There have always been heated discussions about the dangers of U.S. over-reliance on foreign oil. As a result, many companies are engaged in researching alternative energy sources. Recognizing that the growth of the sector is important to the health of the American economy, thousands of investors have also become interested in putting money here. Accordingly, investment options are now plentiful in the industry, ranging from companies that design and produce biofuels to companies that manufacture engines that run on biofuels.............