Effects of compost particle size, moisture content and binding agents on co-compost pellet properties

Composting is one of the sustainable answers for the management of organic municipal waste. Bulky nature of loose compost is one of the main drawbacks in promoting compost in agriculture and pelletization of compost can offset these drawbacks. In this study, the optimum conditions in a die and roller pelletizer to form pellets with desirable properties; bulk density, compressive strength, pellet length and disintegration ability with compost particles of different mesh sizes (2.5, 3.5, 5 mm), moisture contents (25%, 30%, 35%, 40%, 45%), different amounts and types of binding agents (1%, 2%, 3% by weight of Rice Flour (RF), Lime, Rock Phosphate (RP)) were investigated. Pelletizing increased the bulk density of compost. Compost with ≤5 mm particles and 25% moisture content resulted pellets with the highest compressive strength and a higher percentage of long pellets. However, the tested properties varied with the type and the amount binding agents used with compost. Disintegration was not observed in pellets free of binding agents during the tested period but binding agents enhanced disintegration. Both machine efficiency and production efficiency decreased with increased moisture in compost and increased with increased compost particle size. However, increased amounts of binding agents in compost reduced the machine efficiency. This work shows that compost pelletizing with and without binding agents, enhanced properties of compost required in transportation, storage and application in agriculture.