Tier 3 Low Sulfur Gasoline: How Low Can We Go?

摘要

On May 21, 2013, the United States Environmental Protection Agency (U.S. EPA) proposed new "Tier 3" motor vehicle emission and fuel standards to further control air pollution from motor vehicles across the Unites States. If finalized, this proposal would establish more stringent vehicle tailpipe emissions standards and reduce the allowable sulfur content of gasoline beginning in 2017. The proposal follows the approach of previous standards; coupling new requirements for motor vehicle manufacturers along with requirements for fuel producers. The logic is that a lower gasoline sulfur standard would make emission control systems more effective for both existing and new vehicles, and would enable more stringent vehicle emissions standards. Low sulfur levels in gasoline would reduce sulfur dioxide (SO2) emissions from gasoline combustion. SO2 contributes to acid rain, smog, and particulate matter. Sulfur in gasoline also decreases the lifetime and effectiveness of a vehicle's selective catalytic converters used to control tailpipe emissions. Thus, lowering gasoline sulfur levels helps motor vehicle manufacturers meet the increased control technology effectiveness requirements also included in the proposed rule.