Summary

 
 

SECTION 9.3
WILDFIRES

 

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EMISSION INVENTORY SOURCE CATEGORY

  Natural (Non-Anthropogenic) Sources / Wildfires  

EMISSION INVENTORY CODES (CES CODES) AND DESCRIPTION
  930-934-0200-0000 (90035) Wildfires - All Vegetation

METHOD SUMMARY

Emissions reported in this category result from the wildfires that burned in 2002 on all vegetation types. The updated methodology described here was also used to calculate emissions for wildfires that burned between 1994 - 2003. Projected emission pre-1994 and beyond 2003, are based on a 10-year average. A wildfire is a natural event that burns a verity of vegetation types ranging in age, size and density. This category does not include prescribed burns, agricultural burns or wildland use fires (WFU). A prescribed burn is a fire ignited by a planned management action whereas a WFU is a naturally ignited lightning fire that is managed for resources benefit.


EMISSION ESTIMATION SYSTEM (EES) MODEL: Wildfire emissions are calculated using the Geographic Information System (GIS) based EES model developed for ARB by UC Berkeley's Center for the Assessment and Monitoring of Forest and Environmental Resources (CAMFER) laboratory. The EES implements the Forest Service First Order Fire Effects Model (FOFEM 4.0) methodology to calculate emissions. Known fire perimeters polygons are overlaid in California vegetation, establishing the specific vegetation burned in each fire. Fuel loading characteristics are assigned to each vegetation type that burned in each fire. The EES then calculates the tons of fuel consumed by the fire and applies the appropriate emission factor to generate smoke emissions per wildfire event.

ACTIVITY DATA: Wildfire perimeter data was obtained as a GIS polygon shapefile from the California Department of Forestry and Fire Protection (CDF) Fire and Resources Assessment Program (FRAP). Additional wildfire activity on National Park Service land was obtained from individual parks. The dataset was further augmented with the missing ignition dates for large wildfires.

EMISSION FACTORS: Emission factors for PM10, PM2.5, and CO were initially developed by FOFEM. FOFEM developed emission factors for the ten different fuel components that comprise a vegetation landcover. Fuel components are grouped into six categories. CAMFER used this same fuel component method and further expanded the suite of emission factors to include NOx, SO2, N20, NH3, CH4, and TNMHC by using an "emission ratio" approach. The approach is based on the observation that emissions correlate with CO or CO2 depending on whether the compound is evolved primarily in the flaming or smoldering phase of fire. Table 1 below shows the emission factors by fuel component for each pollutant.

 

PM10

PM2.5

CO

CH4

Fuel Component

Wet

Mod

Dry

Wet

Mod

Dry

Wet

Mod

Dry

Wet

Mod

Dry

Litter, wood 0-1 in

9.3

9.3

9.3

7.9

7.9

7.9

52.4

52.4

52.4

2.1

2.1

2.1

Wood 1-3 in

14.0

14.0

14.0

11.9

11.9

11.9

111.4

111.4

111.4

4.5

4.5

4.5

Wood 3+ in

26.6

21.6

19.1

22.5

18.3

16.2

268.9

205.8

174.4

10.8

8.2

7.0

Herb, shrub, regen

25.1

25.1

25.1

21.3

21.3

21.3

249.2

249.2

249.2

10.0

10.0

10.0

Duff

28.2

30.4

30.4

23.9

25.8

25.8

288.6

316.1

316.1

11.5

12.6

12.6

Canopy Fuels

25.1

25.1

25.1

21.3

21.3

21.3

249.2

249.2

249.2

10.0

10.0

10.0

 

TNMHC

NH3

NOx

SO2

Fuel Component

Wet

Mod

Dry

Wet

Mod

Dry

Wet

Mod

Dry

Wet

Mod

Dry

Litter, wood 0-1 in

3.7

3.7

3.7

0.5

0.5

0.5

8.2

8.2

8.2

2.5

2.5

2.5

Wood 1-3 in

7.8

7.8

7.8

1.1

1.1

1.1

8.0

8.0

8.0

2.5

2.5

2.5

Wood 3+ in

18.8

14.4

12.2

2.7

2.1

1.7

7.3

7.6

7.7

2.2

2.3

2.4

Herb, shrub, regen

17.4

17.4

17.4

2.5

2.5

2.5

7.4

7.4

7.4

2.3

2.3

2.3

Duff

20.2

22.1

22.1

2.9

3.2

3.2

7.2

7.1

7.1

2.2

2.2

2.2

Canopy Fuels

17.4

17.4

17.4

2.5

2.5

2.5

7.4

7.4

7.4

2.3

2.3

2.3


TEMPORAL DATA: Wildfires burn primarily in the summer, with 97% of all wildfire emissions occurring between May and October.

DATE OF THE LAST UPDATE: October 2004

CHANGES IN METHOD AND EMISSION ESTIMATES: The methodology changed significantly with the October 2004 update. Because the EES model uses geolocated wildfire perimeters, the actual location and vegetation burned in the wildfire is far more precise. With the new EES model fuel loading characteristics are vegetation specific, and emission factors are by fuel component group. Wildfire emissions are assigned to a county, air basin and district based on the actual wildfire location.

Previously the methodology was very coarse. The prior methodology had two emission inventory codes (EIC), one for grass and woodlands, and the other for timber and brush. Each EIC had one fuel loading assumption and one emission factor for each pollutant. It was assumed that all the fires that burned in northern California were in timber and brush, and all the fires in southern California burned grass and woodlands.

GROWTH PARAMETER: This category is not grown. Future wildfire emissions are based on a straight 1994-2003 ten-year average.

STATEWIDE EMISSIONS SUMMARY (2002 - ANNUAL AVERAGE TONS / DAY)

ROG