A solution to the world's looming energy problems could literally be in your back garden. Plants are solar energy converters that can provide us with clean "bio-fuel". More research is needed to learn how to harness photosynthesis to produce new forms of biofuels. Dr Claire O'Connell reports
In addition, by artificially replicating the cellular chemistry of plants we could help remove excess carbon dioxide from the atmosphere while harvesting useful energy at the same time, according to Prof Alan MacDiarmid, addressing a meeting in Dublin City University last Friday.
MacDiarmid, who holds professorships at the University of Texas at Dallas and the University of Pennsylvania, was awarded a joint Nobel Prize in chemistry in 2000 for his part in discovering how to modify polymer plastics so they can conduct electricity.
The breakthrough meant that plastics could be used as conductors or semi-conductors in the microelectronics industry. Research into conductive polymers is also central to developing tiny electronic components in the field of nanotechnology.
Most recently MacDiarmid has focused his research on how to access alternative energy sources to fossil fuels. One of his interests is "agri-energy", or deriving fuel energy from agricultural sources, and he believes we should look to the energy naturally stored in the organic matter of living plants.
Their leaves act as a type of solar panel, he told The Irish Times after his talk. They harvest and store energy from the sun through photosynthesis.
"(Man-made) solar panels convert the sunlight into electricity," he says. "And leaves of trees convert the sunlight plus the carbon dioxide from the air into wood and various types of organic matter. So if you chop down a tree and burn the wood in the fire, what is warming you is the heat from the sun that fell on this tree when it was growing perhaps 50 years ago. Its stored energy."
An environmentally useful way of accessing this stored energy from plants is to extract bio-ethanol, a fuel that when burned does not increase net levels of the "greenhouse gas" carbon dioxide in the atmosphere. Bio-ethanol is currently fermented from sources such as sugar cane and corn, but these crops grow in only some regions of the world.
McDiarmid says "the real future" lies in extracting bio-ethanol from cellulose, a constituent of plant cell walls. It is present in all plants and can be grown almost anywhere, and recent advances in enzyme technology mean the price of extracting bio-ethanol from cellulose is predicted to fall, he says.
Plants may also hold clues to reducing the burden of atmospheric carbon dioxide, according to MacDiarmid. In photosynthesis, plants "fix" carbon dioxide from the atmosphere in the presence of sunlight to store energy in organic material. By setting up artificial photosynthesis, we could take carbon dioxide from the air and harness useful energy to boot.
This approach, which is currently being researched, is a more attractive option than trying to bury excess carbon, believes MacDiarmid. "Instead of saying how do we get rid of the carbon dioxide we can turn around and say that carbon dioxide is a very valuable raw material," he says.
Research into alternative energy requires an international and collaborative effort, according to MacDiarmid, who receives funding from the US department of energy and also has laboratories in Brazil, Asia and his native New Zealand. "If you want to be a leader in a country or a company, you have to think not only outside the box but also outside one's own country," he says.
Prof MacDiarmid delivered the keynote address at a symposium on energy and materials hosted by the Adaptive Information Cluster, which receives funding from Science Foundation Ireland.