ABSTRACT
Most of the industrialized world depends heavily on fossil fuels for both electricity generation and transportation. Two major factors will put tremendous pressure on fossil fuel use in the twenty-rst century. The rst is continued concern about global climate change, or the greenhouse effect (Chapter 29). Although CO2 is not the only greenhouse gas, human activities are not the only source of CO2 emissions, and fossil fuel combustion is not the only human activity that generates CO2, concerns about global climate change have already led to increased interest in energy sources and technologies that do not result in a net increase in atmospheric CO2 concentrations. The second factor is the concern about reserves, resources, and geopolitics (Chapter 30). The potentially short lifetime of remaining reserves, especially of oil, makes it prudent to consider other sources of energy that are not likely to be depleted. energy sources that are not subject to depletion are called renewables. Examples include wind, water, solar, and biomass. The term renewables implies that this source of energy is continuously being renewed, either through natural events, as in wind energy or solar energy, or through human intervention, such as the energy crops discussed later in this chapter. Such energy sources that are harvested but then regrown are also known as sustainable energy sources. Renewables do not rely on localized concentrations in seams or reservoirs, as do coal, oil, or natural gas, but rather can be utilized almost anywhere. Therefore renewables are not nearly so likely to be impacted by concerns of geopolitics and possible embargoes as are the fossil fuels.
