There are 50 billion birds on Earth, from solitary condors to shimmering flamingos to flocks of humble sparrows. But more than half of all avians live on factory farms, bred for meat or egg production. Humans eat around 75 billion chickens every year—an order of magnitude more than the next animal (ducks) and vastly more than pigs or cows. Hen eggs are even more popular, with the average person consuming 161 a year—at least before avian flu devastated flocks around the world. So, in the face of a rampant global appetite and a wildly uncertain future, is the chicken or the egg the more sustainable choice?

 

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The Chicken

1.  The nest beats the rest. If you choose to eat meat, chicken is your best choice for the climate. Poultry has a carbon footprint 90% lower than beef and 20% lower than pork. And because 99% of chickens live in compact, efficient factory farms, it’s good for land sparing, too. In 2017, University of Edinburgh researchers calculated that a diet that replaced 50 percent of normal meat consumption with chicken could release a third of today’s farmland for arable crops or rewilding.

2.  Yellow chicken = green chicken. Chicken feed is no chicken feed when it comes to carbon. About 80% of a chicken’s carbon footprint comes from its feed, which is largely based on soya. Replacing the soy with protein from insects or algae can reduce its climate impact without affecting its taste—although it does add a distinctive yellow hue to the uncooked meat. Switching to alternative feeds also reduces chicken’s land use even further: one square meter of insects can produce the same amount of protein as 1500 square meters of soybeans. 

3.  The omnivore’s dilemma. The problem with switching to chicken on climate grounds is that it means a step-change in animal suffering. It takes three cows to produce one ton of beef, but nearly 600 chickens to produce the same amount of poultry meat. Cattle also tend to have more pleasant lives (up to the point of slaughter) than intensively-raised broiler chickens. Most chickens farmed for meat have been selectively bred to reach slaughter weight in just six weeks. Most such Frankenchickens suffer painful and debilitating leg problems that make it difficult for them to walk or even stand. 

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The Egg

1.  Less cruelty, less carbon. Eggs have only around half the carbon footprint of chicken meat per kilogram, and don’t require the slaughter of billions of animals. There’s another advantage, too. The Swedish University of Agricultural Sciences carried out a fascinating meta-study in 2021 that compared organic and non-organic food production methods. It found that organic chickens have a noticeably higher carbon footprint than conventionally raised birds—up to four times higher—due to their considerably longer lifetimes, requiring more feed. Organic eggs, on the other hand, had a similar or lower climate impact than their intensively-produced counterparts, although other researchers to date have not seen much difference.

2.  A carbon-free egg? Dutch company Kipster markets “carbon-neutral” eggs in the US and the Netherlands. Over 85% of its chicken feed is agricultural or food surplus and byproducts, such as oat hulls and broken pasta. Waste heat from the hens’ free range sheds is captured and reused, and the eggs’ remaining carbon footprint is offset using external carbon-reduction projects. To avoid the common practice of culling male chicks, the company now plans to use in-egg sensing technology to divert male eggs to animal feed at an earlier stage. A Cambridge University study of a similar producer in the UK concludes that even a carbon negative egg is possible. 

3.  Greenwashing eggs. We’ve written a lot about regenerative farming. Now it’s starting to show up in the supermarket aisles, particularly as a buzzword on egg cartons. Grist has this readable deep-dive into whether all the claims you see about carbon storage and happy chickens can be believed. Maybe, maybe not. Grist quotes Jayson Lusk, head of the agricultural economics department at Purdue University: “It strikes me that in many ways ‘regenerative’ is the new ‘sustainable,’ which was the new ‘local,’ which was the new ‘organic.’ It’s a halo treadmill.”

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What To Keep An Eye On

1. Chicken without eggs. One problem with alternative meats is that they’re proving difficult to scale up to compete economically with factory farms. Researchers in Israel recently developed a way to culture meat cells in a lab at four times the density of existing processes. They calculate it should enable production of cultured chicken at around the same cost of organic supermarket poultry. 

2. Egg-free meds. Egg white protein, aka albumin, is extensively used in commercial food as a protein and foaming agent, but also in the production of numerous drugs and medicines, including cancer therapies. Now Finnish scientists have designed a fungus that can produce albumin using one-tenth the amount of feed of a hen egg, and a similar reduction in land use. Overall, fungal albumin had a carbon footprint about half of the original egg variety.  

3. Feathery fuel cells. The world kills and eats so many chickens that it has a problem with chicken feathers—six billion tons of them every year. Most are wasted but millions of tons are burned, adding sulfur dioxide and carbon to the atmosphere. In 2023, engineers at the Swiss Federal Institute of Technology successfully incorporated keratin from chicken feathers into a membrane for a fuel cell making electricity from hydrogen. Membranes made using feathers should have a lower environmental impact, and cost only half as much as existing devices, they claim.

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