21.2 EPA-developed estimates
21.2.1 Activity Data
The activity data for generating emissions for campfires is the amount of wood burned in campfires by county, and this is broken out into two parameters: 1) the number of campsites per county, and 2) the amount of wood burned in campfires per campsite. Here, a campsite is a part of the campground where people camp and build a campfire. One campground may have multiple campsites.
21.2.2 Campground database
The raw data used for the number of campsites per county is a list of the U.S. Campgrounds [ref 1] which provides only publicly owned campgrounds. The original data have campgrounds residing in both in US and Canada. For more detailed information and meta data, please refer to the website listed in ref 1.
The excel workbook “US_campgrounds_f.xlsx” provided on the 2023 NEI Supplemental nonpoint data FTP site, contains only US campgrounds (13,470 total in US). In the original dataset, 21 campgrounds have missing longitudes and latitudes. Therefore, in the spreadsheet “v1”, the column “filled_Google” indicates whether it was filled by Google search.
The columns “state” and “fips” were assigned based on latitude and longitude of each campground by GIS.
The column “sites” indicates the number of campsites in a campground. In the original dataset, 5,056 campgrounds have missing information of “sites”. We used the 10th percentile (# sites per campground) to gap fill campgrounds that don’t have this information. Therefore, each campground without data on the # of sites per campground was assumed to have 7 sites. The column “sites_filled” indicates whether it was gap-filled.
The spreadsheet “county level counts” provides the number of campgrounds and number of sites by county based on the v1 data on county “fips”.
21.2.3 Assumptions for calculating wood consumption
To compute the wood consumption (e.g., number of cords of firewood) per site per year, several assumptions were made to estimate the volume of firewood per campsite event.
- It was assumed to be 2 to 5 bundles per campsite event or 2 to 5 bundles per day. [ref 2]
- It was indicated that a typical bundle contains 4 to 6 pieces of firewood with a total volume between 0.75 to 1 cubic foot of wood. [ref 2]
A cord of wood is 128 cubic feet; therefore, the cords of wood per campsite per day was calculated to be 0.012 to 0.039 (see Equation (21.1) and (21.2) below).
\[\begin{equation} \text{Lower bound:} \frac{0.75\,\mathrm{ft}^{3}\times 2}{128\,\mathrm{ft}^{3}} = 0.012 \frac{\text{cords}}{\text{day}} \text{per campsite} \tag{21.1} \end{equation}\]
\[\begin{equation} \text{Upper bound:} \frac{1\,\mathrm{ft}^{3}\times 5}{128\,\mathrm{ft}^{3}} = 0.039 \frac{\text{cords}}{\text{day}} \text{per campsite} \tag{21.2} \end{equation}\]
- Assuming the number of burning days in a year at a campsite to be 50, it was calculated to be 0.6 to 1.95 cords per campsite per year. Taking the average, the wood consumption is assumed to be 1.3 cords per campsite per year.
The density (ton wood/cord wood) can use the Wagon Wheel table “Wood Density Factors”.
The emission activity levels estimated by EPA were compared to a survey conducted by the state of Minnesota (shown in Table 21.1).
| 2020 | 2017 | |
|---|---|---|
| Cords burned at campsites in MN | 27,529 | 36,045 |
| Total MN campsites* | 13,786 | 13,786 |
| cords/campsite | 2.00 | 2.61 |
*The data from the campground database used in EPA’s estimation method; MN did not have an estimate of the number of campsites
While MN’s values for cords/campsite are higher than EPA’s, it should be noted that the number of campsites in MN may be greater than those in EPA’s database as EPA’s database only included the public campgrounds and also EPA defaulted campgrounds without data on the number of sites to 7. For MN, this defaulting was done for 135 of the 444 campgrounds in MN.
21.2.4 Emission factors
Campfire emissions will adopt the fireplace emission factors (SCC 2104008100). These fireplace emission factors are being used for RWC outdoor wood burning for which we assume campfires is most similar.
| Pollutant | Pollutant Code | Type | Emission Factor (lb/ton wood) |
|---|---|---|---|
| Ammonia | NH3 | CAP | 1.8 |
| Carbon Monoxide | CO | CAP | 149 |
| Nitrogen Oxides | NOX | CAP | 2.6 |
| PM Condensible | PM-CON | CAP | 1.1092 |
| PM10 Filterable | PM10-FIL | CAP | 22.4908 |
| PM10 Primary (Filt + Cond) | PM10-PRI | CAP | 23.6 |
| PM2.5 Filterable | PM25-FIL | CAP | 22.4908 |
| PM2.5 Primary (Filt + Cond) | PM25-PRI | CAP | 23.6 |
| Sulfur Dioxide | SO2 | CAP | 0.4 |
| Volatile Organic Compounds | VOC | CAP | 18.9 |
| Mercury | 7439976 | HAP | 4.26E-05 |
21.2.6 Emissions
Emissions are quantified using county-level estimates on the number of campsites per county, the estimated cordwood used per campsite, the density of cordwood and the emission factors above, assumed fuel loading per incident, and the emission factors provided above as follows:
\[\begin{equation} \text{Emissions}_{p,c} = \text{Number of Campsites}_{c} \times \text{Cords per Campsite}_{c} \times \text{Density}_{c} \times \frac{\text{EF}_{p}}{2000} \tag{21.3} \end{equation}\]
Where:
\(\text{Emissions}_{p,c}\) = Estimated annual emissions for campfires for pollutant (p), county (c), in tons
\(\text{Number of Campsites}_{c}\) = Estimated number of campsites in county (c)
\(\text{Cords of Campsites}_{c}\) = Estimated number of cords used per campsite in county (c) for campfires for the year
\(\text{Density}_{c}\) = Density of wood in county (c) in tons per cord wood (dry) (c)
\(\text{EF}_{p}\) = Emissions factor for pollutant (p), in lbs/ton
\(\text{c}\) = County
\(\text{p}\) = Pollutant
State and Local data submitters have the option to provide more local information on the number of campsites in each county and cords per campsite per year. See Section 3 for more details.
21.2.7 Example calculations
Example calculation for Autauga County (FIPS 01001) annual PM2.5 emissions:
- Per “county level counts” spreadsheet in US-campgrounds.xlsx workbook 01001 has 7 sites.
- Per the Wood Density Factors, the density is 1.3062 ton wood/cord.
- The below calculation is for a yearly estimate (the 1.3 cord/site is cords per site per year)
\[\begin{equation} 1.3 \frac{\text{cords}}{\text{site}} \times 7 \times 1.3062 \frac{\text{ton wood}}{\text{cord}} \times 23.6 \frac{\text{lb PM2.5}}{\text{ton wood}} = 280.52 \text{ lb PM2.5} \tag{21.4} \end{equation}\]