|2010 engines emissions reduction relative to 2010, 2007, and 2004 US emission standards. Source: CRC. Click to enlarge.|
A rigorous emissions testing of modern heavy-duty diesel engines in the US has demonstrated a greater than 94% reduction in the levels of nitrogen dioxide (NO2 - an important contributor to ozone smog), and substantial reductions in all other pollutants, even when compared to engines first marketed to meet 2007 standards, according to a study released today by the Coordinating Research Council (CRC).
For a number of the most important pollutants, levels were substantially lower than required by regulations. The study, the Phase 2 Report of the comprehensive Advanced Collaborative Emissions Study (ACES) (earlier post), found that emissions of NO2 and other nitrogen oxides—which can have direct health effects and contribute to the formation of smog—were approximately 61% below the 2010 EPA standard and 99% lower than in 2004 engines. These reductions came while emissions of fine particles were also 92% lower than the 2010 standard 99% lower than 2004 emissions.
Emissions of carbon monoxide and hydrocarbons were also significantly below required 2010 levels: 97% and more than 99.9%, respectively.
The Phase 2 ACES study was conducted by the Southwest Research Institute in San Antonio, Texas, under the oversight of the CRC. Investigators tested heavy-duty diesel engines from the three major manufacturers of these engines (Cummins, Detroit Diesel, and Volvo), and subjected them to well-established federal test procedures, and to a much more rigorous 16-hour operation cycle designed especially for ACES.
All the engines were equipped with after-treatment devices to reduce the emissions of particulate matter as well as oxides of nitrogen. They were tested on multiple repeats of these cycles, and measurements of more than 300 regulated and unregulated air pollutants were made in accordance with the highest laboratory standards.
ACES is a multi-party five year initiative to test the emissions and health effects of new technology diesel engines to document the improvements that have been made and to ensure that there are no unintended emissions from this new technology. The study is being undertaken by the Health Effects Institute (HEI)3 and the CRC with support from a wide range of government and private sector sponsors, including the US Department of Energy, US Environmental Protection Agency, California Air Resources Board, Engine Manufacturers Association, American Petroleum Institute, and manufacturers of emission control equipment.
Overall design and management of ACES—and all laboratory testing of health effects—is being undertaken under the aegis of HEI. All emissions characterization for ACES is being overseen by CRC.
The Health Effects Institute is an independent, non-profit research institute funded jointly by government and industry to provide credible, high quality science on air pollution and health for air quality decisions.
Background. In 2010, EPA’s stringent NOx limit of 0.20 g/hp-hr became fully enforceable; the NOx emissions limit decreased from an average level of 1.2 g/hp-hr between 2007 and 2009 to a level less than or equal to 0.20 g/hp-hr in 2010.
To comply with the 2010 NOX limit, on-highway heavy-duty engine manufacturers utilized a urea-based selective catalytic reduction (SCR) catalyst in engine exhaust placed downstream of a diesel oxidation catalyst (DOC) and a catalyzed diesel particulate filter (DPF) used for particulate matter (PM) emissions control.
The engine manufacturers devoted substantial efforts to calibration of the urea dosing and mixing, SCR catalyst formulation, and engine control to achieve the desired NOx reduction while maintaining a controlled level of ammonia slip using an ammonia oxidation (AMOX) catalyst downstream of the SCR catalyst.
Improvements were also made in PM emissions control, eliminating the need for active regeneration (onboard cleaning via exhaust fuel injection upstream of DOC) of the DPF during ACES Phase 2 testing, compared to the several regeneration occurrences with the 2007 technology engines tested in ACES Phase 1.
CRC Report: ACES Phase 2. Phase 2 Of The Advanced Collaborative Emissions Study.