California proposes carbon dioxide emission standards from light-duty vehicles

15 June 2004

The California Air Resources Board proposed a new regulation to control emissions of greenhouse gases (GHG) from light-duty vehicles, which calls for a 30% GHG emission reduction phased-in from 2009 to 2014. The proposal has been developed under the California bill AB 1493, adopted in 2002, which requires the ARB to develop and adopt, by 1 January 2005, regulations that achieve the “maximum feasible reduction of greenhouse gases emitted by passenger vehicles and light-duty trucks”. It is the first legislation in US history to regulate carbon dioxide and other greenhouse gas emissions from cars and light-duty trucks.

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The proposal covers vehicle climate change emissions comprised of four main components: (1) carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O, not to be confused with the regulated NO_x emissions, which include NO and NO₂) emissions resulting directly from operation of the vehicle, (2) CO₂ emissions resulting from operating the air conditioning system (indirect AC emissions), (3) refrigerant emissions from the air conditioning system due to either leakage, losses during recharging, or release from scrappage of the vehicle at end of life (direct AC emissions), and (4) upstream emissions associated with the production of the fuel used by the vehicle.

The climate change emission standard proposal introduces CO₂-equivalent emission standards (where the other GHG emissions are converted to CO₂ based on their climate warming potential), which are incorporated into the current California LEV program. Accordingly, there would be a CO₂ equivalent fleet average emission requirement for the passenger car/light-duty truck 1 (PC/LDT1) category and another for the light-duty truck 2 (LDT2) category, just as there are fleet average emission requirements for criteria pollutants for both these categories.

The ARB considers the following groups of technologies for meeting of the CO₂ emission standards:

1. Engine, Drivetrain, and Other Vehicle Modifications—valvetrain, transmission, vehicle accessory, hybrid-electric, and overall vehicle modifications designed to reduce engine exhaust CO₂ emissions from conventional vehicles
2. Mobile Air-Conditioning System—air conditioning unit modifications to reduce vehicle CO₂ emissions and refrigerant modifications to reduce emissions of HFC refrigerants, such as HFC-134a
3. Alternative Fuel Vehicles—the use of vehicles that use fuels other than gasoline and diesel to reduce the sum of exhaust emissions and “upstream” fuel delivery emissions of climate change gases
4. Exhaust Catalyst Improvement—exhaust aftertreatment alternatives to reduce tailpipe emissions of CH₄ and N₂O (the latter gas being a common by-product generated in three-way catalytic converters)

High speed direct injection diesel engines are named as a technology that can provide significant CO₂ reductions when compared to conventional gasoline engines. Other engine and drivertrain technologies analyzed by the ARB include valvetrain and charge modifications, variable compression ratio, gasoline direct injection, homogeneous charge compression ignition, and more.

The regulation is expected to be challenged in court by the automotive industry and, possibly, by the federal government. The manufacturers will likely argue that CO₂ emission regulation is in fact a disguised form of more stringent fuel economy standards, which are outside California jurisdiction. On the other hand, the California move will trigger similar actions by other states, many of which are disappointed with the indifference about climate change by the federal government.

California ARB: Proposed regulation | Climate change page | New York Times | Sacramento Bee