Data & Methods

The sections below describe in detail the data sources and methods used to generate the maps and other summary statistics presented throughout each section of the Track & Trace website.

Forest Trend Map Data Sources & Methods

Map Data Source: FIA

The data displayed on the Forest Trend Map page are from the USDA Forest Service’s Forest Inventory and Analysis (FIA) program for the inventory time periods covering 2000 through 2016. The summary charts below the map show estimates of total forest area (in acres) and forest growing stock inventory, or the volume of live trees above 5 inches in diameter at breast height growing in the forest (in cubic feet). The forest area data were also used to fill each county on the map with varying shades of green according to the total percentage of the county area covered in forest.

FIA Program

The FIA program collects data on U.S. forest extent and conditions using field measurements gathered from a fixed set of field plots throughout the country. The program maintains one field plot site for every 6,000 acres, and 15-20 percent of the plots are revisited every year. This means that the “2016” annual inventory data, for example, might represent plot measurements collected during the 2011–2016 survey cycle. However, because inventory changes slowly, small differences in measurement years are usually insignificant.

Filling in FIA Data Gaps

Because the FIA annual inventory system was not fully implemented until recently, there are occasional years for individual states where data are missing or incomplete. For years within the time frame of this analysis (2000-2016) for which there are no FIA data available, data from the most recent adjacent year in that state are substituted. The table below shows where substitutions were made, with a “×” noting years for which concurrent inventory data are available. For years where concurrent inventory data are not available, the substitute data year that was used as proxy is listed.

  AL AR FL GA KY LA MS NC SC TN VA WV
2000  × 2005 2004  × 2004 2008 2006 2002 2001  × 2001  ×
2001  × 2005 2004  × 2004 2008 2006 2002  ×  ×  × 2000
2002  × 2005 2004  × 2004 2008 2006  ×  ×  ×  × 2000
2003  × 2005 2004  × 2004 2008 2006  ×  ×  ×  × 2000
2004  × 2005  ×  ×  × 2008 2006  ×  ×  × 2003  ×
2005  ×  × 2004  ×  × 2008 2006  ×  ×  ×  ×  ×
2006  ×  × 2004  ×  × 2008  ×  ×  ×  ×  ×  ×
2007  ×  ×  ×  ×  × 2008 2006  ×  ×  ×  ×  ×
2008  ×  × 2007  ×  ×  × 2006 2007  ×  × ×   ×
2009  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2010  ×  × ×   ×  ×  ×  ×  ×  ×  ×  ×  ×
2011  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2012  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×  ×
2013  ×  ×  ×  ×  × ×   ×  ×  ×  ×  ×  ×
2014  ×  ×  ×  × 2013  ×  ×  ×  × 2013  ×  ×
2015  × ×  2014 2014 2013 2014  ×  ×  × 2013 2014  ×
2016  × ×  2015 2015 2015 2015  ×  ×  × 2015 2015  ×

Track & Trace Data Sources & Methods

T&T Data Collection

When Enviva is contacted by a supplier who is interested in setting up a contract to sell wood from a new harvest tract, we first determine whether the tract meets the requirements of our Responsible Wood Supply Program. If we decide to move forward with the purchase, the tract will be set up in the Track & Trace (T&T) database, which includes collecting the following information from the supplier:

  • Supplier: Name of timber vendor who purchased stumpage and harvesting rights
  • Logging Contractor: Name of logging crew who will perform harvest
  • Landowner: Name of landowner who sold harvesting rights to supplier
  • Tract Name: Name of tract or some identifying feature
  • State & County: Tract location
  • Landowner Type: Nonindustrial Private Landowner (Family Forest Owner), State/Federal, or TIMO/REIT (Industrial Owner)
  • Age Class: 10 year range estimate of forest age (choose overstory age class in case of uneven age management)
  • Harvest Type: Clearcut (final harvest), Thinning, Selection Harvest, understocked/unmanaged, site prep/second entry, or longleaf pine restoration
  • Estimated Acres: Approximate acres to be harvested
  • Intent to Reforest: Yes, No, or N/A (in case of thinnings, understocked/unmanaged, site prep/second entry, or longleaf pine restorations). If ‘No’ is chosen, the transaction is aborted.
  • GPS Coordinates: Tract geolocation in decimal degrees
  • Merchandising Percentage to Enviva: Estimated percent of total volume from the harvest that is sent to Enviva
  • Majority Forest Type: Cover type on the majority of the tract. May include Oak-Pine (Mixed HW & SW), Bottomland Hardwood, Upland Oak (Upland Hardwood), or Southern Yellow Pine
  • Certification Type: American Tree Farm System, Forest Stewardship Council, Sustainable Forestry Initiative, or N/A
  • Certification Number: Unique ID issued to the certified entity
  • Certification Description: Forest Management, Chain of Custody, N/A

All of these details are entered into the database, and a unique ID number is generated for the tract.

At Amory, approximately 85% of the wood is purchased from sawmills and other wood processing facilities. The 15% of the wood that is delivered from the forest comes from one supplier, and so the T&T program is not deployed in the same way in this supply area. Instead of entering individual harvest tracts in the T&T database, Amory’s forestry team receives regular updates from the supplier on the forest type, harvest type, and age class of the forests from which the wood was sourced.

T&T Data Monitoring & Validation

Enviva foresters audit a subset of the tracts in the database while the harvest is active to verify the information entered into the T&T database and ensure the logging crew has the training credentials required in our contracts. A further subset of tracts are visited upon completion of the harvest to collect additional T&T information, including an assessment of the logging crew’s adherence to soil and water quality Best Management Practices (BMPs). All tract information that was entered into the T&T database is then checked for accuracy.

Enviva enlists NSF, a global third-party certification organization, to perform an annual independent audit of our T&T program, procedures, and sampling methods. The audit also includes site visits to assess the accuracy of the data entered into the database. Beyond the T&T audits themselves, the T&T procedures are subject to additional auditing throughout the year, as data from the T&T program provide evidence for Enviva’s other third-party forestry and sustainability certifications.

T&T Data Display

Enviva achieved full T&T coverage in June of 2016 for nearly all wood sourced directly from the forest. A small subset of tracts that make up less than 5% of total wood supply are not included in the mapped database because of agreements with suppliers prohibiting the mapped display of harvest data. Enviva collects summary T&T data from these forests and includes them in feedstock origin summaries.

The Wood Supply Map displays the tracts entered into the T&T database during the reporting period as point data.

When the user hovers over a point on the map, detailed information on that harvest from the T&T database is displayed, including the county of origin, forest type, harvest type, landowner type, dominant forest age class, tract size, and the estimated percentage of the total harvest volume that is sold to Enviva.

Preserving Supplier Confidentiality

To maintain the privacy Enviva’s suppliers and landowners, tract points are located in the vicinity, but not the precise location, of the harvest. The tract GPS coordinates are fuzzed for security, and then altered again randomly to within 10 miles of their original location each time they are rendered in the map tool.

Infographic Data Sources & Methods

FIA Data for Southeast Forest Characterization

The information presented in the infographic on the T&T introductory page regarding the southeastern United States is derived from the FIA data discussed above. Here, we use the available data to estimate the increase in the forested area and in inventory volume since Enviva opened its first mill in 2011.

T&T Data for Summary Statistics

The T&T database also generates infographic summary statistics displayed on the T&T introductory page and below the Wood Supply Map, including the number of tracts Enviva sourced from, states and counties where those tracts were located, average tract age, and average percentage of the total volume of wood from final harvests sent to Enviva.

The unique tract ID number that is generated when a harvest is entered into the T&T database is also recorded whenever a load of wood is delivered to a mill from that specific harvest. This allows us to keep track of how much wood each of Enviva’s mills receives from each harvest and analyze Enviva’s feedstock sources by volume. The volume-based analysis also provides summary statistics displayed on the T&T introductory page and below the Wood Supply Map, including the percentage of hardwood and pine feedstocks received and the percentage of wood delivered from each origin, i.e. forest type, sawmills, and/or wood processing facilities.