Application of pretreatment methods and life cycle assessment in the production of wood vinegar substitutes via hydrothermal oxidation of cotton stalks

Abstract

To enhance the efficient utilization of agricultural and forestry waste and support carbon neutrality, this study examines the production of wood vinegar substitutes (WVS) via hydrothermal oxidation, emphasizing the effects of reaction conditions and pretreatment methods on product properties. The optimal conditions were identified as a reaction temperature of 180 °C, a reaction time of 90 min, and 5 mL of oxidant (0.075 wt%), with the oxidant playing a crucial role in lowering the product’s pH. Among the pretreatment methods, hydrochloric acid (HCl) was the most effective, increasing the proportion of amorphous cellulose in cotton stalks, thereby promoting acidic product formation and improving product acidity and yield compared to previous studies. Life Cycle Assessment (LCA) is applied to systematically quantify the environmental impacts of the whole preparation process including pretreatment, which consequently provides empirical evidence for process optimization strategies. The analysis revealed that liquid nitrogen use was the main environmental burden. A −80 °C freezer is proposed to replace the liquid nitrogen use, which results in 98.74 % decrease of the generated carbon dioxide equivalent (35.95 kg to 0.454 kg CO₂ eq). according to the LCA analysis result, recycling hydrochloric acid can significantly minimize resource consumption. three recycling cycles experiment indicates that the utilization rate of HCl increases by 142 %. This study fills the research gap regarding the impact of pretreatment processes on the preparation of WVS from cotton stalks via hydrothermal oxidation. Meanwhile, it provides new ideas for developing low-energy, low-carbon, and sustainable processes through LCA.