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Contributors to Emissions
Energy conversion (chemical energy of fossil fuels to electrical or mechanical)
systems account for, by far, the largest contribution to emissions of carbon
into the atmosphere as is shown in Figure
1. Other
industries, agriculture, and waste processing account for modest amounts, and
the forest industry is a negative contributor, being a net sink for atmospheric
carbon dioxide.
The distribution by economic sector of carbon dioxide emissions (Figure 2) shows that utilities are the largest contributor, followed by transportation and industrial. Residential and commercial emissions are small by comparison with the previous three. Utilities (stationary combustion sources) primarily use coal, while transportation (mobile combustion sources) use petroleum almost exclusively. Industrial sources use primarily petroleum and natural gas, with a small amount coal.
Of the various types of energy consumed in the US in 2001 (Figure 3), as given by the US Energy Information Administration, petroleum accounts for about 39%, followed by natural gas at 24% and coal at 23%. Nuclear electric power contributes 8% and renewables contribute 6%.
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