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Enteric methane conversion factors (IPCC defaults, not GLEAM).

Source: R/livestock_coefs.R
gleam_enteric_params.Rd

Ym (% of gross energy converted to CH4) by species and production system. Despite the object name, the values are IPCC defaults, mixed across the 2006 and 2019 editions, plus one unsourced row; none is a GLEAM value. No function in R/ reads this object; the Tier 2 enteric chain uses ipcc_tier2_ym_values instead.

Usage

gleam_enteric_params

Format

A tibble with species, system, ym_percent, notes.

Source

Traced row by row against the published tables (whep#959):

  • Cattle and buffalo 6.5% (grazing, mixed) and feedlot cattle 3.0% are the 2006 IPCC Guidelines, Vol 4, Ch 10, Table 10.12, which gives 6.5% for every non-feedlot cattle and buffalo class and 3.0% for cattle fed diets of 90 percent or more concentrates. They are not the 2019 Refinement's Table 10.12 (Updated), which resolves Ym by production level and digestibility (5.7 / 6.0 / 6.3 / 6.5 for dairy cows and buffalo, 7.0 / 6.3 for non-dairy, 4.0 for grain feedlots and 3.0 only for steam-flaked-corn feedlots).

  • Sheep 6.5% is the 2006 Table 10.13 "Mature Sheep" value (lambs under one year are 4.5% there). The 2019 Refinement's Table 10.13 (Updated) replaces it with a single 6.7% for all sheep.

  • Goats 5.5% is the 2019 Refinement, Vol 4, Ch 10, Table 10.13 (Updated); the 2006 edition has no goat Ym.

  • Pigs 0.0% ("negligible") appears in no IPCC table. Assumed, unverified. IPCC gives swine no Ym, only a Tier 1 enteric factor of 1.5 (developed) and 1.0 (developing countries) kg CH4 head-1 yr-1 (2006 Table 10.10; the same in the 2019 Table 10.10 (Updated)).

GLEAM does not publish fixed Ym values of this shape. FAO. 2018. Global Livestock Environmental Assessment Model, Model description, Version 2.0, Revision 5, Table 4.12, p. 67, computes Ym for non-feedlot cattle, buffalo and adult small ruminants as 9.75 - 0.05 x ration digestibility (7.75 - 0.05 x digestibility for young small ruminants), uses 3 for feedlot cattle, and gives pigs 1.01 (adult reproductive) and 0.39 (replacement and fattening), not 0. The GLEAM 2.0 and 3.0 Supplement S1 workbooks in data-raw/ contain no Ym table. The Version 3.0 model description was not checked.

Examples

gleam_enteric_params
#> # A tibble: 10 × 4
#>    species system  ym_percent notes                 
#>    <chr>   <chr>        <dbl> <chr>                 
#>  1 Cattle  Grazing        6.5 IPCC default          
#>  2 Cattle  Mixed          6.5 IPCC default          
#>  3 Cattle  Feedlot        3   High concentrate diet 
#>  4 Buffalo Grazing        6.5 IPCC default          
#>  5 Buffalo Mixed          6.5 IPCC default          
#>  6 Sheep   Grazing        6.5 IPCC default          
#>  7 Sheep   Mixed          6.5 IPCC default          
#>  8 Goats   Grazing        5.5 IPCC default          
#>  9 Goats   Mixed          5.5 IPCC default          
#> 10 Pigs    All            0   Negligible enteric CH4