Parametric study of corn cob biochar (CCBc) yield via microwave pyrolysis

Department of Chemical Engineering, College of Engineering and Agro-Industrial Technology, University of the Philippines Los Banos, 4030 Laguna, Philippines

Corresponding author: kalawas@up.edu.ph

Abstract

In the long-run, microwave pyrolysis can be a simpler and low energy-requiring alternative to conventional pyrolysis for the thermochemical conversion of biomass to useful products. However, there are still research gaps in its mechanism. Thus, this study investigated the various factors affecting the biochar yield using a half resolution (2^k-1) factorial design on the microwave pyrolysis of corn cob wastes. A viable biochar product was produced within minutes of the reaction; wherein, the statistical analysis confirmed the exposure time, microwave output power and their interaction as significant in the CCBc yield. The highest yield obtained was 52.87% when exposure time and output power were set to 5 min and 450W, respectively. A general decreasing effect on the yield was observed from increasing exposure time and output power. This was due to the rapid heating experienced by the corn cob wastes causing the hydrocarbons to react and transform into permanent gases at higher temperatures. To confirm the carbon content of the CCBc, elemental analysis showed an average of 67.11% C at low time-low power (LTLP) of 450 W for 5 min and 81.32% C for the samples operated at high time-high power (HTHP) of 700 W for 10 min.