Trees have the answer to everything

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This was published 12 years ago

Trees have the answer to everything

A clean source of fuel is just one of the promises held out by scientists on a mission to emulate trees' ability to harness and store sunlight, writes Deborah Smith.

The answer to many of the world's problems lies all around us, gently waving in the breeze.

Trees, with their green leaves, are not just things of grace and beauty, they are the smart end product of more than 2 billion years of evolution, producing food and fuel almost out of thin air, from sunlight, water and carbon dioxide. They have a lot to teach us. And some scientists - led by an Australian researcher - believe it is time for a global project to emulate their impressive natural feat as quickly as possible.

"Success sounds too good to be true. Artificial photosynthesis would provide a clean course of fuel - hydrogen - as well as carbohydrates for basic food."

"Success sounds too good to be true. Artificial photosynthesis would provide a clean course of fuel - hydrogen - as well as carbohydrates for basic food."Credit: Peter Rae

This month, world experts in artificial photosynthesis - along with lawyers, ethicists, photovoltaic specialists, quantum physicists and school students - will gather on Lord Howe Island to discuss the latest research and plan for the future.

Associate Professor Thomas Faunce, who has organised this inaugural conference, Towards Global Artificial Photosynthesis, says capturing, converting and storing energy from the sun, as plants do, is one of the most important technical challenges of the 21st century.

''It is perhaps even more important for human health than was decoding the human genome,'' says Faunce, of the college of law and the college of medicine, biology and the environment at the Australian National University.

The World Heritage-listed island was chosen because of its ''symbolic resonance'' with the conference's aim. Photosynthesis is a ''gift from nature'' and artificial photosynthesis might need to be protected as ''the common heritage of humanity'', just as natural heritage sites are, Faunce says.

More solar energy strikes the Earth in an hour than the energy used by all human activity in a year. Scientists can already use solar energy to split water into oxygen and hydrogen but it is very expensive. And it will be much more difficult to mimic the second stage of photosynthesis, in which plants draw carbon dioxide from the atmosphere to produce carbohydrates.

But if some of the world's brightest minds can join forces - as they did with giant projects such as the Human Genome Project, the Large Hadron Collider and the Hubble space telescope - the promise of artificially improved photosynthesis could be realised much sooner, Faunce says.

Success sounds almost too good to be true. Artificial photosynthesis would provide a clean source of fuel - hydrogen - as well as carbohydrates for basic food. It would tackle climate change by removing carbon dioxide from the atmosphere and reducing the use of fossil fuels.

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Less land, water and fertiliser would have to be devoted to growing crops, further reducing environmental degradation. ''It could lower geopolitical and military tensions over fossil fuel, food and water scarcity,'' Faunce says. Every building, car, plane or ship could produce its own fuel, minimising energy use in transport.

But for any global project to succeed, legal and ethical problems need to be addressed from the start.

Some people might have a moral objection to the research, believing artificial photosynthesis is ''playing God'', Faunce says. Others might argue that there are simpler ways to address food shortages than a big technological project. ''You have to be able to answer those legitimate concerns.''

A big governance question is how best to protect the intellectual property of scientists involved while letting the research proceed as quickly as possible. Another problem may be preventing ''patent troll'' firms from acquiring patents on parts of the process so they can profit from the evolving needs of researchers.

Some might argue patents are unacceptable, Faunce says. ''The process of photosynthesis is as central to life on Earth as DNA. There are likely to be similar major debates over whether patents should be allowed over any part of the photosynthetic process.''

US President Barack Obama recently invested $US122 million ($111 million) in a Joint Centre of Artificial Photosynthesis in the US. Its director, Professor Peidong Yang, of the University of California, Berkeley, will attend the Lord Howe Island conference, with leading scientists from Australia, Europe and the US. Among them will be Massachusetts Institute of Technology professor Daniel Nocera, who announced a major advance this year to the American Chemical Society.

Nocera's team has developed a prototype ''artificial leaf'' device the size of a playing card. Using the sun and a bucket of water, it could supply a house in a developing country with enough electricity for a day. ''Our goal is to make each home its own power station,'' he says.

The silicon device, coated in a catalyst, splits water into oxygen and hydrogen. The big advance is that the chemical catalysts the team has developed are made of cheap, widely available materials - nickel and cobalt.

The prototype device is robust and can operate continuously for at least 45 hours without a drop in activity, says Nocera, who has founded a company, Sun Catalytix, to develop the technology. In his vision, the hydrogen and oxygen produced would be stored and recombined in a fuel cell to produce electricity for use at night.

Another speaker, Australian National University Associate Professor Ron Pace, says Nocera has made a ''great breakthrough'' with his device based on nickel and cobalt ''but we think manganese is the way to go - the one that nature chose''.

Pace is an expert in how plants capture sunlight and split water - a process that occurs in a protein complex called photosystem II, which has manganese atoms at its core.

Plants have ''set the bar'' for humans, showing it is possible to carry out this reaction with very high efficiency, Pace says. ''The way nature splits water is really brilliant and that is really worth copying.'' He believes this aspect of artificial photosynthesis will be commercially available within a decade.

One possibility is that each house will have a photovoltaic or other renewable energy system generating power that is used to split water, rather than feed into the grid. Even more likely, as fossil fuels become more costly, big amounts of hydrogen will be produced commercially from water to replace them. Unfortunately, plants are not as impressive when it comes to the second part of the photosynthetic process, when they use carbon dioxide to produce carbohydrates.

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Plants rely on a protein called RuBisCO to do this and they need lots of it because it is such a ''lousy'' enzyme and carries out the process inefficiently, Pace says. He suspects we will need a different approach - perhaps a high-temperature chemical process that nature could not use - to accomplish the second part of photosynthesis. Although still a distant prospect, the ability to carry out ''dry agriculture'' would be of great benefit because conventional agriculture is so inefficient, he says.

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