# Presentation: 358865

## Preparation of Fine Particulate Emissions Inventories 

***Preparation of Fine Particulate Emissions Inventories ***

**Chapter 6 – Nonpoint Sources**

**Notes:**
After completing this lesson, participants will be able to:
describe the approach used to identify nonpoint sources for inclusion in an emissions inventory 
list the methodologies for estimating emissions from nonpoint sources
reconcile fugitive emissions data with ambient data

## How Do I Identify and Estimate Nonpoint Sources of PM Fine or NH3 Emissions? 

- The nonpoint source inventory includes any stationary source that is not included in the point source inventory

**Notes:**
A nonpoint source refers to any stationary source that is not included in the point source inventory.  For emission inventory development purposes, EPA has traditionally used the term “area sources” to refer to stationary air pollutant emission sources that are not inventoried at the facility-level.  

The Consolidated Emissions Reporting Rule specifies reporting thresholds for point and area sources of criteria air pollutants.  These will vary depending on the pollutant and the attainment status of the county in which the source is located.  

The Clean Air Act defines area sources of Hazardous Air Pollutants for the purpose of identifying regulatory applicability.
The CAA defines an area HAP source as “any stationary source that emits or has the potential to emit considering controls, in the aggregate, less than 10 tons per year of any HAP or 25 tons per year of any combination of HAPs.” 

Sources that emit HAPs above these thresholds are categorized as “major sources.”  

To reduce confusion between these two sets of area source definitions, EPA has adopted the term “nonpoint” to refer to all criteria air pollutant and HAP stationary emission sources that are not incorporated into the point source component of the NEI.

## How Do I Identify and Estimate Nonpoint Sources of PM Fine or NH3 Emissions? (cont.)

- EIIP Area Source Guidance (Volume III)
- Lists PM fine categories for which EIIP guidance is available
- AP-42
- Existing inventories
- National Emission Inventory (NEI)
- Toxics Release Inventory (TRI)

**Notes:**
Volume III of the EIIP Area Source Guidance lists the PM fine categories for which the EIIP guidance is available.  

AP-42 and existing emission inventories also can help identify nonpoint source categories that are sources of fine PM and ammonia emissions. 

Existing inventories include: 
National Emissions Inventory
Toxics Release Inventory
inventories developed through regional planning organizations or state and local agencies. 

## EIIP Area Source Guidance (Volume III) for Sources of PM Emissions
Chapter 2: Residential Wood Combustion, Revised Final, Jan. 2001
Chapter 16: Open Burning, Revised Final, Jan. 2001
Chapter 18: Structure Fires, Revised Final, Jan. 2001
Chapter 24: Conducting Surveys for Area Source                  Categories, Dec. 2000

- Chapter 2: Residential Wood Combustion, Revised Final, Jan. 2001
- Chapter 16: Open Burning, Revised Final, Jan. 2001
- Chapter 18: Structure Fires, Revised Final, Jan. 2001
- Chapter 24: Conducting Surveys for Area Source                  Categories, Dec. 2000

*How Do I Identify and Estimate Nonpoint Sources of PM Fine or NH**3** Emissions? (cont.)*

**Notes:**
The chapters of Volume III of the EIIP Area Source Guidance that are useful for identifying nonpoint source categories of fine PM and ammonia are listed here.

## Area Source Category Method Abstracts for Sources of PM Emissions
Charbroiling, Dec. 2000
Vehicle Fires, May 2000
Residential and Commercial/Institutional Coal Combustion, April 1999
Fuel Oil and Kerosene Combustion, April 1999
Natural Gas and Liquefied Petroleum Gas (LPG) Combustion, July 1999

- Charbroiling, Dec. 2000
- Vehicle Fires, May 2000
- Residential and Commercial/Institutional Coal Combustion, April 1999
- Fuel Oil and Kerosene Combustion, April 1999
- Natural Gas and Liquefied Petroleum Gas (LPG) Combustion, July 1999

*How Do I Identify and Estimate Nonpoint Sources of PM Fine or NH**3** Emissions? (cont.)*

**Notes:**
The EIIP also has “area source category method abstracts” for charbroiling, vehicle fires, residential and commercial/institutional coal combustion, fuel oil and kerosene combustion, and natural gas and liquefied petroleum gas combustion. 

## PM 1-Pagers: Nonpoint Sources

- PM 1-Pagers: Overview
- Location:  PM Resource Center
- Web site: http://www.epa.gov/ttn/chief/eiip/pm25inventory/areasource.html
- Purpose:
- Summarize nonpoint source NEI methods for specific categories of PM10, PM2.5, and NH3

**Notes:**
The PM2.5 Resource Center, which is available on the CHIEF website, contains “PM one-pagers.” 

These documents contain an overview of the NEI methods and summarize nonpoint source NEI methods for specific categories of PM10, PM2.5, and ammonia.  

## PM 1-Pagers: Nonpoint Sources (cont.)

- Contents:
- Source Category Name, SCC
- Pollutants of Most Concern
- Current NEI Methodology
- How can States, Locals, and Tribes improve upon methodology?
- Uncertainties/Shortcomings of Current Methods
- Activity Variables Used to Calculate Emissions:
- Current Variables/Assumptions Used
- Suggestions for Improved Variables
- Where can I find Additional Information and Guidance?
- References

**Notes:**
The PM one-pagers provide the source category name and SCC, the pollutants of most concern, current NEI method, and how state, locals, and tribal agencies can improve on the NEI method, uncertainties and shortcomings.  

They also contain activity variables used to calculate the emissions, current variables and assumptions used in the methods, suggestions for improving the variables, and where to find additional information and guidance for the categories. 

## PM 1-Pagers: Nonpoint Sources (cont.)

- Open Burning
- Residential Yard Waste (Leaves) and Household Waste
- Residential, Nonresidential, and Road Construction Land Clearing Waste
- Structure Fires
- Wildfires & Prescribed Burning
- Managed Burning - Slash

**Notes:**
The open burning categories covered by the one-pagers include residential yard waste for leaves, household waste, residential, nonresidential, and road construction land clearing waste, structure fires, wildfires and prescribed burning, and managed or slash burning. 

## PM 1-Pagers: Nonpoint Sources (cont.)

- Fugitive Dust
- Paved and Unpaved Roads
- Residential Construction
- Mining and Quarrying
- Residential Combustion - Fireplaces and Woodstoves

**Notes:**
Fugitive dust categories covered by the one-pagers include paved and unpaved roads, residential construction, and mining and quarrying.  

There are also one-pagers covering residential combustion (i.e., fireplaces, woodstoves, and other residential home heaters that burn natural gas or fuel oil). 

## Typical Source Categories of Filterable PM Emissions

- Fugitive Dust Sources (Crustal PM Fine)
- Construction
- Mining and quarrying
- Paved/unpaved roads
- Agricultural tilling
- Beef cattle feedlots

**Notes:**
This list represents typical area source categories of fugitive dust sources of filterable PM emissions.  

## Typical Categories of Filterable and Condensible PM Emissions

- Open Burning Sources (Carbonaceous PM Fine)
- Open burning
- Residential municipal solid waste burning
- Yard waste burning
- Land clearing debris burning
- Structure fires
- Prescribed fires
- Wildfires
- Agricultural field burning

**Notes:**
This list contains typical area source categories of open burning sources of filterable PM emissions.

## Typical Categories of Filterable and Condensable PM Emissions (cont.)

- External/Internal Fuel Combustion (Carbonaceous PM Fine):
- Residential wood combustion
- Other residential fuel combustion
- Industrial fuel combustion
- Commercial/institutional fuel combustion

**Notes:**
This list shows typical area source categories of filterable and condensable PM emissions.

## Typical Source Categories of NH3 Emissions

- Typical source categories of NH3 emissions include:
- Animal husbandry
- Agricultural fertilizer application
- Agricultural fertilizer manufacturing
- Wastewater treatment

**Notes:**
This list presents typical area source categories of ammonia sources.

## How Do I Estimate Emissions?

- Emissions data prepared and reported by Source Classification Code (SCC)
- 10-digit SCC defines an nonpoint emission source
- EPA SCCs located at:  http://www.epa.gov/ttn/chief/codes/index.html#scc
- Report actual emissions; not allowable or potential emissions

**Notes:**
Nonpoint source inventories are prepared and reported by the 10-digit SCC source classification code. 

EPA’s master list of SCCs are available on the CHIEF website.  This is a dynamic list that can be updated (with EPA’s approval) to add SCCs.  

For example, SCCs should be added if there are several subcategories within a general nonpoint source category and a state or local agency is estimating emissions at that level. 

Also, actual emissions, not allowable or potential emissions are reported for the NEI. 

## How Do I Estimate Emissions? (cont.)

- Calculate emissions using:
- Activity data
- Emission factors
- Control efficiency data
- Rule effectiveness/rule penetration
- Follow EIIP methods when available
- Provides preferred and alternative methods for collecting activity data and use of emission factors
- Improve on existing inventory methods

**Notes:**
To calculate emissions from nonpoint sources, multiply the activity data by the emission factor, control efficiency data, rule effectiveness, and rule penetration.  

EPA guidance specifically excludes applying default RE/RP assumption values for PM inventories.   

You should follow EIIP methods, since these were developed with state and local input and they reflect the most current standardized procedures for preparing emission inventories.  

The EIIP provides preferred and alternative methods for collecting activity data and the use of emission factors, and contains suggested improvements on existing inventory methods.   

## How Do I Estimate Emissions? (cont.)

- Emission estimation equation:
- CAEA = (EFA)(Q) [(1- (CE)(RP)(RE)]
- CAEA	= Controlled nonpoint source emissions of 					pollutant A
- EFA 	= Uncontrolled emission factor for pollutant A
- Q 	= Category activity
- CE 	= % Control efficiency/100
- RE 	= % Rule effectiveness/100
- RP 	= % Rule penetration/100

**Notes:**
This equation is used to estimate emissions.   

## How Do I Estimate Emissions? (cont.)

- Obtain activity data from:
- Published sources of data
- National, regional, or state-level activity data often require allocation to counties using county-level surrogate indicator data
- Survey performed to obtain local estimate of activity

**Notes:**
Activity data is obtained from various published sources of data or surveys.  However, the use of use national, regional and state level activity data requires allocation to the counties using county-level surrogate indicator data.  

Consequently, surveying is the preferred approach to obtain the local activity estimates(i.e., a bottom-up approach, rather than a top-down approach). 

## How Do I Estimate Emissions? (cont.)

- Sources of PM and NH3 emission factors
- Factor Information Retrieval (FIRE) System
- http://www.epa.gov/ttn/chief/software/fire/index.html
- AP-42
- http://www.epa.gov/ttn/chief/ap42/index.html
- Emission factor ratios
- PM2.5 emissions calculated from PM10 emissions using ratio of PM2.5-to-PM10 emission factors
- State or local emission factors are preferred

**Notes:**
You can obtain emission factors for PM and ammonia from FIRE and AP-42.  

As an alternative, you can use the emission factor ratio or particle size multiplier.    This involves calculating the PM2.5 emissions from the PM10 emissions using the ratio of PM2.5 to PM10 emission factors in AP-42.   

However, the use of state, local, and tribal emission factors are preferred over any other approach because they are always specific. 

## How Do I Estimate Emissions? (cont.)

- Control efficiency (CE)
- Percentage value representing the amount of a source category’s emissions that are controlled by a control device, process change, reformulation, or management practice
- Typically represented as the weighted average control for an nonpoint source category

**Notes:**
Control efficiency is the percentage value representing the amount of a source category’s emissions that is controlled by a control device, process change, reformulation, or a management practice.  

Typically, the value is represented as the weighted average control for a nonpoint source category. 

## How Do I Estimate Emissions? (cont.)

- Rule effectiveness (RE)
- Adjustment to CE to account for failures and uncertainties that affect the actual performance of the control
- Rule penetration (RP)
- Percentage of the nonpoint source category that is covered by the applicable regulation or is expected to be complying with the regulation

**Notes:**
Rule effectiveness is an adjustment to the control efficiency to account for failures and uncertainties that affect the actual performance of the control method.  

Rule penetration represents either the percentage of the nonpoint source category that is covered by the applicable regulation, or that which is expected to be in compliance with the regulation.  

## Spatial and Temporal Allocation

- Available national, regional, or state-level activity data often require allocation to counties or subcounties using surrogate indicators
- S/L/T agencies should review estimates developed in this manner (e.g., NEI) for representativeness
- Available temporal profiles to estimate seasonal, monthly, or daily emissions for specific categories may be limited
- States are encouraged to reflect local patterns of activity in their emission inventories

**Notes:**
The available national, regional, or state-level activity data often require allocation to counties or subcounties using surrogate indicators.  

State, local, and tribal agencies should review emission estimates developed in this manner for representativeness.  

The available temporal profiles to estimate seasonal, monthly, or daily emissions for specific categories may be limited, so states are encouraged to reflect local patterns of activity in their emission inventories.  

For example, residential home heating emissions from fuel oil combustion can be allocated to the county level by using the number of households in each county in the state. 

## EI Development Approaches

- Approaches Available to State, Local, and Tribal (S/L/T) Agencies:
- S/L/T Agency develops its own inventory following EIIP procedures
- Compare S/L/T activity data and assumptions to NEI Defaults – Use S/L/T data to replace NEI defaults if data will improve estimates
- Use NEI default estimates

**Notes:**
The approaches that are available to state, local, and tribal agencies for developing an emissions inventory include:
develop an emissions inventory following the EIIP procedures 
compare the state, local, tribal activity data and assumptions to the NEI defaults and replacing the defaults, as necessary
use the NEI default estimates

## Triage Approach to Improving the EI

- Consider each NEI Category - Is it important ?
- What’s its potential impact on AQ, considering emissions, receptor modeling & other available info
- May give *some weight* to emission reductions potential
- If yes, focus improvement efforts on the important categories
- Review the available guidance (Course materials, one pagers, EIIP guidance)
- Decide what is feasible in the near and long term

**Notes:**
The triage approach to improving the emissions inventory involves:
considering the importance of each NEI category
examining the potential impact on air quality
considering emissions, receptor modeling, and other available information  

Improvements should be made to those categories that are determined to be important using the suggestions and references provided in this training course.  This includes reviewing the available guidance and deciding on feasible approaches. 

## Crustal Materials (Mainly Fugitive Dust)

- Main Sources:
- Unpaved roads
- Agricultural tilling
- Construction
- Windblown dust, Fly ash

**Notes:**
The main sources of crustal materials are unpaved roads, agricultural tilling, construction, and wind-blown dust.  

## Crustal Materials (Mainly Fugitive Dust) (cont.)

- Huge Disparity Between EI & Ambient Data
- Ambient Data
-  < 1 ug/m3 in most of US
- Exception: > 1 ug/m3 in much of Southwest, California
- Emissions: 2.5M TPY (comparable to Carbon Emissions)
- Fugitive Dust has low “Transportable Fraction”

**Notes:**
There is a huge disparity between the crustal data in an emissions inventory and the ambient air quality data.  

The amount of crustal material on the ambient filters is less than expected, given the large estimates of fugitive dust emissions in the NEI.  The reason for this apparent anomaly is that fugitive dust has a low transportable fraction. 

## Fugitive Dust Emissions in VISTAS States

**Notes:**
The data on this graph shows that PM2.5 inventories in the states included in the VISTAS area have fugitive dust in the 20-40% range.  

The rest of PM in the inventory is from sources that are primarily carbonaceous. 

## Urban (EPA STN) Annual AveragesSep 2001-Aug 2002

**Notes:**
Comparing the data in the previous slide with the data presented in this figure shows that the ratio of crustal PM2.5 emissions to total carbonaceous matter emissions does not match the ratio of crustal to total carbonaceous PM2.5 based on the ambient data. 

## Role of Surface Cover (Vegetation & Structures) in Fugitive Dust Removal

- Early work by AQ Modelers
- Stilling Zone – Lower 3/4 of canopy
- Windbreaks – wind erosion “staple”
- Traditionally to slow wind on leeward side
- Research by Raupach
- Entrapment effects
- Dust transmittance through a windbreak is close to the optical transmittance

**Notes:**
In the process of developing models, the stilling zone under the canopy of vegetation was recognized.  
The air in this zone (the bottom three-fourths of the height of the vegetation) is still.  This promotes gravitational settling and impaction and filtration by the vegetation. 

In the western states it is common to see wind breaks.  These are rows of trees or other tall vegetation designed to slow the wind speed on the leeward side.  
The objective is to prevent the wind from picking up the soil and causing erosion.  

Another important feature of windbreaks is the entrapment effect involving the transmittance of dust through a wind break.  Research shows that the dust that goes through a wind break is similar to the optical transmittance of light through a wind break. The remainder is trapped in the windbreak. 

## Role of Surface Cover (Vegetation & Structures) in Fugitive Dust Removal (cont.)

- Capture Fraction (CF)
- Portion of Fugitive Dust Emissions (FD) removed by nearby surface cover
- Transport Fraction (TF)
- Portion that is transported from the source area

**Notes:**
Capture fraction is the portion of fugitive dust emissions that are removed by nearby surface cover.  

Transport fraction is the portion that is transported out of the source area.  

Adding the two sums produces the fugitive dust emissions inventory. 

## Capture Fraction ~ Conceptual Model and Field Measurement Results 

**Notes:**
This graph plots a capture fraction value and the type of vegetation qualitatively described as going from densely forested to barren.   

The test data plotted on this graph suggest a relationship between the amount of vegetation and the capture fraction.  

Specifically, the data suggest that tall leafy dense vegetation has a high capture fraction and the short sparse scattered vegetation has a low capture fraction.  

## Estimates of  CF for Specific Surface Conditions

| Surface Cover Type | CF (Estimated) |
| --- | --- |
| Smooth, Barren or Water | 0.03 – 0.1 |
| Agricultural | 0.1 - 0.2 |
| Grasses | 0.2 - 0.3 |
| Scrub and Sparsely Wooded | 0.3 - 0.5 |
| Urban  | 0.6 - 0.7 |
| Forested | 0.9 - 1.0 |

**Notes:**
The conceptual model suggested by the data in the previous graph has yet to be integrated with air quality models, but it does allow for the assignment of capture fractions to the variety of vegetation shown here. 

## Example CF’s for Counties in NV & GA

- CF (County)  =  ∑ CF (Land Use Types) *   County Fractional Land Use
- Types
- TF = 1 - CF

**Notes:**
By using land use databases that contain data on fractional land use in six different areas (barren and water, agriculture, grass, urban, scrub and sparse vegetation, and forest) it is possible to compute the capture fraction.  

As shown in this table, the capture fraction for a given area is the sum of capture fraction by land use type times the county fractional land use amount.  The transport fraction is equal to one minus the capture fraction.  

For example, the transport fraction from the source in Churchill County, Nevada is much higher than the amount that gets away from the source in Oglethorpe County, Georgia.  The main difference is the amount of trees in those two areas.  In general, the transport fraction is fairly low in those areas of the country that are very heavily forested, or in cities with a lot of buildings. 

## Fugitive Dust Modeling Issues

- Gaussian Models
- Have many CF removal mechanisms built-in
- rarely utilized
- Application requires empirical coefficients ~
- limited data & guidance
- Grid Models
- Remix particles w/in lowest layer at each time step (underestimates removal by gravitational settling)
- Ignore removal processes in initial grid
- Very significant omission (unless grid is VERY small)

**Notes:**
There are modeling issues associated with using this approach to account for different transport characteristics of dust in different parts of the country.  

Gaussian models actually have removal mechanisms built in to them to accommodate capture fraction through the use of empirical coefficients.  Unfortunately, there is limited data and guidance on how to apply these coefficients, so they are rarely used.    

Grid models on the other hand are not equipped to handle particle transport. They tend to remix particles within the lowest layer during each time step, resulting in an underestimation of gravitational settling removal.  

Within a time step of the model particles have had a chance to settle down, but not settle out.  In the next time step they are remixed into the whole lower mixing cell, so they may never get out.  

Also, in the initial grid removal processes, even gravitational settling is ignored.  This is a very significant omission unless the grid is very small.  However, modeling very small grids is not really practical. 

## Cautions on Use of the TF in Emissions Inventory & Modeling Applications

- Do NOT use to reduce the emissions inventory
- Do NOT use with Gaussian Models
- Instead, use features of model properly
- Use with Grid Models (with proper caveats)
- There ARE other issues with the inventory – the TF concept should NOT be expected to fully account for overestimation of crustal fraction of ambient measurements
- TF concept is evolving
- Grid Model modifications could (over time) eliminate need for TF concept

**Notes:**
Transport fractions should not be used to reduce the emission inventory, nor should they be used with Gaussian models.  

They can be used with grid models with the proper caveats.  Because there are other issues with the inventory, there will not be instantaneous agreement between the fugitive dust emissions and the ambient data.  

For example, there are issues with applying the unpaved road factors properly.  The transport fraction concept is evolving and over time grid model modifications could eliminate the need for this approach. 

## Crustal Materials ~ Conclusions

- Crustal materials are a relatively small part of PM2.5 in the ambient air
- Fugitive dust is released near the ground and surface features often capture the dust near its source
- The **Capture / Transport Fraction** concept *does* provide a useful way to account for near source removal when used with Grid Models
- This area of research offers many opportunities to improve model performance
- There is much work to do to refine the concept

**Notes:**
Crustal material is a relatively small part of PM2.5 in the ambient air.  

Fugitive dust is released near the ground and surface features often capture the dust near its source.  

Finally, the capture/transport fraction concept provides a useful way to account for near source removal when used with grid models.  This area of research offers many opportunities to improve model performance.