The wide range of energy project opportunities brings with it a variety of environmental issues. Most energy technologies have technology-specific environmental attributes, some positive and some negative. As a class, renewable energy projects have fewer environmental issues than conventional energy technologies, but in a few areas (for example, wind farms and avian migratory patterns) renewables have special issues that must be addressed. In addition to air and water issues, energy projects must be respectful of cultural, spiritual, and historic issues that may be involved in project siting. Of all the options, energy efficiency technologies are often the most environmentally benign, as well as being the most cost effective.
Due to the large difference in emissions between conventional fossil technologies and renewable energy options, "emissions trading" programs are starting to emerge that can provide a quantitative, financial benefit for electric generation technologies that do not pollute the air. Increasingly, "green tags" (tradable renewable energy certificates) are being sold on the open market that can provide significant additional income to a project, over and above the value of the electricity being sold.
Further details on technology-specific environmental issues, emissions trading, and historic and sacred sites can be found under Environmental Considerations.