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

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 (2k-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.

Optimization of process parameters of self-purging microwave pyrolysis of corn cob for biochar production

“…The ANOVA result revealed that only the microwave power output and its interaction with exposure time have significant effects (p < 0.05) on the biochar yield. This is in contrast to the study by Lawas et al (2019), which reported that both factors and their interaction to be significant. The model generated is presented by the following equation: 3.…”

“…This work followed the parametric study conducted by Lawas et al (2019) on the microwave pyrolysis of corncobs. Using self-purging microwave pyrolysis and polypyrrole as the absorber, the optimal settings for microwave power and exposure time were established to maximize the biochar yield from corncob.…”

“…The corn cob wastes were purchased and collected from the public market of Los Baños, Laguna, Philippines. All the reagents and sample preparation methods are the same as described in the parametric study previously conducted by Lawas et al (2019). The J o u r n a l P r e -p r o o f FeCl3 hexahydrate (analytical grade) and pyrrole monomer (98% pure) were purchased from Sigma-Aldrich, and the silica gel (self-indicating, 5-10 mesh) was from LABCHEM.…”

“…This work builds upon the parametric study conducted by Lawas et al (2019), which determined the microwave power and exposure time as significant factors in biochar production using corn cobs. Before the experiment, the results from the said study were first validated through a series of verification runs.…”

“…Using Design Expert, Table 2 shows the experimental design generated for the optimization of biochar yield. The high and low values considered are within the range of values used by Lawas et al (2019). After determining the optimal microwave power and exposure time setting, five (5) additional runs were conducted under this condition for validation.…”