Scientists see the future in natural resources

By Tim Radford

LONDON, 30 April, 2016 – Danish scientists have taken a lesson from the plant world, reversed it,and used the cocktail of sunlight and chlorophyll to turn vegetation into chemistry.

And in an irresistible twist, Californian researchers have learned how to turn carbon dioxide and plant waste into plastic bottles.

Meanwhile, scientists in Stockholm have found a way to turn one of Sweden’s great products, wood, into something transparent that could be used for solar panels or even for windows.

Not far to the southwest of Stockholm, in Linköping, energy-conscious chemists have devised a new kind of supercondenser that can store the heat of the sun and release it as electricity.

All are yet further instances of the astonishing resource and ingenuity deployed in the world’s laboratories to sidestep fossil fuel sources, find ways to exploit waste, and even turn a greenhouse gas into an exploitable resource.

Plant biomass

The latest advances – all still some way from commercial exploitation – start with the relationship between plants, sunlight and atmosphere.

Claus Felby, professor biomass and bioenergy at the University of Copenhagen, and colleagues report in Nature Communications that sunlight collected by chlorophyll and paired with a specific oxidative enzyme − these are responsible for turning the skin of apples and other fruit brown − could break down plant biomass such wood shavings, wheat stalks, maize husks or grass mowings into by-products that could be turned into fuels and biochemicals for plastics.

“This is a game-changer, one that could transform the industrial production of fuels and chemicals, thus serving to reduce pollution significantly,” Professor Felby says.

“It has always been right under our noses, and yet no one has ever taken note: photosynthesis by way of the sun doesn’t just allow things to grow, the same principles can be applied to break plant matter down, allowing the release of chemical substances. In other words, sunlight drives chemical processes.”

Matthew Kanan, assistant professor of chemistry at Stanford University in California, hopes to cut short the 100 million-year process that turned Carboniferous foliage into fossil fuel, and then into plastics.

“Our goal is to replace petroleum-derived products
with plastic made from CO₂ . . . you could dramatically
lower the carbon footprint of the plastics industry”

He and colleagues report in Nature journal that they simply found a way to skip the 100 million years and the crude oil pathway.

Plastic products start with the polyethylene terephthalate, known as polyester. Fifty million tons of the stuff is made each year, from petroleum and natural gas, in the course of which 200 million tons of carbon dioxide are released into the atmosphere.

The Stanford researchers found a way to turn agricultural waste products and carbon dioxide into a compound called 2-5-Furandicarboxylic acid, to be the basis of a low-carbon plastic alternative. It is, they say, just a first step.

“Our goal is to replace petroleum-derived products with plastic made from CO₂,” Dr Kanan says. “If you could do that without using a lot of non-renewable energy, you could dramatically lower the carbon footprint of the plastics industry.”

Lars Berglund,  head of biocomposites research at the Wallenberg Wood Science Centre at Sweden’s Royal Institute of Technology in Stockholm, and colleagues report in Biomacromolecules journal that they have devised another way to cut building costs and save electrical energy: they have made an optically transparent timber.

They extracted lignin, an opaque natural component from a wood veneer, and then impregnated the remaining white veneer with a transparent polymer. With a bit of nanotechnological adjustment, they were able to end up with a fabric that could be either transparent or semi-transparent, to let in natural light but preserve privacy.

Renewable resource

“Transparent wood is a good material for solar cells, since it’s a low-cost, readily available and renewable resource,” Professor Berglund says. “This becomes particularly important in covering large surfaces with solar cells.”

And soon the heat of the sun could be charging batteries. Xavier Crispin, professor of physics and electronics at the Laboratory for Organic Electronics at Linköping University in Sweden, and colleagues report in Energy & Environmental Science journal that, after years of experiment, they have devised a supercondenser with fluid electrolyte based on conductive polymers that can be charged by the sun.

It is made of inexpensive, safe materials and could possibly be manufactured on an industrial scale. Patents are pending.

The experimental electrolyte can convert heat to electricity 100 times better than standard electrolytes. But there are questions to resolve.

“We still don’t know exactly why we’re getting this effect,” Professor Crispin says. “But the fact is we can convert and store 2,500 times more energy than the best of today’s supercondensers linked to thermoelectric generators.” – Climate News Network\