Air Pollution as a Climate Forcing: A Workshop

Day 3 Presentations

Global Trends in Motor Vehicle Pollution Control

Michael P. Walsh
Independent Consultant, 3105 North Dinwiddie Street, Arlington, VA, U.S.A.

You may download a MS PowerPoint version (9.6 MB) of this presentation.


Introduction. Continuing vehicle air pollution problems have been stimulating innovative pollution control approaches around the world. Steady progress in reducing certain air pollution problems is occurring. For example, in the United States, emissions of all criteria pollutants except oxides of nitrogen are down significantly since 1970 in spite of a more than doubling in vehicle miles traveled and gross domestic product (GDP). Similar reductions are beginning to occur in Europe. Globally, the use of advanced pollution control technology, especially catalysts, has been spreading, as has the use of unleaded gasoline.

However, spurred by continued growth in the vehicle population and lingering air quality problems, as well as newly emerging problems such as toxic emissions and climate modification, the US, Europe, Japan and other countries are pushing for even tighter future controls. Recent major developments include:

  • The European Union has tightened standards on light duty vehicle emissions and fuel quality for 2000 and 2005, broadened coverage (e.g., cold temperature), and imposed low sulfur requirements for diesel fuel and gasoline; Euro 3, 4 and 5 standards for heavy duty trucks and buses, will require advanced NOx and PM post combustion pollution control systems. The auto industry has agreed to a voluntary commitment to reduce CO2 emissions per kilometer driven by 25% by 2008;
  • The California Air Resources Board (CARB) tightened CO, HC, NOx and PM requirements and established principles of fuel neutrality (diesel vehicles meet the same standards as gasoline vehicles) and usage neutrality (light trucks and sport utility vehicles used primarily as passenger cars must meet the same standards as cars); CARB decided that diesel PM is a toxic air contaminant leading to an effort to further reduce PM emissions from existing diesel vehicles;
  • The US EPA, in conjunction with CARB imposed the largest enforcement action in history on the heavy engine industry; EPA adopted stringent national PM and NOx standards for heavy duty trucks and buses and mandated low sulfur diesel fuel to enable the advanced technologies necessary to achieve these requirements;
  • China and India adopted the Euro 1 auto and truck emissions standards and are phasing out the use of unleaded gasoline;
  • Japan tightened the gasoline fueled automobile standards for the first time in twenty years and tightened diesel vehicle requirements; PM filters will be required on all new diesel engines by 2005, and diesel fuel sulfur levels will fall to a maximum of 50 PPM;
  • Taiwan adopted step 4 of its motorcycle control program, effectively banning two stroke motorcycles by 2004.

New Vehicle Emissions Standards. Figure 1 below shows the heavy duty diesel engine NOx and PM emissions standards that will be phased in over the next several years in the EU, Japan and the US. Precise comparisons are difficult because of different test procedures, but it is clear that very significant reductions will occur in all three markets.

-- FIGURE 1 --

It is clear that major countries of the world have concluded that fundamental advances in heavy truck pollution controls and post-combustion technology are both necessary and feasible. A critical precondition of emission reduction, however, will be the introduction of very low or near-zero sulfur levels in fuels.

CO2 Emissions. In the three major markets for light-duty vehicles in the developed world — the United States, Western Europe, and Japan — policies for improving fuel efficiency have evolved in sharply different directions. In the United States, from the mid 1970's to the mid 1980's, the focus was on the Corporate Average Fuel Economy (CAFE) program, whereby annual fuel economy standards were set which each manufacturer was required to comply with on average across its entire fleet of light-duty vehicles. Separate CAFE requirements were put in place for passenger cars and light trucks. In recent years, as fuel prices have dropped and CAFE pressures to improve fuel efficiency have diminished, US new-car fuel efficiency has begun to slip (Figure 2). More recently, the government had emphasized shared research and development (the Partnership for a New Generation of Vehicles and Freedom Car) and tax incentives for certain high-efficiency vehicles (proposed but not yet enacted).

-- FIGURE 2 --

In Europe, the European Car Manufacturer's Association adopted a voluntary agreement pledging to reduce per-vehicle greenhouse emissions by 25% by the year 2008. In Japan, the government has established a series of weight-class fuel economy standards that require an approximately 23 percent improvement in the fuel economy of gasoline-fueled light-duty vehicles by 2010.

Air Pollutants. As a result of adopted pollution control programs, emissions of most pollutants are expected to decline throughout the OECD (Figure 3). With the exception of CO2 and N2O, emissions from road vehicles should be well below 1990 levels beyond 2030.

-- FIGURE 3 --

In non-OECD countries, progress in reducing emissions from new vehicles is also occurring, but at a much slower pace. Most Asian countries have adopted at least the so-called EURO 1 requirements for passenger cars and several have laid out future steps as well (Figure 4).

-- FIGURE 4 --

A critical step in adopting these standards is the phase-out of leaded gasoline, which had been a major impediment to the introduction of the catalytic converters that are needed to comply with even EURO 1 standards. Having moved aggressively on lead, most developing countries are facing an even more difficult fuel challenge, that of lowering sulfur. Sulfur has a similar effect as lead, especially in the context of advanced engines that hold the promise of substantially lower emissions and increased fuel economy. For example, new engine designs such as gasoline direct injection (GDI) can raise the fuel economy of gasoline engines substantially. Similarly, advanced diesel engines can achieve comparable increases in fuel economy compared to current versions. But in doing this, both the advanced gasoline and diesel engines increase emissions of oxides of nitrogen. Advanced NOx adsorbers can eliminate much of this pollution, but sulfur disables them in much the same way that lead poisons the three-way catalyst. Thus, the presence of sulfur in gasoline and diesel fuels effectively bars the path to fuel savings and climate protection as well as low emissions of conventional pollutants. Not surprisingly, therefore, the EU, Japan and the US have taken steps to lower sulfur levels in both gasoline and diesel fuel significantly. However, such low sulfur fuels are not yet spreading rapidly to most developing countries. As a result, it is proving very difficult for these countries to adopt the more advanced standards for cars or trucks.

China, for example, recently tightened its sulfur limits to 800 PPM for gasoline and 2000 PPM for diesel fuel. The EURO 4 standards, which will apply across the EU in 2005, will require fuels with a maximum of 50-PPM sulfur and the EU will soon thereafter limit sulfur levels to 10 PPM. This problem is especially critical in many developing countries because the vehicle populations are expected to grow very rapidly.

Vehicle Growth Trends. Growth in the production of motor vehicles, since the end of World War II has been dramatic, rising from about five million motor vehicles per year to almost 55 million (Figure 5).

-- FIGURE 5 --

North America dominated vehicle production through the 1950's. The first competition came from Europe, and by the late 1960s European production surpassed that of the United States. Over the past two decades the car industry in Asia, led by Japan, has grown rapidly and now rivals those in the United States and Europe. Latin America and Eastern Europe appear poised to grow substantially in future decades. Vehicle production in South America, mainly in Brazil, now exceeds two million units per year. Motorcycle production, not included in Figure 5, has grown rapidly, especially in Asia. China is the world's largest producer by far, building over 10 million motorcycles per year, more than half the world total.

Motor vehicle production is increasing much more rapidly than vehicle scrappage, so worldwide vehicle registrations are sharply accelerating. Europe (including Russia) and North America each have about 35 percent of the world's motor vehicle population, with the remainder divided among Asia, South America, Africa, and Oceania (Australia, New Zealand, and Guam), in that order.

The world's roads in 2000 were supporting about 800 million vehicles, almost 500 million of which are cars and the remainder trucks, buses, motorcycles and scooters. The United States, Japan, and Europe account for the lion's share of motor vehicles, but future growth is expected to be most rapid in Asia and Latin America.

Vehicle population is projected to increase by 50-100% by 2030. As a result, vehicles will continue to apply pressure to the environment. Figure 6 illustrates that emissions of all pollutants will be significantly higher in 2030 than today, unless additional controls on emissions are implemented.

-- FIGURE 6 --

Conclusions. The last 25 years have seen a reduction in pollutants produced by motor vehicles using control technologies and cleaner fuels. However, pollution persists, worldwide production of vehicles is growing, and the quest for cleaner air has hardly begun in many regions. Global emissions standards that meet or exceed the strictest standards now in effect will be needed to substantially reduce threats to human health and global climate in coming decades.

There are outstanding programs to reduce each important pollutant (including greenhouse gases) and to develop advanced technology vehicles, but no country or region has a complete set. Some nations have excellent strategies to reduce particulates; others take CO2 reduction more seriously. It seems appropriate to begin to define a "gold standard" for emissions, greenhouse gases, fuels, and technologies, one that all the large auto-intensive countries can move toward. A significant effort toward defining this gold standard took place in Bellagio, Italy last summer, resulting in a set of 43 principles that could guide future policies. The principles that embody the most specific and urgent calls to action are:

  1. Lead should be immediately banned in all fuels.
  2. Near-zero sulfur (10 ppm or less) should be introduced in all fuels except residual bunker fuel.
  3. Emissions standards worldwide should be based on the best available technology.
  4. Measures to reduce greenhouse gas emissions from all vehicles (including at least 25 percent average reduction for new personal passenger vehicles over the next decade) should be adopted. Mechanisms could include 1) voluntary agreements with manufacturers, 2) fuel efficiency standards, 3) tailpipe greenhouse gas standards, and 4) financial incentives.


  • 1. Bellagio Memorandum on Motor Vehicle Policy: Principles for Vehicles and Fuels in Response to Global Environmental and Health Imperatives, Consensus Document: 19-21 June, 2001, The Energy Foundation

Workshop Homepage * Background
Summaries: Overview, Gases, Aerosols, Tech., Health, Agri./Eco.
Abstracts: Day 1, Day 2, Day 3, Day 4, Day 5 * Participants