Business 21C - Published by UTS Business

Carbon capture and storage (CCS) is the great hope of the fossil-fuel industry. If generators could capture and store the carbon dioxide (CO2) emitted from burning hydrocarbons such as coal, the fossil-fuel industry could continue to operate without paying a penalty price for the carbon it emits.

In 2009, the Australian Federal Government joined the long list of hopeful alchemists in pursuit of a viable CCS solution, committing $100 million to the grandly named Global Carbon Capture and Storage Institute. No-one doubts there is a multibillion dollar win waiting for the group that solves the CCS conundrum. But is CCS really viable? Here are some first-principle, back-of-a-napkin calculations examining the issues facing CCS in Australia.

Carbon capture and storage

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The fuel

Let’s look at the dominant carbon fuel: coal. Australia burns approximately 140 million tonnes of coal per year. When combusted, 1 tonne of coal creates about 2.4 tonnes of CO2. That’s because each released carbon molecule combines with two oxygen molecules and the atomic weight of oxygen is higher than that of carbon. So, calculation number one: Australia creates about 336 million tonnes of CO2 per year from the burning of coal.

The volume

One tonne of CO2 occupies approximately 550 cubic metres. How did I arrive at this figure?

• 1 tonne = 1000 kilograms
• 1 cubic metre = 1000 litres
• 1 mole CO2 = 44 grams
• 1 tonne contains 22,730 moles of CO2
• 1 mole is 24.47 litres (at 25°C and ground level)
• 1 tonne of CO2 = 22,730 moles × 24.47 litres/mole = 556,200 litres = 556.2 cubic metres

So, calculation number two: Australia emits 184 billion cubic metres of CO2 per year from the burning of coal.

Capture

Let’s imagine we wanted to capture and sequester, say, 20 percent of this – a reasonable target in line with European emissions-reduction targets. That’s 40 billion cubic metres or 67 million tonnes of CO2.

Transport

Transporting 40 billion litres of anything isn’t easy, especially gas. Let’s imagine all the storage facilities are on land. But let’s assume they’re too far away to build a pipeline, so that the CO2 needs to be transported by road.

This could be done using cryogenic road tankers. The CO2 would need to be cooled down to its liquefied state. This would require an estimated 20–40 percent extra energy.

But let’s ignore the extra energy requirement and assume that the CO2 politely freezes itself and forces itself into the waiting tankers. To my knowledge, the largest tankers available in Australia carry about 6 tonnes. We have to transport 67 million tonnes per year.

Calculation number three: we have to make approximately 11 million tanker trips per year. That’s one way. And the tankers use fuel, emitting carbon.

Storage

The idea is that we pump the CO2 down into underground reservoirs where it remains in perpetuity. We’re looking for 40 billion cubic metres of storage per year. That’s 40 trillion litres. To put that into context, my personal favourite unit of measure is the SydHarb: the volume of water contained within Sydney Harbour. One SydHarb is 500 gigalitres or 500 billion litres of water.

Calculation number four: we need to find eight Sydney Harbours’ worth of storage space, every year. And there must not be a single crack or leak in any of them.

It appears to me that even if we are able to develop a cost-effective method of capturing CO2, the logistics of transporting and storing the vast quantities produced represent an enormous challenge.

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Carbon capture and storage: the reality

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