Abstract

Greenhouse gas (GHG) emissions from food production represent 19-29% of global anthropogenic GHG and the dairy sector alone is estimated to contribute around 3%. This thesis assessed GHG estimates for milk production (i.e. milk carbon footprint (CF)) in a life cycle perspective. Uncertainties in milk CF were examined for two contrasting milk production systems (an intensive system in Sweden (SE) and a more extensive system in New Zealand (NZ)) and variations in milk CF estimates between Swedish dairy farms were determined. GHG emissions from feed production and enteric fermentation, representing around 85% of milk CF, were estimated on herd level for different feeding strategies related to regional conditions for feed cultivation. The methodology used was Life Cycle Assessment with the system boundary 'cradle to farm gate'. National average milk CF for SE and NZ was estimated to be 1.16 and 1.00 kg carbon dioxide equivalents (CO₂e)/kg energy corrected milk (ECM) respectively, with uncertainty of approximately ±30% due to uncertainties in emissions factors predicting enteric CH₄ and soil N₂O emissions, which were among the most influential parameters for milk CF estimates. The most influential variable was feed intake. Milk CF was found to vary by approximately ±17% between Swedish dairy farms due to differences in management practices, indicating potential for reducing GHG emissions on farm level. GHG emissions from different feeding strategies varied between 0.42 and 0.53 kg CO₂e/kg ECM for feed production, and between 0.50 and 0.52 kg CO₂e/kg ECM for corresponding enteric CH₄. Thus differences in feeding strategy affected GHG emissions from feed production more than enteric CH₄ production. Roughage production contributed >50% of the emissions and grass silage CF varied markedly (by 17%) between regions and influenced the overall emissions. It was also influenced by feed losses from silage storage and feeding. Grass silage nutrient quality also influenced emissions from feed production and enteric CH₄ production. Replacement animals contributed approximately 20% of these GHG. The large uncertainties in milk CF indicate that values should not be compared unless estimated with harmonised methods and that caution is needed when they are used in mitigation studies. Efficient use of all resources is an important general mitigation measure. Measures with varying effects need to be evaluated at farm level.

Keywords

carbon footprint; farm level; feed production; greenhouse gases; life cycle assessment; land use; milk production; mitigation; NorFor; uncertainties; variations

Published in

Acta Universitatis Agriculturae Sueciae
2014, number: 2014:28
ISBN: 978-91-576-8004-4, eISBN: 978-91-576-8005-1
Publisher: Department of Biosystems and Technology, Swedish University of Agricultural Sciences

SLU Authors

• Henriksson, Maria

  • Department of Biosystems and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Climate Research
Soil Science
Environmental Sciences related to Agriculture and Land-use


Permanent link to this page (URI)

https://res.slu.se/id/publ/52669