Types of By-products in Poultry Industry

The global poultry industry is one of the largest food-producing sectors in the world – but only a portion of every bird ends up as the meat or eggs we consume. A significant share of total production weight consists of materials that never reach the dinner table: feathers, blood, offal, manure, eggshells, and hatchery waste. Rather than discarding these materials, modern poultry operations systematically process and convert them into valuable products. Understanding the different types of poultry by-products – and where they originate – is the first step in appreciating how the industry supports sustainability and circular resource use.

What are poultry by-products? 🔗

The term “poultry by-products” refers to all materials generated during poultry production and processing that are not directly consumed as human food. According to a review published in PMC, materials in this category include viscera, meat scraps, bone, blood, feathers, and hatchery waste such as infertile eggs and dead embryos. These are processed using rendering – a thermal treatment method that converts raw by-products into stable, marketable outputs like animal feed-grade fats, protein meals, and feather meal.

Poultry by-products are generally grouped into three categories based on the stage of production at which they arise: the production phase, the hatchery phase, and the processing plant phase. Each category has its own distinct set of materials and processing pathways.

Production phase by-products: manure and litter 🔗

During the live bird production phase on the farm, the primary by-product generated is poultry manure and the litter it accumulates in. Research published in Frontiers in Sustainable Food Systems notes that poultry litter is composed of bedding material, feathers, manure, and wasted feed, and contains important plant nutrients including nitrogen (N), phosphorus (P), and potassium (K). This nutrient profile makes it a natural candidate for use as an agricultural fertilizer.

Beyond fertilizer, poultry manure has significant energy potential. The U.S. Environmental Protection Agency (EPA) highlights anaerobic digestion (AD) as an approach to convert poultry litter into biogas and organic fertilizer. The biogas produced can be used to generate electricity or heat on-farm, while the digestate is applied as a certified fertilizer for crops. A review in Environmental Chemistry Letters further confirms that the biogas generated through AD typically contains 50-75% methane, which can substitute for natural gas. However, the high nitrogen content in poultry manure can cause ammonia inhibition during digestion, which is a known technical challenge that producers must manage carefully.

Poultry litter also shows promise for pyrolysis – a thermal process that converts it into biochar, which can improve soil structure and adsorb heavy metals when applied in agriculture.

Hatchery by-products: eggshells, infertile eggs, and dead embryos 🔗

Commercial hatcheries produce a steady stream of organic waste that is distinct from both farm-level and processing plant by-products. According to Feedipedia, hatchery by-products include shells of hatched eggs, infertile eggs, dead embryos at various stages of development, and dead or culled chicks. The scale of this waste is considerable – in a typical commercial hatchery, around 15-20% of eggs processed become by-products requiring proper management.

Eggshells 🔗

Eggshells are one of the most structurally uniform hatchery by-products. A typical eggshell contains approximately 95% calcium carbonate, making it an excellent raw material for producing calcium supplements for animal feeds. Hatchery equipment specialist Petersime explains that eggshells can be separated from other hatchery waste using suction vacuums, vibrating sieve belts, or cyclone forced-air separators. Once separated, shells can be ground into eggshell meal – a bioavailable calcium source particularly useful in diets for laying hens, which have high calcium demands for shell formation.

The inner eggshell membrane is another high-value component. It contains approximately 10% collagen, which has applications in medicine – including wound dressings, dental procedures, and osteoporosis treatment – as well as in food processing and biodegradable plastics.

Infertile eggs and dead embryos 🔗

Infertile eggs and eggs containing dead embryos can be rendered into hatchery by-product meal through cooking, drying, and grinding. Feedipedia’s feed ingredient database notes that this meal is suitable for feeding livestock, with a calcium content that varies based on the proportion of eggshells included. It can be incorporated at levels of 8-16% in layer diets without negative effects on egg production, and at 3-8% in broiler starter and grower diets as a protein and energy source. Co-extrusion with soybean meal or lactic acid fermentation are alternative processing routes that yield safe, palatable feed ingredients.

The Poultry Site emphasizes that to achieve pathogen-free status, hatchery by-product meal must be processed by autoclaving, extrusion with temperature disinfection, or pressure boiling and drying. Many countries regulate or restrict the use of hatchery by-products in animal feed, so producers must verify local requirements before use.

Processing plant by-products: the largest and most diverse category 🔗

The slaughter and processing plant generates the broadest range of poultry by-products. According to ScienceDirect’s overview of poultry meal, processing by-products include feathers, heads, feet, viscera, and meat trimmings – each of which is handled through distinct processing pathways to extract maximum value.

Feathers and feather meal 🔗

Feathers are one of the most abundant by-products at the processing plant. Research published in Discover Animals (Springer Nature) reports that feathers constitute around 7-8% of a chicken’s total weight, resulting in over 50 grams of feather waste per bird. Since feathers are composed largely of keratin – a protein that is nearly insoluble in its raw form – they must be processed before their nutritional value can be unlocked.

This is done through hydrolysis, in which feathers are subjected to steam pressure at 30-50 psi for around 45-60 minutes. ScienceDirect notes that this process breaks peptide and disulfide bonds, after which the material is dried and ground into feather meal – an ingredient that is an excellent source of the amino acid cysteine. Hydrolyzed feather meal typically contains 80-85% crude protein and is used in animal feeds, particularly for ruminants and in aquaculture diets. It also serves as a nitrogen-rich organic fertilizer.

Beyond feed applications, keratin extracted from feathers is being explored for use in cosmetics, medical devices, and biodegradable plastics – areas where its unique structural properties offer functional benefits.

Blood and blood meal 🔗

Poultry blood, collected during slaughter, is another high-value processing by-product. Wikipedia’s entry on blood meal describes it as a dry powder made from blood, used both as a high-nitrogen organic fertilizer and a high-protein animal feed supplement. By weight, blood meal typically contains around 12% nitrogen, making it one of the richest non-synthetic nitrogen sources available.

In animal nutrition, blood meal is particularly valued for its lysine content – an essential amino acid that is often a limiting nutrient in plant-based diets. It is used as a rumen-undegradable protein source in dairy cattle diets, and as a dietary supplement for fish and poultry. The method of drying significantly affects nutritional quality: spray drying preserves the highest amino acid availability, while batch drying tends to reduce digestibility. It is worth noting that the European Union and United Kingdom prohibit feeding blood products to ruminants due to concerns related to transmissible spongiform encephalopathies.

Offal and poultry by-product meal 🔗

Offal refers to the internal organs and viscera separated during poultry processing – including intestines, liver, and other organs not consumed as human food. These materials are rendered into poultry by-product meal, which is one of the most important animal-derived protein ingredients used in livestock and pet food. Feedipedia’s profile of poultry by-product meal explains that this meal is made by combining by-products from poultry slaughterhouses, and that worldwide, more than 55.5 billion broilers slaughtered in 2009 yielded about 16.5% offals – translating to an estimated 17 million tons per year of broiler offal alone.

The rendering process involves collecting and stabilizing offals (often by reducing pH through fermentation or acid treatment), followed by cooking, sterilization, and drying to around 8% moisture. According to Feedipedia, modern dry-rendering has replaced the older wet-rendering (steam pressure cooking), yielding meals of higher quality. The finished meal is a palatable, golden-to-brown product with a strong amino acid profile, used extensively in poultry, pig, aquaculture, and companion animal diets.

The Poultry Products Formulators and Renderers organization defines poultry by-product meal as the rendered product from ground, clean parts such as necks, feet, undeveloped eggs, and intestines – exclusive of feathers (except in unavoidable trace amounts). It must meet guaranteed minimums for crude protein, fat, phosphorus, and calcium.

Heads, feet, and other carcass parts 🔗

Heads and feet, though not commonly consumed in many Western markets, are highly valued in Asian and African markets for direct food consumption. Where they are not sold as food, they are incorporated into rendering streams to produce protein and fat fractions for animal feed. Organs such as the liver, which is nutrient-dense and high in vitamins and minerals, are processed into meals or used in pet food manufacturing when not consumed by humans.

Why proper by-product processing matters 🔗

The three categories of poultry by-products together represent a large share of the total mass generated by the industry. Processing these materials efficiently – rather than disposing of them as waste – reduces the environmental burden of poultry production, generates additional revenue streams for producers, and contributes to the sustainability of the global food system.

Improper disposal of by-products carries real risks: a peer-reviewed study in the journal Sustainability notes that poorly managed hatchery waste and processing effluents can cause nitrate and phosphate contamination of groundwater, greenhouse gas emissions, and pathogen distribution. The PMC review on meat and poultry processing by-products also highlights the need for integrated or independent rendering plants that operate with strong quality controls to prevent Salmonella contamination in the final feed ingredients.

At the same time, innovations in processing – from hydrolyzed feather meal with improved digestibility to anaerobic digestion systems that produce both biogas and certified fertilizer – continue to expand the range of value that can be extracted from these materials. The poultry industry’s approach to by-products is increasingly guided by circular economy principles: every part of the bird has a role to play, and every output of the production system is a potential input for another.

What do you think? Given the wide range of by-products generated at each stage – from the farm to the hatchery to the processing plant – which category do you think holds the most untapped potential for value addition? And how might stricter regulations around pathogen control in by-product processing affect the economics of poultry production in developing regions?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC3614052/
2. https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2018.00046/full
3. https://www.epa.gov/agstar/anaerobic-digestion-poultry-farms
4. https://link.springer.com/article/10.1007/s10311-023-01618-x
5. https://www.feedipedia.org/node/212
6. https://www.petersime.com/hatchery-development-department/responsible-disposal-of-hatchery-waste/
7. https://www.thepoultrysite.com/articles/responsible-disposal-of-hatchery-waste
8. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/poultry-meal
9. https://link.springer.com/article/10.1007/s44338-025-00102-w
10. https://en.wikipedia.org/wiki/Blood_meal
11. https://www.feedipedia.org/node/214
12. https://www.poultryrenderers.org/products.cfm
13. https://www.mdpi.com/2071-1050/3/1/216