6. Oil

Oil is a very convenient source of energy because it is concentrated (9 to 13 kWh/kg, compared with 5 to 9 kWh/kg for coal). It's a liquid that's easy to transport and use. Burning oil generates less CO ₂ than coal (figure 7 ). It also emits fewer pollutants than the latter. For example, an old power plant burning heavy fuel oil discharges an average of 4.7 Mt of CO ₂ , 90,000 t of SO ₂ if the fuel oil is not desulfurized, 6,000 t of NO _...