Introduction and Overview

Reducing carbon emissions to levels consistent with the stabilization of greenhouse gas concentrations in the atmosphere will require enormous amounts of clean energy supplies to displace current fossil fuel combustion. Renewable energy supplies are one source of such clean energy.

This chapter focuses on terrestrially based renewable energy options. As used here, renewable energy is defined simply as any form of energy that can be used without diminishing the resource. Some forms of renewable energy, like solar and wind, are essentially limitless. Others, like geothermal, may be depleted in the short term, but are eventually regenerated. Some, like hydroelectricity, municipal solid waste, landfill gas, and biomass must be regenerated continually. But none are totally depleted forever.

Renewable energy is generally clean. Most forms of renewable energy do not involve combustion and, therefore, do not emit gases to the atmosphere. In particular, renewables are attractive because they generally emit no net carbon dioxide. What is just as important for those countries experiencing severe local air pollution problems is that non-combusting renewables, like solar and wind, produce energy without emitting sulfur dioxide, nitrogen oxides, particulate matter, or toxic materials. In addition, renewable electric technologies, like photovoltaics and wind that do not use heat to produce electricity, require no water resources for cooling towers, and have no water effluents.