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California ARB calls for stricter locomotive emission standards

15 April 2017

California Air Resources Board (ARB) chair Mary D. Nichols requested the US EPA take action to adopt more stringent emission standards for locomotives, saying that the move is needed to clean up the air in “high-risk” communities in and around railyards.

The purpose of this request is to accelerate the movement to zero- or near-zero emission locomotives, said the ARB. Proposed emission standards include a NOx limit of 0.2 g/bhp-hr and a PM limit of 0.01 g/bhp-hr, representing emission reductions by 85% and 66%, respectively, below current Tier 4 levels. Newly manufactured locomotives would have some zero-emission mile capability. The new standards would become effective from 2025.

In the formal petition submitted for US EPA Rulemaking to reduce locomotive emissions, Nichols made it clear that recent studies have found that there are significant diesel exposure disparities by race and income among residents living in close proximity to most of the major railyards in California.

To further reduce locomotive emissions, the ARB is requesting the development of updated emission standards, including standards for newly manufactured and remanufactured locomotives. California is requesting that US EPA respond to the petition by Summer, 2017.

US EPA first established locomotive emission standards in 1998, and the standards were last revised in 2008. The current Tier 4 line haul locomotive standard is effective for locomotives manufactured from 2015.

While the Tier 4 standards were originally designed to require aftertreatment technologies—such as SCR catalysts and particulate filters—on locomotive engines, manufacturers were able to meet the Tier 4 emission limits (NOx = 1.3 g/bhp-hr; PM = 0.03 g/bhp-hr) through exhaust gas recirculation, Miller valve timing, increased fuel injection pressure and other in-cylinder technologies. Current Tier 4 line haul locomotives from GE do not use any aftertreatment, and those by EMD use diesel oxidation catalysts only.

Source: California ARB