The ecological impact of eggs has become a growing concern as intensive egg production practices have rapidly expanded to meet global demand. The egg industry, comprised of both small-scale egg farmers and intensive farms, has undergone significant transformations in recent decades. While free-range laying hens may enjoy a more natural environment and potentially incur a lesser impact on the planet, most of the industry relies on intensive farming methods.
In this article, we look at the environmental cost of these practices, exploring the ecological footprint of egg production and seeking sustainability solutions. But first, let’s look at how intensive livestock farming began.
The history of humans and chicken eggs goes back several millennia. Evidence of the consumption of eggs was present in the history of the Roman Empire. In the 19th century, they bred chickens with various traits that were exhibited in Europe.
Modern chickens are members of the gallus genus that were domesticated thousands of years ago in South East Asia, descending from red jungle fowl and green jungle fowl2.
The egg industry began with local farmers and their egg-laying hens. They gathered the eggs for consumption or sold them to their friends and neighbors. Starting from the 1920s, Americans began farming eggs which they sold locally to their neighbors.
Farmers started experimenting with mass egg production during the 1930s and 1940s in response to growing demand. Hen care improved as farmers took more caution and protected their flock from the weather, predators, and diseases. Egg production shortly after became a specialist farming discipline.
During the early 20th century, The United Kingdom took steps to help ensure quality eggs. The National Mark Scheme of 1928 was the first trial to introduce voluntary standards for reliable, high-quality, and properly grown eggs.
During world war II, a restriction was placed on eggs. People had to have an egg voucher to purchase eggs. Then, the government established the National Egg Distributors' Association Limited and put the organization in charge of egg supply.
From 1957 to 1971, the British Egg Marketing Board (BEMB) brought stability to the market. The board aimed to provide consumers with a regular supply of quality eggs and provide those active participants in the egg industry with the best profits8.
The board required farmers with 50 and more laying hens to register, and BEMB was required to accept all eggs offered for sale. From 1957 to 1970, the sales of a dozen eggs increased by 14%. While BEIC, the current egg production association, has 11 trade associations covering the egg production process. Intensive livestock farming began, and they monitored rearing, breeding, hatching, packaging, and marketing.
In America, the Food Safety Inspection Service implemented the Egg Production Act in 1970 to monitor the production of eggs and their products.
In recent times, egg production has reached all-time highs. The total global egg production in 2012 was 66.4 million tons, with Asia, America, Europe, Africa, and Oceania responsible for 57.8% of the output. China led the production chart by producing over 24 million eggs, followed by the United States.
The United States produced 5.4 million tons of eggs. India, the third largest egg-producing country, produced 3.6 million tons of eggs, while Japan and Mexico produced 2.5 million tons and 2.3 million tons, respectively.
The transformation of the egg industry from small, local farms with laying hens to expansive, intensive poultry farms has been a dramatic one, driven by a combination of technological advancements, increased demand, and the pursuit of efficiency.
The productive aspects of modern egg farming have been amplified by incorporating environmental technology and the transition from the typical farm setting to large-scale operations.
Many of us may have considered the animal welfare issues the poultry industry might be experiencing when choosing free-range or organic eggs at the supermarket. However, we may not have yet considered the environmental impacts of the intensive livestock farming needed for egg production to meet our demand for the tons of eggs we consume worldwide every year. Here are some impacts of egg production on the environment:
First, let's discuss the egg's industry environmental footprint. A group of scientists analyzed the environmental impact of intensive egg production and its adverse effects on the environment. These environmental implications include water and land toxicity, climate change, ozone depletion, human toxicity, land occupation, etc.
The egg industry’s environmental footprint is a culmination of greenhouse gasses and other harmful emissions that occur during every stage of egg production. It includes the economic and productive aspects. Some scientists obtained a carbon footprint of 2.7kg of CO2 equivalent per dozen eggs. The scientists affiliated with the University of Oviedo stated that the carbon footprint of a dozen eggs is similar to that of other basic foods of animal origin7, like milk.
Also, manure is a major source of greenhouse gas pollution in the poultry industry1. Manure waste produces methane, nitrous oxide, and ammonia. Ammonia, when exposed to the environment, causes water and land toxicity, whereby an intensive poultry farm located near the water does not adequately control its runoff. Ammonia decomposes when it is in the soil or oxidizes in the air, and the byproduct of the decomposition is nitrous oxide.
The emission of these greenhouse gasses damages the atmosphere, leading to ozone depletion and climate change. Research conducted on the broiler hen, a species of egg-laying poultry, showed that its manure damages the surface and groundwater system and its quality3.
Housing systems for laying hens also play a significant role in determining the environmental footprint of egg production. Free-range hens, for example, generally have more space to move and forage, leading to a more natural way of life and potentially reduced stress levels.
However, the land requirements for free-range systems are typically higher than those for intensive egg production, where they house the hens in smaller, confined spaces. The annual production of eggs per hen can differ between housing systems, with higher efficiency often associated with intensive egg farming methods.
Despite the increased productivity, the environmental costs of intensive systems, such as higher greenhouse gas emissions, resource consumption, and waste production, must be weighed against the benefits.
Generally, layering or housing systems used for commercial egg production often need to be revised. There are about 4 to 5 hen housing systems;
The caged systems do not particularly improve the layer's state of living. In the United States, most domestic hens are in cages. Some intensive farms use free-range housing systems to give the hens more outdoor space to move around. However, the majority use battery cages.
Battery cages do not cater to animal welfare. They overcrowd the space and restrict animal movements. It raises several animal welfare issues because the lack of room for the hens leads to stress and physical health problems, hindering their behavioral expressions.
For instance, battery cage systems weaken their leg mobility5. Cage systems also make the birds susceptible to diseases, like the avian flu, responsible for causing egg shortages in 2022.
Also, some caging systems fall short of proper waste disposal methods. So they end up contaminating the environment and atmosphere. Most egg-producing factories treat the livestock like producing machines. A wild chicken lays about ten eggs annually, but farmers breed layers to ensure they lay almost 300 eggs yearly.
The European Union made it illegal to keep hens in battery cages in 2012. However, some farmers keep them in ‘furnished or enriched cages.’ These furnished cages are more spacious than battery cages. Sadly, some laying hen farms still use the battery cage system.
In the intensive poultry farm environment, elder hens are often subject to challenging conditions due to the economic and productive aspects of the egg industry. As laying hens age, their egg production declines, and they become less profitable for producers.
To minimize the environmental footprint of these operations and maximize efficiency, older hens are typically removed from the production cycle and replaced with younger, more productive birds.
Unfortunately, this often means they cull elder hens (slaughtered), as their feed conversion ratio needs to be higher. This harsh reality underscores the need for sustainable solutions that balance the industry's demands with the welfare of animals and the environmental consequences of intensive egg farming.
The egg industry's reliance on chicken feed, particularly in intensive poultry farming, poses environmental challenges beyond the immediate needs of laying hens. The production of feed crops, such as soy, can contribute significantly to deforestation, habitat destruction, and increased GHG emissions. These factors worsen climate change and disrupt ecosystems, with implications for both animal welfare and the availability of other basic foods for human consumption.
Hen feed leaves an environmental footprint with its GHG emissions. Feed production and transportation carry a bulk of carbon dioxide emissions from fuel consumption and N2O emissions from fertilizer production and application. The production of the feed requires the production of crops like soya6. Planting these crops consumes energy, produces gas emissions, and transportation over long distances burns fuel.
There are two classifications of chicken feed: organic and conventional. Organic feed is free of additives and chemicals like pesticides, hormones, and antibiotics. It has the lowest land occupation and GHG emissions. However, conventional chicken feed refers to grains that contain complex carbohydrates4, i.e., wheat, soybean, rapeseed, and barley.
Many stores and supermarkets sell eggs in plastic packs and crates. And many shoppers don’t bring reusable egg crates when grocery shopping. So, we pile up plastic egg trays each time we go shopping. Over time, we tire of the pile and throw it away.
The plastic egg trays end up in landfill and take hundreds of years to decay. We should also consider the environmental footprint produced during the production of plastic trays and crates.
Further, incorrect disposal contributes to higher levels of plastic pollution in the environment. Instead, manufacturers should use paper or cardboard for egg trays that have less impact (as many do, although plastic remains common). We should also learn how to reuse and recycle plastic egg trays or crates to reduce environmental plastic pollution.
Related: Are egg cartons recyclable, and how to properly dispose of them?
The widespread use of antibiotics in the egg industry, particularly in intensive poultry farming, has raised concerns about the potential consequences for human health. Administering antibiotics to laying hens is a preventive measure to control diseases and promote growth, but this practice can inadvertently contribute to antibiotic resistance in humans.
As resistant bacteria emerge within poultry farms, they can enter the environment and the food chain, increasing the risk of human toxicity from resistant infections. This poses a threat to public health and generates negative effects on animal welfare, as the overuse of antibiotics can lead to the development of hard-to-treat diseases in both animals and humans.
The rise of the intensive poultry farm is a pressing concern as the egg industry expands and the demand for these protein-rich foods grows. Intensive poultry farming has led to various issues, including increased GHG emissions, ozone depletion, and animal welfare challenges. To mitigate the environmental footprint of egg production, the industry has begun to explore and adopt environmental technologies and sustainable practices.
However, as consumers, we also have a role in reducing the environmental impact of the eggs we consume. By choosing eggs from free-range hens, we can support farming practices prioritizing animal welfare and those with a smaller ecological footprint.
Making informed choices about the eggs we purchase for human consumption promotes a healthier and more sustainable egg industry. Further, it encourages farmers to adopt eco-friendly practices that benefit our planet and its inhabitants.
Poultry Industry’s Contribution to GHG Emissions (pdf) | Mississippi State University Extension Service. (2023, February 1).
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Ulrich Kreidenweis, Jannes Breier, Christiane Herrmann, Judy Libra, Annette Prochnow, Greenhouse gas emissions from broiler manure treatment options are lowest in well-managed biogas production, Journal of Cleaner Production, Volume 280, Part 2, 2021, 124969, ISSN 0959-6526
Huber, M., Van de Vijver, L., Parmentier, H., Savelkoul, H., Coulier, L., Wopereis, S., . . . Hoogenboom, R. (2010). Effects of organically and conventionally produced feed on biomarkers of health in a chicken model. British Journal of Nutrition, 103(5), 663-676. doi:10.1017/S0007114509992236
Sinclair, M., Lee, N. Y., Hötzel, M. J., de Luna, M. C., Sharma, A., Idris, M., Islam, M. A., Iyasere, O. S., Navarro, G., Ahmed, A. A., Curry, M., Burns, G. L., & Marchant, J. N. (2022). Consumer attitudes towards egg production systems and hen welfare across the world. Frontiers in Animal Science, 3.
Leinonen, I., & Kyriazakis, I. (2016). How can we improve the environmental sustainability of poultry production? Proceedings of the Nutrition Society, 75(3), 265-273. doi:10.1017/S0029665116000094
Rocío Abín, Amanda Laca, Adriana Laca, Mario Díaz. Environmental assesment of intensive egg production: A Spanish case study. Journal of Cleaner Production, 2018; 179: 160 DOI: 10.1016/j.jclepro.2018.01.067
History | BEIC. (2017, October 11). History | BEIC.
Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.
Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.