## 4 Case Study
### Background
#### 4.1.2 Analysis of Mobile Phone Recycling Value  
At present, the recycling value of mobile phones is mainly divided into three parts. First, popular phones return to the market after cleaning and refurbishing. Second, defective popular phones are dismantled and sold as parts. Third, after professional processing and extraction of precious metals, the scrap machine can recover gold, silver, copper, palladium and other precious metals from the waste mobile phone [38]. By comparing popular phones in the market, it is assumed that the average weight of mobile phones is 125 g/unit, and the proportion of disassembled mobile phones, recyclable parts mobile phones, re-sold mobile phones that can be renovated and scrapped by each testing and classification center is 20%, 30%, 40% and 10%, respectively.  
To better measure the recycling value of a mobile phone, the recycling of waste mobile phones is divided into three levels, which include a refurbishing machine, parts dismantling machine and material dismantling machine. The parts are divided into two parts: the main board and the casing. The processing cost and selling price list of the repairable machine and parts are obtained as shown in Table 3.  
For the dismantling material, by referring to the data and comparing with the actual situation, mobile phone motherboards and mobile phone shells accounted for 80% of the weight and 20% of mobile phone, respectively. The material disassembly ratio of the two modules is listed as shown in Tables 4 and 5. In addition, the processing cost and selling price list of various materials can be obtained as shown in Table 6.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Gold** & **Silver** & **Copper** & **Palladium** & **Other metals** \\ \hline
0.03\% & 0.02\% & 13\% & 0.01\% & 86.94\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Material composition of mobile phone motherboard.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**City** & **Population** & **Mobile Phone Number** & **Mobile Phone Obsolescence** & **The Recycling Number** \\  & **(Ten Thousand)** & **(Ten Thousand)** & **(Ten Thousand)** & **(Ten Thousand)** \\ \hline Changchun & 748.90 & 823.79 & 411.90 & 82.38 \\ Jilin & 415.35 & 456.89 & 228.44 & 45.69 \\ Siping & 338.00 & 371.80 & 185.90 & 37.18 \\ Sonyuan & 288.00 & 316.80 & 158.40 & 31.68 \\ Tonhua & 232.00 & 255.20 & 127.60 & 25.52 \\ Yanbian Korean & 227.00 & 249.70 & 124.85 & 24.97 \\ Autonomous Prefecture & & & & \\ Baishan & 129.00 & 141.90 & 70.95 & 14.19 \\ Liaoyuan & 118.00 & 129.80 & 64.90 & 12.98 \\ Baicheng & 190.90 & 209.99 & 105.00 & 21.00 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Recycled mobile phones in Jilin Province in 2017.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **The Whole** & **Mobile Phone** & **Mobile Phone** \\  & **Mobile Phone** & **Motherboard** & **Mobile Phone Shell** \\ \hline Processing cost & 60 & 15 & 5 \\ Selling price & 500 & 34 & 20 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Part of disposal costs and prices of used mobile phones (unit: CNY/unit).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Gold** & **Silver** & **Copper** & **Palladium** & **Other metals** \\ \hline
0.03\% & 0.02\% & 13\% & 0.01\% & 86.94\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Cell phone shell material composition.