Optimum Conditions for Pelleting Dairy Manure Compost

Primary Author: Femi Alege

Faculty Sponsor: Pius Ndegwa


Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Engineering and Environmental Science

Campus: Pullman





Excess manure-nutrients near locations of animal production is a major threat to environmental health in such areas. This is due, mainly, to the bulkiness and high moisture content (MC) of manure or manure-compost. The overall goal of this study is to concentrate nutrients and reduce MC via pelleting to enhance nutrients transport, utilization, and storage to mitigate potential adverse environmental impacts at the source.



The optimum conditions for pelleting dairy manure compost were investigated with MC ranging from 10 – 35% (w.b.) and two die sizes (6-mm and 8-mm). The relationship between MC, pellet recovery, and pellet durability, as well as the effect of pelleting on nutrients concentration, were also determined. Properties and nutrient analyses of products were determined according to established ASABE and TMECC standard procedures.



Results showed that pelleting reduced the MC by >40% and increased the nutrients’ concentration by about 25%. The optimum MC for pelleting with the 6-mm and 8-mm dies were approximately 27 and 21%, respectively. No significant differences were observed between pellets recovery and pellets durability at MC between 20 and 30% for either die. Pellets produced within these conditions will thus reduce production downtime, materials wastage, costs of energy and labor, and the overall cost of transportation of the nutrients. The significant reductions in MC and increased nutrients concentration in the pellets significantly reduce transportation cost of the manure-nutrients to other regions where they can be beneficially applied on the land with less potential negative impact on the environment.