Potassium recovery from tropical biomass ash

Abstract

Biomass is a potential alternative fuel in Indonesia and other tropical countries. Combustion of biomass produces ash that may contain various beneficial compounds, including potassium. Potassium recovered from the biomass ash can be used as the raw material for producing fertilizer solution, thus reducing Indonesia’s dependence on fertilizer import. This study aims to assess the feasibility of potassium recovery from the ashes of oil palm empty fruit bunch (OEFB), banana peel, and corncob. The biomass ash samples are prepared by the following steps: drying, fixed-bed carbonization, and ashing. Single-stage batch extractions are carried out at 80 °C for 4 hours using demineralized water. The ash to solvent mass ratios used is 1:4, 1:5, 1:6, and 1:8, respectively. Measured ash content on dry basis is 10.75% for banana peel, 2.60% for OEFB, and 1.67% for corncob. Banana peel and OEFB ash extracts contain potassium exceeding the national standard for fertilizer solution, which is set at 30,000 ppm of equivalent K2O. The highest potassium yield with respect to total potassium content in the ash is obtained from corncob ash within the ash to solvent ratio of 1:8, with the potassium yield of 62.29%. By contrast, banana peel ash extraction at ash to solvent ratio of 1:4 results in the lowest potassium yield of 21.41%.