Rotz C Alan, Briggs Kaitlyn, Hristov Alexander N, Leytem April, Young Eric, Hagevoort Robert, Mullinax Denise
USDA-ARS, Pasture Systems and Watershed Management, University Park, PA 16802.
Dairy Management Incorporated, Rosemont, IL 60018.
J Dairy Sci. 2025 Sep;108(9):9755-9777. doi: 10.3168/jds.2025-26392. Epub 2025 Jul 8.
The US dairy industry has set the goal of attaining GHG neutrality by mid-century. Reaching this goal requires the implementation of multiple strategies for mitigating and offsetting GHG production. A large range of animal feeding, manure handling, cropping and energy saving strategies were evaluated alone and in combination to quantify their potential for reducing the farmgate life cycle carbon (C) footprint of milk production. Representative dairy farms in major dairy regions of the United States were simulated without and with these mitigation strategies using the Integrated Farm System Model. The benefit was quantified as the change in milk C footprint with a given strategy or combination of strategies compared with that of current practices in each region. Without consideration of economic constraints, strategies were modeled for plausible and maximum possible emission reductions. For plausible scenarios, C footprint reductions achieved with individual strategies ranged from 0.3% to 18%. Strategies with the most benefit included anaerobic digestion of manure, a covered manure storage using a flare for methane destruction, and the use of a feed additive for mitigating enteric methane. A combination of strategies provided an average reduction in the C footprint over all farms of 44%. Offsets that might be achieved on a few farms through soil carbon sequestration or use of food waste in anaerobic digestion provided further potential reductions of 7% and 4.9%, respectively. With the use of maximum strategies representing an upper limit in potential mitigation, GHG reductions for individual strategies ranged from 0.3% to 32%. A combination of maximum strategies gave a reduction averaging 70% over all farms, falling short of GHG neutrality. Considering alternative metrics for quantifying the global warming effects of methane as a short-lived gas in the atmosphere provided a possible short-term solution for demonstrating climate neutrality of US dairy farms. If implementation of mitigation strategies over the next several years reduced total methane from all farms at a rate greater than 1% per year, alternative metrics such as global warming potential star would predict no effect on global temperature rise. For the long-term, mitigation strategies have the potential for providing large reductions in GHG emissions, but achieving GHG neutrality over all US dairy farms appears improbable.
美国乳制品行业设定了到本世纪中叶实现温室气体中和的目标。要实现这一目标，需要实施多种策略来减轻和抵消温室气体排放。对一系列广泛的动物饲养、粪便处理、作物种植和节能策略进行了单独评估和综合评估，以量化它们减少牛奶生产从农场大门算起的生命周期碳足迹的潜力。使用综合农场系统模型，对美国主要乳制品产区的代表性奶牛场在有无这些减排策略的情况下进行了模拟。收益被量化为采用特定策略或策略组合时牛奶碳足迹相对于每个地区当前做法的变化。在不考虑经济限制的情况下，对可能实现的和最大可能的减排策略进行了建模。对于合理的情景，单个策略实现的碳足迹减少幅度在0.3%至18%之间。收益最大的策略包括粪便厌氧消化、使用火炬销毁甲烷的有盖粪便储存以及使用饲料添加剂减轻肠道甲烷排放。多种策略的组合使所有农场的碳足迹平均减少了44%。通过土壤碳固存或在厌氧消化中使用食物垃圾，少数农场可能实现的抵消措施分别进一步减少了7%和4.9%的碳足迹。采用代表潜在减排上限的最大策略时，单个策略的温室气体减排幅度在0.3%至32%之间。最大策略的组合使所有农场的减排平均达到70%，仍未实现温室气体中和。将甲烷作为大气中一种短期存在的气体来量化其全球变暖影响的替代指标，为证明美国奶牛场的气候中和提供了一种可能的短期解决方案。如果在未来几年实施减排策略，使所有农场的总甲烷排放量每年以超过1%的速度减少，那么全球变暖潜能值星级等替代指标将预测对全球气温上升没有影响。从长期来看，减排策略有可能大幅减少温室气体排放，但要使美国所有奶牛场实现温室气体中和似乎不太可能。
