Optimization of Pelletizing Process of Sugarcane Bagasse Compost Using Response Surface Methodology and Evaluation of Release Rate of Nitrogen from Pellet

To increase the applicability of compost for agricultural utilizations on a large scale as a sustainable slow-release nitrogen fertilizer, as well as reducing the limitations of their handling, transportation, and storage, it is important to improve their physical and mechanical properties, and pelletization is the most applicable process to achieve these goals. In the present study, the pelletizing process of sugarcane bagasse compost using a closed-end die within a single pelletizer unit was investigated. Composted hammer milled sugarcane bagasse with three particle size (1, 2.5, and 4 mm), three moisture content (8, 12, and 20 %) under three compaction pressure (50, 100, and 150 MPa) was densified and the effect of these factors on specific energy consumption, maximum breaking strength and density of produced pellets were evaluated and optimized by response surface methodology (RSM). The optimum value of specific energy consumption (2.11 MJ/t), maximum breaking strength (28.35 kg), and particle density (0.871 g/cm3) were suggested from BBD-RSM for pelletization of sugarcane bagasse compost under optimal conditions of using 4-mm particle size, 20 wb% moisture content and 50 MPa compaction pressure with desirability function of 0.706. Then, the rate of nitrogen release in soil and water for pelletized mixed sugarcane bagasse compost-urea fertilizer at a ratio of 1:1 wt% was investigated. The results of the nitrogen release rate showed that 61% of nitrogen was released into the water during five days while the release of nitrogen in soil was 80% during 98 days for pelletized mixed compost-urea fertilizer. In general, the findings of this study showed that the pelletized fertilizers produced from the compost-urea mixture are capable to supply nitrogen to the plant for a longer period relative to conventional nitrogen fertilizers such as urea. It could be deduced from this research that pelletized mixed compost-urea fertilizers have great potential for use in crop nutrition as a sustainable slow-release nitrogen fertilizer.