Transportation Sector

Emissions from the transportation sector are growing at a fast rate, and are projected to grow at 2% per year globally [7], driven by developing countries such as China and India, with a combined population of 2.5 billion. It is second only to the power generation sector in importance for the foreseeable future. There are two major technology categories: vehicles and fuels. Technology is currently commercially available capable of major reductions in CO2 emissions per mile traveled, especially for light-duty vehicles. Table 1.3 summarizes the status of major technologies. Again, for each of the two categories, the technologies are listed in the order of their potential impact in 2050 according to IEA's Blue Scenario. The first two rows illustrate that major CO2 reductions could be achieved by incorporating the most efficient internal combustion, chassis, A/C, and tire components. Also, hybrid technology, if optimized for efficiency and utilized with high-efficiency chassis components, can have a substantial positive impact. The main impediment to more robust utilization of these commercially available technologies appears to be higher initial costs for hybrids and buyer preferences that, in North America and more recently in Europe, are for larger, heavier, less-efficient vehicles. To the extent vehicle efficiency can be improved and renewable fuel options developed; major savings can be realized in the transportation sector.

IEA [6, 7] projected that substantial quantities of CO2 will be emitted by gas and coal to liquid processes in what they refer to as the energy transformation sector as demand for oil exceeds global petroleum and natural gas extraction capability. Such processes would produce fuels primarily for the transportation sector. Such processes generating liquid fuels from tar sands and oil shale would be major emitters as well, unless the CO2 is sequestered. In addition to concerns about large CO2 emissions, such processes have the potential of generating large quantities of air and water pollutants and hazardous wastes, yielding serious environmental impacts. However, improvements in vehicle and engine technology to enhance conversion efficiency will lessen the need for such carbon intensive energy transformation processes.

Of all the biomass processes, thermo-chemical processes that can convert biomass to bio-diesel or other transportation fuels using gasification, pyrolysis, or Fischer-Tropsch technology, appear to have the most potential for CO2 mitigation and should be considered for an aggressive RD&D program.

In addition, ethanol production by biochemical processing of biomass offers the potential for large-scale displacement of gasoline. However, breakthroughs will be necessary in the ability to chemically break down major biomass components to sugar for fermentation to produce ethanol.

Hydrogen/fuel cell vehicle technology is still in the development stage, since the fuel cell stack still has limitations in terms of cost and longevity, and hydrogen storage in vehicles remains problematical. Also, EPA [16] and IEA [7] assessments suggest that CO2 savings would not be substantial unless or until the hydrogen could be generated from low-emission, renewable sources.

Despite the serious technical issues, in light of the ultimate potential of fuel cell/ hydrogen and biochemical ethanol, the author believes both are also strong candidates for an aggressive RD&D focus with the aim of breakthrough technology.

Note that for biomass to make significant contributions to climate mitigation, thousands of square miles of dedicated plantations will be necessary. It will be important to ensure that such plantings are configured and maintained to minimize environmental damage by avoiding depletion of aquifers, pollution of surface and groundwater supplies, and degradation of soil quality. It is also necessary to understand the potential for excessive water utilization, especially in water stressed areas. Finally, there must be some level of confidence that such plantations will maintain their productivity as the climate changes in the decades ahead and that adverse impact on food production is avoided.

Note that Chap. 3: Coal and Biomass to Liquid Fuels, evaluates biofuels production technologies and Chap. 6: Mobile Source Mitigation Opportunities, discusses evolving low carbon vehicle propulsion technologies.

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