NONROAD MOBILE Emissions Modeling Alison K. Pollack ENVIRON International Corporation Golden Gate Plaza 101 Rowland Way, Suite 220 Novato, CA 94945 Christian E. Lindhjem U.S. Environmental Protection Agency Assessment and Modeling Division 2565 Plymouth Road Ann Arbor, MI 48105 Paper proposed for presentation at The Emission Inventory: Planning for the Future October 28-30, 1997 Research Triangle Park, North Carolina ABSTRACT This paper describes the EPA nonroad mobile source emissions model now under development. The NONROAD model, as it is called, will be released in a beta version in early 1998, and then in final version in late summer 1998. The current working version of the model estimates emissions from nonroad agricultural, construction, industrial, recreational marine, and lawn and garden equipment; emissions from commercial marine, locomotive, and aircraft equipment may be added before the final release of the model if resources are available. Engine types covered by the model include two- and four-stroke gasoline and diesel engines, and CNG/LPG engines. These engines are used in both rural and urban areas, and their operation can range from primarily steady-state (e.g., generators) to extremely transient (e.g., backhoes or other construction equipment). Modeling emissions from the nonroad sector is especially challenging because of difficulties in determining in-use population, activity, load, and emission rates. The in-use population for nonroad engines is difficult to determine because the equipment is not registered or permitted as it is for highway mobile or stationary sources. In this paper, the capabilities, structure, basic calculations, input data required, and output of the model will be described. The paper will also include a discussion of the current sources of in-use population estimates, equipment age distribution, emission factors, activity estimates, growth estimates, and geographic and temporal allocation factors.