World demand is so enormous that alternative technologies, as they exist today, can't possibly replace the energy being extracted from fossil fuels. Too much is required in too many different applications. Even working in combination, alternative technologies can't replace a single fossil fuel -- coal, petroleum, or natural gas. The consensus among energy experts is that fossil fuels, along with nuclear energy, will continue to fulfill our basic energy needs for decades to come. Inventions may occur suddenly, but commercialization and infrastructure development take time. Even if a technological breakthrough occurred tomorrow, it would take at least two decades to implement. After all, it took a century to create today's fossil fuel infrastructure.
Consider the transportation sector. The disadvantages of burning gasoline are well known, but global dependence on gas-burning internal combustion engines seems unlikely to change anytime soon. To begin with, the cost of replacing the current infrastructure seems prohibitive. The induction of a new automotive fuel, for example, would require the replacement of hundreds of millions of engines, the refitting of hundreds of thousands of filling stations, and the reconstruction (or new construction) of hundreds of new refineries.
Energy economists are particularly concerned about what will happen when the populations of developing giants such as China and India - accounting for 2.5 billion people, or nearly 40 percent of the world population - begin to buy cars in large numbers as well. China already has serious air pollution problems, and in 2006 it overtook the United States as the world's leading emitter of carbon dioxide. Its citizens will hardly be able to afford the extra cost of buying "green" cars, and even if they could, the capacity to produce so much green transportation simply doesn’t exist, at least not yet. (‘The Bedside Baccalaureate’, edited by David Rubel)