# The Life-Cycle Environmental Impact of Recycling of Restaurant Food Waste in Lanzhou, China
## 3 Results and Discussion  
### Environmental Impact of Different Methods of Treating Restaurant Food Waste  
We assessed the environmental impact of the life cycle of different treatment techniques of restaurant food waste in Lanzhou. Table 2 lists the assessment results. Here, S1 is the anaerobic digestion-aerobic composite technique. This method is currently used in Lanzhou. S2 is the landfill technique, in which restaurant food waste is collected and transported to a trash landfill yard for disposal. S3 is the incineration technique, in which restaurant food waste is transported to an incineration plant for a burning along with municipal solid waste. As shown in Table 2, standardized values of environmental impact of S1, S2, and S3 were \(9.84\times 10^{-12}\), \(2.19\times 10^{-11}\), and \(2.34\times 10^{-11}\), respectively. The overall environmental impact of S1 was the lowest, that of S2 was medium, and that of S3 was the highest. Anaerobic digestion-aerobic competing technique is an ideal method for food waste disposal. S1 showed greater freshwater aquatic ecotoxicity potential, human toxicity potential, marine aquatic ecotoxicity potential, and underground ecotoxicity than S2 and greater eutrophication potential than S3. The main reason for this is that food waste has the characteristics of high moisture content (e.g., Lanzhou beef no \begin{table}
\begin{tabular}{c c c} \hline \hline
**Resources/Substance/Emissions** & **Phase** & **Data Source** \\ \hline Diesel, CO\({}_{2}\), CH\({}_{4}\), NOx\({}_{\text{X}}\), SO\({}_{2}\), VOC, CO, HC, Pb & Collection and transportation & Chinai Bioenergy; [41; 42; 43] \\ \hline Water, electricity, grease, liquid phase, solid phase, H\({}_{2}\)S, NH\({}_{3}\), COD, BOD, SS, NH\({}_{3}\)-N & Pre-processing & Chinai Bioenergy \\ \hline Electricity, biogas, biogas residue, biogas slurry, wastewater, CO\({}_{2}\), CH\({}_{4}\), COD, BOD, NH\({}_{3}\)-N, SS & Anaerobic digestion & Chinai Bioenergy; [8; 44] \\ \hline Electricity, CO\({}_{2}\), CO, CH\({}_{4}\), NOx\({}_{\text{X}}\), SO\({}_{2}\) & Biogas power generation and heating & Chinai Bioenergy; [9] \\ \hline Water, aerobic composting additive, CO\({}_{2}\), CH\({}_{4}\), SO\({}_{\text{X}}\), VOC, NH\({}_{3}\), PM\({}_{10}\), Cd, phosphate, sulfate & Composting & Chinai Bioenergy; [8; 44] \\ \hline Wastewater, ferric chloride, electricity, sludge, NH\({}_{3}\), Pb, Cd, Cr, Hg, COD, BOD, NH\({}_{3}\)-N, SS, H\({}_{2}\)S & Wastewater treatment & Chinai Bioenergy; [24] \\ \hline \hline \end{tabular} Notes: VOC: Volatile Organic Compounds; COD: Chemical Oxygen Demand; BOD: Biochemical Oxygen Demand; SS: Suspended Solid; PM\({}_{10}\): Particulate Matter (PM10).  
\end{table} 
Table 1: Data sources related to the different phases. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Category** & **Unit** & **S1** & **S2** & **S3** \\ \hline Acidification potential & kg SO\({}_{2}\)-Equiv & 0.2 & 0.34 & 0.5 \\ Eutrophication potential & kg phosphate-Equiv & 0.11 & 0.3 & 0.1 \\ Freshwater aquatic ecotoxicity potential & kg DCB-Equiv & 0.34 & 0.02 & 0.03 \\ Global warming potential & kg CO\({}_{2}\)-Equiv & 274.57 & 592.65 & 757.8 \\ Human toxicity potential & kg DCB-Equiv & 0.6 & 0.32 & 1.58 \\ Marine aquatic ecotoxicity potential & kg DCB-Equiv & 53.05 & 4.92 & 67.26 \\ Photochemical ozone creation potential & kg ethene-Equiv & 0.04 & 0.16 & 0.05 \\ Terrestrial ecotoxicity potential & kg DCB-Equiv & 0.1 & 0.01 & 0.22 \\ Environmental impact normalized value & - & \(9.84\times 10^{-12}\) & \(2.19\times 10^{-11}\) & \(2.34\times 10^{-11}\) \\ \hline \hline \end{tabular} Notes: DCB: dichlorobenzene.  
\end{table} 
Table 2: Environmental impact of different methods of treating restaurant food waste. Equiv— equivalent. digestion-aerobic composite technique requires a certain amount of freshwater for pretreatment, which produces more wastewater.