铁铝土泥浆包覆与淬灭强化荔枝木炭化物的碳固存率

生物质炭作为一种富碳多孔材料，具有固碳、减污和培肥等多重功效。基于当前限氧高温热裂解制炭技术及炭改性方法，该研究以亚热带地区常见的荔枝木为原材料、选取铁铝土制成泥浆，通过泥浆包覆和淬灭实现生物质“自限氧”和“水”淬灭，探讨铁铝土泥浆在荔枝木炭化过程中的作用及其对炭质的影响机理。结果表明：铁铝土泥浆包覆和淬灭制得的荔枝木炭的碳含量和碳固存率最高，分别为83.5%和83.9%，较无包覆水淬灭炭品的碳含量和碳固存率提高了16.7和37.8个百分点。扫描电镜-能谱分析的结果表明，铁铝土泥浆包覆和淬灭生成的炭品的碳骨架结构规整且其表面有铁铝矿物负载。一方面，泥浆通过涂层包覆形成了包覆壳，以物理阻隔作用截留了碳（防止炭化物中的碳在持续燃烧中生成CO_X）；另一方面，铁铝矿物在高温热裂解过程中与炭化物结合，形成了矿质（Fe/Al）-碳质复合体，实现了碳固存。研究可为生物质炭的制备提供新的便捷、廉价的技术思路，以生物质就地炭化和应用的碳负排放方案助力碳中和。

Enhanced carbon capture capacity in biochar from pyrolysis of Litchi branches with soil (Ferrasols) slurry

Biochar is one of the most important carbon-rich minerals with a porous structure in the carbon sequestration, immobilization of metal and organic contaminants, as well as soil fertility improvement. However, its large-scale use is very limited in the agriculture and environment, due to the high cost of production and transportation from agricultural biowaste to plant. In this study, a new technology was explored to directly convert from agricultural biowaste to biochar in the field. The local applications had significantly reduced the costs of biochar. Inspired by nature, biochar production was also proposed in the field, where only agricultural biowaste, water, and fire were required for biomass carbonization and charcoal formation; Specifically, Litchi branches sourced from subtropical regions were utilized as feedstock to explore an on-site production of biochar. Soil (Ferralsols) slurry was applied as a coating and quenching agent to create an oxygen-limited environment during fire-water coupled carbonization of the feedstock. This self-limiting oxidation approach was used to minimize the expenses of production, transportation, and utilization. Biochar that was produced with soil slurry coating and quenching also displayed the highest carbon content (83.5%) and carbon capture capacity (83.9%), exceeding unconverted biomass and biochar produced without coating by 16.7% and 37.8%, respectively. The burning process of Litchi branches was divided into three stages: 1) Surface was charred immediately but with an unburned core; 2) Surface was grayed out, while the core was in a self-ignition state with high temperature and limited oxygen, and the dark red char fell to the ground; and 3) The dark red char gradually burned out to be ash. Spraying water on the dark red char was used to prevent the occurrence of the 3rd stage, thus favoring the formation of biochar instead of ash. Furthermore, the soil coating likely acted as a barrier, thus reducing carbon monoxide or carbon dioxide release during combustion. Additionally, the soil integration was facilitated to form the mineral-carbon composite for the carbon capture. Scanning electron microscopy and energy spectroscopy analysis show that the regular structure of the carbon skeleton was observed after coating and quenching the iron-aluminum slurry. The iron-aluminum minerals were also loaded on the surface. A novel approach to carbonization accelerated a paradigm shift in biochar production from a sophisticated stationary facility to a simple way for practical use in the field. Low cost greatly contributed to the agricultural and environmental application of biochar. The economically viable combination of fire and soil (Ferralsols) slurry coupled carbonization can be expected to provide valuable insights for biochar adoption and carbon neutrality. In conclusion, the readily available agricultural residues and soil-based coatings can be integrated to mitigate the environmental impact of biochar production, in order to enhance the efficacy as a carbon capture. These findings can offer significant implications for the broader adoption of biochar as a sustainable solution, in order to promote climate and soil health.