With the increasing environmental awareness of the public, government and industry seek to replace nonrenewable energy sources with renewable ones to lower greenhouse gas emissions. At the same time, energy demand continues to increase due to the development of industry and the exponential growth of the population. These concerns have the potential to be balanced with the use of wood as a fuel source. Wood is a sustainable, renewable, and low-cost resource and unlike conventional fuel sources, the use of wood for energy applications limits CO2 emissions, thus the negative impact on the atmosphere. The thermal properties of wood in energy can be improved by torrefaction, which is thermal treatment at 200-300°C in an inert atmosphere. Thermochemical conversion processes are efficient methods to produce biofuels from biomass; of these methods, torrefaction has the lowest global warming potential. Torrefied biomass is known to have higher calorific values, higher bulk and energy densities, lower biological degradation, and higher hydrophobicity. Potassium (K) is a mineral naturally present in wood and responsible for the plant’s growth. Past studies have shown K to have catalytic effects on the thermal degradation of wood powder. Since it has a major role in the degradation of lignocellulosic biomass, it is of interest to see the effect of K impregnation on the torrefaction of wood blocks instead of powder. Consequently, 14 x 6 x 2 cm3 blocks of beech were impregnated with demineralized water, 0.004 M, 0.008 M, and 0.012 M of K2CO3 solutions and torrefied at four different durations:  5 min, 15 min, 30 min, and 60 min at 275 °C. Pre-torrefaction, atomic emission spectroscopy (ICP-AES) was used to check the diffusion of K throughout the wood block's thickness and found that the surface has more K than the heart of the wood. This finding spurred interest in the examination of the effect of K and the thermal treatment throughout the wood’s thickness. Post-torrefaction, samples from the surface and core of the wood were pyrolyzed using thermogravimetric analysis (TGA) to obtain TG and DTG profiles. Likewise, X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the effect of K and heat treatment on crystallinity and the char’s porosity.

Effect of potassium impregnation and torrefaction on the thermal degradation of wood blocks

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