ON-sheep-LCA

Sheep LCA model using Ontario-specific sheep farming data

This script package is intended to be used as supplementary material for the manuscript: Life cycle impacts of sheep sector in Ontario, Canada by Akul Bhatt and Bassim Abbassi

This script package imports parameter values (representing farming practices and environmental factors) and LCIA impact factors stored in MATLAB_inputs_outputs.xlsx, and stores them as MATLAB variables. The variables are used as input arguments in the LCA model (sheep_LCA_model.m), which outputs life cycle impacts in the categories of global warming (GW), energy demand (ED), and water depletion (WD).

The full LCA outputs for the data presented/summarized in the manuscript Life cycle impacts of sheep sector in Ontario, Canada can be obtained by executing the script sheep_LCA_farmdata.m. Its execution will import (from the spreadsheet MATLAB_inputs_outputs.xlsx) the foreground data on sheep farming practices as well as relevant environmental factors and impact factors into the LCA model. It will also export the LCA outputs back into the spreadsheet. The image below conceptualizes this interaction.

Sensitivity and uncertainty analysis for the LCA model can be done through the execution of the scripts sheep_LCA_RSV.m and sheep_LCA_MC.m, respectively. Execution of script sheep_LCA_RSV.m will import (from the spreadsheet MATLAB_inputs_outputs.xlsx) the baseline parameter values for foreground data on sheep farming practices as well as relevant environmental factors, export the RSV sensitivity outputs back into the spreadsheet, and plot the sensitivity graphs. Executing the script sheep_LCA_MC.m will import the statistical distributions of all parameters into the LCA model for uncertainty analysis, export the LCA outputs back into the spreadsheet, and plot the dispersion of the impact scores. The image below conceptualizes this interaction.

The live script sheep_LCA_IO.mlx may also be used as an example to see how input arguments in MATLAB_inputs_outputs.xlsx can be passed on to the LCA model. Model results deemed important (e.g., life cycle impacts per functional unit, total daily matter intake (DMI), etc.) are also tabulated at the end of this live script.

Model file requirements:

The scripts sheep_LCA_farmdata.m or sheep_LCA_IO.mlx requires the following files to work:

• spreadsheet MATLAB_inputs_outputs.xlsx
• LCA model script sheep_LCA_model.m
• The followings scripts in the 'Modules' folder: enteric_ferm.m, forage_amount.m, manure_mgmt.m, LCA_farm_operations.m, LCA_feed.m, LCA_fertilizer.m, and LCA_total_FU.m

Model input parameter/variable description:

The file sheep_LCA_model_param_info.pdf contains description, baseline value, and source of input parameters/variables accepted into the LCA model. The baseline values represent average sheep farming practices in Ontario, Canada.

Model script description

• sheep_LCA_model.m: This script does the following:
  • a) combines related variables into arrays,
  • b) displays error, aborts calculations if invalid inputs are detected,
  • c) estimates forage amount through iterative energy balance, and
  • d) runs subsequent scripts in 'Modules' to determine cradle-to-gate life cycle impacts
• enteric_ferm.m: Calculates livestock's net energy (NE) and gross energy (GE) requirements, and per-head enteric CH4 emissions
• forage_amount.m: Estimates DMI from roughage/grazing
• manure_mgmt.m: Estimates manure CH4 emissions and nitrogen-based GHG emissions (through nitrogen balance)
• LCA_feed.m: Tallies the total feed intake and calculates impacts of feed production
• LCA_fertilizer.m: Calculates impacts of fertilizer production and fertilization
• LCA_farm_operations.m: Calculates impacts of farm infrastructure (outdoor area, barns/sheds, etc) and misc. farming operations (water, electricity, heating fuel, diesel, tilling, plastic, and transportation)
• LCA_total_FU.m: Calculates allocation factor and estimates life cycle impacts per functional unit

A note on allocation:

Allocation towards sheep meat and wool is done using protein mass allocation (PMA), assuming protein content of meat and wool to be 18% and 65%, respectively. If primary enterprises are sheep milk and meat (i.e., enterprise = 3) then the ratio of NE lactation : (NE lactation + NE growth) is used for allocation instead.