1 kilowatt-hour electricity = 3,412 Btu
1 barrel crude oil = 5,800,000 Btu
1 barrel gasoline = 5,200,000 Btu
1 barrel fuel ethanol = 3,500,000 Btu
1 cubic foot of natural gas = 1,028 Btu
1 tonne coal = 22,230,000 Btu
Carbon dioxide (CO2) emissions from energy production and use are expressed in tonnes. The term tonnes of CO2equivalent (CO2 eq) indicates the global warming potential of other greenhouse gases (e.g., methane) in terms of CO2 quantities. The United States emits about 7 billion tonnes of CO2 eq per year, about 6 billion of which is CO2 arising primarily from energy production and use (see Figure 1.3 in Chapter 1). Average CO2 emissions in the United States are about 20 tonnes per person.