# The Life-Cycle Environmental Impact of Recycling of Restaurant Food Waste in Lanzhou, China
## 4 Conclusions  
Considering the environmental impact, the underlying threat to food safety, and the recycling potential of food waste in cities, the Chinese government made great effort to recycle food waste while reducing resource consumption and environmental impact to the greatest extent. Therefore, it is very important to analyze the life-cycle environmental impacts of certain patterns of food waste treatment to identify the best method of food waste recycling. This study assessed the life-cycle resource consumption and environmental impact of restaurant food waste treatment in Lanzhou city, which is a pilot city of food waste recycling in China. The conclusions are provided below. Among the three methods of restaurant food waste treatment, i.e., anaerobic digestion-aerobic composting, incineration, and landfill disposal, our results showed that the anaerobic digestion-aerobic composting technique showed the least environmental impact, the landfill method had a medium impact, and incineration had the greatest impact on the environment. In particular, the latter two techniques may significantly exacerbate global warming. The anaerobic digestion-aerobic composting technique also showed better economic and social benefits. During the life cycle of the anaerobic digestion-aerobic composting treatment, the consumption of renewable and other resources was highest during the pre-processing phase. The collection and transportation and wastewater treatment phases primarily consumed hard coal and crude oil. The solid composing phases primarily consumed clay, attapulgite, and organic acid. The pre-processing phase primarily consumed water resources. In the whole life cycle of food waste recycling, the environmental impact of global warming was found to be the most pronounced of any factor evaluated here, and terrestrial ecotoxicity had the least pronounced effect. The environmental impact in different phases showed heterogeneity. The maximum environmental impact in the collection and transportation phase is photochemical ozone creation potential. The maximum environmental impact of the pre-processing and biogas slurry composting phases is acidification potential. Wastewater treatment mostly affects marine aquatic ecotoxicity, and the remaining stages affect global warming. Our sensitivity analysis and comparison demonstrated that the CML2001 method is a reliable means of assessing the life cycle of food waste. All environmental impacts were found to be mostly sensitive to electricity, diesel, and water. The eutrophication and photochemical ozone creation had a low sensitivity to all variables. The results of this work showed that the anaerobic digestion-aerobic composting technique has the smallest effect on the environment, especially greenhouse gas emissions,which is consistent with the findings of previous works. The collection and transportation phase showed the least effect on the environment in the entire life cycle. In this technique, the biogas residues and biogas slurries are used for composting and have a less pronounced effect on the environment than other methods of disposal. This may provide a reference for restaurant food waste treatment in other parts of China. Since food waste is produced in huge amounts along with rapid urbanization and a lack of good sorting at the source of municipal solid waste, recycling in a biotreatment model may contribute to the creation of new production chains and, therefore, to new markets. In the case of Lanzhou, because the production chain is incomplete (the absence of grease processing), the study did not involve the use of grease in the production of biodiesel or as a secondary pollutant of the compost product. As for most cities like Lanzhou, it is not able to process the grease due to economic and technical reasons, opting instead to trade it to cities with the ability to process it. The remote material flow between Lanzhou and the processing city was also ignored in this study. Future research should explore expanding both the system boundaries and space boundaries.