My wife and I were discussing the DieselEarth project earlier today with our one year old baby girl in the car. I asked her to give me a topic for today’s post and she recommended safety. After all, isn’t vegetable oil is safer than gasoline? She’s always been the smart one, so I put aside my preconceived notions and investigated the idea that diesel fuel in general and in particular using vegetable oil or biodiesel in a diesel engine is safer than gasoline.
Here are some important definitions:
Flash point: Tthe temperature at which a liquid vaporizes. Flammable liquids do not burn directly – the resulting flame comes from the vapor gas produced by the liquid. When a fuel source reaches its flash point it produces flammable vapor and has the potential to ignite given the proper conditions. This sounded weird to me because I always assumed that it was the liquid itself that was burning and gasoline, for example, would burn under any conditions. According to the chart below gasoline would be unable to ignite at temperatures below -40°C/-40°F. Please comment below if I’m incorrect on this – I’m not pretending to be a chemist :).
Ignition Temperature: The minimum temperature required for material to burn or explode. When a fuel source reaches its ignition temperature, it will ignite. Note that gasoline will ignite at 495°F. I live in Texas and I can vouch for the remarkable temperatures achieved in storage sheds, radiated by outdoor metal objects, etc. One of my mother’s friends recently received a serious burn after leaning her bare arm against the black metal aluminum screen door to her house. If you don’t believe gasoline can ignite under the normal conditions of a summer day, come visit me in Texas in July. It’s a bright 102°F today and expected to get hotter.
To address the potential danger of one fuel source over another, we must first find their respective flash points and ignition temperatures. Fuels with a higher flashpoint will be considered safer because they will remain inert at lower temperatures and will need more heat to become gaseus and flammable. At the same time, fuels with higher ignition temperatures will be less apt to combust and cause a potentially dangerous situation. Remember, all three of the fuels tested will power an automobile with relatively the same efficiency.
|Material||Flashpoint||Flashpoint||Ignition Point||Ignition Point|
|Gasoline||-40 to -60°C||-40 to -76°F||257°C||495°F|
|Petro Diesel||60 to 80°C||140 to 176°F||494°C||921°F|
|Biodiesel||100 to 170°C||212 to 338°F||N/A||N/A|
*Unfortunately, I wasn’t able to find the ignition point of either biodiesel or vegetable oil. After observing a direct relationship between flashpoint temperature and the ignition point, I’m fairly comfortable in assuming that biodiesel and vegetable oil would have ignition points reflective of their flash points. Again, I have no research to confirm this but I feel it’s a reasonable observation. Please let me know if you have any numbers to lend to the theory.