4 July 2006

The US Environmental Protection Agency (EPA) has adopted a final rule to reduce emissions of air pollutants from stationary diesel internal combustion engines. The regulation applies to stationary diesel engines such as those used in power plants and chemical and manufacturing plants to generate electricity, to power pumps and compressors, as well as to engines used in emergencies to produce electricity and to pump water for flood and fire control.

The final standards, known as New Source Performance Standards (NSPS), will limit emissions of NOx, PM, CO, and HC from stationary diesel engines to the same levels required by EPA emission standards for mobile nonroad diesel engines. The rule will reduce emissions gradually from 2005 to 2015, with overall reductions of 90% or more from baseline levels in some cases. The rule will apply to new, modified and reconstructed stationary diesel engines.

The rule will take effect in three increasingly stringent stages:

  1. Before model year 2007, owners or operators can comply by purchasing an emission certified nonroad engine for stationary use. They can also purchase non-certified engines, but in that case they will have to demonstrate compliance with the pre-2007 emission limits.
  2. Beginning in model year 2007, engine manufacturers will be required to certify that all new, modified or reconstructed stationary diesel engines meet the same emission levels that are required for the same size engine and model year for nonroad diesel engines (Tier 1 ... 4), with a few exceptions. Stationary emergency diesel engines will be required to be certified to meet emissions limits through Tier 3 and also Tier 4, however, Tier 4 requirements for them do not require add-on controls.
  3. Beginning with 2011 model year engines, add-on controls will be required to achieve the emission limits for non-emergency engines.

In addition to emission standards, the final rule requires the use of diesel fuel of a maximum sulfur content of 500 ppm beginning October 1, 2007. Beginning October 1, 2010, ultra low sulfur fuel (maximum 15 ppm S) must be used in stationary diesel engines with a displacement of less than 30 liters per cylinder.

Compared with the earlier proposal, the final rule relaxed the proposed emission standards for the largest engines, above 30 liters per cylinder, and exempted them from ultra low sulfur fuel requirements (these engines are subject to the 500 ppm fuel requirements only). The final rule also increased the time allowed for maintenance and testing of emergency engines from 30 to 100 hours per year.

Until now, emissions from stationary engines have not been regulated by federal emission standards (rather, they were subject to numerous state and/or local regulations and permit policies). By 2015, EPA estimates that 81,500 new stationary diesel engines will be subject to the rule.

Source: US EPA (fact sheet | final rule)