What are the major obstacles for sustainable energy? - earth - 08 February 2007 - New Scientist Environment

What are the major obstacles for sustainable energy? -

What are the major obstacles that lie between our fossil-fuel guzzling present and a future dominated by renewable and sustainable forms of energy? Inadequate ways of storing solar energy, building photovoltaic cells, burying carbon dioxide and converting sugars into fuel are some of the answers given by scientists in a special issue of the journal Science.
No part of the challenge of sustainability "is more complex or more demanding than its energy dimension", writes John Holdren, president of the AAAS in an editorial. "Simply expanding what we are already doing is not merely unsustainable; it is a prescription for disaster."
According to the scientists, the key issues requiring big boosts in research efforts include:
• Developing a full understanding of the chemistry of carbon dioxide, and a better understanding of photosynthesis
• Less costly production of photovoltaic cells – the building blocks of solar panels
• Better systems for converting solar energy into a usable form, and storing it
• Improved methods of converting plant sugars into bioethanol, currently one of the most promising sources of renewable energy
• Better understanding of the risks of capturing carbon dioxide released from the burning of fossil fuels and storing it underground
Some of the issues are already being tackled. Clint Chapple at Purdue University, US, is studying the metabolic pathways that produce lignin, a substance found in wood that stiffens its cell walls. But lignin also acts as a barrier between cellulose and the enzymes used to break it down into sugars and then convert it to ethanol. By studying how lignin is made in poplar trees, and genetically engineering trees to contain more or less of it, Chapple is hoping to help poplar trees become a better source of bioethanol.
Grass and corn
Sugar molecules recovered from biofuel plants such as poplars, grasses, and corn are fermented and converted to ethanol by microbes, including yeasts. But ethanol is often toxic to the microbes, limiting the amount of fuel that can be produced.
"Engineering ethanol-tolerant strains of microbes is of the utmost importance," says Gregory Stephanopoulos of the Massachusetts Institute of Technology, US. In December 2006, he and his team successfully genetically modified a yeast to make it more tolerant of alcohol.
And in the area of solar power, Andrew Blakers and Klaus Weber, at the Australian National University in Canberra, have devised a way of making solar cells that might reduce the cost of solar panels by up to 75%. Their trick is a better way of making thin wafers of silicon.
Deep underground
Yet despite some advances in renewable and sustainable fuels, many energy-hungry countries – China and the US among them – appear unlikely to turn away from the dirtiest source of energy: coal.
Possibly as a result of this, there has been growing interest in carbon capture and sequestration. This technology captures carbon dioxide emissions and then injects the gas deep underground, removing it from the atmosphere and avoiding its harmful greenhouse effect.
The technology is being used on a small scale in some oil fields, where the pressure provided by pumping CO2 into the oil field squeezes out remaining oil and increases yields.
But there is insufficient research to assess how much CO2 would leak out of such reservoirs, says Daniel Schrag of Harvard University, US. He notes deep saline aquifers offer "more than enough capacity to handle centuries of world coal emissions".
But he bemoans the fact that generous allocations in the European emissions trading scheme have so far meant that the price of emitting CO2 in the atmosphere remains small.
As a result, says Schrag, there is little financial incentive to invest in research into carbon capture and storage. If carbon sequestration is to be ready for it is needed, he says, "it is time to get going, not just with small test projects but with full scale industrial experiments".
Journal reference: Science (vol 315, p 781)
Energy and Fuels - Learn more about the looming energy crisis in our comprehensive special report.