Coal and natural gas are the primary fossil fuels used as energy sources in the United States. These fossil fuels both contain mixtures of hydrocarbons, which are a chemical compound of carbon and hydrogen (Olah, 2005). Currently, fossil fuels provide eighty-five percent of the world's commercial and business energy, and that eighty-five percent doesn't even take into account residential use. Imagine if residential energy consumption was factored into that eighty-five percent (Davison, 2007). According to Goodell (2006), “Between 1950 and 2000, the world's population increased by 140 percent and the consumption of fossil fuels increased by 400 percent. By 2030, global energy demand is expected to more than double, with most electricity generation coming from fossil fuels, primarily coal. The world is extremely dependent on many fossil fuels, not just coal and natural gas, and many countries do not use these fossil fuels in moderation. Fossil fuels have already become significantly depleted and almost no one takes into account the fact that these fuels are not renewable because it takes the Earth millions of years to produce them. Although fossil fuel reserves are not infinite, there is currently no shortage, but as fossil fuels continue to be depleted, their cost will increase significantly. Although these fuels are not renewable, these resources will remain the primary source of energy, but as these fuels become less available, the world will become more and more dependent on energy conservation and alternative energy sources ( Olah, 2005). Coal and natural gas are very different fossil fuels, particularly with regard to environmental issues, content and life cycle, as well as cost and demand. The main problem with...... middle of article......, John (2007): Performance and costs of power plants with CO2 capture and storage. Energy 32(7), 1163-1176Goodell, John (2006): Big Coal: The Dirty Secret Behind America's Energy Future. Library of Congress Cataloging-in-Publication Data Jaramillo, Paulina et al (2007): Comparative life cycle air emissions from coal, domestic natural gas, LNG, and SNG for electricity generation. Environmental Science and Technology41(17), 6290-6296Kaplan, Stan M. (2010): Displacing Coal by Generation from Existing Natural Gas Power Plants. Congressional Research Service Olah, George A. (2005): Beyond Oil and Gas: The Economics of Methanol. Angewandte Chemie International Edition 44(18), 2636-2639Spath, Pamela L. and Margaret K. Mann (2000): Life cycle analysis of a natural gas combined cycle power generation system. National Renewable Energy Laboratory