Air Pollution as a Climate Forcing: A Workshop

Day 3 Presentations

Vehicle Contribution to Climate Change

T. J. Wallington
Scientific Research Laboratories, Ford Motor Company, Dearborn, MI, U.S.A.

You may download a MS PowerPoint version (2.6 MB) of this presentation.

Abstract

Climate change is an important environmental issue. Accurate data concerning the emissions of CO2, N2, CH4, R-134a, NMHCs, NOx, NH3, CO, and particulate matter from vehicles are needed to quantify the vehicle contribution to global climate change. Vehicle CO2 emissions can be calculated in a straightforward manner from gasoline/diesel production data available from the petroleum industry. Assessment of vehicle emissions of N2, CH4, R-134a, VOCs, NOx, NH3, CO, and particulate matter is not such a simple task. Work is ongoing in the Scientific Research Laboratories of Ford Motor Company to quantify, and to develop practical technologies to reduce, such vehicle emissions.

An assessment of R-134a emissions has been performed using a Sealed Housing for Evaporative Determination (SHED) facility. In such SHED tests vehicles are placed in a sealed chamber and "parked" for 24 or 48 hours. Grab samples of air within the SHED are analyzed to determine the leak rate of R-134a from air conditioning systems in 28 different vehicles from 5 different manufacturers. When combined with leakage associated with vehicle operation, servicing, and disposal the lifetime average R-134a emission rate from an AC equipped vehicle is estimated to be 0.41±0.27 g/day (the majority of emissions are associated with vehicle servicing and disposal) [1].

To provide data for N2 emissions, "real world" N2 emissions measurements from road vehicles in a tunnel in Wuppertal, Germany, were combined with "laboratory" emission measurements conducted at the Ford Motor Company using a chassis dynamometer with a standard driving cycle for 22 different cars and trucks. Laboratory data for the emission of NMHC, CO, CO2, NOx, NO, N2, and NH3 for the vehicles studied are given in Table 1. The data in Table 1 provides a comprehensive picture of the emissions of N-containing compounds from modern vehicles [2]. Consistent results were obtained from "laboratory" and "real world" studies of N2 emissions suggesting that a good approximation of the average emission factor (g N2/ g CO2) = (6±2) × 10-5 [2]. This corresponds to an emission rate of 16-8 mg N2 /km for vehicles with fuel economies of 12-6 liters / 100 km (20-40 miles /U.S. gallon).

Assuming that the average vehicle travels 10,000 miles per year it is estimated that the global warming impact of R-134a leakage from an AC equipped vehicle is approximately 4-5% of that of the CO2 emitted by the vehicle. N2 emissions from vehicles have a global warming impact which is 1-3% of that of the CO2 emissions from vehicles.

Table 1: Vehicle tailpipe emission data. Fuel identification: Cert, U.S. Certification fuel; CRF, California reformulated fuel; M-85, a mixture of 85% methanol and 15% gasoline (by volume): Diesel, U.S. number 2 diesel fuel; CNG, compressed natural gas.
Vehicle Identifier Fuel NMHC
(mg/km)
CO
(g/km)
CO2
(g/km)
NOx
(mg/km)
NO
(mg/km)
NO2
(mg/km)
N2
(mg/km)
NH3
(mg/km)
Car A Cert 63±16 0.84±0.07 293±2 134±11 92±8 nd 21±2 49±6
B Cert 67±11 0.23±0.02 288±5 146±30 71±18 5±2 11±2 3±3
C CRF 85±2 1.16±0.02 239±1 205±13 157±8 3±1 25±2 165±1
D CRF 66±2 0.68±0.02 258±2 91±6 57±6 2±1 8±1 3±1
E CRF 97±6 0.59±0.04 285±1 24±4 15±3 2±1 5±2 81±3
F CRF 41±2 0.53±0.02 295±3 74±8 50±5 nd 10±1 10±4
G CRF 94±6 0.86±0.02 286±2 124±4 76±4 3±1 32±2 31±3
H CRF 31±3 0.23±0.02 305±4 44±2 29±3 nd 9±2 28±1
I CRF 14±3 0.15±0.05 217±2 55±3 33±4 2±1 4±1 11±2
J CNG 8±1 0.23±0.02 247±2 6±2 8±2 4±1 2±1 44±4
K M-85 18±2 0.59±0.05 244±9 86±6 17±4 nd 4±1 29±4
L Diesel 107±19 0.30±0.02 193±11 475±25 315±15 17±2 4±1 nd
M Diesel 116±86 0.53±0.23 161±2 804±8 492±56 90±78 14±9 nd
Truck A Cert 54±11 0.44±0.06 394±3 69±12 45±4 nd 6±1 11±2
B Cert 61±2 1.16±0.07 289±4 262±32 177±21 3±1 22±3 59±3
C Cert 51±3 0.44±0.03 293±4 147±22 91±14 2±1 7±1 13±2
D CRF 83±3 2.16±0.06 259±2 430±6 298±8 4±1 27±1 48±3
E CRF 43±2 0.48±0.04 268±2 59±9 36±5 2±1 4±2 19±1
F CRF 83±6 0.69±0.05 339±2 77±12 68±14 3±1 11±2 104±18
G CRF 78±8 0.97±0.06 345±2 77±5 52±3 3±1 17±2 43±4
H CRF 61±3 1.36±0.09 381±40 210±8 130±2 2±1 17±2 44±2
I CNG 18±2 0.32±0.09 329±4 102±10 69±14 nd 24±4 84±11
Car Average 62 0.53 255 174 109 14 11 35
Truck Average 59 0.89 322 160 107 3 15 47

References

  • 1. Siegl, W. O.; Wallington, T. J.; Guenther, M. T.; Henney, T.; Pawlak, D.; Duffey, M., Environ. Sci. Tech., 2002, 36, 561.
  • 2. Becker, K. H.; Lörzer, J. C.; Kurtenbach, R.; Wiesen, P.; Jensen, T. E.; Wallington, T. J., Environ. Sci. Tech., 1999, 33, 4134.

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