Andreas Späth

Catching carbon

2013-08-19 18:30

Andreas Späth

If there's too much CO2 in the atmosphere, why don't we just build machines to remove some of it before the planetary climate goes into a tail-spin?

That's pretty much what proponents of carbon capture and storage (CCS) technology are suggesting we should do. But how realistic are the prospects of success?

Nature's carbon cycle is the perfect CCS machine. Living organisms of all sorts incorporate carbon from the air into their bodies and keep it locked up in trunks, shells, forests and soils. Even animals such as beavers make a contribution by sequestering surprising amounts of carbon-rich organic matter in their dams and the wetlands they create.

On a longer time-scale, geological processes put carbon into deep underground storage as carbonate rocks, coal seams and pockets of oil and natural gas.

Humans have short-circuited this well-balanced natural cycle in numerous places by decimating forests and other high-carbon ecosystems, causing widespread erosion of carbon-bearing topsoil, and digging up and burning fossil fuels with abandon.

Proposals for "scrubbing" CO2 out of the air directly - you may have come across grandiose geoengineering blueprints for forests of "artificial trees" - are extremely expensive and unlikely to be financially viable on the scale required for the foreseeable future.

Trapping CO2 at the source of emission - a gas field, power station or oil refinery, for instance - is more feasible and has already been put into practice in a handful of places. The website of the Global CCS Institute lists 62 large-scale projects worldwide, but only 17 are designated as "active" and of those, just four are actually in operation.

For example, CO2 is extracted from natural gas at two Norwegian offshore gas fields and re-injected into rock layers beneath the seafloor. A similar set-up has been in operation on land at In Salah in the Algerian Sahara since 2004. In Illinois, over 300 000 tonnes of CO2 (to be increased to a million tonnes) are captured at a bio-ethanol refinery per year, compressed into liquid form, transported to a disposal site and pumped into a sandstone layer some two kilometres underground.

So what's the problem?

Well, there are several:

- Funding for many proposed CCS projects has stalled in recent times, most commonly because projected costs have become prohibitive.

- There are severe doubts about whether the technology can in fact be scaled up to the gigantic levels that would be necessary to effectively mitigate global CO2 emissions. For one thing, vast underground storage reservoirs would be required, making long-term feasibility questionable.

- Most of the CCS projects currently being proposed involve using the captured CO2 for a process called enhanced oil recovery in which it is injected into existing oil wells to raise production - to allow us to burn even more fossil fuels!

- Long-term CO2 storage in geological formations has been shown to only be an effective measure against climate change if leakage can be kept to 1% or less per 1000 years - a tall order. Research suggests potential problems with the cement used in well linings and seals since cement is unstable in CO2-rich environments, and warns about potentially significant leakage from underground storage reservoirs through natural fractures and faults and abandoned wells.

- Not just any old rock formation can be used for CO2 storage and those that are suitable are frequently very far from emission sites.

So while the fossil fuel industry will continue to try and sell us their "capture-ready", "clean" coal-fired power plants instead of ones that come with actual integrated CCS systems (much like the nuclear industry will peddle their "clean" technology before they’ve worked out what to do with the toxic waste it generates), let’s not allow them to use pie-in-the-sky solutions to keep us hooked to their dirty products.

At this stage, CCS is the equivalent of sweeping our mess under a global carpet and we all know that that’s never been a sustainable approach to housekeeping.

Let's remember that we already have the know-how to solve the CO2 problem, by:

- reducing energy consumption and wastage;

- replacing coal, oil and gas with renewable energy sources;

- protecting, rehabilitating and expanding natural ecosystems, not to use them as commercial resources to be harvested for profit later, but to do their job as the most efficient carbon sinks we know; and

- adopting farming methods that build carbon-rich soils instead of washing them into the oceans.

- Andreas is a freelance writer with a PhD in geochemistry. Follow him on Twitter: @Andreas_Spath
 
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