The document discusses various alternative fuels that could potentially replace or supplement gasoline and diesel fuels. It notes that conventional fossil fuels are depleting and contributing to pollution and global warming. Some key alternative fuels discussed include ethanol, methanol, vegetable oils/biodiesel, natural gas, propane, and hydrogen. The document provides details on production methods and potential benefits and drawbacks of different alternative fuels for internal combustion engines. Overall it evaluates options for more sustainable fuel sources.