過去幾年石油價(jià)格大幅上漲，人們對(duì)能源安全的擔(dān)憂，以及對(duì)全球變暖的日益擔(dān)憂，極大地增加了人們對(duì)在美國發(fā)展可再生能源的興趣。用可再生能源替代化石燃料將減少二氧化碳（CO2）的排放，二氧化碳是全球變暖中最普遍的“溫室氣體”。通過降低對(duì)石油的需求，可再生燃料的替代可以促進(jìn)國家能源安全。此外，從農(nóng)村地區(qū)增加可再生能源供應(yīng)可以提高美國農(nóng)村的收入。

Sharply higher prices for oil over the past several years, concerns about energy security, and growing worries about global warming have greatly increased interest in expanding renewable energy in the United States. Substituting renewable energy for fossil fuels would reduce emissions of carbon dioxide (CO2), the most prevalent “greenhouse gas” (GHG) associated with global warming. By lowering demand for oil, substitution of renewable fuels could contribute to national energy security. In addition, increased renewable-energy supplies from rural areas could enhance rural incomes in the United States.