A Fuel-Based Motor Vehicle Emission Inventory

Abstract

A fuel-based methodology for calculating motor vehicle emission inventories is presented. In the fuel-based method, emission factors are normalized to fuel consumption and expressed as grams of pollutant emitted per gallon of gasoline burned. Fleet-average emission factors are calculated from the measured on-road emissions of a large, random sample of vehicles. Gasoline use is known at the state level from sales tax data, and may be disaggregated to individual air basins. A fuel-based motor vehicle CO inventory was calculated for the South Coast Air Basin in California for summer 1991. Emission factors were calculated from remote sensing measurements of more than 70,000 in-use vehicles. Stabilized exhaust emissions of CO were estimated to be 4400 tons/day for cars and 1500 tons/day for light-duty and medium-duty trucks, with an estimated uncertainty of ±20% for cars and ±30% for trucks. Total motor vehicle CO emissions, including incremental start emissions and emissions from heavy-duty vehicles were estimated to be 7900 tons/day. Fuelbased inventory estimates were greater than those of California's MVEI 7F model by factors of 2.2 for cars and 2.6 for trucks. A draft version of California's MVEI 7G model, which includes increased contributions from high-emitting vehicles and off-cycle emissions, predicted CO emissions which closely matched the fuel-based inventory. An analysis of CO mass emissions as a function of vehicle age IMPLICATIONSThe fuel-based methodology presented in this study may be used to calculate a motor vehicle emission inventory for any geographic area for which emissions data are available. The fuel-based approach requires fuel use data, which is obtained from state tax records, and onroad emissions data, which are becoming more available as remote sensing devices are used in Inspection & Maintenance programs around the country. Currently, the fuel-based method may be used to verify official emission inventories of CO. With further development of the methodology and advances in remote sensing capabilities for NOx and HC, the fuel-based approach could become the standard emission inventory methodology.revealed that cars and trucks which were ten or more years old were responsible for 58% of stabilized exhaust CO emissions from all cars and trucks.

Summer and Winter Nonmethane Hydrocarbon Emissions from On-Road Motor Vehicles in the Midwestern United States

“…The volumetric air dilution rate determined for each tunnel test from SF 6 measurements and calculations were combined with vehicle counts and measurements of CO, CO 2 , and CH 4 to calculate average vehicle miles traveled per unit of fuel consumed in the tunnels. 9,12 Gasoline density of 0.7 g mL Ϫ1 and gasoline carbon content of 0.83 g per gram of fuel were assumed, similar to other studies. 9 Increases in concentrations (g m Ϫ3 ) of species between the tunnel inlet and outlet were converted to emission rates.…”

“…All NMHC samples collected in tunnel tests (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) and parking garage test (PG). Comparison between the collocated sample measurements from each laboratory was used to validate the data.…”

Estimated Emission Reductions from California's Enhanced Smog Check Program

“…Correlations were also observed between ASM test results and remote sensing measurements of the same sample of vehicles, grouped by model year (8). In studies of emissions variability by driving mode (14,15), mild to moderate loads similar to that encountered on the ASM generally result in HC, CO and NO X emissions that are lower than those encountered at higher loads. Under lower loads and decelerations, HC is typically higher and NO X is lower than at ASM-type loads.…”

“…Conversion to mass emission rates was necessary for the estimation of total mass emission reductions. The calculation, described in detail elsewhere (8,14,15) uses a carbon balance to relate reported pollutant exhaust concentrations (ppm HC, ppm NO X , %CO, %CO 2 ) to the total carbon content of the fuel. Typical fuel properties were used to normalize emissions to fuel consumption.…”

Source Contributions to the Mutagenicity of Urban Particulate Air Pollution

“…In the present study, a fleet average ratio of EC to particulate organic compounds from on-road diesel vehicles first was computed from the literature review of diesel engine emissions characteristics as a function of production era reported by Sawyer and Johnson 44 combined with estimates of relative annual mileage accumulation by trucks and autos of different ages. 45,46 The analysis suggests that diesel engine emissions in the South Coast Air Basin surrounding Los Angeles in 1993 should consist of ϳ33% EC and 31% organic compounds by mass, plus trace amounts of Si and Al, as measured in diesel exhaust by Hildemann and co-workers. 26 The combined diesel engine profile used in the present study thus consists of EC, Al, Si, and total organics in those proportions, with the relative composition of the organic compounds taken from the GC/MS analysis of filter samples taken during the source tests of Hildemann and co-workers.…”