California approves MTBE ban and tightens other gasoline pollutant standards

The California Air Resources Board (CARB) has approved gasoline laws that ban the additive MTBE while tightening standards for two other pollutants and relaxing standards that affect how cleanly gasoline burns.


The new laws are intended to help refiners produce non-MTBE gasoline while preserving current air quality. The State of California is also seeking permission from the US EPA to make the addition of ethanol to gasoline optional. This, it is hoped, will reduce the pressure on refiners to increase gas prices in the light of the new law.

The new rules, known as the Phase 3 gasoline regulation, prohibit the formulation of gasoline with MTBE in California after December 31, 2002.

MTBE (methyl tertiary butyl ether) is an oxygenate added to gasoline to reduce exhaust emissions. However, it is estimated that between 5% and 10% of drinking water supplies in high-oxygenate-use areas contain detectable amounts of MTBE. MTBE is more difficult to remove from water than other components and, in small amounts, renders drinking water unusable (see related story).

In March, California’s Governor, Gray Davis, directed CARB to develop a regulation prohibiting MTBE use, while maintaining air-quality standards.

Cleaner-burning gasoline reduced smog-forming emissions from motor vehicles by more than 15 percent upon its introduction in 1996, equivalent to 3.5 million cars. “Cleaner-burning gasoline was the single most effective measure in this decade to improve air quality,” said CARB Chairman Dr. Alan Lloyd. “Unfortunately, concern over MTBE in water has overshadowed much of that success. These new rules will eliminate environmental risks posed by MTBE while ensuring the air-quality gains achieved with cleaner-burning gasoline will continue into the next century.”

Although some non-MTBE gasoline is currently sold in certain parts of California, some refiners will need up to three years to make plant modifications needed to convert their entire production volume to non-MTBE gasoline. In order to help refiners produce non-MTBE gasoline, the new regulation changes several ARB cleaner-burning gasoline specifications. These include more stringent standards for sulphur and benzene in gasoline and the relaxation of two standards for distillation temperatures – which affect how cleanly gasoline burns. The regulation also adds flexibility to Reid Vapor Pressure standard that controls gasoline’s tendency to evaporate.

With the prohibition of MTBE, ethanol use is expected to become commonplace in California. Federal law currently requires gasoline in Southern California and the greater Sacramento area to contain an oxygenated additive such as MTBE or ethanol. If the law remains in effect, gasoline in those areas would have to contain ethanol beginning in 2003. However, if the use of ethanol is not required by law, refiners would have more options for making cleaner-burning gasoline and allow them to keep gasoline prices down.

In the light of a recent assessment that found that the use of ethanol in gasoline has no significant effect on air quality (see related story), the Davis Administration has asked the US EPA to waive the requirement and make the use of ethanol optional throughout California. A decision from EPA is pending.

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