Optimum Moisture Content of Compost for Fertilizer Pellets Produced Using an Extruding Device

Agglomeration followed by pelleting is an efficient method to decrease transport costs and increase economic efficiency of composting municipal waste. The moisture content of compost is the most important parameter of the pellet making process for any type of manufacturing device. The experiments in this study were done at moisture contents of 35%, 45% and 50% at extruder shaft rotational speeds of 100, 150, 200 and 250 rpm. The materials were first processed using a mixer and kneading device then made into pellets using a single screw extruder. The durability of the pellets at different moisture contents were tested to determine the optimum moisture content and its effect on the properties of the pellets. The results showed that moisture content of the compost, rotational speed of extruder screw and the interaction of these parameters significantly affected the durability of the pellets. Durability increased from 35.86% to 78.29% as moisture content increased from 35% to 45% (w.b.). Durability was increased significantly at all rotational speeds as moisture content increased from 35% to 45% (w.b.). Increasing the moisture content produced no significant effect for the strength of the pellets at a rotational speed of 150 rpm. The strength was higher at 35% moisture content than for 45% moisture content.