New patent boosts CO2 capture hopes

LONDON, 16 September, 2016 – A technology that could in theory catch 90% of carbon dioxide from coal-fired power stations has been patented by US government scientists.

Employing an enzyme-based membrane fabric 10 times thinner than a soap bubble, it could separate carbon dioxide from nitrogen or oxygen and speed up its dissolution in water by a factor of 10 million. And its triumphant designers say that, in laboratory trials, it does the job − at a cost-effective $40 a ton.

“If we applied it to a single coal-fired power plant, then over one year we could avoid CO₂ emissions equivalent to planting 63 million trees and letting them grow for 10 years,” says Susan Rempe, a research professor in biological engineering at Sandia National Laboratories in Albuquerque, New Mexico.

Carbon capture technology is – and has looked so for some time – a last resort for a world of climate change.

Global temperatures

Greenhouse gas emissions from coal, gas and oil combustion since the dawn of the 19th century and the coming of the machine-age century have pushed carbon dioxide ratios in the atmosphere from less than 300 parts per million to 400ppm everywhere, and global average temperatures have risen by 1°C.

The nations of the world agreed in Paris last December to try to reduce emissions and hold global warming to significantly less than 2°C altogether, but there is evidence that national plans tabled so far may not be enough.

Meanwhile, there are 600 coal-fired power stations in the US alone, and researchers have argued for years that carbon dioxide could be trapped and buried, or turned into some useful biofuel.

Some have argued that it cannot be safely done and is too risky, while other research groups have shown that, in theory at least, carbon dioxide once captured could be safely stored.

But the commercial technologies used now bubble CO₂ into a chemical-based solution designed to absorb the gas. The process demands high pressure facilities and uses about a third of the energy the plant generates.

“Over one year we could avoid CO₂ emissions equivalent to planting 63 million trees
and letting them grow for 10 years”

Overall, prospects have not been hopeful for successful capture at speed, cheaply and on a huge scale.

So the Sandia enzyme-based membrane – its trademark name is CO₂ Memzyme– at least offers a new approach. But it’s still a laboratory product, and commercial use is a long way off.

Scaling up to power station practicality remains a challenge, but Professor Rempe and her colleagues think the technology can meet the US Department of Energy’s target of 90% of CO₂ emissions by 2025, at $40 a ton.

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