The reduction of emissions and fuel consumption using fuels that are renewable and have lower emission rates can provide considerable benefits for national parks such as Yosemite. One fuel that has shown considerable promise in meeting these needs is biodiesel. To date, a number of studies have demonstrated emissions reductions for biodiesel fuels relative to ordinary diesel fuel (U.S. Environmental Protection Agency, 2002). Biodiesel is commercially available and also more readily implemented than other alternative fuels, such as natural gas. Biodiesel requires no modifications to the engine and only minor modifications to existing fuel practices. An added benefit of biodiesel fuels is that they can be derived from renewable, domestic resources, such as crops or waste grease. As such, biodiesel has been designated as an alternative fuel under the Energy Policy Act (EPACT). This allows fleet operators to meet the EPACT alternative fuel vehicle (AFV) acquisition requirements. Biodiesel is added to conventional diesel at blends of 20 percent and higher. The use of biodiesel in fleet and other applications has expanded considerably in recent years, from essentially negligible levels in 1998 to 20 million gallons in 2002 (McCormick, 2003). This includes municipal fleets, military applications, postal applications, and others. The production capacity in the U.S. could be 150 million gallons per year. In Europe, production is currently at 200 million gallons, with a capacity of 600 million gallons. As the use of biodiesel continues to expand, fleets are continuing to examine potential applications of biodiesel. Yellowstone National Park has conducted a demonstration program (University of Idaho and Montana Department of Environmental Quality, 1999). Channel Island National Park is also using biodiesel on a regular basis. Currently, DNC Parks and Resorts at Yosemite, Inc. (DNC) is considering the use of biodiesel in its fleet vehicles for applications in the park. DNC generates approximately 48 tons of used restaurant grease per year that is currently being transported back to Fresno where it is used to make biodiesel. However, the biodiesel is not returned to Yosemite for use in their fleet. The DNC goal is to make use of its restaurant grease and at the same time provide a renewable fuel for use in its fleet vehicles. Prior to full-scale application of the biodiesel, DNC proposed a pilot program to examine the use of biodiesel in their fleet in terms of emissions benefits, maintenance, use during cold weather, and other considerations. If the application of the fuel proves to be successful, eventually the program could lead to development of a small-scale plant on the park grounds that could process the restaurant grease into biodiesel on-site. The present project is a pilot demonstration program in the DNC fleet vehicles. The overall program included an investigation of feasibility of a biodiesel plant, emissions testing, and characterization of fuel mileage and maintenance issues with biodiesel use. The program is a collaborative effort between DNC, the California Integrated Waste Management Board, the University of California at Riverside, the Air Resources Board, Clean Air Technologies, Inc., and Biodiesel Industries.
In recent years, automobile manufacturers have been producing gasoline-fueled vehicles that have very low tailpipe and evaporative emissions to meet stringent certification standards set by the U.S. Environmental Protection Agency and the California Air Resources Board. These extremely low-emitting vehicles are 98% to 99% cleaner than the catalyst-equipped vehicles produced in the mid-1980s. To understand better the emissions characteristics of these extremely low-emitting vehicles, as well as their potential impact on future air quality, researchers at the University of California, Riverside, have conducted a comprehensive study consisting of (a) an emissions measurement program, (b) the development of specific emissions models, and (c) the application of future emissions inventories to air quality models. Results have shown that in nearly all cases, these vehicles have emissions that are well below their stringent certification standards, and the vehicles continue to have low emissions as they age. On the basis of the measurement results, new modal emissions models have been created for both ultra-low-emission-certified vehicles and partial-zero-emission-certified vehicles. The model results compare well with actual measurements. With these models, it is possible to predict accurately future mobile source emissions inventories that will have an increasing number of these extremely low-emitting vehicles in the overall vehicle population. It is expected that the large penetration of these vehicles into the vehicle fleet will have a significant role in meeting ozone attainment levels in many regions.