Solar Sponges to the Rescue? Mopping Up Carbon

As the news continues to get more depressing about the advance of climate change – hurtling forward toward worst case scenarios – we’re seeing beginning efforts to create technologies that will counter it.

Not that we believe technology will fix this problem, but we do think it will help in significant ways, especially during the decades it will take to stop using fossil fuels.

In 2012, atmospheric carbon levels jumped to the highest level yet, leaving scientists little hope that world temperatures won’t rise above 2 degrees C.

Last year, carbon levels rose 2.67 parts per million to just under 395 parts per million in total – the biggest one year rise other than 1998. Carbon concentrations in the atmosphere must stay at or below 350 ppm to keep temperature rise at or below 2 degress C.

More coal-burning power plants, almost all in China and other developing counries are behind the steep rise, even as emissions decline in the US and other advanced nations, thanks to clean energy and energy efficiency.

The world’s oceans are saturated with carbon and can’t absorb much more and last year, plants and the ocean absorbed less carbon. Those rates vary from year to year though, John Reilly, co-director of Joint Program on the Science and Policy of Global Change, told Associated Press.

Until the 1960s, carbon rose less than 1ppm a year, rising to 1ppm a year through 1999 and jumping to 2ppm a year since then, largely due to China and India’s recent rapid growth.

Solar Sponges to the Rescue

Many start-ups and researchers are focused on how to capture and recycle carbon emissions into useful products, rather than just injecting back into the earth and storing it.

There’s progress on recycling carbon emissions from power plants and industrial sources into a wide array of products from cement and plastics and even into fuel, but so far the process of doing so is itself energy intensive.

Researchers at Australia’s national science agency, CSIRO, think they’ve hit on a much better way – using only concentrating solar energy.

"Solar sponges" would mop up the carbon, after which it would be "rung out" and reused.

"The capture and release process can be compared to soaking up water with a sponge and then wringing it out. When UV light hits the material its structure bends and twists and stored gas is released," explains Dr. Matthew Hill, who won a 2012 Eureka Prize for this work. "This is an exciting development for carbon capture because concentrated solar energy can be used instead of further coal-based energy to drive the process."

The ‘sponge’ is made from a material called a MOF – metal organic framework – which adsorbs carbon dioxide and then instantaneously releases it when it’s exposed to sunlight.

Known as dynamic photo-switching, this capture-and-release method is extremely energy efficient and only requires UV light to trigger the release of CO2 after it’s been captured from a mixture of exhaust gases.

Only one gram of MOF absorbs as much as a litre of nitrogen gas. That’s because the material has the surface area of a football field in just one gram. Gases can be soaked up like a sponge to all of the internal surfaces within.

"The MOFs are impregnated with light-responsive azobenzene molecules which react to UV light and trigger the release of CO2. It is this reaction, and the material’s ability to bend and flex, which makes the material we have created so unique," says lead researcher Richelle Lyndon.

The Department of Energy’s "Fuels from Sunlight Energy Innovation Hub" is developing ways to turn that carbon directly into transportation fuels using concentrating solar.

Their goal is to create a solar fuels industry.

Read about some of the more interesting technologies developing to capture and reuse carbon.

Read "Carbon Recycling: Mining the Air for Fuel," at National Geographic:

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