A new study suggests that organic, free-range eggs have a greater climate impact than eggs from caged hens, as free-range systems require more birds to produce the same number of eggs, since caged hens are more efficient producers. This challenges the common assumption that higher-welfare farming methods are automatically better for the environment, and researchers say egg production has received less scrutiny than meat and dairy in sustainability debates despite laying hens being the largest group of caged animals worldwide.

The Oxford University-led research, published in Royal Society Open Science, found that switching all UK egg production to organic free-range methods would generate greenhouse gas emissions equivalent to 2,316,000 tonnes of CO2, compared with 1,184,000 tonnes under a fully caged system; the current mixed system emits an estimated 1,439,000 tonnes. Organic free-range farming also scored worst for water eutrophication, acidification, land use and chicken mortality. However, the study relied on 2009-2010 data and did not account for factors such as pesticide use or biodiversity, and critics, including the Soil Association, argued it presents an incomplete picture of overall environmental impact.