Cars: No.1. in HC Emissions* - Understanding US and EU Emissions Regulation Programs
Automobiles are the greatest source of hydrocarbon air pollution* in the world today. They emit by-products from fuel combustion and evaporation of the fuel itself. Even with the engine switched off, evaporative losses from fuel, engine and drive train systems represent a high proportion of the total hydrocarbon (HC) pollution from cars. On hot days, evaporative loss has been defined as the No. 1 contributor to total automotive HC emissions.
Most countries already have automotive emissions regulations in place. In the USA and Europe regulations abound, and so do acronyms — from LEV II, ZEV, Partial ZEV, SULEV in the USA to Euro 2, Euro 3 and Euro 4 in Europe, plus CARB, NLEV, EPA and more.
This article reviews the current state of US and EU emissions regulations, and seeks to clarify what may seem a complex and daunting minefield of requirements, phases and challenges.
Automotive emissions are regulated in two ways:
1) Limits are set on the volumes of gaseous pollutants and particulates/smoke, and also on evaporative hydrocarbon emissions.
2) Parameters are set on exhaust toxicity and the performance of exhaust gas after-treatment devices.
Regulated tailpipe components are:
- carbon monoxide (CO)
- total hydrocarbons or non-methane hydrocarbons (THC or NMHC)
- nitrogen oxides (sum of nitrogen oxide and dioxide, NOx)
- particulates (PM)
US regulations differentiate between methane and non-methane hydrocarbons in the exhaust. Methane has low photochemical reactivity and low toxicity, and is therefore not regulated.
Current (Tier I) and future US Federal emissions regulations and California standards for light duty vehicles consist of the following programs and evaporative emissions limits:
Table 1. |
The acronyms are:
- TLEV: Transitional Low-Emission Vehicles
- LEV: Low Emission Vehicles
- ULEV: Ultra-Low Emission Vehicles
- SULEV: Super Ultra-Low Emission Vehicle
- ZEV: Zero Emission Vehicles
New Federal Tier II emission regulations are being phased in from 2004 to 2009 and are being introduced progressively depending on the vehicle classes above.
LEV II, designed by CARB (California Air Research Board), is an aggressive California State emissions reduction regulation requiring light trucks including sports utility vehicles (SUVs), pick-up and small vans from 2004 model year to meet the same emission standards as passenger cars. Diesel powered vehicles are subject to the same standards as gasoline powered vehicles. The durability standards are extended from 100,000 to 120,000 miles.
This CARB program requires that 2% of vehicles produced for sale in California in 2003 must be ZEV compliant, increasing to 10% of vehicles produced for sale in 2005.
The ZEV program was recognized by CARB as too ambitious because zero emissions technology is too expensive for commercialization in the near future (e.g. fuel cell systems that produce only water vapor).
Since a number of new propulsion systems are emerging having extremely low emission characteristics (but not zero), CARB has allocated "partial ZEV credits" to the cleanest technologies that provide near zero emissions. This is intended to support natural gas, fuel-cell and hybrid electric vehicle technologies, and help generate sales volume and economies of scale to enable these developments to compete with diesel and gasoline engines.
LEV II allows manufacturers to meet up to 60% of ZEV requirement through the sales of partial zero emission vehicles: five PZEVs being sold in place of each ZEV required.
PZEV requires that the vehicle meets the new SULEV emission standards for 150,000 miles. In addition manufacturers must extend their performance and defect warranties to 15 years/150,000 miles from the current 10 years/100,000 miles standard for non-PZEV vehicles.
Intermediate between ULEV and ZEV — has also been adopted as part of LEV II.
EPA (the US Environmental Protection Agency), adopted the most stringent California LEV standards when introducing the NLEV (National Low Emissions Vehicle) program. This is intended to harmonize individual state standards across the country. NLEV standards are the precursor of the Federal Tier II regulations.
European Union (EU) emissions regulations for cars and light commercial vehicles are specified in Directive 70/220/EEC. This has been amended several times from Euro 1 to Euro 4 during the period 2000 to 2005. Euro 5 is scheduled for introduction in 2008. Emissions levels have yet to be established, but are expected to equate to the US PZEV/SULEV limits.
Current light-duty evaporative emissions regulations for Europe are:
Table 1. |
Although there are some differences in the driving cycles, comparisons can be made between the US and the European limit values (see Table 1. "Low Emissions Regulations in the USA and Europe", and Table 2. Emissions Limits in Europe vs USA - Comparative Table).
- Tier I limits correspond roughly to Euro 2 limit values.
- California LEV and ULEV are aimed at reducing hydrocarbon emissions. Thus the HC limits are stricter than Euro 3, whereas the NOx limits are at roughly the same level.
- The hydrocarbon limit of Euro 4 corresponds roughly to the hydrocarbon limit of LEV, but the Euro 4 NOx limit is stricter.
China and India have adopted, or are in process of adopting, Euro 2 and Euro 3 limits. Japan has adopted its own Heisei 12 limit which equates to Euro 3, but is expected to introduce new emissions regulations in 2006.
