Air quality and environmental impacts of alternative vehicle technologies in Ontario, Canada

Abstract

This study is focused on the province-wide emissions in Ontario, Canada and urban air pollution in the city of Toronto. The life-cycle (LC) impacts of utilizing alternative fuels for transportation purposes is considered in terms of six major stressors for climate change, acidification and urban air quality. The vehicles considered are plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs) and fuel cell plug-in hybrid electric vehicles (FCPHEVs). Modeling of the penetration rates for these types of vehicles has been completed based on the maximum base-load capacity of Ontario's electricity grid to accommodate the generation of hydrogen and charging of vehicles using grid electricity. Results show that the reduction in greenhouse gas emissions from adoption of PHEVs or FCVs will exceed 3% of the current emissions from the transportation sector in Ontario while FCPHEVs may achieve almost twice this reduction. All vehicles exhibit similar impacts on the precursors for photochemical smog although the province-wide effects differ significantly.

Introduction

The economies of the developed world are increasingly expanding to include “green” technologies and processes that take into account the social, environmental and economic consequences of each decision. Western society as a whole is demanding that the products and services that they use are increasingly less harmful to human health and to the environment. The transportation industry has made significant advances in fuel efficiency of the vehicle power trains and reduction of emissions in the past decades, but more is expected from this sector. As the price of gasoline rose in combination with this societal “green shift”, vehicle companies have commenced production of hybrid electric vehicles and other fuel-efficient vehicle types. The impetus of this shift was to supply consumers with vehicles that would decrease their ecological footprint as well as reduce the cost associated with purchasing fuel. In recent years, energy security has also become a driving force for change in fuel type. One of the societal concerns often overlooked is the impact of alternative-fuel vehicle usage on the air quality in the urban environment. It is the purpose of this study to assess the impact on air quality stemming from the operation of alternative-fuel vehicles in urban environments.

While several studies have based the comparison of alternative fuel vehicles (AFVs) on least-cost comparisons or other economic metrics [1], [2], [3], [4], [5], this study is purely focused on air pollution. The effects on overall air quality are considered with respect to global warming potential and acidification. The special focus of this study is on urban air quality as it can be of major concern in large centres of population.

This study is concentrated on the province of Ontario and specifically the city of Toronto for two major reasons. The primary reason for this focal point is that Ontario represents the most highly-populated province in Canada which naturally leads to a higher level of concern from the increased number of individuals affected. The second reason is that urban air quality in Toronto is specifically an area of concern due to the estimated fatalities in this city specifically. Traffic volumes in smaller cities would induce less concern as the concentration of urban air pollutants is directly proportional to the emissions from vehicle traffic. In addition, the data availability for Ontario in general and Toronto specifically is more widely available due to the concerns mentioned above and to the increased government resources attributed to gathering and analyzing this data.

The alternative-fuel vehicles considered for this analysis are fuel cell vehicles, plug-in hybrid electric vehicles and fuel cell plug-in hybrid electric vehicles. The reason that these vehicle types were chosen is that they represent the most promising technologies for partially replacing gasoline and diesel in traditional vehicles. The transition of vehicle drive trains will begin with electrification of the vehicle drive train which allow for hybridization with electric motors. Then these hybrid electric vehicles (HEVs) can make modest gains in fuel efficiency mainly through the use of regenerative braking. Once the drive train is completely electrified the power train can be composed of a combination of batteries and some type of range extender technology (e.g. gasoline or diesel engine, or fuel cell) to recharge the batteries onboard or provide electricity in parallel with the batteries [6]. This differs from the methodology considered by Thomas [7] as this work includes electric vehicles with range extenders and is not a comparison between FCVs and battery-electric vehicles (BEVs) considered by Thomas [7]. FCV in this case refers to compressed gaseous hydrogen as the technology is simpler and would likely be commercialized before options that use liquefied hydrogen as the fuel. The FCPHEV would operate as a normal plug-in vehicle except that the energy supply for the charge-sustaining mode would be supplied by hydrogen fuel cells and not by gasoline. Other AFVs could also be compared on an emissions-per-distance basis but the interest of this study was on the impact that could be achieved through greater utilization of base-load electricity. As such, this study focuses on the near term transition technology of the PHEV which will use electricity to recharge batteries, and the FCV which use base-load electricity to generate hydrogen. This analysis also represents the most promising near term technology transition to PHEV, and the technology with the greatest potential for emissions reduction in the long term (FCV). The transition between the near term adoption of PHEVs to the eventual transition to FCVs is examined by Suppes [8].

Thomas [9] states that FCVs are the only vehicle technology that has potential to virtually eliminate problem relating to urban air pollution. In this study, the effects of vehicles on urban air pollution are considered similarly to the work of Thomas [9]; however, the limitations of the Ontario's electricity grid are incorporated into the calculations. As such there are some notable differences in the environment, assumptions and potentially the results. Specifically, the Ontario grid makes much less use of coal as a generation source than the system Thomas [9] assumed, and greater use of nuclear and renewable (mainly hydro) sources. Also this study assumes that only surplus base-load power is used for the transportation sector, and thus represents a more feasible transition scenario for the transportation sector, as the electricity is available and not used at this time.

The emissions from manufacturing the vehicles are not included as part of this study at this time and will be considered in future analyses; however, these types of vehicles also have increased emissions resulting from the manufacturing process would likely have less impact on urban air emissions and likely be insignificant for this study where the main focal point is urban air quality. It should be noted that preliminary estimates for the production of both types of AFV considered in this study show that current production methods of traditional vehicle production emit less pollution and consume less energy than current methods of AFV production. These preliminary results would also be affected if centralized, large-scale production of AFVs were to exist on the same level as traditional vehicle manufacturing.

Developing infrastructure has been considered by several authors for Southern California [1], [2], [10] with special focus again on the economics of its development. It is assumed for this study that the distribution of hydrogen is available and thus the construction of a distribution network is not included in the results of this study.

Toronto Public Health estimates that the number of annual deaths in Toronto from urban air pollution is 1700 annually [11]. Estimates from the Ontario Medical Association (OMA) [12] and Health Canada [13] estimates the number of fatalities is 5800 throughout Ontario. These deaths attributed to air pollution are most predominantly from lung diseases but air pollution also partakes in increasing the rate of atherosclerosis which is a contributor to heart disease and stroke [11].

The life cycle of hydrogen and its impacts have been studied previously [14], [15] in an attempt to characterize the effect of hydrogen production in terms of life-cycle emissions and sustainability. The use of hydrogen for a transportation fuel has also been considered but comparisons between hydrogen and other transportation fuels are only now being developed [16], [17]. It is important to consider hydrogen as a transportation fuel relative to other fuels in order to visualize the consequences related to its mainstream adoption as a transportation fuel. PHEVs have also been studied from a life-cycle perspective by several authors [18] and this study is intended to compare these different types of AFV using a realistic basis of penetration and adoption.

Overall and urban emissions from AFVs were both considered to be important since overall emissions may affect climate change, acidification and other effects related to generalized emissions into the air. Urban emissions were considered specifically for the purposes of analyzing a possible decrease in fatalities caused by poor urban air quality.

Photochemical smog is particularly an issue when considering the large volumes of traffic that occur during the rush-hour times in the greater Toronto area (GTA). Due to the location and specifics of Toronto, the smog formation in this region is limited by the amount of nitrogen oxides (NO_x) in the air. According to the empirical kinetic modeling approach to photochemical smog, a reduction in NO_x would yield a much more pronounced effect on the reduction of photochemical smog than would an even greater reduction in volatile organic compounds (VOCs).

When considering urban air emissions, four major pollutants and one additional stressor are considered. Two classifications of particulate matter, one having diameter less than 10 microns (PM₁₀) and one of diameter less than 2.5 microns (PM_2.5), are generally considered to be the most harmful to human health and are also the eventual products from some other pollutants [19]. This small particulate matter is capable of penetrating deep into the lungs, causing irritation and not being rejected by natural human mechanisms [19]. VOCs and NO_x react with sunlight to form photochemical smog which is generally the largest contributor to urban air pollution in industrialized countries. Reducing the synthesis of photochemical smog is a top priority for individuals involved with addressing urban air quality in major cities. In Athens, Greece and Beijing, China among several other cities that have made similar laws, institution of bi-daily driving was initiated in an attempt to partially curb the creation of photochemical smog. Sulfur oxides are the remaining stressor and are generally viewed to be more of a significant factor with regard to acidification than urban air pollution; nevertheless, it does contribute to producing aerosols and particulate matter in the troposphere.