The main components of automobile exhaust are carbon dioxide (CO2) and water vapor (H2O). Carbon dioxide is the most important anthropogenic greenhouse gas (GHG) and the most significant Greenhouse Gas emitted in the U.S. (with 82-84% of all U.S. emissions). Increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change.
- The European Union is moving towards fuel mandatory CO2 standards and USA has reflected it in the Greenhouse Gas Score.
- There are information, but no mandatory, standards for CO2 limits in vehicle (engine) emissions, excepting some state regulations (i.e. California). See hybrid vehicles.
CO2 mass emission in vehicles is measured in g/km (g/mi * 0.621371192 = g/km).
Low carbon fuel standard
The Californian Governor Arnold Schwarzenegger issued an Executive Order in January 2007 for California adopt a Low-Carbon Fuel Standard (LCFS). The LCFS requires oil refineries to ensure that the mix of fuel they sell in the California Market meets, on average, a declining target for greenhouse gas emissions measured in CO2-equivalent grams per unit of fuel energy sold. By 2020, the LCFS will produce a 10 % reduction in carbon intensity from production and use of transport fuels in California.
- July 1999 SBC Newsletter
- IPCC, "Climate Change 2007: The Physical Science Basis" (PDF). (2.20 MiB) .
- "Gov. Schwarzenegger Issues Directive to Establish World's First Low Carbon Standard for Transportation Fuels". Press Release by Governor Arnold Schwarzenegger. 2007-01-07. Retrieved 2009-04-23.
- "Low-Carbon Fuel Standard Program". California Air Resources Board. Retrieved 2009-04-23.