths (usually 1km or more) mean that it remains that way. There are a number of factors keeping it secure, including: dissolving into salty water found underground, getting trapped in pore spaces of rocks, and event reacting with the rocks themselves to form a new mineral.
      Regards,
      Ellen
      CSIRO Social Media

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