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B Contribution of U.S. Transportation Sectorto Greenhouse Gas Emissionsand Assessment of Mitigation Strategies
Pages 210-266

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From page 210...
... Energy Information Agency's annual publication Emissions of Greenhouse Gases in the United States provides estimates of transport sector emissions of CO2, CH4, and N2O. In 2003, CO2 accounted for 97 percent of the total, when each gas is converted into its global warming 210
From page 211...
... those produced in the extraction, production, and distribution of transport fuels and (b) those produced in the manufacture, distribution, and disposal of transport vehicles.2 A rough idea of the relative significance of these additional categories of emissions can be obtained from life-cycle studies that attempt to track all emissions related to a vehicle and its fuel.
From page 212...
... has published detailed modal estimates of emissions from fuel combustion for 2000 and projec tions at 5-year intervals to 2050 (World Business Council for Sustainable Development 2004) .5 The SMP also published estimates and projections of CO2, N2O, and CH4 emissions from the production and distribution of transport fuels.
From page 213...
... 14000.0 12000.0 Africa Latin America 10000.0 Middle East India Megatonnes 8000.0 Other Asia China 6000.0 Eastern Europe FSU 4000.0 OECD Pacific OECD Europe OECD North America 2000.0 0.0 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 Year FIGURE B-1 Transport greenhouse gas emissions by region (all modes)
From page 214...
... STRATEGIES FOR REDUCING TRANSPORT-RELATED GREENHOUSE GAS EMISSIONS The charge to the committee quoted above recognizes that a range of possible approaches exist by which transport-related GHG emissions 6 "International aviation and marine bunkers" denotes fuel loaded on transport vehicles in the United States but consumed in international operations. Generally speaking, "international bunkers" are not included in national totals, though they are included in the world totals cited above.
From page 215...
... Road vehicles 1,464.1 78.9 Automobiles 630.2 3.4 0.0 633.6 34.2 Light-duty trucks 460.9 17.6 0.0 0.3 478.8 25.8 Other trucks 39.6 301.1 0.5 341.2 18.4 Buses 0.3 8.0 0.6 0.0 8.9 0.5 Motorcycles 1.6 1.6 0.1 Rail 39.6 3.2 42.8 2.3 Waterborne 82.1 4.4 Ships and boats 17.0 29.5 46.5 2.5 Ships (bunkers) 6.0 18.6 24.6 1.3 Boats (recreational)
From page 216...
... The committee believes that the best way of organiz ing the present discussion of this range of approaches is through the use of the "ASIF decomposition." The CO2 emissions from fuel combustion by transport vehicles can be characterized by the following equation: G = A∗Si∗Ii∗Fi,j where G = CO2 emissions from fuel combustion by transport; A = total transport activity; Si = modal structure of transport activity; Ii = energy consumption (fuel intensity) of each transport mode; and Fi,j = GHG emissions characteristics of each transport fuel (i = trans port mode, j = fuel type)
From page 217...
... or Altering the Modal Structure of Transport Activity (S) The SMP report projects that worldwide personal transport activity, which totaled 32.3 trillion passenger-kilometers (pkm)
From page 218...
... According to the United Nations Conference on Trade and the Environment, in 2000, worldwide waterborne transport activity totaled 43.9 trillion tkm.) (Source: World Business Council for Sustainable Development 2004, Figure 2-5, p.
From page 219...
... FIGURE B-4 Per capita personal travel activity versus per capita real income. (Source: Data generated by IEA/SMP Spreadsheet Model.)
From page 220...
... FIGURE B-5 Projected change in real per capita personal transport demand versus projected change in real gross domestic product per capita (purchasing power parity basis)
From page 221...
... Rate of Population Growth The projected trends in real per capita income growth, if realized, will be a powerful force serving to increase transport activity. However, another factor that has exerted a powerful influence in increasing transport activity in the recent past -- population growth -- will be waning in importance in the future.
From page 222...
... .17 In contrast, urban populations in countries located in the less developed regions will grow rapidly. Spatial Organization of Urban Areas (Urban Form)
From page 223...
... (Reprinted with permission of the United Nations Population Division.) people talk about eliminating "unnecessary" travel or "unlinking" economic growth from transport activity, they generally are referring to the deliberate alteration of urban areas' spatial organization to influence the total volume of personal and goods transport activity, the choice of modes by which the demand for that activity is fulfilled, and the capacity utilization rates (i.e., load factors)
From page 224...
... Thus, the widespread ownership of motorized road vehicles allowed workers to both live and work almost anywhere they wished within a metropolitan region. The resulting decline in average residential and employment densities has undermined the viability of public transport, 18Indeed, the first traffic count of people entering the 1 square mile City of London between 8 a.m.
From page 225...
... Only cities that have managed to maintain strong CBDs and that developed high-speed public transport systems before the automobile came to dominate personal travel have managed to keep the share of commuting travel by private car relatively low.19 And this is only true for workers traveling to work in the CBD; those with jobs outside the CBD generally commute to work by car. Magnitude of the Impact of the Spatial Organization of Urban Areas on Transport Activity and Modal Choice Studies have demonstrated a statistically significant relationship between the spatial organization of urban areas and the volume of personal travel activity.
From page 226...
... accounts for approximately 40 percent of all U.S. public transport trips.
From page 227...
... Transforming a city with the spatial organization of Atlanta into one with the spatial organization of Boston would be a tremendous task requiring many decades, if it could be accomplished at all. Making marginal changes over time might be practical, but even this would not be easy.
From page 228...
... 0.12 0.58 0.44 0.28 0.35 0.44 0.41 0.58 Population centrality (standardized) 0.11 0.22 0.11 0.17 0.15 0.13 0.20 0.20 City shape 0.04 0.99 0.26 0.82 0.48 0.80 0.73 0.36 Predicted average vehicle miles traveled 16,899 12,704 14,408 15,685 9,453 16,493 per household Predicted average probability of driving to 0.87 0.73 0.74 0.90 0.40 0.84 work by workers Predicted average commute miles driven 5,450 4,565 4,620 5,641 2,496 5,247 a Refers to sample of 114 urban areas.
From page 229...
... of studies describe and analyze the potential of various technologies to reduce the fuel consumption of transport vehicles. Most of these studies focus on personal vehicles -- by far the most numerous road vehicles.
From page 230...
... Addressed in turn are technologies with the potential to reduce the fuel consumption of road vehicles, those with the potential to reduce the fuel consumption of nonroad vehicles, factors influencing the extent to which the potential of a technology to reduce transport-related GHG emissions is realized, and the impact of vehicle capacity utilization (load factor) on energy use.
From page 231...
... Controlled auto ignition (CAI) is another new combustion process being actively explored to improve fuel economy and lower the exhaust emissions of spark-ignition internal combustion engines.
From page 232...
... The cost of making vehi cles fully compatible with E10 is negligible, and the cost remains very low for full compatibility with E85 (an 85 percent ethanol fuel blend.) If engines were designed exclusively for pure ethanol or ethanol-rich blends, their costs would be roughly the same as today, but their fuel economy (expressed in liters of gasoline equivalent per 100 km)
From page 233...
... The formation of NOx can be reduced by using cooled intake-air compression (whereby an intercooler and aftercooler lower the temperature of the air-to-fuel mix in the cylinder) and by exhaust 25 Variable valve control, already described for gasoline engines, also offers improvements in diesel engines, although its ability to reduce fuel consumption is lower for compression-ignition engines than for spark-ignition engines because the latter suffer from higher pumping losses.
From page 234...
... , while an internal combustion engine powers the drivetrain. In mild hybrid configurations, the electric motor may also provide extra torque and extra power when needed.
From page 235...
... On the basis of a 2003–2015 gasoline internal combustion engine vehicle equal to 100, Table B-8 shows an index of the emissions from each engine type during each of the three periods. Fuel Cell Vehicles A fuel cell is an electrochemical device that converts hydrogen and oxygen into water and produces electricity in the process.
From page 236...
... Time Period Engine Technology 2003–2015 2015–2030 2030–2050 Spark ignition Gasoline ICEa 130–234 122–219 114–204 Dedicated ethanol ICEb 120–215 112–200 103–185 Flexible fuel vehicle ICEc 133–239 125–224 116–209 Light hybrid, gasoline ICEd 119–214 111–199 103–185 Mild hybrid, gasoline ICEd 108–194 99–178 94–168 Full hybrid, gasoline ICEd 99–178 94–169 89–160 Compression ignition Diesel ICEe 108–193 105–188 102–183 Light hybrid, diesel ICEf 96–173 94–168 91–163 Mild hybrid, diesel ICEf 87–155 83–149 80–143 Full hybrid, diesel ICEf 83–148 80–143 77–138 Note: These estimates refer to a midsized vehicle and assume that roughly half of the potential improvements due to advanced vehicle technologies will improve vehicle fuel economy. (In the case of hybrids, this share rises to 100 percent, but hybrid power trains could also be used to increase performance rather than fuel economy.)
From page 237...
... Time Period Engine Technology 2003–2015 2015–2030 2030–2050 Spark ignition Gasoline ICE 100 94 88 Dedicated ethanol ICE 92 86 79 Flexible fuel vehicle ICE 102 96 89 Light hybrid, gasoline ICE 92 85 79 Mild hybrid, gasoline ICE 83 76 72 Full hybrid, gasoline ICE 76 72 68 Compression ignition Diesel ICE 83 81 78 Light hybrid, diesel ICE 74 72 70 Mild hybrid, diesel ICE 67 64 62 Full hybrid, diesel ICE 64 62 59 Note: ICE = internal combustion engine. Source: Derived from Table B-7.
From page 238...
... Depending on the pace of technological development, the stack cost of a PEM fuel cell could decline to $35 to 70 per kW by 2030. If this were to happen, the cost of a fuel cell vehicle at that time would exceed that of a conventional internal combustion engine vehicle by $2,200 to $7,600.
From page 239...
... Another source of weight reduction is the replacement of mechanical or hydraulic systems by electrical or electronic systems. Steering can be accomplished by electric motors actuated by joysticks rather than by mechanical linkages between the steering wheel and the wheels of the car.
From page 240...
... At high way speeds, aerodynamic losses are estimated to account for 21 percent of the energy use of a heavy-duty truck–trailer combination unit. Technologies to Reduce the Energy Requirements of Onboard Equipment The energy consumption of air conditioners and other onboard appliances can account for up to half of a vehicle's fuel consumption under certain con ditions.
From page 241...
... Technologies with the Potential to Reduce Fuel Consumption by Nonroad Vehicles While LDVs are, in the aggregate, the largest consumers of transport fuel and emitters of GHGs, vehicles such as medium and heavy trucks, commercial aircraft, locomotives, and large waterborne vessels actually use much more energy per vehicle each year. In 2003, the average U.S.
From page 242...
... inland waterways are rated at over 10,500 horse power. Fuels used by waterborne transport vehicles are "heavy" grades of diesel fuel and an even "heavier" petroleum product known as "residual fuel oil." Typically, these fuels are higher (often much higher)
From page 243...
... Railroad Engines33 Railroad engines account for 3 percent of transport energy use worldwide and for 2 percent of transport energy use in the United States. Most railroad engines use electricity generated externally or diesel fuel carried on board as their primary energy source.
From page 244...
... In addition, diesel locomotives have become subject to emissions standards and, in some places, to noise standards. Interest is growing in the use of fuel cells to provide auxiliary power for diesel locomotives.
From page 245...
... Although fuel use and emissions are much greater when a locomotive is operating at full power than when it is idling, the potential improvements in both are nontrivial. Factors Influencing the Extent to Which the Potential of a Technology to Reduce Transport-Related Greenhouse Gas Emissions Is Realized One of the most controversial issues in the debate over the use of new technologies to reduce GHG emissions is how effective these technologies will be when incorporated into actual transport vehicles in normal service.
From page 246...
... Figures B-9a and B-9b show similar data for the evolution of vehicle iner tia weight.35 The sharp decline in inertia weight, rather than any radical change in vehicle technology, largely explains the dramatic improvement in new vehicle fleet fuel economy that occurred between the late 1970s and the early 1980s. By the mid-1980s, as new energy-saving technologies began to be introduced in a major way into LDVs, average vehicle weight 35 Inertia weight is defined as the curb weight of the vehicle (including fuel)
From page 247...
... Contribution to Emissions and Assessment of Strategies 247 30 Combined City/Highway MPG (as tested)
From page 248...
... Car and (b) truck 55/45 laboratory MPG versus inertia weight by model year.
From page 249...
... for new model year 2005 cars, trucks, and the total LDV fleet. The next two rows show estimates of what the 2004 fuel economy would have been had the inertia weight and 0–60 acceleration time been what they were in 1981 and 1987.
From page 250...
... government to increase its vehicle energy efficiency standards once they reached their peak in the mid-1980s. Whatever the reason, technological improvements have not automatically translated into improved fuel economy over much of the period shown.
From page 251...
... According to EPA, adoption of this new adjustment factor would result in the 2006 TABLE B-12 Timescales for New Light-Duty Vehicle Power Train Technologies Implementation Phase (years) Penetration Across Market New Vehicle Major Fleet Total Time Vehicle Technology Competitive Productiona Penetrationb for Impact Turbocharged gasoline engine 5 10 10 20 Low-emissions diesel 5 15 10–15 30 Gasoline hybrid 5 20 10–15 35 Hydrogen fuel cell hybrid 15 25 20 55 a Accounts for more than one-third of new vehicle production.
From page 252...
... new vehicle fleet's adjusted fuel economy being reduced from its "as tested" level of 24.6 mpg (9.6 L/100 km)
From page 253...
... The figure illustrates that for transport fuels such as hydrogen and for power train technologies such as fuel cells, the WTT portion totally dominates total transport-related CO2 emissions.
From page 254...
... . (Source: World Business Council for Sustainable Development 2004, Figure 3.1, p.
From page 255...
... FIGURE B-12 Well-to-wheels (well-to-tank + tank-to-wheels) GHG emissions for various fuel and propulsion system combinations (CGH2 = gaseous hydrogen; CNG = compressed natural gas; CO2 = carbon dioxide; DI = direct injection; EU = European Union; FC = fuel cell; FT = Fischer–Tropsch; HEV = hybrid electric vehicle; ICE = internal combustion engine; LH2 = liquid hydrogen; NG = natural gas; RME = rapeseed methyl ester)
From page 256...
... Analysts differ on how each these factors should be treated in "scoring" the WTT emissions characteristics of different transport fuels produced by different processes from different primary energy sources. Therefore, anyone reviewing the literature on this topic can expect to encounter a range of estimates.
From page 257...
... In this final section, the committee attempts to indicate how much transport-related GHG emissions might be reduced given the trends thus far described. As stated at the outset, the fundamental challenge is to reduce the emissions produced per unit of transportation services provided more rapidly than the demand for transportation services grows.
From page 258...
... It was intended merely to help the SMP under stand the impact on GHG emissions from road vehicles if the actions described were taken. This enabled the SMP to compare its results with those of other studies that likewise did not consider technical or economic feasibility in deriving their results.
From page 259...
... Diesel internal combustion engine technology (using conventional diesel fuel) was assumed to have an 18 percent fuel consumption benefit compared with the prevailing gasoline internal 36 A very high proportion of heavy trucks and buses are already diesel powered.
From page 260...
... The fuel con sumption benefit relative to gasoline internal combustion engine technology was assumed to be 36 percent for diesel hybrids, 30 percent for gasoline hybrids, and 45 percent for fuel cell vehicles. From this single-technology assessment, it is evident that even if implemented worldwide, diesels and hybrid internal combustion engines fueled with conventional gasoline and diesel fuel or fuel cells fueled with natural gas–derived hydrogen could no more than slow the growth in road transport CO2 emissions during the period 2000–2050.
From page 261...
... Gasoline hybrids were assumed to consume an average of 30 percent less fuel than current gasoline internal combustion engines, and diesel hybrids were assumed to consume an average of 24 percent less fuel than current diesels.39 Increment 3. Conventional and advanced biofuels: It was assumed that the quantity of biofuels in the total worldwide gasoline and diesel pool would rise steadily, reaching one-third by 2050.
From page 262...
... It also was assumed that fuel cell–equipped vehicles consume an average of 45 percent less energy than current gasoline inter nal combustion engines. Increment 5.
From page 263...
... would be required to return 2050 CO2 emissions from road vehicles to their 2000 level. SUMMARY Any global warming that will be experienced during the next several decades will largely be the result of GHG emissions that have already occurred.
From page 264...
... This means that if transport-related GHG emissions are to be reduced to below their current levels by 2050, steps must be taken now to begin to implement certain of these approaches. REFERENCES Abbreviations BTS Bureau of Transportation Statistics IEA International Energy Agency IMO International Maritime Organization IPCC Intergovernmental Panel on Climate Change UN United Nations
From page 265...
... 2000. Study of Greenhouse Gas Emissions from Ships: Final Report to the International Maritime Organization.
From page 266...
... World Business Council for Sustainable Development.


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