in the atmosphere, and does not directly contribute to the problem of greenhouse gas. It is really a way of catching and storing solar energy; it is a renewable energy. However, as with other "renewable" energy sources, there may be a (relatively small) carbon footprint associated with production or distribution of vegetable oil. Safety Vegetable oil is far less toxic than other fuels such as gasoline, petroleum-based diesel, ethanol, or methanol, and has a much higher flash point (approximately 275-290 °C). The higher flash point reduces the risk of accidental ignition. Some types of vegetable oil are edible. Generation and storage Technologies of hydrogen economy, batteries, compressed air energy storage, and flywheel energy storage address the energy storage problem but not the source of primary energy. Other technologies like fission power, fusion power, and solar power address the problem of a source of primary energy but not energy storage. Vegetable oil addresses both the source of primary energy and of energy storage. The cost and weight to store a given amount of energy as vegetable oil is low compared to many of the potential replacements for fossil fuels. Type of vegetable oil The list of vegetable oils article discusses which types of vegetable oil are used for fuel and where different types are grown. Transportation Vegetable oil is used for transportation in four different ways: Vegetable oil blends - Mixing vegetable oil with diesel lets users get some of the advantages of burning vegetable oil and is often done with no modification to the vehicle. Biodiesel - Biodiesel can be produced from vegetable oil through the process of transesterification. Biodiesel burns like normal diesel and works fine in any diesel engine. The name just indicates that the fuel came from vegetable oil. Straight vegetable oil - Straight vegetable oil works in diesel engines if it is heated first. Some diesel engines already heat their fuel, others need a small electric heater on the fuel line. How well it works depends on the heating system, the engine, the type of vegetable oil (thinner is easier), and the climate (warmer is easier). Some data is available on results users are seeing. As vegetable oil has become more popular as a fuel, engines are being designed to handle it better. The Elsbett engine is designed to run on straight vegetable oil. However, as of the start of 2007, it seems that there are