Comprehensive Guide to Poultry Processing By-products

When a bird goes through a poultry processing plant, roughly 35-40% of its live weight never reaches the dinner table. Feathers, blood, heads, feet, and intestines – materials collectively called offal – are separated at various stages of slaughter and dressing. Far from being discarded, these materials have become valuable raw inputs for animal feed, fertilizers, biofuels, and industrial products. Understanding what these by-products are, how they are processed, and what they ultimately become is central to appreciating how modern poultry production works as a near-zero-waste system.

What counts as a poultry processing by-product? 🔗

Offal from a poultry processing plant includes feathers, blood, intestines, evisceration waste, heads, and feet – all classified as inedible parts of the bird even though some, like feet, are consumed in certain markets. The AAFCO definition of poultry by-product meal specifies ground, rendered clean parts such as necks, heads, feet, undeveloped eggs, and intestines, exclusive of feathers. Feathers are handled separately because of their distinct protein composition. Together, these materials form the raw material base for an extensive secondary processing industry.

It is worth noting that a single broiler of average slaughter weight yields roughly 0.3 kg of offal, and global broiler slaughter produces an estimated 17 million tonnes of offal per year – a scale that makes efficient by-product utilisation not just economically attractive but environmentally essential.

Feathers and feather meal 🔗

Feathers are among the most abundant by-products at any poultry facility. They make up about 5-7% of a bird’s live weight and are composed primarily of keratin – a fibrous structural protein that is virtually insoluble in its raw state. This insolubility is the central processing challenge: raw feathers pass through the digestive tract of animals largely undigested.

Hydrolysis: making keratin digestible 🔗

The standard solution is hydrolysis. Feathers are processed under pressure of 30-50 psi for approximately 45-60 minutes, which breaks the peptide and disulfide bonds holding the keratin structure together. The resulting feather meal contains a high concentration of amino acids and has a low ash content that aids digestibility across different animal species. Hydrolyzed feather meal is used in feed formulations for ruminants, aquaculture, poultry, and pet food. It is also a valuable input for organic fertilizer production due to its high nitrogen content.

Industrial uses of keratin 🔗

Beyond feed and fertilizer, feather keratin has attracted research interest in materials science. Keratinase – an enzyme secreted by bacteria such as Bacillus licheniformis – can ferment feathers into a digestible protein source through biotechnological pathways. Keratin extracted from feathers is also being investigated for use in biodegradable plastics, insulation materials, and cosmetic ingredients, extending its industrial value well beyond the feed sector.

Blood and blood meal 🔗

Blood accounts for approximately 3-4% of a bird’s live weight. Fresh poultry blood contains around 18-20% protein and is rich in essential amino acids – particularly lysine. Rapid collection after slaughter is critical: delays allow coagulation and reduce the nutritional quality of the final product.

Processing methods for blood 🔗

Collected blood is processed by one of three main methods: batch-dry rendering, spray rendering, or ring-dried rendering. Each produces blood meal – a dried, high-protein powder. Blood meal is among the highest non-synthetic sources of nitrogen, containing approximately 12% nitrogen by weight. In animal nutrition, it is particularly valued for its lysine content, which is often the limiting amino acid in plant-based diets. It is used in feed for cattle, fish, and poultry.

For organic agriculture, blood meal serves as a slow-release nitrogen fertilizer that supports sustained plant growth without the environmental risks associated with synthetic nitrogen inputs. Blood can also be fractionated into plasma and cellular components: plasma proteins are especially valuable in pet food manufacturing and in specialised feeds for young animals. In some processing streams, blood is directed toward pharmaceutical applications.

It should be noted that feeding blood products to ruminants is prohibited in the United Kingdom and the European Union due to regulations relating to transmissible spongiform encephalopathies, so market access for blood meal varies by region and end-use.

Heads and feet 🔗

Poultry heads account for approximately 2% of total bird weight and are generally not consumed in Western markets, though they are directed to livestock feed production or processed into meal. Research has shown that chicken heads are a significant source of collagen-rich proteins, making them a promising raw material for gelatin production. Gelatin derived from chicken heads has applications in the food, pharmaceutical, and cosmetic industries, and the solid residues remaining after gelatin extraction can themselves be used as fertilizers.

Feet (also called paws) are a different case. They are a commercially important edible product in several Asian and African markets, where they are consumed directly. Chicken feet are a source of gelatin and fat. When not destined for direct consumption, feet are rendered together with other offal or processed into poultry by-product meal. Both heads and feet contribute calcium and phosphorus when processed into bone meal, making them useful mineral supplements in feed formulations.

Intestines and internal organs 🔗

The viscera removed during evisceration include the heart, liver, gizzard, and intestines. Some organs – hearts and livers in particular – are sold in edible markets. The remainder enters the by-product processing stream. Intestines and glands can be employed in the production of hormones and enzymes. Intestines are also processed into natural casings for sausage production – one of the oldest by-product applications in the meat industry – or converted into protein meals.

Organs not consumed by humans are processed into meals or used in pet food manufacturing, as they are extremely nutrient-dense and contain high levels of vitamins and minerals. Poultry by-product meal produced from a combination of these inedible viscera, along with feet, heads, and undeveloped eggs, is one of the most important sources of animal protein for domestic animals, alongside meat and bone meal, blood meal, feather meal, and fish meal.

Technical fats from poultry rendering 🔗

Fat is recovered as a separate fraction during the rendering process. Rendering involves cooking by-products at high temperatures – typically 115-145°C – to separate proteins, fats, and moisture, while simultaneously sterilising the material. The fat that separates during this process has several distinct end-use pathways depending on its quality and regulatory category.

Feed-grade and technical applications 🔗

High-quality poultry fat is incorporated into animal feed formulations as a concentrated energy source and palatability enhancer. Fat from rendering can also be used in technical applications or as a raw material for biofuel production, including lubricants and industrial chemicals. In Europe, only Category 3 rendered fat is permitted in animal feed; Category 1 and 2 fats are directed to technical uses such as fuel.

Poultry fat as a biofuel feedstock 🔗

Chicken fat is noted for being high in linoleic acid, an omega-6 fatty acid, and has been used in the production of biodiesel through transesterification and supercritical methanol treatment. Poultry fat has a carbon-intensity score that is up to 80% lower than conventional diesel fuel, positioning it as a potential feedstock for renewable diesel and sustainable aviation fuel (SAF). Demand for animal fats in biofuels is projected to triple by 2030 compared to 2021, though supply constraints remain a challenge given that fat availability is directly tied to the volume of animals slaughtered.

The rendering process: central to by-product value recovery 🔗

Rendering processes are used to convert the by-products of poultry processing into marketable products, including edible and inedible fats and proteins for agricultural and industrial use. Plants integrated directly into processing facilities handle fresh material, while independent rendering plants collect from multiple off-site sources. The key steps are grinding, cooking under controlled temperature and pressure, separation of fat from solid protein residue, and drying. The solid output becomes meal – feather meal, blood meal, poultry by-product meal, or meat and bone meal depending on the input – while the liquid fraction becomes fat.

According to the American Feed Industry Association, the rendering process reduces greenhouse gas emissions by 72% and fossil fuel use by 80% compared to landfilling or composting animal waste, underlining its environmental significance alongside its economic role.

Economic value and sustainability implications 🔗

Every component recovered from processing by-products – feather meal for feed, blood meal for fertilizer, technical fat for biofuel, bone meal for mineral supplementation – represents revenue that would otherwise be lost and waste that would otherwise require costly disposal. Poultry by-product meal is in high demand from the pet food and aquaculture industries, with recommended inclusion levels for fish feed in the 5-25% range. For ruminants, the heat treatment applied during processing makes poultry by-product meal a valuable source of rumen-undegraded protein.

The efficient handling of offal also reduces wastewater treatment requirements: screening poultry processing wastewater to remove particulate matter reduces treatment costs while simultaneously increasing the collection of materials for rendering. In this way, waste management and value recovery reinforce each other operationally.

What do you think? As poultry production scales up globally to meet protein demand, how should processing plants prioritise between high-value by-product uses – such as pharmaceutical-grade plasma proteins – and bulk applications like biofuel? And given regional regulatory differences on blood meal and other by-products, what role should international harmonisation play in unlocking the full economic potential of poultry processing waste?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC3614052/
2. https://www.dutch-poultry-tech.com/products/processing-solutions/by-product-offal-handling/
3. https://www.feedipedia.org/node/214
4. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/poultry-meal
5. https://nara.org/2023/12/15/products-from-rendering/
6. https://en.wikipedia.org/wiki/Blood_meal
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC7037018/
8. https://www.alfalaval.com/industries/food-dairy-beverage/food-processing/protein-processing/meat-poultry-processing/dry-rendering-process/
9. https://efpra.eu/2025/10/15/animal-fats-are-a-sustainable-feedstock-for-biofuel/
10. https://en.wikipedia.org/wiki/Chicken_fat
11. https://www.biobased-diesel.com/post/yes-you-can-use-poultry-fat-as-a-renewable-feedstock
12. https://www.poultryworld.net/the-industrymarkets/market-trends-analysis-the-industrymarkets-2/growing-demand-for-animal-fats-biofuels/
13. https://www.fortunebusinessinsights.com/rendered-poultry-products-market-107256