Wet torrefaction of shea nut chaff to improve its fuel properties

Abstract

AbstractBiomass is a renewable alternative energy source with almost zero‐carbon footprint. This work focused on the physicochemical analysis and wet torrefaction of shea nut chaff (SNC) biomass. The SNC is a semi‐solid waste generated during the production process of shea nut butter and is least studied for its bioenergy potential. Wet torrefaction or hydrothermal carbonization studies of sun‐dried SNC were conducted at different temperatures (180–260°C), residence times (15–30 min) and water‐to‐biomass (W/B) ratios (5–15:1). Characterization studies of the torrefied biomass for different temperatures were conducted using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) analyses. The best‐fit analysis of variance (ANOVA) model for wet torrefaction mass yield was 2FI, with p‐values of <0.05, and a regression coefficient (R2) of 0.9443. The yield of torrefied SNC attained at 260°C, 45 bar, W/B ratio of 5, and 10‐min residence time was 55.5 wt.%, and the corresponding energy yield was 89.5%. Both temperature and W/B ratio had significant effect on torrefaction yield. There was a significant improvement in the volatile matter, fixed carbon, moisture, and heating value reduction in the torrefied SNC compared to the raw SNC making it a potential bioenergy source. However, high ash content is a major concern even after torrefaction.