According to the 37 page report published by the IFMA titled "Sustainability in the Food Service Environment" in 2011, it is estimated that 80% of the total energy spent at US restaurants are wasted. From the same report it was determined that the wasted energy comes from inefficient appliances, AC and ventilation system, and refrigerators producing excess heat and noise.
When fossil fuels are burned, they release large amounts of carbon dioxide, a greenhouse gas, into the air. Greenhouse gases trap heat in our atmosphere, causing global warming.