This work conducts a single-factor experiment to study the effects of biomass types on the relax density, volume expansion, durability, hydrophobicity, and processing energy consumption. We analyze the differences in the quality of the pellets, and optimize the compaction conditions suitable for different biomass types including straw, hardwood, shell, and herbaceous plant. The results indicated that with a compressing force of 60~1500 N, compressing time of 10 s, powder size of less than 0.5 mm, and moisture content of 10%, the relax densities of corn straw, rice straw, selenium-rich rice straw, weigela japonica branches, and camphor leaves range from 360 to 820 kg/m³, with a processing energy consumption of 17,360 to 28,740 J/kg; meanwhile, the relax densities of argy wormwood, forage grass, green grass, and peanut shells range from 340 to 840 kg/m³, with a processing energy consumption of 33,510 to 73,700 J/kg. Therefore, the compaction pretreatment effectively regulates the density of biomass pellets and reduces the processing energy consumption. This study analyzed the differences in the quality of pellets caused by the inherent characteristics of biomass, providing strong support for the directional depolymerization and enhanced pretreatment technology for the scaled production of biomass alcohol fuels.

Fast pyrolysis of microcrystalline cellulose (MC) was carried out by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The effects of temperature, time, and a catalyst on the distribution of the pyrolysis products were analyzed. The reaction temperature and time can significantly affect the types and yields of compounds produced by cellulose pyrolysis. A pyrolysis temperature of 500–600 °C and pyrolysis time of 20 s optimized the yield of volatile liquid in the pyrolysis products of cellulose. In all catalytic experiments, the relative contents of alcohols (1.97%), acids (2.32%), and esters (4.52%) were highest when K₂SO₄ was used as a catalyst. HZSM-5 promoted the production of carbohydrates (92.35%) and hydrocarbons (2.20%), while it inhibited the production of aldehydes (0.30%) and ketones (1.80%). MCM-41 had an obvious catalytic effect on cellulose, increasing the contents of aldehydes (41.58%), ketones (24.51%), phenols (1.82%), furans (8.90%), and N-compounds (12.40%) and decreasing those of carbohydrates (5.38%) and alcohols (0%).

To progress towards the “dual carbon” goal and reduce the cost and increase the efficiency of solid oxide fuel cells, this study conducts a full life cycle analysis of solid oxide fuel cells, in which the environmental impact caused by the operating devices’ manufacturing, fuel gas catalyst reforming, single-cell manufacturing, cell stack manufacturing, and energy consumption and emissions are systematically analysed. In this study, we establish an assessment model for solid oxide fuel cells by using the cut-off criterion. The results show that 96.5% of the global warming potential in the use of solid oxide fuel cells comes from the stack operating subsystem. The stack manufacturing subsystem, operating device manufacturing subsystem, and waste stack processing subsystem all contribute greatly to acidification, accounting for 32.89%, 44%, and 35.82% of the total acidification, respectively. These three subsystems also contribute significantly to eutrophication, contributing 23.11%, 22.03%, and 42.15%, respectively. Compared with traditional thermal power generation systems, solid oxide fuel cell power generation systems have slightly higher overall environmental benefits, and the reductions in greenhouse gas emissions and acidification potential reach 6.22% and 18.52%, respectively. The research results have guiding significance and reference value for subsequent energy-saving and emission reduction design and improvement efforts for solid oxide fuel cells.

It is important to clarify the distribution of pyrolysis products from lignocellulosic biomass for its thermal transformation to produce high-quality bio-oil. Influences of the reaction temperature and catalysts on the pyrolysis product distribution from aspen wood (AW) and rice husk (RH) were studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The difference in components from the lignocellulosic biomass results in different pyrolysis characteristics of the biomass raw materials. The reaction temperature significantly influences the product distribution from AW and RH pyrolysis. In all AW catalysis experiments, acids (8.35%), ketones (3.79%), phenols (4.73%), and esters (1.50%) have the lowest content while carbohydrates (48.75%) demonstrate the highest content when taking zinc chloride (ZnCl₂) as the catalyst; the HZSM-5 molecular sieve (HZSM-5) promotes the generation of esters (7.97%) and N-compounds (22.43%) while inhibiting production of aldehydes (2.41%); addition of an MCM-41 molecular sieve (MCM-41) is conducive to increasing the contents of aldehydes (21.29%), furans (5.88%), ketones (22.30%), acids (20.46%), and hydrocarbons (4.85%), while reducing the contents of alcohols (0) and carbohydrates (0). In all RH catalysis experiments, the addition of ZnCl₂ helps increase the content of carbohydrates (39.16%) and decrease the contents of ketones (3.89%), phenols (5.20%), alcohols (2.34%), esters (1.13%), and N-compounds (3.09%); when applying HZSM-5 as the catalyst, hydrocarbons (18.28%) and alcohols (6.66%) reach their highest content while acids (13.21%) have the lowest content; MCM-41 promotes the generation of aldehydes (25.33%) and furans (5.55%) while inhibiting that of carbohydrates (1.42%).

To study the water absorption characteristics of corn, rice, and wheat straw after thermal pretreatment (120 ~ 200 °C). This work introduces an internal particle diffusion model for the moisture adsorption mechanism and measures the water contact angle to assess hydrophobicity, establishing a linear relationship between the water absorption kinetic parameters and temperature. The results show that when the temperature rises to 200 °C, the hygroscopicity reduction extent of corn straw, rice straw and wheat straw are 58.45%, 28.32% and 12.12%, respectively, significant increase in hydrophobicity. The three-stage internal particle diffusion equation can effectively describe the adsorption process of straw to moisture. At 70% humidity, the diffusion rate constant decreased and the boundary layer thickness increased. The ASABE equation can accurately predict the moisture content of corn straw; the water absorption process of rice and wheat straw conforms to the Peleg equation, which is significant for the subsequent large-scale high-quality utilization of straw.

Torrefaction is an effective method for upgrading biomass. Cedar torrefaction is carried out in a fixed bed reactor at the temperature of 200–300 °C. The structural parameters are obtained from elemental analysis and ¹³C nuclear magnetic resonance (NMR). Thermal degradation behavior of raw and torrefied cedar is monitored by thermogravimetry analysis. The results show that carbon structure varied during torrefaction has a significant effect on thermal degradation of cedar. Some unstable oxygen functional groups, such as C1 of hemicellulose, β-O-4 linked bonds, and amorphous C6 of cellulose, are decomposed at mild torrefaction of torrefied temperature ≤ 200 °C. The temperature of maximum weight loss rate increases from 348 °C of raw cedar to 373 °C of C-200. The amorphous cellulose is partly re-crystallized at moderate torrefaction of torrefied temperature 200–250 °C. The aromaticity of torrefied cedar increases from 0.45 of C-200 to 0.73 of C-250. The covalent bond in the side chain of aromatic rings in cedar was further broken during torrefaction at severe torrefaction of torrefied temperature 250–300 °C. The area percentage of DTG mainly signed at 387 °C of C-300. The proton aromatic carbon increases from 12.35% of C-250 to 21.69% of C-300. These results will further facilitate the utilization of biomass for replacing fossil fuel to drive carbon neutrality.