Pellets are small, compressed cylinders made from different materials depending on their purpose. Wood heating pellets are made from sawdust and wood shavings. Plastic pellets are made from petroleum-based resins. Animal feed pellets combine grains, proteins, and binders. The word “pellet” refers to the shape, not a single material, so the composition varies widely across industries.
Wood Heating Pellets
Wood pellets, the type burned in pellet stoves and boilers, are made almost entirely from compressed sawdust, wood shavings, and other lumber byproducts. Most contain no synthetic glue. Instead, the wood’s own natural binding compound, lignin, holds everything together. During manufacturing, raw sawdust is forced through a metal die under high pressure. The friction generates heat, typically reaching 75 to 125°C, which softens the lignin inside the wood fibers. That softened lignin acts as a built-in glue, fusing the particles into a solid cylinder as it cools.
Without that heat, pellets fall apart easily. Biomass compressed at room temperature has significantly lower strength because the natural binders never activate. Some manufacturers add small amounts of corn starch or wheat starch (1 to 5% by weight) to improve durability and lubricate the machinery during production. Kraft lignin, a byproduct of paper manufacturing, is sometimes added for extra binding strength as well.
Certified premium pellets (rated ENplus A1, the most common grade for home heating) must contain less than 0.5% ash and no more than 6% moisture. They deliver about 5.1 kWh of energy per kilogram. The low ash and moisture requirements are why premium pellets use clean softwood or hardwood with bark removed, since bark increases ash content. Sulfur content is capped at 0.03%, making them a relatively clean-burning fuel.
Grilling and Smoking Pellets
Food-grade smoking pellets are also made from compressed wood, but the wood species matters more than anything else because it determines the flavor. High-quality smoking pellets are 100% hardwood with no fillers, oils, or artificial flavoring agents. Common single-species options include hickory, mesquite, apple, cherry, pecan, and oak. Blends are popular too: oak and hickory together produce a classic barbecue smoke, while apple and pecan create a milder, sweeter profile suited to pork and poultry.
The manufacturing process is identical to heating pellets. The key difference is that cheaper brands sometimes use a base of oak or alder filler and add only a small percentage of the “flavor” wood. If you want a strong, consistent smoke flavor, look for pellets labeled as 100% single species or a named blend with no filler wood listed.
Plastic Pellets
Industrial plastic pellets, often called nurdles or resin pellets, are the raw material for nearly every plastic product. They look like small lentil-sized beads, and each one is made from a specific type of plastic resin. The most common types are polyethylene (used in bags, bottles, and containers), polypropylene (packaging, automotive parts), PVC (pipes, flooring), polystyrene (foam cups, insulation), and PET (water bottles, food packaging). ABS pellets are used for harder products like electronics housings and LEGO bricks.
These pellets start as raw petroleum or natural gas, which is processed into polymer chains and then extruded and chopped into uniform pellets. Beyond the base resin, manufacturers often mix in chemical additives before or during pelletization. Processing stabilizers prevent the plastic from degrading under heat during manufacturing, while antioxidants slow yellowing and breakdown over time. UV stabilizers may be added for products that will spend time in sunlight. Colorants and flame retardants are other common additions. The pellets are then shipped to factories, where they’re melted and molded into finished products.
Biodegradable alternatives are growing in the market. These include pellets made from polylactic acid (derived from corn starch or sugarcane) and other plant-based polymers, as well as recycled resin pellets made by shredding and reprocessing existing plastic waste.
Animal Feed Pellets
Livestock and poultry feed pellets are made from a mixture of ground grains, protein meals, vitamins, and minerals, all compressed into uniform cylinders. The exact recipe depends on the animal. Chicken feed pellets might emphasize corn and soybean meal, while cattle pellets could include alfalfa, barley, or cottonseed meal. The ingredients are ground to a fine consistency, mixed, steam-conditioned, and pressed through a pellet die.
Binders keep the pellets from crumbling during transport and in feeders. Molasses is one of the most common, a byproduct of sugarcane processing that adds both stickiness and a touch of energy. Its binding ability comes from the natural viscosity of its sugars. Bentonite, a type of clay, is another option that improves hardness and durability. Some formulations use simple sugars or starches as binding agents instead. The goal is a pellet firm enough to handle without breaking apart, but one that dissolves readily once eaten.
Iron Ore Pellets
In steel production, iron ore pellets are marble-sized balls made from finely ground iron ore concentrate. The ore is mined, crushed, and ground into a powder, then mixed with a small amount of binder and rolled into spheres in a large rotating drum. Bentonite clay is the traditional binder, typically added at around 1 to 2% by weight. The green (unfired) pellets are then heated in a kiln to temperatures exceeding 1,200°C, which hardens them into durable spheres strong enough to withstand the weight and conditions inside a blast furnace. Some producers are experimenting with polymer-based binders that allow less bentonite, since bentonite introduces impurities like silica that reduce the iron content of the final pellet.
Hormone and Medication Pellets
In medicine, pellets refer to tiny implants placed under the skin to deliver hormones or other medications over months. Testosterone pellets, for example, are made from pure crystalline testosterone with no fillers or binders. Each pellet is typically about the size of a grain of rice. Once implanted (usually in the hip or buttock area), the pellet dissolves gradually in the body. A standard 200 mg testosterone pellet releases about 1.3 mg per day, providing steady hormone levels for roughly six months before a replacement is needed. Estradiol pellets for hormone replacement therapy work on the same principle, using compressed crystalline hormone that absorbs slowly into surrounding tissue.
What All Pellets Have in Common
Across every industry, pelletization solves the same basic problem: taking a loose, inconsistent material and compressing it into a uniform shape that’s easier to store, ship, measure, and use. The core ingredients vary wildly, from sawdust to iron ore to crystalline hormones, but the physics are similar. Pressure and heat (or in some cases, a kiln or chemical process) force particles together tightly enough that they hold their shape. Natural or added binders fill the gaps between particles and lock the structure in place. The result is a dense, handleable pellet that performs more predictably than the raw material it came from.