The History of Gasoline Emissions Reduction

Emissions regulations and the usage of emissions reduction technologies have evolved at different rates throughout the world. Generally, The United States and western European countries have been forerunners in these areas.

In the United States, the Clean Air Act of 1970 granted the United States Environmental Protection Agency (EPA) authority to regulate motor vehicle pollution, and the Agency’s emission control policies have become progressively more stringent since the act’s inception. EPA standards dictate how much pollution vehicles may emit, but manufactures decide how to achieve compliance with the agency’s standards. Emissions reductions in the early 1970’s occurred primarily because of fundamental improvements in engine design, the addition of charcoal canisters to collect hydrocarbon vapors, and the installation of exhaust gas recirculation valves to reduce nitrogen oxides.

The advent of [two-way] catalytic conversion technology in 1975 significantly reduced hydrocarbon and carbon monoxide emissions. The use of catalytic converters also provided an enormous ancillary environmental benefit. Because lead contained in fuel irreversibly damages catalysts, 1975 initiated the widespread introduction of unleaded gasoline. The reduction and subsequent elimination of lead from gasoline resulted in dramatic reductions in ambient lead levels and alleviated many lead-related environmental and human health effects.

The next major milestone in vehicle emission control technology came in 1980-81. These years witnessed the introduction of one of the most commonly used emissions systems for gasoline powered vehicles—one that falls into the exhaust-gas after-treatment category—the “Three-Way Catalyst”. These systems convert carbon monoxide and hydrocarbon emissions into carbon dioxide and water. And they also reduce nitrogen oxides to elemental nitrogen and oxygen. Additionally, three way catalysts employ on-board computers and oxygen sensors which help optimize systems’ reduction efficiencies.

In response to increasingly stringent emissions standards, manufacturers continue to equip new cars with ever more sophisticated emission control systems. The enduring evolution of emissions reduction technology has occurred in three principle arenas: 1) engine design, 2) fuel related technologies, and 3) exhaust gas after-treatment (12).

In the arena of diesel emission reduction, Diesel Particulate Filters (DPFs) and Diesel Oxidation Catalysis (DOCs) have gained widespread use in locations where their application is not impeded by excessively high fuel sulfur concentrations. These devices can significantly reduce the amount of Diesel Particulate Material (DPM) that is emitted into the environment.

As previously mentioned, the elimination of lead from gasoline in the mid-seventies and early-eighties helped to significantly reduce the consequential severity of vehicular emissions. Intense international attention is now focused upon efforts to reduce or eliminate sulfur from gasoline and diesel fuels. The elimination of sulfur from diesel will facilitate the ubiquitous employment of catalytic technologies in gas and diesel applications. Because sulfur in diesel increases SOX emissions—which are known to oxidize in catalytic devises and combine with moisture to create sulfuric acid (H2SO4)—the elimination of sulfur will mitigate environmental consequences associated with sulfuric acid, i.e. acid rain which causes acidification of waterways, crop damage, etc.

In the U.S., vehicle emissions were subjected to further reductions by provisions of the 1990 Amendments to the Clean Air Act. The Amendment’s mobile source provisions required: increased durability, improved control of evaporative emissions and computerized diagnostic systems that identify malfunctioning emission controls (13).

Other nations, acting alone or in concert have also instituted progressive emissions guidelines and legislation. Some of the more widely known include the United State Clean Air Act, the European Commission’s “Euro Standards”, Switzerland’s VERT Standards and the Kyoto Protocol to the United Nations Framework Convention on Climate Change. While, many countries have developed their own standards, or are participating in “cross-regional programs”, others countries such as Brazil have chosen to adopt the standards of other nations. Brazil, for example, plans to achieve compliance with “Euro 4” standards by 2009.

Efforts to clean the environment through emissions reductions strategies continue to evolve. Several non-governmental and supranational organizations which serve as valuable sources of information include:

The Clean Air Initiative

  • The Clean Air Initiative
  • The National Resource Defense Counsel
  • United Nations Environment Program
  • The UN Partnership for Clean Fuels & Vehicles