FORMULATION AND OPTIMISATION OF SPENT BLEACHING EARTH-BASED BIO ORGANIC FERTILISER

Abstract

Spent bleaching earth (SBE) generated from the palm oil refinery is convertible into value-added products instead of being discarded as waste to landfills. An alternative approach is to develop SBE-based bio organic fertiliser through co-utilisation with other sources of biomass of contrasting nutrients properties. The feasibility of blending SBE with various forms of biomass – oil palm trunk (OPT), oil palm frond (OPF), empty fruit bunch (EFB) and chicken litter (CL) – in different mixing ratios was studied and its optimum ratio determined. The mixtures of SBE and various biomass at different mixing ratios were analysed for their macronutrient and micronutrient content, pH, organic carbon (OC), total nitrogen, carbon:nitrogen ratio (C:N) and organic matter (OM) content. The optimised blend of SBE:OPT:CL at the ratio of 1:1:0.5 exhibited sufficient nutrient contents (N: P 2 O 5 : K 2 O = 0.65:1.59:1.63) and good physicochemical properties (pH = 5.4, OM = 40% and C:N = 36:1) as a base material for bio organic fertiliser production. This optimum formulation was further enriched with urea (46% N), Christmas Island rock phosphate (CIRP, 25% P 2 O 5 ) and muriate of potash (MOP, 66% K 2 O) to produce a bio organic fertiliser suitable for vegetable crops with desired nutrients N:P 2 O 5 :K 2 O ratio of 2:2:2.