# The Life-Cycle Environmental Impact of Recycling of Restaurant Food Waste in Lanzhou, China
## 3 Results and Discussion
### Assessment of Environmental Impact of Anaerobic Digestion-Aerobic Compositing Technique
#### 3.3.2 Main Factors Influencing Different Types of Environmental Impacts  
Figure 3 shows the main influencing factors of different types of environmental impacts in the life cycle of restaurant food waste across the whole process and different phases. The acidification potential is 0.20 kg SO\({}_{2}\) equivalent (eq), its standardized latent value is \(8.36\times 10^{-13}\), and it mostly originates from solid composting. The main factors influencing acidification potential are, in order, ammonia, nitrogen oxides, sulfur oxides, and hydrogen sulfide. The most influential factor generated during pre-processing, solid composting, and biogas slurry composite is ammonia. The most influential factor produced during collection and transportation and biogas power generation and heating is nitrogen oxides. The most influential factor produced during anaerobic digestion is sulfur oxides, which indicates the acidification is mainly affected by ammonia and nitrogen oxides. The eutrophication potential is 0.11 kg phosphate-eq, its standardized value is \(7.16\times 10^{-13}\), and it is produced mostly during the anaerobic digestion phase. The most influential factors affecting eutrophication potential are chemical oxygen demand, ammonia, phosphate, and nitrogen oxides. In particular, chemical oxygen demand is the main factor influencing anaerobic digestion and wastewater treatment. The main factor influencing pre-processing and biogas slurry composite is ammonia. The main factor influencing solid composting is phosphate. The main factor influencing other phases is nitrogen oxides, which indicated that eutrophication is affected by wastewater emissions more than by any other factor. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Category** & **Adification** & **Eutrophication** & **Freshwarate Aquatic** & **Global Warning** & **Human Toxicity** & **Marine Aquatic** & **Photochemical Ozone** & **Terrestrial** \\  & **Potential** & **Potential** & **Ecolatively Potential** & **Potential** & **Potential** & **Ecolatively Potential** & **Creation Potential** & **Ecolatively Potential** \\ \hline Sum & \(8.36\times 10^{-13}\) & \(7.16\times 10^{-13}\) & \(1.45\times 10^{-13}\) & \(6.56\times 10^{-12}\) & \(2.31\times 10^{-13}\) & \(2.73\times 10^{-13}\) & \(9.86\times 10^{-13}\) & \(8.8\times 10^{-14}\) \\ Collection and transportation & \(2.11\times 10^{-14}\) & \(7.28\times 10^{-15}\) & \(3.71\times 10^{-15}\) & \(9.07\times 10^{-14}\) & \(1.1\times 10^{-13}\) & \(2.12\times 10^{-14}\) & \(2.11\times 10^{-13}\) & \(9.14\times 10^{-15}\) \\ Pre-processing & \(2.17\times 10^{-13}\) & \(6.87\times 10^{-14}\) & 0 & 0 & \(1.36\times 10^{-15}\) & 0 & 0 & 0 \\ Solid computing & \(2.37\times 10^{-13}\) & \(1.46\times 10^{-13}\) & \(1.12\times 10^{-14}\) & \(1.81\times 10^{-12}\) & \(1.91\times 10^{-14}\) & \(4.12\times 10^{-14}\) & \(2.3\times 10^{-13}\) & \(3.61\times 10^{-21}\) \\ Aracobetic digestion & \(5.02\times 10^{-14}\) & \(3.47\times 10^{-13}\) & \(1.47\times 10^{-20}\) & \(2.36\times 10^{-12}\) & \(3.72\times 10^{-16}\) & \(3.54\times 10^{-23}\) & \(4.17\times 10^{-13}\) & \(3.61\times 10^{-21}\) \\ Bops power generation & \(8.73\times 10^{-14}\) & \(3.31\times 10^{-14}\) & 0 & \(1\times 10^{-12}\) & \(1.88\times 10^{-14}\) & 0 & \(5.22\times 10^{-14}\) & 0 \\ Bopss haung & \(1.14\times 10^{-13}\) & \(4.33\times 10^{-14}\) & 0 & \(1.3\times 10^{-12}\) & \(2.46\times 10^{-14}\) & 0 & \(7.53\times 10^{-14}\) & 0 \\ Bopss slurry & \(1.08\times 10^{-13}\) & \(3.33\times 10^{-14}\) & 0 & 0 & \(6.79\times 10^{-16}\) & 0 & 0 & 0 \\ Wastewater treatment & \(6.09\times 10^{-16}\) & \(3.73\times 10^{-14}\) & \(1.3\times 10^{-13}\) & 0 & \(5.59\times 10^{-14}\) & \(2.11\times 10^{-13}\) & 0 & \(7.89\times 10^{-14}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Normalized value for each environmental impact type. The global warming potential is 274.57 kg CO\({}_{2}\)-eq, and its standardized value is \(6.56\times 10^{-12}\).