Black is the new green

by Rebecca Priestley / 18 April, 2013
Turning waste biomass into carbon holds promise for tackling climate change.
A potato exploding in a microwave – a teenage cooking attempt – led Chris Turney to a discovery that could one day reduce carbon emissions. After 40 minutes in a microwave, Turney discovered, the potato is transformed into a piece of charcoal and the microwave is broken.

Photo/Thinkstock


Fast-forward two decades and Turney is a scientist and author (his 1912: The Year the World Discovered Antarctica was one of the Listener’s best books of 2012) and a technology based on his discovery is being commercialised by CarbonScape, a Marlborough clean-tech company led by Nick Gerritsen.

Turney’s climate research – he is climate change professor at the University of New South Wales – led him to wonder if microwaves could turn waste biomass into useful carbon-neutral carbon products. He approached Gerritsen through a family connection.

“When someone comes to me and says they almost blew something up and think they’ve invented something, it’s often a good indication there is novelty,” says Gerritsen. “We started to play around with microwave technology to see how we could turn low-value ubiquitous biomass like pine sawdust into high-value carbon products.”

In a pilot plant developed by CarbonScape, which Turney and Gerritsen co-founded with two colleagues, biomass is first fed into a dehydrator to remove volatile gases and bio-oils. A microwave cooks the dehydrated remains until it looks a little like Turney’s charcoaled potato. Gases and heat removed in the dehydration process are converted to electricity, making the plant self-sustaining.

“Our idea is not rocket science, in the sense that the whole idea is to speed up fossilisation,” says Gerritsen. These freshly “fossilised” products can then be used in place of fossil fuels, or put back into the ground as a way of storing, in an inert form, the carbon the plant extracted from the atmosphere during its growing life.

CarbonScape’s products so far include activated charcoal, a molecular sieve used in a variety of industrial and manufacturing processes, and biochar, a soil conditioning and carbon-sequestration product. The company is also confident it has produced graphene, a single-atom layer of carbon described by one of its 2010 Nobel Prize-winning discoverers as “the thinnest known material in the universe and the strongest ever measured”.

But it is green coke, a charcoal-like product comparable to coking coal, that is likely to be first to market. Late last year, CarbonScape’s green coke was named runner-up in a global clean-tech contest, and early this year, the company signed an agreement to supply the product to New Zealand Steel.

The green coke exceeds the steel-maker’s technical specifications and meets the market on price, says Gerritsen. It’s also a safer, more consistently high-quality product than coke derived from coal. So how is it going to reduce carbon emissions? Green coke is made from recycling atmospheric carbon through trees rather than withdrawing multimillion-year-old fossil carbon from the ground. Replacing fossil coke with green coke “reduces the overall carbon footprint of the steel facility by about 25%”, says Gerritsen.

But he doesn’t see green coke displacing coking coal in steel manufacturing anytime soon: to do so on a global scale would require about 20% of nature’s annual supply of waste biomass. The industry is so huge, though, that even becoming a significant niche player “is a mind-boggling business opportunity”.

CarbonScape now needs to raise $2 million to build a plant to provide the first test sample to New Zealand Steel. After that, the world awaits. l Green coke “reduces the overall carbon footprint of the steel facility by about 25%”.
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