Carbon capture and geological storage (CCS) is underway yet people still ask “Does it work? Is it safe?”
Carbon dioxide (CO2) is only a very small part of air and we cannot easily extract it. But we can capture it before it gets into the atmosphere from large sources such as power stations or industrial plants using liquids, very fine sieves or minerals.
Right now this is being done at various places around the world. However we are not doing this at anywhere near the scale that is required, partly because it is expensive to capture the CO2. A great deal of research is underway to develop cheaper and more efficient ways to capture the CO2. Like all technologies, we expect that the cost will come down steeply as it becomes more widely available.
Once we have the separated CO2, we compress it to a fairly dense liquid form and then we transport it to a storage site by pipeline. Already millions of tonnes of CO2 are transported by pipeline every year. At the storage site we inject the liquid CO2 into the ground at a depth of around a kilometre or more.
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Vast amounts of CO2 are trapped naturally in the ground for millions of years through normal geological processes. This CO2 is used in the food industry — the bubbles in that can of Coke you recently drank were probably once CO2 in the ground.
Over the past 30 years, around 100 million tonnes of CO2 has been injected underground as a means of getting more oil into oil wells. Over the past 12 years, about 20 million tonnes of CO2 has been geologically stored as part of natural gas and petroleum production in Norway, Canada and Algeria since. In Australia we recently (April 2008) started our first CO2 storage project – the CO2CRC Otway Project — in western Victoria and have already injected 10,000 tonnes of CO2 into suitable rocks 2km deep.
How do we know that the CO2 will stay safely in the ground at a site such as the Otway Project? First, we very carefully study the geology of the site to make sure we have the right rocks that can trap and retain the CO2. Then, whilst we do not expect that there will be any leakage whatsoever, to make doubly sure, we carefully monitor the site 24/7. We use a wide range of very sophisticated instruments that measure CO2 underground, in the soil and in the air.
But if despite all this care and attention, what if some CO2 did leak? Well first, CO2 is not a poisonous gas – we breathe it out, plants need it, and our soft drink is full of it! While in large quantities CO2 can asphyxiate you, any leakage from a geological storage site will be very small and would be quickly detected.
CCS is certainly not the total answer to greenhouse concerns, but it is an essential part of the answer along with energy efficiency, greater use of renewables and lower carbon fuels. Each year China puts in more new coal fired power stations than we have in the whole of Australia now – and those power stations will be emitting CO2 for the next 40 or 50 years. So we just have to get cleaner and smarter in using fossil fuels – which is where CCS comes in!
For those still unconvinced that CCS will work all I can say is that we must ensure it does work or we are indeed in deep trouble!!
This item was commissioned by the Australian Coal Association.