牛津大学的研究团队发现，有机散养鸡蛋的气候影响远大于笼养鸡蛋。[1]根据这项研究，如果英国全部转向有机散养生产模式，排放量将达到231.6万吨二氧化碳当量，而全笼养系统仅产生118.4万吨。[1]研究人员指出，这一差异源于生产效率的根本区别——有机散养模式需要更多鸡只才能生产相同数量的鸡蛋，而笼养鸡的饲养效率更高。[1]
该研究还评估了多个环境影响指标。[1]结果显示有机散养在水体富营养化、酸化和土地利用方面造成的影响最为严重，同时鸡只死亡率也最高。[1]牛津大学研究员哈丽特·巴特利特表示："有机和散养等通常被认为对动物福利更好的农场类型，实际上可能需要更多鸟类来生产相同数量的鸡蛋。"[1]这项研究基于2009-2010年的数据，已发表于《皇家学会开放科学》期刊。[1]
A research team from Oxford University's Smith School of Enterprise and Environment has released findings indicating that organic free-range eggs carry significantly greater environmental consequences than eggs from caged systems.[1] If the United Kingdom were to transition entirely to organic free-range production, annual emissions would reach 2.316 million tonnes of CO2 equivalent, compared to just 1.184 million tonnes under a fully caged system.[1] The current mixed production model generates 1.439 million tonnes annually.[1]
The disparity stems from production efficiency differences between the two systems. According to Dr Harriet Bartlett, an Oxford researcher involved in the study, "farm types often considered better for animal welfare, such as organic and free-range, may actually require more birds to produce the same quantity of eggs."[1] Beyond climate impact, the research identified organic free-range production as having the most severe effects across multiple environmental metrics, including water eutrophication, acidification, and land use.[1] The study also found that mortality rates among free-range chickens exceed those in caged systems.[1] The research data was gathered from 2009–2010 and was published in the Royal Society Open Science journal.[1]