Energy affects all aspects of modern life. There is a clear correlation between energy use per capita in a country and issues that we value highly, such as life expectancy, literacy, as well as productivity per capita. By the end of next century, close to three quarters of the world's population is likely to be urbanized, with intense pressures on housing, sanitation, air and water quality, health care and congestion. However, at the turn of the millennium, 2 billion people -- a third of the world's population -- still have no access to modern energy services.

During the 1990s, global energy capital expenditures have been over $200 billion per year. It appears that economic development over the next century will not be constrained by geological resources. Environmental concerns, financing and technological constraints appear more likely as sources of future limits.

One of the key issues in improving the standard of living of the poor is to make clean energy available to them at affordable prices. This challenge is all the more urgent when we consider that the world population is expected to double by the end of the twenty-first century, from the present 6 billion to approximately 10.4 billion by 2100 -- and virtually all growth is expected in the South.

By 2100, according to studies of the World Bank and the United Nations, the population of the developed countries will drop to less than 10 per cent of the world total, while developing countries will account for about 80 per cent of the global energy demand. Energy per capita availability in the developing countries is likely to be far less than in the rest of the world -- perhaps only 50 to 60 per cent of that in the Organization for Economic Cooperation and Development area.

Energy issues should be viewed in their total -- global, social and institutional, as well as economic and environmental -- perspective. In particular, people demand not energy as such but the services which energy can provide: heating, cooling, cooking, lighting, mobility and motive power. In 1990, the world's primary energy was provided by oil (34%), coal (24%), gas (19%), renewables (18%) and nuclear (5%).

In 1993, the World Energy Council's (WEC) Commission developed three energy cases (later expanded into six alternative scenarios) to illustrate future possibilities, each case representing different assumptions in terms of economic development, energy efficiencies, technology transfer and the financing of development around the world. The principal focus is on the period between 2020 and 2050.

In all scenarios there is a significant expansion of renewables. The peak of the fossil fuel era has passed. Fossil energy consumption grows more slowly than total primary energy needs.

Oil, gas and coal remain important transitional sources of energy, but their percentage share in total primary energy gradually declines throughout the next century. In absolute amounts, however, future oil and gas requirements are huge compared with current levels.

Traditional uses of renewables (fuel wood) are expected to be gradually replaced by high-quality energy carriers, including those from "new" renewable sources such as modern biomass, solar, wind and geothermal energy. Hydro power and traditional biomass are already important factors in the world's energy mix, contributing about 18 per cent of the total, whereas the "new" renewables contribute only about 2 per cent of the world primary energy use. The period until 2020 is considered a very important transitional period for renewables in the energy market, especially as one of the potentially largest single contributors of the "new" renewables, namely solar energy for electricity production, is still not commercially competitive with conventional energy sources. Modern biomass, wind and geothermal energy are, however, making a relatively fast progress. The WEC Commission estimated that the "new" renewables might in 2020 contribute 3 to 4 per cent of the total energy demand with minimum policy support, and 8 to 12 per cent of the world energy demand with major policy support.

There are many areas of conflict on the horizon in meeting the future energy requirements of the world. Take, for instance, the increase of use of biomass for energy production. Both agricultural food production and biomass production for energy require land, thus creating a potential land-use conflict between agriculture and biomass energy. In Asia, for example, expanding agricultural production and achieving maximum biomass use would require the entire arable land by 2100.

The future of biomass will in all likelihood be constrained, particularly in densely populated regions such as Asia.

Increasing the use of nuclear energy pose similar conflicts of interest. Problems associated with the safety of nuclear plants and the storage of nuclear waste are of much public concern. This has led many of the industrialized countries to stop building nuclear plants. Sweden, for example, decided to phase out by 2010 the nuclear plants which have provided over 40 per cent of the electricity since the mid-1980s. Besides nuclear safety and waste disposal problems, international concern for the proliferation of weapons-grade fissile materials will increase as more and more nations rely on nuclear plants.

It is clear that no single energy source is going to take over from the polluting fossil fuels. The integration of local energy sources in individual countries into grids that make use of the best local and imported energy is important if we are to find solutions to regional and global energy problems. In the developing countries in particular, the expansion of the energy sector must go hand in hand with infrastructure, social development and economic growth.

United Nations agencies such as the United Nations Development Programme have played a major role in the development of the energy sector in a large number of developing countries, not least in the development of renewable energy sources such as hydro power and geothermal energy. The World Bank has been instrumental in financing and conducting quality control on major energy projects around the world. But it is in implementing international agreements on the sustainable use of energy resources that UN agencies have a major role to play.

- Excerpts from a paper presented at the UNU Millennium Conference in Tokyo, Japan.