Atmospheric Environment 41 (2007) 5647–5658 Regulated emissions from biodiesel fuels from on/off-road applications Thomas D. Durbin a,Ã , David R. Cocker III a , Aniket A. Sawant a , Kent Johnson a , J. Wayne Miller a , Bruce B. Holden b , Norman L. Helgeson b , Jason A. Jack c a Department of Chemical and Environmental Engineering, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92521, USA b Naval Facilities Engineering Service Center, Port Hueneme, CA, USA c US Army Aberdeen Test Center, Aberdeen Proving Grounds, MD, USA Received 7 November 2006; received in revised form 23 February 2007; accepted 28 February 2007 Abstract This research is one of the largest studies of biodiesel in both on-road and off-road uses. The testing was conducted for the military and encompassed a wide range of application types including two medium-duty trucks, two Humvees, a heavy heavy-duty diesel truck, a bus, two stationary backup generators (BUGs), a forklift, and an airport tow vehicle. The full range of fuels tested included a California ultra-low sulfur diesel (ULSD) fuel, different blend ratios of two different yellow-grease biodiesels and one soy-based biodiesel, JP-8, and yellow-grease biodiesel blends with two different NO x reduction additives. The B20-YGA, B20-YGB, and B20-Soy did not show trends relative to ULSD that were consistent over all applications tested. Higher biodiesel blends were tested on only one vehicle, but showed a tendency for higher total hydrocarbons (THC) and carbon monoxide (CO) emissions and lower particulate matter (PM) emissions. The JP-8 showed increases in THC and CO relative to the ULSD. r 2007 Published by Elsevier Ltd. Keywords: Emissions; Biodiesel; Diesel; Vehicles 1. Introduction The reduction of tailpipe emissions and petro- leum-based fuel consumption can provide consider- able benefits in transportation applications. The use of renewable fuels also has important implications for the reduction of greenhouse gas inventories. In federal fleets, the use of alternative fuels has been mandated for several years under the Energy Policy Act. Biodiesel has shown considerable promise in meeting these requirements. Biodiesel is commer- cially available, compatible with existing vehicle and fuel systems, and can be produced from renewable and domestically available feedstocks. The Depart- ment of Defense (DoD) authorized biodiesel use in 1999 and is the largest user of biodiesel in the United States today, with over 5 million gallons of B20 (20% biodiesel) used in 2005. Biodiesel has been extensively studied in the past to quantify its emissions characteristics. The US Environmental Protection Agency (EPA) conducted ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter r 2007 Published by Elsevier Ltd. doi:10.1016/j.atmosenv.2007.02.048 Ã Corresponding author. Tel.: +1 951 781 5794. E-mail address: durbin@cert.ucr.edu (T.D. Durbin).