Until about 8000 years ago humans relied on hunting and gathering for food, and burning wood to keep warm. Their exact energy demands can at best only be estimated, but to survive they probably needed about as much energy as it takes to run a couple of ordinary domestic light bulbs continuously. Later, agriculture developed, and although wood was still the chief fuel, animal power, animal dung and charcoal were also used. Even today, such energy sources based on natural biomass dominate the lives of human populations in the so-called ‘Third World’ or ‘developing countries.
The 19th century heralded a large increase in energy use in what were to become industrialised countries particularly the use of coal. Homes and other buildings were heated; factories and railways were powered by steam engines, mining and chemical industries developed and agriculture became more mechanised. The emergence of technological societies in the 20th century resulted in an even larger increase in energy use for manufacturing, agriculture, transport and a host of other applications. In technologically advanced countries the largest increases have been in using gas for heating, oil products for transport, and electricity as a convenient means of transferring energy generated by a variety of sources.
2.6 billion people do not have access to clean and energy-efficient cooking technologies. Biomass, like wood, dung, agricultural residues, is the most commonly used source of energy in poor rural areas worldwide, and it is predominantly burned on inefficient traditional stoves and open fires. Only a third of sub-Saharan Africa’s inhabitants have access to electricity. Renewable energy usually is believed to be a solution to the rising energy demands and as a measure against environmental damage. Renewable energy sources such as solar and wind don’t emit carbon dioxide and other greenhouse gases that contribute to global warming.
