Studying Compaction Behavior of Fractionated Poultry Litter and Use of Pyrolysis Condensate as Binder During Pelletizing

Abstract

Excessive poultry litter has caused nutrient imbalance in some watersheds, resulting in water quality impairment. Fractionation is an option suggested to concentrate nutrients into a fine fraction (particle size < 0.85 mm), thereby reducing the total mass to be transported out of the problem area. Pelletizing this fine fraction has been considered to reduce waste volume and to increase bulk density. This article investigated compression behavior of the fine fraction of poultry litter. In this study, the fine fraction of poultry litter was pelletized using a single pelleter unit at 100C and compressive loads of 500, 1000, 2000, 4000, 6000, and 8000 N. The compressive pressure versus pellet density data obtained from this experiment were fit with models developed by Heckel, Jones, Walker, Cooper and Eaton, and Kawakita and Ludde to explain the compression behavior. Pyrolysis condensate (aqueous phase and bio-oil phase) obtained from pyrolysis of the coarse fraction (particle size > 0.85 mm) of poultry litter was used to study its binding properties. To test the binding properties of pyrolysis condensate, the aqueous and bio-oil phase were mixed with the fine fraction at levels of 5% and 10% on weight basis. Pellets were made from the mixtures using a single pelleter unit under the same set of loads. These pellets were tested for hardness. Results show that the compaction of the fine fraction of poultry litter started by particle rearrangement at 0.06 MPa, followed by elastic deformation at 4.87 MPa and plastic deformation at 26.32 MPa, achieving a pellet density equal to 1.04 times that of true density. Although pyrolysis oil is used to make phenolic resin (a binding glue), neither aqueous phase nor bio-oil phase affected pellet hardness.