Calculating GHG emissions in the dairy sector – SAI Platform
|Source : SAI Platform|
In 2008, SAI Platform’s Dairy Working Group identified Greenhouse Gas (GHG) emissions as one of the main topics to be tackled urgently.
The SAI Platform’s Dairy Working Group supports the desire to standardise ‘carbon footprint’ methods; however, such standardization should be internationally agreed and should accommodate goal and sector-specific considerations where appropriate.
The purpose was not to review the specific data and results, but rather to gain insight into the methodological approaches used in the absence of any standardized / sector approaches, specifically:
- The degree of commonality between the studies (methods, critical choices, scope and system boundaries etc.)
- The opportunity for harmonization of approaches
1. SAI Platform 2008 identified 27 studies in the dairy sector that applied a life cycle-based approach to calculate the GHG emissions of dairy products e.g. milk, cheese, ice cream….. (see List on page 3 of Annex).
2. The studies were undertaken to address a variety of objectives, including:
- Identification of life cycle / supply chain activities which contribute most to GHG emissions (hotspot analysis) e.g. to inform GHG reduction activities
- Comparison of products to inform new product innovation
- Environmental benchmarking of products e.g. to inform target setting or year-on-year improvement
- Support for external claims (e.g. carbon neutrality)
Boundaries of a LCA for our purpose is farm gate and contains both on and off dairy farm emissions. The key impacts of GHG emissions need to be included:
- On farm 1) methane from enteric fermentation (± 40 %), 2) nitrous oxide from Nitrogen-fertilizer applied to grass fields and from manure management (± 20 %), 3) methane from manure management (± 10 %), 4) production of feed, 5) energy use on-farm;
- - Off farm (± 20-30 %) 4) carbon dioxide from fertilizer production, 5) nitrous oxide from N-fertilizer applied to crop fields, 6) carbon dioxide from transportation (of feed, fertilizer, pesticides and other inputs).
- Based on the research, we think fertilizers production for both grassland and feed production should be included.
- At this stage (mid 2009) we do not include production facilities like machines and building as these are often not included and do not seem to be hotspots (but further research on this is needed).
The methodological allocation choice to link the impacts to co-products is critical.
Until now most studies focus on the economic allocation (in an average currency e.g. dollars) due to an easier access to data. With such a choice however, the estimation of GHG emissions can fluctuate greatly due to external factors (such as price), making it difficult to communicate about progress with farmers and to compare results between countries (see below table for a summary of allocation types’ strengths and weaknesses). We recommend doing more research on alternative allocation types such as:
- physical inputs/outputs properties (mass, molar flows, energy or protein contents, volume),
- biological causality or physico-chemical allocation (reflecting the causalities of production functions in dairy to determine average resource use, e.g. protein),
- system allocation based on life cycle stage (e.g. growing, finishing stag in years) (ISO 14044, 2006; Guinée, 2002,2004; Feitz et al, 2007).