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Transport Beyond Oil
Policy Choices for a Multimodal Future
By John L. Renne, Billy Fields ISLAND PRESS
Copyright © 2013 Island Press
All rights reserved.
ISBN: 978-1-61091-043-9
CHAPTER 1
The Role of Transportation in Climate Disruption
Deborah Gordon and David Burwell
The Earth's rapidly warming temperatures over the past several decades cannot be explained by natural processes alone. The science is conclusive: both man-made and natural factors contribute to climate change. Human activities—fossil-fuel combustion in transportation and other sectors, urbanization, and deforestation—are increasing the amount of heat-trapping gases in the atmosphere. These record levels of greenhouse gases are shifting the Earth's climate equilibrium.
Climate impacts differ by sector. On-road transportation—cars and trucks—has the greatest negative effect on climate, particularly in the short term. This is primarily because of two factors unique to on-road cars and trucks: (1) nearly exclusive use of petroleum fuels, the combustion of which results in high levels of the principal climate-warming gases (carbon dioxide, ozone, and black carbon); and (2) minimal emissions of sulfates, aerosols, and organic carbon from on-road transportation sources to counterbalance warming with short-term cooling effects.
Despite its leading role as the largest source of short-term climate forcing, transportation is not shouldering its responsibility in reducing greenhouse-gas emissions. Moreover, the US (and global) transportation situation is especially problematic, given the dependence on oil that characterizes this sector today. There are too few immediate mobility and fuel options in the United States beyond oil-fueled cars and trucks. Moreover, many of the new oils being tapped—oil sands and shale oil, for example—emit more carbon than conventional oil. Clearly this sector, as a major contributor to climate change, should be the focus of new policies to mitigate warming. Government must lead this effort, as the market alone cannot bring about the transition away from cars and oil.
Policy makers need to remember four essential findings when developing new strategies for ensuring that the United States maintains its Copenhagen commitment to reduce greenhouse-gas emissions (17–20 percent below 2005 levels by 2020) while also retaining its leadership position in the global economy. First, on-road (car and truck) transportation is an immediate high-priority target in the short term for reducing greenhouse-gas emissions and mitigating climate change in the United States and around the globe. Second, the transportation sector is responsible for high levels of long-lived carbon dioxide and ozone precursor emissions that will warm the climate for generations to come. Third, the United States (and other nations) must transition quickly to near-zero greenhouse-gas-emission (GHG) cars and trucks, largely through low-carbon electrification for plug-in vehicles. And finally, America's transportation culture must adapt to relying less on fossil fuels through technological innovation, rational pricing, and sound investments that expand low-carbon mobility choices and that fundamentally shift travel behavior.
Climate is a condition that will define the twenty-first century, especially global mobility. There are reasons to be optimistic about the challenges ahead. Climate scientists find that cutting on-road transportation climate-changing and air-pollutant emissions would reduce climate forcing and benefit public health in the near term. Supporting a new, low-carbon, location-efficient, productive, and high-growth economy will be key to thriving in an increasingly competitive global marketplace.
Climate as a Condition
According to the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA), global surface temperatures have risen by 0.6°C since the middle of the twentieth century. The current decade has been the warmest worldwide on record, 0.2°C warmer than the 1990s. According to the US Environmental Protection Agency (EPA), the evidence of the Earth's warming is clear.
The Earth's global average temperature is projected to rise 1.7–3.9°C by 2100, and continue to warm in the twenty-second century. Scientists are certain that human activities are changing the composition of the atmosphere and that increasing the concentration of greenhouse gases will change the planet's climate. But they are still working to better understand the precise mechanisms of climate change, how much or at what rate temperature will increase, and what the likely effects will be.
Still, scientists warn that the floods, fires, melting permafrost and ice caps, torrid heat, droughts, tornadoes, and other forms of extreme weather witnessed in the past couple of years are signs of troubling climate change already under way. As shown in figure 1.1, about two new high-temperature records were set for every one low-temperature record during the 2000s. And the ratio of record high to record low temperatures has increased since the 1960s. Scientific evidence strongly suggests that man-made increases in greenhouse gases account for most of the Earth's warming over the past fifty years.
The National Research Council reports in Climate Stabilization Targets: Emissions, Concentrations, and Impacts of Decades to Millennia that carbon dioxide (CO2) accounts for more than half of the current effect on the Earth's climate. Scientists are more concerned about the climate effects of anthropogenic (man-made) carbon dioxide emissions than any other greenhouse gas. The atmospheric concentration of carbon dioxide is at its highest level in at least 800,000 years.
Carbon dioxide flows into and out of the ocean and biosphere. Man-made carbon dioxide creates net changes in these natural flows, which accumulate over time; such extreme persistence is unique to carbon dioxide among major warming gases. Black carbon and greenhouse gases, such as methane, can also affect the climate, but these changes are short-lived and are expected to have little effect on global warming over centuries or millennia.
But even if carbon dioxide emissions were to end today, scientists expect that changes to Earth's climate that stem from carbon dioxide will persist and be nearly irreversible for thousands of years. Scientists' best estimate is that for every 1,000 gigatonnes (GtC) of anthropogenic carbon emissions, average global temperatures will increase 1.75°C. Therefore, each additional ton of carbon dioxide released into the atmosphere forces warming.
Untangling the Connection Between US Transportation and Climate
Direct Greenhouse Gas Emissions from Transportation
The direct greenhouse-gas (GHG) emissions—carbon dioxide, methane, nitrous oxide, and synthetic halocarbons—can be accounted for in different ways. Carbon dioxide, which has an atmospheric lifetime of at least 100 years, dominates direct GHG emissions from energy-related activities, primarily due to fossil fuel combustion. Regardless of the method chosen, the direct GHG emissions are measured in terms of their carbon dioxide-equivalent (CO2 Eq.) levels based on their relative ability to force climate warming.
Climate researchers suggest that climate science needs to shift from looking at the impact of individual chemicals to examining output by economic sector. Each economic sector emits a unique portfolio of gases and aerosols that affect the climate in different ways over different time frames. The IPCC disaggregates emissions into the self-defined sectors, including energy, industrial processes, solvent and other product use, agriculture, land use, and waste. When the energy sector is further disaggregated and fuel-combustion related emissions are accounted for, the following economic sectors are considered: transportation, industry, commercial, and residential. Transportation edges out industry as the largest source of carbon dioxide emissions and thus as a key driver of climate change.
Each sector's share of direct GHG emissions can be reported with or without electric power generation included. Electric power supplies energy to most of the economic sectors, except for transportation. When broken out, the electric power industry generates more direct carbon-equivalent climate gases overall than any economic sector. Transportation has the second-highest direct GHG emissions, followed by industry, commercial, and residential sectors. The agriculture sector is reported in GHG inventories but is not included here, given its large emission "sinks" that counteract emission sources.
Another way to evaluate direct climate-gas-emission inventories is to distribute electricity-related emissions based on actual use by each economic sector. The transportation sector uses essentially no electricity (actually 0.003 percent) but still has nearly the same direct GHG emissions as industry (about 30 percent).
Air Pollutant Climate Precursor Emissions from Transportation
In addition to carbon dioxide and the other direct GHGs mentioned above, the transportation sector accounts for a significant portion of additional emissions that react to form air pollution (known as precursors). These emissions, detailed below, affect the climate through a variety of complex chemical reactions. The transportation sector is responsible for the majority of air pollutant precursor emissions—a full 85 percent of carbon monoxide (CO), 50 percent of black carbon (BC), 34 percent of particulate matter of 2.5 microns (PM2.5), 55 percent of nitrogen oxides (NOx), and 41 percent of non-methane volatile organic compounds (NMVOC). The utility sector, on the other hand, is responsible for 86 percent of total sulfur dioxide (SO2) emissions. In the United States, on-road transportation is not responsible for SO2 emissions. These figures represent current emission levels from burning conventional oil as the primary fuel source. The increased use of unconventional oil (oil sands, oil shale, ultra-heavy and ultra-deep oils, and coal-to-liquids) is likely to increase direct GHG emissions and air pollution precursors, resulting in an even greater air pollution emission share from tomorrow's transportation sources.
On-road transportation sources emit both NMVOC and NOx in large amounts. These ozone precursors react to form ozone, or what the public often calls smog. Carbon monoxide is produced when carbon-containing fuels fail to fully combust in cars and trucks, and nitrogen oxides (NO and NO2) are created from the nitrogen in the air when burning fossil fuels.
Black carbon (BC) is another air pollutant precursor that acts as a climate agent. BC is rarely measured in its pure form. Instead, it is part of particulate matter, which constitutes a broad array of carbonaceous substances, sometimes referred to as soot. The incomplete combustion of fuel (from transportation and other sources) results in black carbon (and organic carbon), fine particles that are suspended in the atmosphere. These particles are identified by their size: PM2.5 and PM10, or less than 2.5 µm (micrometers) and 10 µm, respectively. Diesel fuel combustion, moving freight in heavy-duty trucks, is the major source of black carbon in the United States, but the EPA does not report black carbon (PM) emissions in its GHG Trends Reports. However, PM is inventoried for air pollution modeling.
Air pollutants and direct greenhouse-gas emissions are intimately connected atmospherically. While regional air pollutants influence climate change, a warmer climate can also exacerbate air pollution. This effect occurs because heat accelerates many air-pollutant reactions. Thus, an increase in global warming precipitates an increase in regional pollution, and vice versa.
Probing the Relationships Between US Transportation and Energy
US Transportation, Energy, and Oil Use
Energy consumption and climate change are inextricably linked; the energy sector in its entirety accounts for 86 percent of total direct GHG emissions. The energy requirements of each economic sector (transportation, industry, commercial, and residential) are responsible for the bulk of all man-made climate-change gases. Transportation represents a significant portion of emissions in the Intergovernmental Panel on Climate Change (IPCC) energy sector.
In 2010, the transportation sector consumed 27.5 quads (quadrillion, or 1015 BTU) of direct energy, mostly in the form of refined liquid fuels, chiefly gasoline and diesel fuel. Transportation's share of energy consumption is similar to its share of greenhouse-gas emissions, at 34 percent. The linkages between energy use and climate gases are evident in all economic sectors.
Unlike other economic sectors, transportation runs nearly exclusively on petroleum, which fuels 94 percent of this sector's energy demands. In 2011, US. mobility (cars, trucks, airplanes) required nearly 14 million barrels per day (mbpd) of oil, out of 18.8 mbpd total US oil consumption. Transportation used three times more oil than did all industries combined. And the transportation sector consumed ten times more oil than the commercial, residential, or utility sectors.
Energy, Oil Use, and Carbon Emissions
There is near parity between energy use and emission of the principal greenhouse gas, carbon dioxide. Essentially all of the carbon contained in fossil fuels, which are hydrocarbons, is converted to carbon dioxide when burned. Solar, wind, hydroelectric, geothermal, wave, and nuclear energy contain no carbon and, therefore, have no direct effect on GHG inventories. Biofuels, on the other hand, contain carbon. Biofuels, a myriad of plant- and waste-based fuels, have a complex relationship to the climate. Their GHG emissions depend on their individual chemistries, how they combust, and even how their feedstocks are grown.
The amount of carbon released into the atmosphere is primarily determined by the fuel's carbon content. Today, the on-road (car and truck) transportation system runs almost exclusively on gasoline and diesel fuels. An average gallon of gasoline, once combusted in air, converts its carbon to 19.4 pounds of CO2 per gallon of gasoline consumed (8.8 kg/gallon). Diesel, the fuel primarily used in heavy-duty trucks and off-road vehicles, has 22.2 pounds CO2 per gallon (10.1 kg/gallon).
Conventional crude-oil-derived fuels are beginning to be replaced by new unconventional oils, such as bitumen (oil sands), tight shale oil, kerogen (oil shale), and coal-to-liquids. Unconventional oils contain as much as triple the carbon as today's crude oil. Moreover, new oils require more energy for their extraction and processing.
Given new policy mechanisms in the longer term, non-oil fuels could replace new oils. There are more than 100 fuel-production pathways and over 70 vehicle and fuel-system pairings, each with its own climate emission impact, as illustrated in fig. 1.2. Again, the carbonization of future fuels will vary, depending on the fuel source and production pathway chosen. Electricity generated by burning coal produces high carbon emissions, but electricity from many renewable and nuclear sources has zero emissions. A comprehensive fuel-cycle analysis offers the best comparison of total emissions. But this calculation must consider all of the carbon in the base fuel resource, whether it yields high-value transport fuels (gasoline, diesel, or jet fuel) or low-value industrial fuels (petroleum coke or residual oils).
(Continues...)
Excerpted from Transport Beyond Oil by John L. Renne, Billy Fields. Copyright © 2013 Island Press. Excerpted by permission of ISLAND PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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