Calculate work energy requirements (for biophysical allocation)

Calculates the energy required for animal work over the assessment period (MJ/cohort/assessment period), based on the daily energy requirement for work, cohort size, and assessment duration.

Usage

calc_work_allocation_energy(
  species_short,
  cohort_stock_size,
  metabolic_energy_req_work,
  simulation_duration,
  ratio_me_to_ne = NA_real_
)

Arguments

species_short

Character. Code identifying the livestock species. Supported values include:

PGS: pigs
CML: camels
CTL: cattle
BFL: buffalo
SHP: sheep
GTS: goats

cohort_stock_size

Numeric. Population size in the cohort at the start of the assessment period (heads).

metabolic_energy_req_work

Numeric. Energy required for work, used to estimate the energy required for draught power for CTL, BFL and CML. (MJ/head/day) Assumed to be 0 for other species. Expressed as net energy for CTL, BFL, SHP, GTS and as metabolizable energy for CML and PGS.

simulation_duration

Numeric. Length of the assessment period (days).

ratio_me_to_ne

Numeric. Ratio of metabolizable energy converted to net energy (fraction).

Value

Numeric. Energy required to provide all draught power (traction/work) by cohort (MJ/cohort/assessment period). Non-zero values are expected only for draught or work-producing species (CTL, BFL CML).

Details

This function provides the work-related energy term used in a biophysical allocation framework to apportion emissions between milk and other co-products in multifunctional livestock production systems.

The approach implements the IDF (2022) standard, adapted from Thoma and Nemecek (2020), and is consistent with FAO LEAP livestock LCA guidelines (FAO, 2016a, 2016b, 2016c) and with ISO 14044:2006 (Section 4.3.4.2, Step 2).

In accordance with ISO 14044:2006 (Section 4.3.4.2, Step 2), known processing or biophysical relationships may be used to assign shared inputs and outputs of a single production unit to individual products or sub-units. In livestock systems, this includes apportioning shared feed and energy use according to physiological energy requirements (e.g., net energy for lactation, growth, etc.). If the resulting process remains multifunctional, these energy terms may subsequently be used to derive allocation factors among co-products.

Total work-related energy is computed for species (CTL, BFL, CML) and cohorts (, FA, MA) assumed to be potentially involved in draught power generation.

The work_allocation_energy is calculated as follows:

\(energy\_allocation\_work = energy\_requirement\_work \times simulation\_duration \times cohort\_stock\_size\)

for cattle (CTL) and buffalo (BFL), and:

\(energy\_allocation\_work = \frac{energy\_requirement\_work \times simulation\_duration \times cohort\_stock\_size} {ratio\_me\_to\_ne}\)

for camels (CML).

where metabolic_energy_req_work can be computed using calc_metabolic_energy_req_work (see also run_metabolic_energy_req_module).

This function is part of the run_allocation_module().

References

ISO. (2006). Environmental management — Life cycle assessment — Requirements and guidelines (ISO 14044:2006). International Organization for Standardization, Geneva.

IDF. (2022). The IDF Global Carbon Footprint Standard for the Dairy Sector. Bulletin of the IDF No. 520/2022. International Dairy Federation, Brussels.

Thoma, G., and Nemecek, T. (2020). Allocation between milk and meat in dairy LCA: Critical discussion of the IDF’s standard methodology. In Proceedings of the 12th International Conference on Life Cycle Assessment of Food (LCAFood 2020) (pp. 83–89), 13–16 October, Berlin, Germany.

FAO. (2016a). Environmental performance of large ruminant supply chains: Guidelines for assessment. Livestock Environmental Assessment and Performance (LEAP) Partnership. FAO, Rome, Italy.

FAO. (2016b). Greenhouse gas emissions and fossil energy use from small ruminant supply chains: Guidelines for assessment. Livestock Environmental Assessment and Performance (LEAP) Partnership. FAO, Rome, Italy.

FAO. (2016c). Greenhouse gas emissions and fossil energy use from poultry supply chains: Guidelines for assessment. Livestock Environmental Assessment and Performance (LEAP) Partnership. FAO, Rome, Italy.