Canada’s Ministry of Agriculture and Agri-Food asked Lumina to translate its spreadsheet for deterministic assessment of methane emissions from livestock into Analytica. The model considers 28 types of animal, including dairy and beef cattle, pigs, sheep, horses, poultry, and bison, over 10 provinces. It uses the IPCC Tier 2 method for cattle and the simpler Tier 1 method for other livestock.
The original Excel spreadsheet file size was 1.60 Megabytes. Rewriting the Excel model into Analytica took 3 person-days. The equivalent Analytica model was 48 Kilobytes, including input data and the added influence diagrams. This reduction by a factor of 34 in file size is a measure of the relative simplicity of the Analytica representation.
The Analytica model extends the spreadsheet to deal with uncertainty on key parameters, and from a single year to a multiyear analysis. It includes live links (using Microsoft OLE) to key inputs in a corresponding spreadsheet – letting users to enter large input tables in a familiar spreadsheet template. Analytica reads these numbers and performs the uncertainty and sensitivity analysis.
The Ministry estimated the relative uncertainty for each input number – that is, half the 95% confidence interval as a percent of its median. Lumina incorporated these into the model, extending it to use Monte Carlo and a complete uncertainty analysis, following the methods specified by the IPCC and the Ministry.
According to Dr. Hutchinson “The process of importing the model into Analytica forced us to obtain a clearer understanding of the model. The result is very much clearer and easier to track. It has helped us do sensitivity analysis to identify the most influential input uncertainties. It helped advance our knowledge and improve our confidence in the treatment of the uncertainty.”
There are several ways to reduce methane emissions from livestock: Biogas digesters can collect the methane from animal manure making it available as a renewable fuel. Burning the methane to generate carbon dioxide reduces its greenhouse potential by 95%. Variations and additives to livestock feed can substantially reduce methane from enteric fermentation in their digestive systems.
A publication summarizing the results from the model is in preparation.