Free-range organic eggs, often seen as the more environmentally friendly choice, actually produce nearly twice as much carbon dioxide as eggs from caged hens, according to a study by scientists at the University of Oxford.
The researchers found that free-range organic farming produces more CO2, uses more land, and puts more pollution into rivers than other egg production systems, even though it may make for happier chickens.
Switching from current UK farming practices to 100 percent organic production would send emissions soaring by 60 percent and double the amount of land used for farming, the study found. If all eggs in the UK came from free-range organic hens, this would produce 2,316,000 tonnes of CO2 every year, more than double the 1,184,000 tonnes that would result from battery farming the same amount of eggs.
"Our research shows there's no one-size-fits-all answer," lead author Dr Harriet Bartlett told the Daily Mail. "Caged systems perform well for some environmental measures, but sustainability is about balancing a range of priorities."
How the systems compare
In the UK, 63 percent of all eggs come from chickens on free-range farms, which are legally required to provide at least four square metres of open space per bird accessible during daylight hours. A smaller share of birds are raised on organic farms, which keep smaller flocks, feed non-genetically-modified crops, and do not trim the birds' beaks.
Battery cages were banned across Europe in 2012, so battery hens now live in "enriched cages" that must include features such as areas for nesting and perching, though up to 90 birds can still be crammed into one cage.
In the study, published in Royal Society Open Science, the researchers said organic free-range farming is the most emission-intensive system, largely because organic birds require more feed per egg produced and organic crops have much lower yields than conventional ones.
According to the study, battery cage farming produces 2.1 kilograms of CO2 per kilogram of eggs, furnished cages produce 1.8 kilograms, barns produce 2.81 kilograms, free-range non-organic farming produces 2.21 kilograms, and free-range organic farming produces 3.52 kilograms. Free-range organic farming also needs about 5.7 square metres of land for every kilogram of eggs, most of it used for growing feed.
Non-organic free-range farms, by contrast, produce just 2.21 kilograms of CO2 per kilogram of eggs, only 0.11 kilograms more than battery farming.
"Our results show that free-range non-organic systems perform much closer to caged systems than organic production for key environmental measures," Bartlett said. "These findings suggest that free-range systems might deliver improvements in animal welfare while keeping environmental impacts relatively modest."
Free-range chickens also have a significantly higher mortality rate than those kept indoors, the study found. Free-range organic farms have a mortality rate of 8 percent, compared with 2.5 percent for hens in enriched cages and 3.5 percent for those raised in barns, which researchers attributed to greater exposure to disease, predators, injury and harmful feather pecking from other hens.
The researchers acknowledged that their findings are based on data from 2009 and 2010, and that free-range farming techniques have since improved.
"The goal should be to develop farming systems that provide good conditions for animals while also reducing their impact on the climate and environment," co-lead author Dr Oliver Martinic, an independent researcher from Croatia, told the Daily Mail. "For cage-free systems, in particular, the focus should be on finding ways to combine high standards of animal welfare with efficient production and a lower environmental footprint."
