Extraction of nitrogen, phosphorus and potassium from food waste under elevated temperature by heat induced bath method

Abstract

38,000 tonnes of waste is generated per day in Malaysia and 15,000 tonnes of that are food wastes. This waste should be recovered to produce a new valuable product that brings benefits such as fertiliser because it contains various nutrients such as proteins, carbohydrates. This study aims to determine the effects of thermal treatment on the macronutrient of food waste that collected from cafeteria of Universiti Sains Malaysia (USM). Hot water bath was employed as thermal treatment of food waste with five different temperatures (60 °C to 100 °C) with two reaction time (30 min and 60 min). The results have demonstrated increases in the percentage of nitrogen (N) and concentration of phosphorous (P) however for the concentration of potassium (K) shows inversely related after subjected to hot water bath. Thermal treatment showed the untreated sample only consists 2.13 % of N and 31.53 mg/L of P, and after the treatment resulted in an increase in N and P by 0.22 % - 3.39 % and 0.33 mg/L - 21.40 mg/L respectively. On the other hand, the concentration of K in the untreated sample is 0.4915 ppm and after treatment it decreases to 0.1051 ppm - 0.2052 ppm. Based on the range of macronutrient in organic fertilisers in Malaysia, only N was in the range and can directly employ as organic fertiliser while for P and K should undergo further treatment.