Life cycle assessment of bio-oil prepared from low-temperature hydrothermal oxide-catalyzed cotton stalk

The technological development of preparing bio-oil from low-temperature hydrothermal conversion of agricultural and forestry waste has positive significance for alleviating the shortage of oil energy supply and reducing environmental pollution. This paper selects typical oxides (Al2O3, CeO2, MgO, SiO2, TiO2, and ZnO) as catalysts to set up a low-temperature (220 degrees C) hydrothermal conversion process of cotton stalk containing pretreatment processes including chopping. For moderate amplification estimation, lab-scale experimental data is used as a benchmark for calculation, and the functional unit for this study is set to be a 1 kg bio-oil product. The results suggest that the cerium dioxide-involved process with the highest bio-oil yield and highest synthetic consumption, and the silica-involved process with the lowest bio-oil yield, caused the highest environmental impact, resulting in greenhouse gas (GHG) emissions of 67.729 kg CO(2)e/kg and 60.001 kg CO(2)e/kg, respectively. It indicates that catalysts need to consider the balance between synthetic consumption and catalytic performance. Magnifying lab-scale data to an industrial scale using scale-up frameworks introduces a low model uncertainty, as the practical value had little effect on the overall evaluation results. However, existing equipment data should be used to reduce the uncertainty of the model itself. The environmental sustainability of bio-oil production by low-temperature hydrothermal liquefaction still needs to be improved, especially by catalyst recovery and bio-oil yield improvement.

Automated summary

The technological development of preparing bio-oil from low-temperature hydrothermal conversion of agricultural and forestry waste has a positive significance for alleviating oil energy shortage and reducing environmental pollution. This study investigates the hydrothermal conversion process of cotton stalk using different oxide catalysts and finds that the cerium dioxide-involved process has the highest bio-oil yield, while the silica-involved process has the lowest bio-oil yield and causes the highest environmental impact. The study suggests that catalysts need to consider the balance between synthetic consumption and catalytic performance.