Wind turbine for powering a pump, Segou, Mali. © Yves Lambert/ADEM

The main source of energy on earth is the sun. It is an amazing thermonuclear reactor, emitting energy from the disintegration of atoms. The heat at the interior of our planet originated from this radioactive mechanism. For millions of years, light from the sun has enabled plants to perform photosynthesis. This biochemical process produces their living tissue and the carbon compounds (sugars and lipids) that feed them. Coal, petroleum and natural gas were formed from the passive accumulation of organic deposits in ancient seas. The supply of these fossil fuels is not inexhaustible. We must start now to find other sources of energy. Who knows? Perhaps the chemists of the future will find a way to use the chlorophyll that transforms light into chemical energy, to provide electricity for our cities.

At any rate, plants will always be an inexhaustible source of energy. We have already found ways to produce hydrocarbons from cultivated plants (sugar cane in Brazil) and are on the verge of discovering others (euphorbia in deserts). In the meantime, solar and geothermal heat, river waters, and wind are non-polluting and under-used sources of energy.