Transit fleets report positive experiences with biodiesel. City bus fleets that have used biodiesel include those in Cedar Rapids, Iowa; Cincinnati, Ohio and St. Louis, Missouri. Bi-State Development Agency in St. Louis conducted one of the first demonstration projects using biodiesel blends in Call-a-Ride vans to evaluate its suitability as a motor fuel. The evaluation revealed that:
- Biodiesel is a viable motor fuel
- Performance and fuel economy were unchanged
- Exhaust emissions improved dramatically
- The fuel was fully compatible with vehicle and fuel dispensing equipment
Biodiesel operates in conventional engines. Just like petroleum diesel, biodiesel operates in combustion-ignition engines. Essentially no engine modifications are required, and biodiesel maintains the payload capacity and range of diesel. Pure biodiesel is not compatible with natural rubber, sometimes found in pre-1994 vehicles. Because it is a solvent, it can degrade natural rubber hoses and gaskets, so those would need to be changed to more modern material if B100 is desired. This is not a problem with B20 blends (20 percent biodiesel/80 percent diesel) and below.
Biodiesel exhaust is less offensive. The use of biodiesel and biodiesel blends results in a noticeable, less offensive change in exhaust odor. In fact, equipment operators have compared it to the smell of french fries. Users also report having no eye irritation. Since biodiesel is oxygenated, diesel engines have more complete combustion with biodiesel than with petroleum.
Biodiesel is safer to use than petroleum diesel. The flash point (the point at which fuel ignites) for biodiesel in its pure form is more than 200 degrees versus about 125 degrees Fahrenheit for regular No. 2 diesel. This makes biodiesel the safest fuel to use, handle and store.
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Biodiesel has a full ASTM fuel specification. The American Society of Testing and Materials (ASTM) issued Specification D 6751 for all biodiesel fuel bought and sold in the U.S. in March of 2002, marking a major milestone for the biodiesel industry.
Having a full standard in place helps protect consumers from poor products and reduce the cost of buying and selling biodiesel. While many adopted the provisional specification in 1999 (PS 121), those that didn't had to negotiate a specification. The final passage of D 6751 streamlines the procurement process.
Those interested in getting a copy of the standard can buy it at www.astm.org. To contact ASTM customer service directly, call (610) 832-9585 or e-mail firstname.lastname@example.org.
Biodiesel reduces emissions significantly. Biodiesel is the first alternative fuel to have fully completed the Health Effects testing requirements of the Clean Air Act. The use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter. Emissions of nitrogen oxides are either slightly reduced or slightly increased depending on the duty cycle and testing methods. The use of biodiesel decreases the solid carbon fraction of particulate matter (since the oxygen in biodiesel enables more complete combustion to CO2), eliminates the sulfate fraction (as there is no sulfur in the fuel), while the soluble, or hydrocarbon, fraction stays the same or is increased. Biodiesel works well with new technologies such as catalysts, particulate traps, and exhaust gas recirculation. Soy biodiesel reduces carbon dioxide by 78% on a life cycle basis.
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