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In the present study, local biomass rick husk (RH) was torrefied by an electronic furnace for improving its thermochemical properties under a wide range of torrefaction temperature (i.e., 240, 280, 320, and 360 °C) and residence time (i.e., 0, 30, 60, and 90 min). In comparison with the thermochemical properties of the starting feedstock, the torrefaction temperature at around 360 °C for residence time of 0 min would be optimal to produce the RH-torrefied product. The calorific value can be raised by 41.2%, increasing from 13.96 to 19.71 MJ/kg. Based on the calorific values of the RH-torrefied products, it was found that torrefaction temperature and residence time are important parameters affecting their fuel properties and applications in solid biofuels. Consistently, their calorific values and carbon-to-hydrogen ratios generally increased at higher torrefaction temperatures for longer residence times. In contrast, the energy yield decreased with an increase in torrefaction temperatures and residence time. These findings also supported the thermal decomposition mechanism of the lignocellulosic biomass by the thermogravimetric analysis (TGA). Using the van Krevelen diagram for all RH-torrefied products as compared to various coals, it showed that several torrefied solids belong to the characteristics of lignite-like coal. However, the RH-torrefied biomass would not be appropriate to be directly reused as an auxiliary fuel in boilers because of the high content of silica (SiO 2 ).

The residue remaining after the water extraction of soapberry pericarp from a biotechnology plant was used to produce a series of biochar products at pyrolytic temperatures (i.e., 400, 500, 600, 700 and 800 °C) for 20 min plant was used to produce a series of biochar products. The effects of the carbonization temperature on the pore and chemical properties were investigated by using N2 adsorption–desorption isotherms, energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). The pore properties of the resulting biochar products significantly increased as the carbonization temperature increased from 700 to 800 °C. The biochar prepared at 800 °C yielded the maximal BET surface area of 277 m2/g and total pore volume of 0.153 cm3/g, showing that the percentages of micropores and mesopores were 78% and 22%, respectively. Based on the findings of the EDS and the FTIR, the resulting biochar product may be more hydrophilic because it is rich in functional oxygen-containing groups on the surface. These results suggest that soapberry pericarp can be reused as an excellent precursor for preparing micro-mesoporous biochar products in severe carbonization conditions.

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In this work, a novel biomass, the extraction residue of Sapindus pericarp (SP), was torrefied by using an electronic oven under a wide range of temperature (i.e., 200–320 °C) and residence times (i.e., 0–60 min). From the results of the thermogravimetric analysis (TGA) of SP, a significant weight loss was observed in the temperature range of 200–400 °C, which can be divided into the decompositions of hemicellulose (major)/lignin (minor) (200–320 °C) and cellulose (major)/lignin (minor) (320–400 °C). Based on the fuel properties of the feedstock SP and SP-torrefied products, the optimal torrefaction conditions can be found at around 280 °C for holding 30 min, showing that the calorific value, enhancement factor and energy yield of the torrefied biomass were enhanced to be 28.60 MJ/kg, 1.36 and 82.04 wt%, respectively. Consistently, the values of the calorific value, carbon content and molar carbon/hydrogen (C/H) ratio indicated an increasing trend at higher torrefaction temperatures and/or longer residence times. The findings showed that some SP-torrefied solids can be grouped into the characteristics of a lignite-like biomass by a van Krevelen diagram for all the SP-torrefied products. However, the SP-torrefied fuels would be particularly susceptible to the problems of slagging and fouling because of the relatively high contents of potassium (K) and calcium (Ca) based on the analytical results of the energy dispersive X-ray spectroscopy (EDS).