APPENDIX C

Nonroad Sources

Bureau of Air Quality

Department of Environmental Protection
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Nonroad Sources

All methodologies described below are taken directly from the November 2013 United States 

Environmental Protection Agency (EPA) document, “2011 National Emissions Inventory,”

Version 1 Technical Support Document, which can be found at:

http://www.epa.gov/ttn/chief/net/2011nei/2011_neiv1_tsd_draft.pdf. 

Starting with 2008, nonroad consists of nonroad engines and equipment. Aircraft engine 

emissions occurring during Landing and Takeoff operations and the Ground Support Equipment 

and Auxiliary Power Units associated with the aircraft are included in the point data category at 

individual airports. Emissions from locomotives that occur at rail yards are also included in the 

point data category. In-flight aircraft emissions, locomotive emissions outside of the rail yards, 

and commercial marine vessel emissions (both underway and port emissions) are included in the 

nonpoint data category.

The data files used for this document were obtained as a download from the EIS gateway. The 

SMOKE files from the gateway were imported into the EMF system in order to apply the 

necessary data filters and summer day averages.

Nonroad Equipment – Diesel, Gasoline and Other

Although “nonroad” is used to refer to all transportation sources that are not on-highway, these 

EIS sectors and this section address nonroad equipment other than locomotives, aircraft, or 

commercial marine vehicles.

Sector Description

The U.S. Environmental Protection Agency’s (EPA) NONROAD model 

(http://www.epa.gov/otaq/nonrdmdl.htm) was used to estimate emissions from all other nonroad 

source categories. These categories include nonroad engines and equipment, such as: lawn and 

garden equipment, construction equipment, engines used in recreational activities, portable 

industrial, commercial, and agricultural engines.

The National Mobile Inventory Model (NMIM) (http://www.epa.gov/otaq/nmim.htm) was 

EPA’s consolidated mobile emissions estimation system that allowed EPA to produce nonroad 

mobile emissions in a consistent and automated way for the entire country for the year 2011. 

EPA encouraged agencies to submit NMIM inputs to the EIS for the 2011 NEI for inclusion in 

the National County Database (NCD). The NCD contains all the county-specific information 

needed to run NONROAD. Although NMIM was designed to also estimate onroad emissions, it 

is no longer used and EPA now uses the MOVES model. Eventually MOVES will be revised to 

also estimate nonroad emissions and NMIM will be retired.

NMIM estimates monthly emissions for total hydrocarbons (THC) used to determine VOC, 

NOX, and CO, as well as calculating monthly fuel consumption. All of the input and activity 

data required to run NMIM are contained within the NCD, which is distributed with the model. 
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EPA-Developed NMIM-Based Nonroad Emissions Data

EPA uses the activity data within NMIM as a basis for air quality modeling, rule development, 

international reporting, air quality trends analysis, and other activities. To that end, a single 

NCD for the 2011 NEI was developed to represent, as accurately as possible, the activity data 

upon which the 2011 NEI emissions are based. This newly developed NCD, named 

NCD20130531_nei2011v1, was created using the approach discussed in the following sections.

Like the emissions, the updates to the NCD were determined using a hierarchy decision model, 

where defaults were replaced with S/L-supplied data. The exception to the hierarchy decision 

model is that EPA-supplied fuel and meteorological data were used for all 2011 NMIM modeling 

runs, as explained below. A copy of NCD20130531_nei2011v1 which includes all the statesupplied updates, as well as EPA’s fuel and meteorological data is named NCD20130531 and is 

provided in the same zip file as the NCD used for the NEI. The zip file name is 

2011nei_supdata_nonroad.zip, and it can be accessed at:

ftp://ftp.epa.gov/EmisInventory/2011v1/doc

The development of the NCD used for the 2011 NEI is explained in the following sections.

4.5.4.1 Default NCD

The default 2011 NCD, NCD20130531_nei2011 is available at:

ftp://ftp.epa.gov/EmisInventory/2011v1/doc, in the zip file “2011nei_supdata_nonroad.zip” and 

is based upon NCD20101201a.1EPA updated fuel and meteorological data for inclusion in the 

new 2011 NCD.

Summary of Quality Assurance Methods

After the NMIM completed its execution, the resulting output databases were checked to ensure 

that no error messages were created during the runs for each geographical area. Furthermore, the 

NMIM generates the same number of output records for each RunID-FIPSCountyIDFIPSStateID-Year-Month combination. Therefore, each of the output tables was checked to 

ensure the number of records for this combination of fields summed to the correct record count. 

As expected, zero error messages were recorded by NMIM and every county produced the same 

number of output records.

 

1 NCD20101201a is the NCD that is included in the current download of NMIM.