Journal of Energy Bioscience 2024, Vol.15, No.3, 197-207 http://bioscipublisher.com/index.php/jeb 201 known to produce higher quality bio-oil. Optimizing the pyrolysis temperature, heating rate, and residence time is crucial. For instance, fast pyrolysis at moderate temperatures (around 500 ℃) and high heating rates can enhance bio-oil yield (Lee et al., 2020; Jha et al., 2022). The use of catalysts can improve the quality of bio-oil by reducing oxygen content and increasing the proportion of desirable hydrocarbons. Combining biomass with fossil fuels or other waste materials can enhance the synergistic effects, improving the overall quality and yield of bio-oil (Yang et al., 2019). 5 Gasification of Forestry Waste 5.1 Mechanism and process conditions of gasification Gasification is a thermochemical process that converts forestry waste into syngas (a mixture of carbon monoxide, hydrogen, and other hydrocarbons) through partial oxidation at high temperatures. The process involves several stages: drying, pyrolysis, oxidation, and reduction. The efficiency of gasification depends on various factors such as temperature, pressure, and the presence of catalysts. Optimal conditions typically involve temperatures ranging from 700 ℃ to 1 000 ℃ and controlled oxygen supply to ensure partial rather than complete combustion (Ong et al., 2020; Song et al., 2020). 5.2 Types of gasifiers and their suitability for forestry waste Several types of gasifiers are used for the gasification of forestry waste, including fixed-bed, fluidized-bed, and entrained-flow gasifiers. Fixed-bed gasifiers, such as updraft and downdraft gasifiers, are suitable for small-scale applications and can handle a variety of feedstocks, including forestry waste. Fluidized-bed gasifiers offer better mixing and heat transfer, making them suitable for larger-scale operations. Entrained-flow gasifiers operate at higher temperatures and pressures, providing higher syngas quality but requiring more stringent feedstock preparation (Ong et al., 2020; Song et al., 2020). 5.3 Syngas composition and applications The composition of syngas produced from forestry waste typically includes hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and other trace gases. The exact composition depends on the feedstock and gasification conditions. Syngas can be used for various applications, including electricity generation, production of synthetic natural gas, and as a feedstock for chemical synthesis, such as methanol and Fischer-Tropsch fuels (Stasiek and Szkodo, 2020). 5.4 Optimization techniques for enhancing gasification efficiency and syngas quality Optimization of gasification processes involves several strategies to enhance efficiency and syngas quality. These include the use of catalysts to lower reaction temperatures and increase reaction rates, co-gasification with other biomass types to improve synergetic effects, and advanced gas cleaning technologies to remove impurities (Perera et al., 2021). Additionally, the integration of gasification with other thermochemical processes, such as pyrolysis, can further enhance overall energy efficiency and product yield. 6 Combustion of Forestry Waste 6.1 Basic principles and process conditions of combustion Combustion is a thermochemical process that involves the oxidation of biomass to produce heat, which can be used for power generation. The basic principle of combustion is the exothermic reaction between the carbon and hydrogen in the biomass with oxygen, resulting in the release of energy, carbon dioxide, and water. The process conditions for efficient combustion include maintaining an adequate supply of oxygen, controlling the temperature to ensure complete combustion, and managing the moisture content of the biomass to optimize energy output (Pang, 2019; Solarte-Toro et al., 2021). 6.2 Direct combustion and co-firing with other fuels Direct combustion of forestry waste involves burning the biomass alone to generate heat and power. This method is straightforward but can be less efficient due to the high moisture content and low energy density of raw biomass. Co-firing, on the other hand, involves burning biomass along with other fuels such as coal. This approach can
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