Figure 3 Evaluation of greenhouse gases emissions by dairy cows
managed under different systems of production. Each number is
associated to a reference. Numbers within a circle indicate organic
systems. Carbon sequestration is not taken into account. Most references
are derived from life cycle assessment methodology. 1: Cederberg and
Mattsson (2000); 2: Johnson et al. (2000); 3: Haas et al. (2001); 4:
Phetteplace et al. (2001); 5: Cederberg and Flysjo (2004); 6: Casey and
Holden (2005); 7: Schils et al. (2005); 8: Hacala et al. (2006); 9: Lovett
et al. (2006); 10: Weiske et al. (2006) and Olesen et al. (2006); 11: Verge´
et al. (2007); 12: Kanyarushoki et al. (2008); 13: Lovett et al. (2008); 14:
Thomassen et al. (2008); 15: Basset-Mens et al. (2009