Dida Mulisa F, Garcia Sergio C, Gonzalez Luciano A
School of Life and Environmental Sciences, Faculty of Science, Sydney Institute of Agriculture, The University of Sydney, Camden, NSW 2570, Australia.
School of Life and Environmental Sciences, Faculty of Science, Sydney Institute of Agriculture, The University of Sydney, Camden, NSW 2570, Australia.
J Dairy Sci. 2025 Oct;108(10):11026-11040. doi: 10.3168/jds.2025-26566. Epub 2025 Jul 22.
Despite extensive research on the environmental effects of dairy farming, comparative GHG emissions from confinement and pasture-based systems remain unclear due to inconsistent findings from prior studies, which were often specific to the local conditions of each system and overlooked carbon sequestration by trees. The present study aimed to compare the GHG emissions of 2 Australian milk production systems (confinement and pasture-based) using a life cycle assessment approach that incorporates C sequestration by trees. The confinement system used a TMR, whereas the grass-based system primarily relied on grazed forage with concentrate supplementation. The Australian Dairy Carbon Calculator, a Tier 3 tool, predicted emission intensity using the National Greenhouse Gas Inventory and Intergovernmental Panel on Climate Change methods, as reported to the United Nations Framework Convention on Climate Change. Emission intensity was calculated as net GHG exchange in CO equivalents (CO), allocated to milk and meat. Animal emissions dominated: 85% of total emissions in confinement systems (54% enteric CH, 31% manure) and 71% in pasture-based systems (58% enteric CH, 13% manure). The confinement system showed 13% lower enteric CH intensity and 88% lower prefarm embedded intensity (kg CO/kg fat- and protein-corrected milk [FPCM]) but 129% higher manure-related GHG intensity than the pasture-based system. Emission intensities for milk (1.02 ± 0.038 vs. 1.07 ± 0.069 kg CO/kg FPCM) and meat (5.51 ± 0.779 vs. 6.76 ± 0.868 kg CO/kg liveweight) were similar between systems. The emission offset by tree C sequestration (kg CO/kg FPCM) was relatively low in both systems, contributing about 1% of total CO emissions in confinement systems and up to 6% in pasture-based systems. Targeted mitigation should address manure emissions in confinement systems, prefarm embedded, and fertilizer emissions in pasture-based systems, and enteric CH in both.
尽管对奶牛养殖的环境影响进行了广泛研究，但由于先前研究结果不一致，圈养系统和基于牧场的系统的温室气体排放比较仍不明确，先前的研究往往特定于每个系统的当地条件，并且忽视了树木的碳固存。本研究旨在采用纳入树木碳固存的生命周期评估方法，比较澳大利亚两种牛奶生产系统（圈养和基于牧场）的温室气体排放。圈养系统使用全混合日粮（TMR），而基于草地的系统主要依靠放牧草料并补充精饲料。澳大利亚乳业碳计算器是一种三级工具，使用向《联合国气候变化框架公约》报告的国家温室气体清单和政府间气候变化专门委员会的方法预测排放强度。排放强度计算为分配到牛奶和肉类的二氧化碳当量（CO₂）中的净温室气体交换量。动物排放占主导：在圈养系统中占总排放量的85%（54%为肠道甲烷排放，31%为粪便排放），在基于牧场的系统中占71%（58%为肠道甲烷排放，13%为粪便排放）。与基于牧场的系统相比，圈养系统的肠道甲烷排放强度低13%，农场前嵌入式排放强度（每千克脂肪和蛋白质校正牛奶[FPCM]的二氧化碳排放量）低88%，但与粪便相关的温室气体排放强度高129%。两种系统的牛奶（1.02±0.038与1.07±0.069千克二氧化碳/千克FPCM）和肉类（5.51±0.779与6.76±0.868千克二氧化碳/千克活重）排放强度相似。在这两种系统中，树木碳固存的排放抵消量（千克二氧化碳/千克FPCM）相对较低，在圈养系统中约占总二氧化碳排放量的1%，在基于牧场的系统中高达6%。有针对性的减排应解决圈养系统中的粪便排放、农场前嵌入式排放以及基于牧场的系统中的肥料排放，以及两种系统中的肠道甲烷排放。
