Why WARM credits landfilled wood with carbon storage
WARM assumes much of the carbon in landfilled wood stays buried rather than decaying, and credits dimensional lumber −1.09 MTCO2E per short ton for it (Exhibit 12-15). That outweighs the 0.15 from landfill methane and 0.02 from transport, giving a net −0.92. Reuse, at −1.66, is still lower.
The components
| Component | MTCO2E per short ton |
|---|---|
| Transport to landfill | 0.02 |
| Landfill CH4 (national average gas capture) | 0.15 |
| Avoided CO2 from energy recovery | (0.00) |
| Landfill carbon storage | (1.09) |
| Net | (0.92) |
Where the storage figure comes from
WARM calculates landfill carbon storage for wood from laboratory measurements of the carbon remaining per wet short ton of wood landfilled, citing Barlaz (1998) and Wang et al. (2011, 2013) (WARM v16, ch. 12).
What it means for pallet programs
Calculators that treat landfilling wood as a large emission and reuse as avoiding all of it overstate the benefit. With WARM, the gain from moving a ton from landfill to reuse is 0.74 MTCO2E, not 1.66. That's still a real gain, and the Pallet Fate Report shows it honestly.
Inventory factors don't include storage at all: EPA's Hub gives landfilled dimensional lumber +0.17 per short ton. See Hub factors.
Sources
- Documentation for Greenhouse Gas Emission and Energy Factors Used in WARM, Version 16: Construction Materials Chapters, ch. 12 Wood Products (EPA-530-R-23-020) U.S. EPA. Accessed October 27, 2026. Exhibits 12-3 (p. 12-3), 12-9, 12-13, 12-15 and 12-16 (p. 12-10).
- GHG Emission Factors Hub 2025, Table 9 (Scope 3 Category 5 and Category 12) U.S. EPA Center for Corporate Climate Leadership. Accessed October 27, 2026. The 2025 Hub is the latest listed on the Hub page on the access date.