Although this talk is about carbon dioxide (CO2), our starting point is energy. From the EIA Annual Energy Outlook (EIA, 2009) we find petroleum liquids, coal, and natural gas dominate the United States (US) energy mix. This energy picture is mirrored around the world. Most projections are that the energy load is going to increase in lock step with the current 1.2% world population growth.
Jeffrey Stewart of Lawrence Livermore National Lab (LLNL) has been publishing diagrams illustrating this energy mix (Figure 1). If you are not used to looking at Stewart diagrams, they appear rather chaotic. But they are full of information about US and world energy use. For the US in 2002, the Stewart diagram shows net energy use of 97 quads (a quad is 1015 BTU). It breaks down such interesting details as domestic and import oil input and oil usage divided between transportation (65%), industrial (10%), and residential (5%) fuels, as well as non-fuel use (13%). For each category of energy use, there is a certain amount of energy loss: usable energy and unused energy lost in the form of heat. We see that none of these energy applications is alarmingly efficient, but oil in transportation use is alarmingly inefficient with 80% of the energy lost.