# Environmental Impact of the Natural Gas Liquefaction Process: An Example from China
## 2 Method
### Life Cycle Impact Assessment
#### 2.3.3 Weightage of the Different Types of Environmental Impact Potential  
After standardization, if two different types of environmental impact potential have the same magnitude, it does not mean that the potential environmental impacts of the two types are equally  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Type of EI** & **Hena** & **Sichuan** & **Inner Mongolia** & **Shaanxi** & **Xinjiang** & **Shanxi** & **Ningxia** & **Hebei** \\ \hline
**GWP** & 0.0665 & 0.0597 & 0.1048 & 0.1006 & 0.0840 & 0.0650 & 0.1027 & 0.0641 \\
**AP** & 0.0070 & 0.0015 & 0.0024 & 0.0013 & 0.0137 & 0.0012 & 0.0005 & 0.0111 \\
**EP** & 0.0079 & 0.0001 & 0.0026 & 0.0014 & 0.0144 & 0.0013 & 0.0003 & 0.0126 \\
**POCP** & 0.5388 & 0.2687 & 1.5381 & 1.6454 & 0.9275 & 0.5030 & 1.5968 & 0.2957 \\
**DU** & 0.0002 & 0.0004 & 0.0003 & 0.0003 & 0.0002 & 0.0001 & 0.0001 & 0.0002 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Standardized value of the liquefied natural gas production in the eight provinces of China (p-a).  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Type of EI** & **Hena** & **Sichuan** & **Inner Mongolia** & **Shaanxi** & **Xinjiang** & **Shanxi** & **Ningxia** & **Hebei** \\ \hline
**GWP** & 578.7756 & 519.1644 & 911.6252 & 874.9307 & 730.3911 & 562.8499 & 893.5984 & 557.3228 \\
**AP** & 0.2534 & 0.0552 & 0.0857 & 0.0469 & 0.4959 & 0.0436 & 0.0175 & 0.3999 \\
**EP** & 0.4824 & 0.0031 & 0.1628 & 0.0833 & 0.8784 & 0.0774 & 0.0210 & 0.7657 \\
**POCP** & 0.3502 & 0.1746 & 0.9997 & 1.0695 & 0.6029 & 0.3269 & 1.0379 & 0.1922 \\
**DU** & 0.0028 & 0.0063 & 0.0048 & 0.0053 & 0.0037 & 0.0019 & 0.0027 & 0.0035 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Impact potential of liquefied natural gas production in the eight provinces of China (p-a).  
serious. Therefore, the importance of impact types needs to be determined; that is, different impact types are given different weightages before they can be compared. This process is called weighted evaluation. The weightage is determined using the \"target distance method\", which is where the severity of an environmental effect is characterized by the distance between the current level of the effect and the target level [24]. This study used the Chinese government's reduction targets for the year 2000 to determine the weightage of the different types of environmental impact in China. The formulae used are shown below  
\[\begin{array}{l}WP(j)=WF(j)\times EP(j)/ER(j)_{90},\\ ER(j)_{\text{T2000}}=\sum EP(j)_{\text{T2000}}/Pop_{90},\\ WF(j)=ER(j)_{90}/ER(j)_{\text{T2000}},\end{array} \tag{4}\]  
where _WP(j)_ is the weightage value, _WF(j)_ represents the weightage factors, _ER(j)_\({}_{90}\) is the standardized value for the year 1990, and _ER(j)_\({}_{\text{T2000}}\) is the standardized value for the year 2000.  
The standardized environmental impact potentials were assigned weightages. The weightage factors of GWP, AP, EP, POCP, and DU were found to be 0.83, 0.73, 0.73, 0.53, and 0.61, respectively [24]. The weightage of the environmental impact potential value can be obtained by multiplying the normalized environmental impact potential value by a weightage factor.  
According to the above-mentioned method, the environmental weightage value of the LNG production process in the eight provinces of China per unit output was determined and is shown in Table 7.