Emissions of regulated pollutants from in-use diesel back-up generators

Recent power outages have highlighted the need for reliable alternatives to the power grid such as diesel back-up generators (BUGs). As many BUGs are operated in close proximity to populations, there is a need for accurate emissions measurements from these units. This paper reports regulated emissions for diesel BUGs of varying model year, engine technology and manufacturer in the 60–2000 kW size and provides the largest emissions database for these engines. The average emission factors for oxides of nitrogen (NOx) were determined to be approximately 41% and 47% lower than EPA's estimates in AP-42 for small and large BUGs, respectively. Average particulate matter (PM) emission factors were approximately 83% and 50% lower than AP-42 estimates for small and large BUGs, respectively. All BUGs tested had lower emissions than used in EPA's AP-42 emissions inventory for NOx and PM. Results indicate that decreases in NOx emission rates for BUGs paralleled the non-road and on-road emission standards. Minimal variation was noted for three engines of the same family and model year but with different hours of operation.