Pelletizing Poultry Litter with Biochar: A Strategy to Enhance Poultry Litter Utilization

Abstract Purpose The rapid growth of the U.S. broiler industry has generated a large amount of poultry litter (PL). This bulky waste is often applied in excessive amounts in nearby agricultural fields due to limited handling, contributing to nutrient runoff and degradation of water quality. A sustainable solution is needed to convert this PL into a value-added resource, offering broader agricultural utilization and nutrient retention to minimize the environmental risks. Methods Biochar (BC) was mixed with PL at different ratios: 0% (PL 100 ), 25% (PL 75 BC 25 ), 50% (PL 50 BC 50 ), 67% (PL 33 BC 67 ), 75% (PL 25 BC 75 ), and 80% (PL 20 BC 80 ) and subjected to pelletization to enhance the handling and nutrient retention properties. Physical (dry matter, particle size, density, hardness, durability) and chemical (C–N ratio, nutrient release) properties were evaluated to study the effect of BC addition and pelletization on PL. The effect of BC addition on pellet production rate and energy consumption was analyzed to evaluate the energy efficiency of the process. Results Pelletization doubled (1.85 times) the density while dry matter was raised by 6.5%. Incorporation of BC (> 50%) significantly reduced the dry matter and density due to the inherent moisture retention capacity of BC. The BC addition (> 50%) decreased pellet hardness, potentially due to low pelletization temperature (r = 0.66, p < 0.001) and increased particle size (r = − 0.66, p < 0.001) formation. Durability remained satisfactory (> 88%) at all PL–BC mixtures. Pelletization and BC addition at 50% (w/w) decreased the phosphate (PO 4 –P) release by 132%, while ammonia (NH 4 –N) release was reduced by 141%, compared to non-pelletized raw PL (PL 100 ). Biochar incorporation significantly increased the pellet production rate while consuming lower energy. Conclusion Preliminary observations suggested that pelletizing PL with a moderate level (≤ 50%) of BC addition offers an optimal balance that can enhance nutrient retention without compromising the pellets’ structural integrity. Future field studies will provide more insight into its field application efficiency and nutrient release characteristics. Graphical abstract