Overview

From earliest times, humankind has burnt wood - a prime source of renewable energy - in order to keep warm and to cook food. Long before fossil fuels were exploited, wood was the universal fuel. Even today, it is still a principal fuel for domestic purposes in many parts of the world, although animal dung is also used in regions where timber is not freely available. These two forms of energy are said to represent the primary fuel supply for more than one-third of the world's population. In western countries where there are good supplies of fossil fuels, many people in rural areas also choose to have log fires and/or closed wood-burning stoves, either as a matter of preference or because they have easy access to low-cost wood.

As we saw in Chapter 1, Table 1.1, combustible renewables (mostly wood) and waste constitute 11% of the world's primary energy supply. This represents over 1000 Mtoe per year and makes biomass the fourth major source of primary energy (after oil, coal, and natural gas), greater than both nuclear power and hydroelectricity. Much of this renewable energy is concentrated in non-OECD countries, and it is the burning of wood, with associated smoke and ash, that is said to be largely responsible for the massive brown cloud that stretches over much of Asia at certain seasons. This is a new form of 'smog', different from the coal-based smog of the 1950s in Europe (see Section 2.3, Chapter 2), and may be attributed...