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Frequently Asked

Questions

 Printed on Recycled Paper

United States

Environmental Protection

Agency

Air and Radiation EPA420-F-03-023

June 2003

Office of Transportation and Air Quality

Draft NONROAD2002a

Emission Inventory Model

What is the draft NONROAD2002a model?

The draft nonroad model calculates past, present, and future emission

inventories (i.e., tons of pollutant) for all nonroad equipment categories

except commercial marine, locomotives, and aircraft. Fuel types included

in the model are: gasoline, diesel, compressed natural gas, and liquefied

petroleum. The model estimates exhaust and evaporative hydrocarbons

(HC), carbon monoxide (CO), oxides of nitrogen (NOx), particulate

matter (PM), sulfur oxides (SOx), carbon dioxide (CO2). The user may

select a specific geographic area (i.e., national, state, or county) and time

period (i.e., annual, monthly, seasonal, or daily) for analysis.

What are the differences between the limited preview

version of NONROAD2002 shown to states and the

draft NONROAD2002a?

The emission inventories produced by the two versions are the same if

the scenario inputs are the same, but NONROAD2002a has a few enhancements:

• National Inventory Format (NIF) 2.0 output option for the National

Emissions Inventory (NEI) from the Reporting Utility

• Update of Florida Dade County (Federal Information Processing

Standards (FIPS) Code 26025) to Miami-Dade County (FIPS

26086)

• More “what-if” analysis ability for fuel sulfur-to-sulfate conversion

rate (this is not expected to be used by state and local air agencies)
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How long is the review period for draft

NONROAD2002a?

The review period for draft NONROAD2002a will last until August 20,

2003, which is the same as the review period for the proposed Nonroad

Diesel Rule.

When will the final NONROAD model be released?

A final NONROAD model will be released in 2004, after the final Nonroad Diesel Engine Rule has been published.

What are the major differences in emission

inventories between the draft NONROAD2002a model

and the previous June 2000 draft version?

Some of the most important changes affect compression-ignition (CI)

engines where the associated NOx and PM inventories are reduced by

about 35 to 50 percent, depending on year and pollutant. The new SOx

inventories are also less than the prior version -- about 75 percent less for

compression-ignition (CI) engines and 65 percent less for spark-ignition

(SI) engines. More details of the inventory changes can be found in the

workshop presentations from November 5, 2002, which are available on

the nonroad modeling web page at: www.epa.gov/otaq/nonrdmdl.htm.

Does the draft NONROAD2002a model reflect all of

EPA’s final nonroad engine emission standards to

date?

No. The model does not fully reflect the new recreational equipment and

large SI engine standards that were published in the Federal Register in

September 2002 (67 FR 68243). These will be added at a later date.

How do I account for emission benefits from the new

recreational equipment and large spark ignition

standards?

Until these benefits are incorporated into the NONROAD model, users

will need to estimate the exhaust, diurnal, hot soak, running loss, and

permeation emissions and benefits based on the information in the September 2002 Regulatory Support Document for this rule (EPA-420-R022). This document can be downloaded from the EPA Office of Transportation and Air Quality web site at: www.epa.gov/otaq/recveh.htm.
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Does the draft NONROAD2002a model reflect the

proposed Tier 4 nonroad diesel engine and fuel

standards?

No. These standards will be incorporated into the final version of NONROAD when the rule becomes final.

What is EPA’s guidance on the use of the draft

NONROAD2002a model for official submissions?

EPA is allowing the use of the draft NONROAD2002a Model and associated default inputs in development of inventories supporting State Implementation Plans (SIPs). Although NONROAD2002a or its default inputs

may change between the public release of the draft and the final version,

now anticipated for 2004, the draft NONROAD2002a Model currently

represents EPA's best tool for estimating nonroad emissions, as evidenced

by the Agency’s use in the Nonroad Diesel Engine Notice of Proposed

Rulemaking (NPRM). Therefore we are allowing state agencies to use

the draft model in SIPs during the period between public release of the

draft and final versions of the model.

EPA will not require that inventories developed using the draft version be

updated following release of the final version. However, since this

release does not include the benefits of the September 2002 final rule for

recreational vehicle, large SI, and diesel recreational marine engines, and

it also doesn’t include the benefits that will be associated with the final

nonroad diesel rule, states may choose to update SIPs after EPA releases

the final version of NONROAD.

After the release of the final version of NONROAD, states that are just

beginning new SIP development, or are in the early stages of SIP development, should use the final version of NONROAD for those new SIPs.

Can the option files used for previous versions of the

model be used for NONROAD2002a?

No. Option files created with previous versions of the model are not

compatible with NONROAD2002a.
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How can I receive assistance if I have questions

about draft NONROAD2002a?

Please send an email with your question to nonroad@epa.gov or write

to:

U.S. Environmental Protection Agency

Assessment and Standards Division

Air Quality and Modeling Center

2000 Traverwood Drive

Ann Arbor, MI 48105