Poultry litter is a complex agricultural byproduct resulting from intensive poultry production. It is composed of bedding material mixed with bird excreta, feathers, and spilled feed. This material results from intensive poultry production, such as in broiler or turkey operations, where birds are raised on a substrate until they are ready for market. The litter serves an important function in the poultry house by absorbing moisture and diluting the manure, thereby maintaining good air quality and animal health. This mixture is now recognized as a valuable resource in agriculture and energy production.
Composition and Source Materials
Poultry litter is a heterogeneous substance whose exact makeup varies based on the type of bird, the diet, and the length of time it is used. The primary component by volume is the bedding material, which is typically an absorbent, fibrous organic material. Common bedding materials include wood shavings, sawdust, rice hulls, peanut hulls, or straw. These materials are spread across the floor of the poultry house, often to a depth of around five centimeters.
The second major component is poultry manure, which contains high concentrations of nitrogen, primarily as uric acid and undigested proteins. Birds excrete nitrogen in a semi-solid form, contributing to the litter’s relatively low moisture content compared to other livestock manures. As multiple flocks are raised on the same bedding, the material accumulates feed, feathers, and manure, transitioning to “spent” litter. The resulting granular mixture is highly variable in its chemical composition and nutrient ratio, depending on management practices.
Use as a Soil Amendment
The most widespread and traditional use of poultry litter is as an organic soil amendment and fertilizer in crop and pasture systems. Applying this material returns substantial organic matter to the soil, improving soil structure, aeration, and water retention capacity. It is considered a complete fertilizer because it contains all 13 plant nutrients necessary for growth, including the macronutrients nitrogen (N), phosphorus (P), and potassium (K).
For instance, broiler litter can contain an average of 62 pounds of nitrogen, 59 pounds of phosphate (P₂O₅), and 40 pounds of potash (K₂O) per ton, although these values are highly variable. Much of the nitrogen is in an organic form, providing a slow-release benefit as soil microorganisms convert it into plant-available forms. This gradual nutrient release sustains plant growth throughout the season. Additionally, calcium compounds in the litter can have a liming effect, helping to reduce soil acidity.
Alternative Energy Applications
Beyond its use as a fertilizer, poultry litter has gained attention as a viable biomass fuel for renewable energy generation. The material’s organic content and relatively low moisture when air-dried give it an energy content in the range of 3,800 to 5,000 British Thermal Units (BTU) per pound, making it suitable for thermal conversion processes. This application provides an alternative management strategy for surplus litter, especially in areas with concentrated poultry production.
The primary conversion methods are combustion or gasification. Direct combustion in specialized boilers generates heat, which produces steam for electricity generation or hot water for heating poultry houses. This thermal process efficiently reduces the material’s volume while conserving phosphorus and potassium. These nutrients are captured in the resulting ash byproduct, which can then be used as a concentrated, high-value fertilizer.
Storage and Treatment Methods
Proper handling and preparation of poultry litter are necessary to maximize its value and minimize environmental or health risks before application or use as fuel. Storage is managed to control moisture content and nutrient loss, typically by stockpiling the material in covered sheds or structures with concrete floors. This protects the litter from rain and runoff, as uncovered storage leads to nitrogen loss through ammonia volatilization and causes water quality issues.
Treatment methods like composting stabilize the material and reduce pathogens. Composting involves stacking and turning the litter to introduce oxygen, allowing microorganisms to break down organic matter and generate heat, often reaching thermophilic temperatures. Another common method is pelletizing, which compresses the loose material into dense, uniform pellets. Pelletizing improves bulk density and durability, making the litter easier and more cost-effective to transport, store, and spread.