Agriculture and Agri-Food Canada, Lethbridge, AB, Canada, T1J 4B1.
Agriculture and Agri-Food Canada, Lethbridge, AB, Canada, T1J 4B1.
J Dairy Sci. 2012 Sep;95(9):5164-5175. doi: 10.3168/jds.2011-5229.
The objective of this study was to conduct a life-cycle assessment (LCA) of greenhouse gas (GHG) emissions from a typical nongrazing dairy production system in Eastern Canada. Additionally, as dairying generates both milk and meat, this study assessed several methods of allocating emissions between these coproducts. An LCA was carried out for a simulated farm based on a typical nongrazing dairy production system in Quebec. The LCA was conducted over 6 yr, the typical lifespan of dairy cows in this province. The assessment considered 65 female Holstein calves, of which 60 heifers survived to first calving at 27 mo of age. These animals were subsequently retained for an average of 2.75 lactations. Progeny were also included in the analysis, with bulls and heifers in excess of replacement requirements finished as grain-fed veal (270 kg) at 6.5 mo of age. All cattle were housed indoors and fed forages and grains produced on the same farm. Pre-farm gate GHG emissions and removals were quantified using Holos, a whole-farm software model developed by Agriculture and Agri-Food Canada and based on the Intergovernmental Panel for Climate Change Tier 2 and 3methodologies with modifications for Canadian conditions. The LCA yielded a GHG intensity of 0.92 kg of CO(2) Eq/kg of fat- and protein-corrected milk yield. Methane (CH(4)) accounted for 56% of total emissions, with 86% originating from enteric fermentation. Nitrous oxide accounted for 40% of total GHG emissions. Lactating cows contributed 64% of total GHG emissions, whereas calves under 12 mo contributed 10% and veal calves only 3%. Allocation of GHG emissions between meat and milk were assessed as (1) 100% allocation to milk, (2) economics, (3) dairy versus veal animals, and (4) International Dairy Federation equation using feed energy demand for meat and milk production. Comparing emissions from dairy versus veal calves resulted in 97% of the emissions allocated to milk. The lowest allocation of emissions to milk (78%) was associated with the International Dairy Federation equation. This LCA showed that greatest reductions in GHG emissions would be achieved by applying mitigation strategies to reduce enteric CH(4) from the lactating cow, with minimal reductions being achievable in young stock. Choice of coproduct allocation method can also significantly affect the relative allocation of GHG emissions to milk and meat.
本研究旨在对加拿大东部一个典型非放牧奶牛生产系统的温室气体（GHG）排放进行生命周期评估（LCA）。此外，由于奶牛养殖既生产牛奶又生产肉类，因此本研究评估了在这些副产物之间分配排放的几种方法。基于魁北克省典型非放牧奶牛生产系统，对一个模拟农场进行了 LCA。LCA 持续了 6 年，这是该省奶牛的典型寿命。评估考虑了 65 头荷斯坦奶牛小牛，其中 60 头小母牛在 27 月龄时首次产犊。这些动物随后平均进行了 2.75 次泌乳。后代也包括在分析中，超过替代需求的公牛和小母牛在 6.5 月龄时作为谷物喂养的小牛肉（270 公斤）完成。所有牛都在室内饲养，饲料是在同一农场生产的饲料和谷物。使用加拿大农业和农业食品部开发的 Holos 软件模型（一种基于政府间气候变化专门委员会 Tier 2 和 3 方法的全农场软件模型，并针对加拿大条件进行了修改）对农场前温室气体排放和清除进行了量化。LCA 得出的 GHG 强度为 0.92 千克 CO2 Eq/kg 脂肪和蛋白质校正乳产量。甲烷（CH4）占总排放量的 56%，其中 86%来自反刍发酵。氧化亚氮占总温室气体排放量的 40%。泌乳奶牛贡献了总温室气体排放量的 64%，而 12 个月以下的小牛贡献了 10%，小牛肉仅贡献了 3%。对肉和奶之间的温室气体排放进行了分配，分配方法为（1）100%分配给奶，（2）经济，（3）奶与小牛肉动物，（4）使用肉和奶生产的饲料能量需求的国际奶业联合会方程。将奶牛与小牛肉犊的排放进行比较，结果表明，97%的排放分配给了牛奶。与国际奶业联合会方程相关的最低牛奶排放分配（78%）。该 LCA 表明，通过应用减少泌乳奶牛反刍甲烷的缓解策略，温室气体排放将最大程度减少，而在幼畜中可实现的减排量最小。副产物分配方法的选择也会显著影响温室气体排放向牛奶和肉类的相对分配。
