Abstract:
Abstract: Biomass has been the only renewable energy that can be directly converted into fuel. The full utilization of biomass can effectively alleviate energy needs in an eco-friendly way. It is also an important path for China to achieve the goal of "carbon neutrality". Therefore, this study aims to focus mainly on the general goal of clean energy production and high-value utilization for straw-based biomass resources in recent years. A systematic analysis was made to evaluate the comprehensive utilization technology and mode of producing gas, liquid, and solid clean energy in the biological or thermo-chemical way. The development status and research progress were concentrated upon the anaerobic digestion for biogas, hydrothermal catalysis for alcohol and hydrocarbon fuel, pyrolysis liquefaction and bio-oil upgrading, and solid fuel production. Particularly, an attempt was addressed on the prospect of biogas, liquid fuel, and solid fuel. More importantly, no matter what biomass conversion technology was adopted, biomass resources utilization should be comprehensive and of high value. Correspondingly, the large-scale application required at least three basic elements. The first was the scale collection and disposal of biomass raw materials at a low cost. The second was the efficient and stable transformation, as well as quality improvement technology. The last was that the terminal fuel products needed to connect smoothly with the current application. Among them, anaerobic digestion for biogas presented the highest level of industrialization in recent years, due mainly to effectively solving raw materials collection in large breeding farms. It infers that the anaerobic digestion and biogas purification technology were relatively mature during this time. As such, biogas was directly used as a source of fuel, power, and thermal production. By contrast, hydrothermal catalysis for alcohol and hydrocarbon fuel, together with pyrolysis liquefaction for bio-oil was relatively difficult to connect with the current application, due mainly to the high conversion cost, difficult product separation, low-quality improvement efficiency, and unstable products. Therefore, the large-scale development level of the two technologies was relatively low during this time. Nevertheless, the technology of biomass preparation was relatively mature for solid fuels. The research and development of supporting stoves also effectively implemented the application of molding fuel. But the biggest difficulty in the scale application lay in the collection and storage of raw materials. Finally, the development prospects were proposed for the biomass conversion technologies. In terms of biogas, the anaerobic digestion was enhanced by multi-ingredients and bio-strengthen to improve biogas production efficiency. A precise control system should be established for the high concentration anaerobic digestion for better stability. Particularly, the comprehensive utilization of biogas slurry was carried out to realize the nutrient recycling, and biological organic fertilizer, or carbon-based fertilizer for nitrogen and carbon fixation, with emphasis on the efficiency of desulfurization and decarbonization. In terms of liquid fuel, the unpolluted depolymerization can be explored from lignocellulose to platform compounds, especially how to realize the efficient separation and quality improvement of platform compounds. During the quality upgrading process, the multi-step reaction combined catalyzer can be used to shorten the process and improve the reaction efficiency. In addition, the efficient conversion of biomass resources into fuel, chemicals, and materials should be developed synchronously for higher-value products. In terms of solid fuel, the heat transfer and bonding mechanism of torrefaction straw should be studied during the molding process, further to realize the low energy consumption and high quality. New efficient molding and combustion equipment needed to be improved the reliability of solid fuel production, particularly on the standardization, series, and package of torrefaction, molding, and combustion equipment. Consequently, the standard production of biomass collection, storage, and combustion should be improved to form biomass solid fuel industry chain from collection, storage, transportation, molding, and distribution. This research can provide a strong reference for the efficient preparation of clean energy and high-value utilization in rural biomass.