Investigation of Preparation of Biochar-based Sustained release Fertilizer from Filter Mud of Sugar Mills and Its Properties

In order to make better use of the filter mud from sugar mills, biochar was prepared by pyrolysis of the mud at 500 degrees C, which was then to absorb urea to produce sustained release fertilizer pellet, using soluble starch as the binder. The pellet shaping, the mechanical properties and the sustained-release effect of the pellet fertilizer were studied. The results showed that 22-26% water content was favorable for pelleting the biochar-based fertilizer, improving the maximum crushing compression force (MCCF) of the pellet. The pelleting rate and its MCCF decreased with the increase of biochar content. The sustained release effect of the pellet fertilizer was better than that of traditional fertilizer, and the sustained release effect increased with the increase of biochar content and soluble starch content. The optimum conditions in terms of pelleting rate, MCCF, sustained release performance and cost-effectiveness were the ratio of urea to biochar of 1:5, the content of soluble starch 10% and the amount of water 24%. The release of the biochar-based fertilizer was in accordance with the first-order release model.