Every factor is sourced, and open to revision
factors.csv holds ten conversion factors for each of roughly 100 food categories.
None of it is a black box: the full derivation for every figure — column by column, category by
category — is documented in Factor_Sources40.pdf, available on the
Downloads page.
Poore & Nemecek (2018)
Retrieved directly, and as incorporated into WRI's Cool Food Pledge calculator. The primary source for calories, CO₂e, carbon opportunity cost, water withdrawals, and land use across most plant and animal categories.
Faunalytics' Number of Animal Lives Calculator
This project uses a revised version of Faunalytics' methodology that has been expanded and updated in consultation with Faunalytics staff and in collaboration with Stanford's Humane and Sustainable Food Lab. It addresses both lives directly consumed and direct-plus-indirect calculations that account for feed animals and pre-harvest sibling mortality.
Feitz et al.
Used to allocate impacts across milk products — butter, cheese, yogurt, whey powder, and more — based on each product's proportion of milk solids relative to whole milk.
International Dairy Federation, 2015 (pg 29)
Informs how impacts are divided between beef and milk production for cows that contribute to both, avoiding double-counting a dairy cow's life across two categories.
Environmental Performance of Blue Foods, Gephart et al. (2021)
Supplies species-specific emissions, water, land, and eutrophication figures for seafood — more granular than the single "finfish" category in most general-purpose calculators.
Welfare Footprint Project
Provides pre-harvest mortality data for farmed aquatic species, used in the total (direct + indirect) animal lives figures.
Aquatic species are split by production method
Because farmed fish carry additional impacts — feed animals, aquaculture-specific mortality — each aquatic category is weighted by an estimate of how much U.S. consumption is farmed versus wild-caught. Species estimated at more than 95% one way are treated as fully that category. Otherwise, a blended figure is used: for example, salmon is treated as 76% farmed, shrimp as 86.7% farmed, and tilapia as 94.3% farmed. If a procurement line specifically states farmed or wild-caught, that designation is used instead of the blend.
| Column | Measures |
|---|---|
| B | Calories (kcal) per kg of food item |
| C | Kilograms of CO₂ equivalent emissions per kg, at time of purchase |
| D | Carbon opportunity cost — kg CO₂e per kg fresh weight, from land no longer able to sequester carbon |
| E | Animals' lives directly expended per lb retail weight |
| F | Total lives per lb — direct plus indirect (feed animals, sibling mortality) |
| G / H | Freshwater withdrawals — liters/kg and gallons/lb |
| I / J | Land use — square meters/kg and acres/lb |
| K | Eutrophication — grams of phosphate equivalents per kg or liter |
Derivations, including the specific worksheet cells and formulas behind every number in
every category, are in Factor_Sources40.pdf.
The FAO's own caveat:
"Much of the published data on which [seafood yield tables are] based is of less value
than it could be, because of the universal failure of authors to appreciate the many factors that can affect
yield and composition... Yield measurements are particularly variable: it is not impossible to find published
yields for a species that vary by a factor of 2." — FAO, cited in Factor_Sources40.pdf
This is one reason factors.csv is a plain, editable file:
institutions are encouraged to update it when and if better data becomes available.
Want the full factor tables?
factors.csv and Factor_Sources40.pdf are both on the Downloads page, along
with everything else needed to run the pipeline.