2.1 Overview of Carbon Emission and Development of Renewable Energy in the US

2.1.1 Carbon Emission and Energy Consumption

According to the report data from UNFCCC，since 1990，US’s greenhouse gas emission has gone up continuously. The fossil energy related greenhouse gas emission in 2006 rose by 14.38% compared with that in 1990（Table 2-1）. If the land use is factored in，the emission in 2006 rose by 14.04% compared with that in 1990. Since 2000，the increase rate of greenhouse gas emission in US has been obviously slowing compared with that in the 1990s，especially the emission in 2006 slightly dropped compared with that in 2005.

Table 2-1 Changes in Greenhouse Gas Emission in US

Kyoto Protocol demands that during the first commitment period from 2008 to 2010，carbon emission in US must be lowered by 7% on the basis of 1900. Although Bush Administration declared to withdraw from Kyoto Protocol in March 2001，the increase rate of carbon emission seems obviously too fast as US is the biggest developed country in the world.

In terms of energy consumption，US still mainly consumes fossil energy（Table 2-2）. In 2007，fossil energy accounted for 84.9% of the total energy consumption. In which，oil held the largest share，accounting for 39.17%. Natural gas and coal were close，accounting for 23.28% and 22.43% respectively. Nuclear power accounted for 8.29%. Renewable energy accounted for 6.71%，which mainly referred to hydropower and bio-electricity.

Table 2-2 Type and Quantity of Energy Consumption in US，2003-2007

Among the renewable energy，the bio-energy and wind energy have seen significant increase since 2000（Figure 2-1）. Compared with those in 2000，the bio-energy consumption and wind energy consumption grew 3.25 folds and 5 folds in 2007