Emission standard

Emission standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emission standards focus on regulating pollutants released by automobiles and other transport vehicles, but they can also regulate emissions from industry, power plants, small equipment such as lawn mowers and diesel generators. Frequent policy alternatives to emission standards are technology standards (which mandate the use of a specific technology) and emission trading.

Standards generally regulate the emissions of NO_x, particulate matter (PM) or soot, carbon monoxide (CO), or volatile hydrocarbons. The main components of automobile exhaust, carbon dioxide (CO₂) and water vapor (H₂O), have so far not been regulated by emission standards, but the European Union is moving towards mandatory CO₂ standards and USA has reflected it in the Greenhouse Gas Score.

EPA and State standards in the U.S.A. (transport vehicles)

In the United States, emissions standards are managed by the Environmental Protection Agency (EPA) as well as some state governments.

Some of the strictest standards in the world are enforced in California by the California Air Resources Board (CARB), following the California AB 1493.

Currently, vehicles sold in the United States must meet "Tier II" standards that went into effect in 2004. "Tier II" standards are currently being phased in—a process that should be complete by 2009. Within the Tier II ranking, there is a subranking ranging from BIN 1-10, with 1 being the cleanest (Zero Emission vehicle) and 10 being the dirtiest (Hummer). The former Tier 1 standards that were effective from 1994 until 2003 were different between automobiles and light trucks (SUVs, pickup trucks, and minivans), but Tier II standards are the same for both types.

A common measurement system for American standards is the somewhat confusing mixed-standard unit of gram per mile.

There are several ratings that can be given to vehicles. A certain percentage of the cars produced by major manufacturers must meet these different levels in order for the company to sell their products in affected regions. Tier 1 has been the baseline used. Beyond Tier 1, in increasing stringency, there are:

TLEV – Transitional Low Emission Vehicle
LEV – Low Emission Vehicle
ULEV – Ultra-Low Emission Vehicle
SULEV – Super-Ultra Low Emission Vehicle
ZEV – Zero Emission Vehicle

The last category is largely restricted to electric vehicles and hydrogen cars, although such vehicles are usually not entirely non-polluting. In those cases, the other emissions are transferred to another site, such as a power plant or hydrogen reforming center, unless such sites run on renewable energy. However, a battery-powered electric vehicle charged from the California power grid will still be up to ten times cleaner than even the cleanest gasoline vehicles over their respective lifetimes.

The above standards are being made even more stringent. Tier 2 variations are appended with "II", such as LEV II or SULEV II. There are other categories that have also been created.

ILEV – Inherently Low-Emission Vehicle
PZEV – Partial Zero Emission Vehicle
AT-PZEV – Advanced Technology Partial Zero Emission Vehicle
NLEV – National Low Emission Vehicle

PZEVs meet SULEV emission standards, but in addition have zero evaporative emissions and an extended (15-year/150,000 mile) warranty on their emission-control equipment. Several ordinary gasoline vehicles from the 2001 and later model years qualify as PZEVs; in addition, if a PZEV has technology that can also be used in ZEVs like an electric motor or high-pressure gaseous fuel tanks for compressed natural gas (CNG) or liquified petroleum gas (LPG), it qualifies as an AT-PZEV. Hybrid electric vehicles like the Toyota Prius can qualify, as can internal combustion engine vehicles that run on natural gas like the Honda Civic GX. These vehicles are called "partial" ZEVs because they receive partial credit in place of ZEVs that automakers would otherwise be required to sell in California.

The Greenhouse Gas Score reflects the exhaust emissions of carbon dioxide (CO2), a greenhouse gas, and one of the biggest by-products of engine combustion. The Greenhouse Gas Score allows you to compare the expected amount of greenhouse gas emissions for different vehicles. The scoring is from 0 to 10, where 10 is the best because it represents the lowest amount of greenhouse gases.

European standards

''Main article: European emission standards.

The European Union has its own set of emission standards that all new vehicles must meet. Currently, standards are set for all road vehicles, trains, barges and 'nonroad mobile machinery' (such as tractors). No standards apply to seagoing ships or airplanes. Find below the standards applicable to heavy duty engines to be fitted in vehicles with a gross weight over 3.5 metric tonnes. The tiers are:

Euro 0 (1988-1992) limits emissions to 12.3 g/kWh CO, 2.6 g/kWh HC, 15.8 g/kWh NOx
Euro I (1992-1995) limits emissions to 4.9 g/kWh CO, 1.23 g/kWh HC, 9.0 g/kWh NOx, 0.4 g/kWh particles
Euro II (1995-1999) limits emissions to 4.0 g/kWh CO, 1.1 g/kWh HC, 7.0 g/kWh NOx, 0.15 g/kWh particles
Euro III (1999-2005) limits emissions to 2.1 g/kWh CO, 0.66 g/kWh HC, 5.0 g/kWh NOx, 0.1 g/kWh particles
Euro IV (2005-2008) limits emissions to 1.5 g/kWh CO, 0.46 g/kWh HC, 3.5 g/kWh NOx, 0.02 g/kWh particles
Euro V (2008-2012) limits emissions to 1.5 g/kWh CO, 0.46 g/kWh HC, 2.0 g/kWh NOx, 0.02 g/kWh particles

Currently there are no standards for CO₂ emissions. The European Parliament has been suggested to introduce mandatory CO₂ emission standards European Parliament resolution on "Winning the Battle Against Global Climate Change", 16 November 2005 to replace current voluntary commitments by the automanufacturers and labelling.