Life Cycle Assessment of Kitchen/Agricultural Waste Hydrothermal Conversion For Bio-Oil Production

Abstract

The treatment of kitchen waste and agricultural solid waste are two major challenges in urban and agricultural environmental protection. The conversion of organic solid waste into bio-oil through mild hydrothermal methods can not only alleviate the environmental problems caused by traditional Lignocellulosic biomass processing but also provide technical support for the sustainable production of fuel oil. Traditional research on hydrothermal conversion of organic solid waste mostly focuses on areas such as catalysts and hydrothermal parameters, while studies on environmental impact assessments are relatively rare. In this study, a process for the co-hydrothermal conversion of kitchen waste and agricultural solid waste biomass was firstly established, with bio-oil as the target product. The analysis results show that the higher the yield and calorific value of bio-oil, the greater its negative impact on the environment, which accounts for 41.41 to 55.24% of the total impact. Groups with more significant Maillard reactions had higher bio-oil yields but also had higher net CO2 emissions, with the highest reaching 25.05 kg CO₂ kg⁻¹. For the consumption of mineral, fossil, and renewable resources, dichloromethane was the largest contributor. Overall, the hydrothermal Liquefaction stage had the greatest environmental impact among all stages, accounting for 42.26 to 56.55% of the total impact. Changes in fertilizer application rates had a certain effect on impact categories other than mineral, fossil, and renewable resource consumption. Reducing the energy consumption of hydrothermal liquefaction can significantly reduce its consumption of fossil fuels and other energy sources, while changes in grinding and filtering energy consumption had little impact on the environment. The research content of this paper will provide some references for the resourceful conversion of kitchen waste and agricultural solid waste from an industrial perspective.