calc_emissions_enteric: Calculate enteric methane emissions

In cowfootR: Dairy Farm Carbon Footprint Assessment

Calculate enteric methane emissions

Description

Estimates enteric methane (CH4) emissions from cattle using IPCC Tier 1 or Tier 2 approaches with practical defaults for dairy systems.

Usage

calc_emissions_enteric(
  n_animals,
  cattle_category = "dairy_cows",
  production_system = "mixed",
  avg_milk_yield = 6000,
  avg_body_weight = NULL,
  dry_matter_intake = NULL,
  feed_inputs = NULL,
  ym_percent = 6.5,
  emission_factor_ch4 = NULL,
  tier = 1L,
  gwp_ch4 = 27.2,
  boundaries = NULL
)

Arguments

n_animals	Numeric scalar > 0. Number of animals.
cattle_category	Character. One of "dairy_cows", "heifers", "calves", "bulls". Default = "dairy_cows".
production_system	Character. One of "intensive", "extensive", "mixed". Default = "mixed".
avg_milk_yield	Numeric >= 0. Average annual milk yield per cow (kg/year). Default = 6000. Used in Tier 2 fallback for dairy cows.
avg_body_weight	Numeric > 0. Average live weight (kg). If NULL, a category-specific default is used (e.g. 550 kg for dairy cows).
dry_matter_intake	Numeric > 0. Dry matter intake (kg/animal/day). If provided (Tier 2), overrides body-weight/energy-based estimation.
feed_inputs	Named numeric vector/list with feed DM amounts in kg/year per herd (e.g., grain_dry, grain_wet, byproducts, proteins). Optional. If given and dry_matter_intake is NULL, DMI is inferred as sum(feed_inputs)/(n_animals*365).
ym_percent	Numeric in (0, 100]. Methane conversion factor Ym (% of GE to CH4). Default = 6.5.
emission_factor_ch4	Numeric > 0. If provided, CH4 EF (kg CH4/head/year) is used directly; otherwise it is calculated (Tier 1 or Tier 2).
tier	Integer 1 or 2. Default = 1.
gwp_ch4	Numeric. GWP for CH4 (100-yr, AR6). Default = 27.2.
boundaries	Optional list from set_system_boundaries().

Value

A list with annual CH4 emissions and annual CO2-equivalent emissions.

• ch4_kg: annual CH4 emissions (kg CH4 yr-1)

• co2eq_kg: annual CO2-equivalent emissions (kg CO2eq yr-1), for compatibility with calc_total_emissions()

• units_ch4 and units_co2eq: explicit unit strings

Examples

# Tier 1, mixed dairy cows
calc_emissions_enteric(n_animals = 100)

# Tier 2 with explicit DMI
calc_emissions_enteric(
  n_animals = 120, tier = 2, avg_milk_yield = 7500, dry_matter_intake = 18
)

# Boundary exclusion: enteric not included
b <- list(include = c("manure", "energy"))
calc_emissions_enteric(100, boundaries = b)$co2eq_kg # NULL → excluded

cowfootR documentation built on Jan. 13, 2026, 5:07 p.m.