Hydrogen has been proposed as a low-polluting alternative transportation fuel. This dissertation analyzes the lifecycle air quality impacts of hydrogen and gasoline use in light duty vehicles, including impacts from fuel production, delivery, and vehicle use. The analysis is conducted for various scenarios in Sacramento, California, for four pollutants: CO, NOx, VOC, and PM10. Three natural gas-based hydrogen supply pathways are considered: onsite hydrogen production via small-scale steam methane reforming (SMR), central SMR production with gaseous hydrogen pipeline delivery, and central SMR production with liquid hydrogen truck delivery. Four gasoline pathway scenarios, as compared to hydrogen pathways, are also investigated in the study. A new method is developed using travel demand model data to estimate air quality impacts of gasoline fleet operations, regression analysis is used to explore the relationship between lifecycle precursor emissions and secondary ozone formation for each hydrogen supply pathway, and a Gaussian atmospheric dispersion model is used to analyze ambient impacts.

The centralized/pipeline hydrogen pathway and the onsite hydrogen production pathway reduce pollution the most. The centralized hydrogen production with liquid truck delivery is the least clean option among the three means of hydrogen supply. The examined gasoline pathway, even with advanced new gasoline vehicles, would lead to much higher ambient concentrations of pollutants than the hydrogen pathways, producing 273 times greater CO, 88 times greater VOC, 8 times greater PM10, and 3.5 times greater NOx concentrations than those caused by the centralized/pipeline hydrogen pathway, assuming the same size vehicle population. The study also estimates the potential impacts of the above hydrogen pathways on secondary ozone air quality. The results indicate that adding a significant number of hydrogen fuel cell vehicles (FCVs) to the region would have a very small impact on secondary ozone pollution; in fact, it does not necessarily increase the peak ozone concentration, and may even cause it to decrease in some cases. The results show that advanced gasoline vehicle technologies significantly reduce air quality impacts of light duty vehicles, but hydrogen vehicle technologies provide still greater benefits, reducing the contribution of light duty vehicles to ambient air pollutant concentrations to near-zero.

Ambient concentrations of pollutants are correlated with emissions, but the contribution to ambient air quality of on-road mobile sources is not necessarily equal to their contribution to regional emissions. This is true for several reasons such as the distribution of other pollution sources and regional topology, as well as meteorology. In this paper, using a dataset from a travel demand model for the Sacramento metropolitan area for 2005, regional vehicle emissions are disaggregated into hourly, gridded emission inventories, and transportation- related concentrations are estimated using an atmospheric dispersion model. Contributions of on-road motor vehicles to urban air pollution are then identified at a regional scale. The contributions to ambient concentrations are slightly higher than emission fractions that transportation accounts for in the region, reflecting that relative to other major pollution sources, mobile sources tend to have a close proximity to air quality monitors in urban areas. The contribution results indicate that the impact of mobile sources on PM10 is not negligible, and mobile sources have a significant influence on both NOx and VOC pollution that subsequently results in secondary particulate matter and ozone formation.

This paper uses a lifecycle approach to analyze potential air quality impacts of hydrogen and gasoline use in light duty vehicles. The analysis is conducted for scenarios in 2005 and 2025 in Sacramento, California for CO, NOx, VOC, and PM10. Three natural gas-based hydrogen supply pathways are analyzed: onsite hydrogen production via small-scale steam methane reforming (SMR), central large-scale hydrogen production via SMR with gaseous hydrogen pipeline delivery, and central hydrogen production via SMR with liquid hydrogen truck delivery. These are compared to gasoline pathways with current and advanced technologies, in terms of lifecycle air quality impacts. The centralized/pipeline hydrogen pathway reduces pollution the most, followed by the onsite hydrogen production pathway and the centralized hydrogen production with liquid hydrogen truck delivery. Gasoline pathway scenarios, even with advanced new gasoline vehicles, would lead to much higher ambient concentrations of pollutants than any of the hydrogen pathways, producing 273 times greater CO, 88 times greater VOC, 8 times greater PM10, and 3.5 times greater NOx concentrations than those caused by the centralized/pipeline hydrogen pathway.

California and other states are pursuing strategies to transition to zero-emission passenger vehicles and trucks, and regulations under development in California will shape multiple states’ transition to zero-emission medium- and heavy-duty trucks. A key factor influencing the pace of these regulations and complementary incentive programs is when battery-electric trucks can be expected to reach cost parity with conventional diesel trucks. Studies on likely purchase cost and total cost of ownership of battery-electric trucks have produced different estimates about these trucks’ current and future competitiveness with diesel trucks. Comparing these studies, their assumptions, and their total cost of ownership estimates can ultimately help policymakers understand the financial impacts fleets will experience in transitioning to zero-emission vehicles, and the likelihood of fleets purchasing zero-emission vehicles independent of regulatory requirements.

Researchers at the University of California, Davis reviewed 10 recent studies of the total cost of ownership of battery-electric trucks, now and in the future, compared to a baseline diesel truck. The researchers did not judge these studies against each other but attempted to derive general findings that are robust across all the studies. This policy brief summarizes the key findings from that research.

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This project aims to assess the current and future performance and costs of battery electric trucking, through reviewing key recent studies in the U.S. and presenting a detailed comparison of their cost modeling scope and coverage. This white paper presents a review of 10 recent studies of the total cost of ownership (TCO) of battery electric trucks (BET), now and in the future, compared to a baseline diesel truck, for the following 3 important types of truck: heavy-duty long-haul trucks, medium-duty delivery trucks, and heavy-duty drayage/short-haul trucks. The researchers break down the studies into their estimates for a range of important cost and operating factors, such as vehicle purchase cost, efficiency, fuel cost, maintenance cost, required range and thus battery pack sizing, and other factors. Of note are differences in major assumptions of studies and variables that are included or excluded from consideration. The authors do not judge these studies against each other but attempt to derive general findings that are robust across studies, areas of significant difference, and areas for further research. Overall, TCO estimates across the studies, for a given truck type, can vary dramatically, though often several studies cluster together. But as this study explores, the differences in TCO link directly to differences in assumptions, parameters and other differences across the studies. The studies vary in important ways that should be taken into account when comparing TCO estimates. Policy makers should consider the context of truck type, truck use and other factors when reading such studies, and pay attention to assumptions. Policies should reflect the wide range of situations that trucks may encounter and avoid assuming a simple average TCO across all situations.

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In this paper we examine the potential air quality impacts of hydrogen transportation fuel from a lifecycle analysis perspective, including impacts from fuel production, delivery, and vehicle use. We assume that hydrogen fuel cell vehicles are introduced in a specific region, Sacramento County, California. We consider two levels of market penetration where 9% or 20% of the light duty fleet are hydrogen fuel cell vehicles. The following three natural gas to hydrogen supply pathways are assessed in detail and compared in terms of emissions and the resulting changes in ambient air quality: (1) onsite hydrogen production; (2) centralized hydrogen production with gaseous hydrogen pipeline delivery systems; and (3) centralized hydrogen production with liquid hydrogen truck delivery systems. All the pathways examined use steam methane reforming (SMR) of natural gas to produce hydrogen. The source contributions to incremental air pollution are estimated and compared among hydrogen pathways. All of the hydrogen pathways result in extremely low contributions to ambient air concentrations of NOx, CO, particulates, and SOx, typically less than 0.1% of the current ambient pollution for both levels of market penetration. Among the hydrogen supply options, it is found that the central SMR with pipeline delivery systems is the lowest pollution option available provided the plant is located to avoid transport of pollutants into the city via prevailing winds. The onsite hydrogen pathway is comparable to the central hydrogen pathway with pipeline systems in terms of the resulting air pollution. The pathway with liquid hydrogen trucks has a greater impact on air quality relative to the other pathways due to emissions associated with diesel trucks and electricity consumption to liquefy hydrogen. However, all three hydrogen pathways result in negligible air pollution in the region.