Life Under the Sun

Can life countinue to survive on the sun's energy harvested by photosynthesis

 
By Lord Porter
Last Updated: Sunday 28 June 2015

-- (Credit: Malay Karmakar)One of the oldest games that we have played has been agriculture, where man has manipulated nature to his own advantage for over 5,000 years. But the game has hardly begun. Agriculture is the latest of the applied molecular sciences, where all the powers of the chemist and biologist will be applied to transforming the plant world. Recalling that it is the plant world which gives us, or has given us, not only all our food and nearly all our fuels, but also materials to build and furnish our homes and to cloth ourselves, the potential for development can hardly be exaggerated, especially when the time comes that we can no longer rely on cheap supplies of fossilised vegetation, like oil and coal.

Agriculture is the latest application of molecular biology where all the powers of the physical and biological sciences will be applied to transforming the plant world. It is a huge industry with great potential for development. The point here is whether life can continue to survive, as it has in the past, on the sun's energy harvested for us by photosynthesis.

Most applications of genetic engineering to plants, which have only appeared in the last few years, have involved the change of one or two genes with a very specific role so as to confer resistance to some disease or pesticide or to improve the shelf life of a product like the tomato for example. Only a few truly transgenic species have been developed and there is little demand for them as foods. Even the need to grow more food is far less pressing than it was, in spite of the rapid increase in population.

There is however one need of mankind that is almost certain to be a problem in the forseeable future and that is the supply of energy. Half the people of the world today obtain their energy in the form of heat from burning wood, dung and other renewable products of the same materials accumulated some three hundred million years ago. There is not enough energy to enable all countries to develop to the living standard of those in Europe let alone the USA and, there is likely to be less rather than more in the future. There are only two sources of energy large enough to supply future needs in the post fossil-fuel era. They are nuclear and solar.

There is over two thousand times more solar energy at the earth's surface than the total consumed by all mankind. Unfortunately photosynthesis, which is the main process used to collect this solar energy, is not very efficient. The energy stored by agricultural products like sugar cane or coppice wood, averaged over the year, is typically less than 1% of the energy from the sun falling on the same area of land.

There are many ways of collecting and using solar energy, photovoltaic cells would be very important sources of electric power if they could be made much more cheaply. But one of the most essential needs of todays world is a liquid fuel for air and road transport and convenient domestic storage. At present this is almost wholly mineral oil which is not a renewable source. Vegetable oils are able to do the same job and are renewable. Oils derived from rape and sunflower seed are esters of glycerol and fatty acids. To be used as fuels, eg in a diesel engine, it is preferable to hydrolyse them and use only the carbon moiety.

The sciences of plant biology and their applied science seem to me to be particularly relevant to a country like India. India is already self sufficient in food production but agriculture has much greater potential than this. Although little more food is needed for indigenous consumption, its export can contribute in an important way to the economy.

Farming these products will become more mechanised but, for many years, in countries like India,it will employ large numbers of people in a life which is more satisfying than most industrial environments because it is carried out on a human scale. It will be a race for better productivity and new products which will draw on the skills of of the local famers as well as on the talents of the country's scientists. Like all races, this one will be won by those who understand their engines and how to improve them. These are the engines of life, powered by our nieghbourly fusion reactor 93 million miles away - the sun.

Lord Porter is professor and chairman of the Centre of Photomolecular Sciences at the Imperial Collage of Science Technology and Medicine, London

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