Multi-objective lifecycle optimization for oil palm fertilizer formulation: A hybrid P-graph and TOPSIS approach

The conversion of biomass (or agriculture residues) to organic fertilizer is a common practice in developing countries. This study aims to develop a novel multi-criteria decision-making approach towards sustainable fertilization that incorporates both organic and chemical fertilizers with the consideration of economic, environmental, and health aspects. A case study of oil palm plantation in Malaysia is adopted to demonstrate the applicability of the proposed framework. Firstly, global warming potential (GWP) of the fertilizer is identified using life cycle assessment. Then, a P-graph model is developed to identify a pool of feasible fertilizer formulations. A clustering approach is then applied to cluster this formulation pool according to the characteristics. Subsequently, TOPSIS (Technique of Order Preference Similarity to the Ideal Solution) is applied to rank the obtained fertilizer formulations based on three sustainability indices (i.e., total annual cost, GWP, 3-MCPD esters (3-monochloropropane-1,2-diol) as the ranking from P-graph is merely economically-driven. According to the results, F30 which comprises a combination of 0.96 wt% urea, 1.14 wt% monoammonium phosphate, 0.10 wt% kieserite, and 97.81 wt% palm-based organic fertilizer, is suggested for the oil palm tree. Notably, F30 falls in CO₂ credit mode where this formulation possesses environment burden reduction in the entire oil palm industry with negative carbon dioxide emission. The annual cost and GWP of F30 which does not possess any 3-MCPD threat is accounted for 205.26 MYR/year (MYR= Ringgit Malaysia) and -34.78 kg CO₂-eqv/year. This formulation is applicable across the growth stage of oil palm after validation comparison among different fertilization practices.