# Life Cycle Assessment of Substitutive Building Materials for Landfill Capping Systems in Vietnam
## 3 Results and Discussions  
### Soil Mechanics Result  
The lab resultsfor the potential sealing layer material indicated very low permeability values for some mixtures of about 10\({}^{-10}\) m/s that meet German quality requirements which require k \(\leq\) 5 \(\times\) 10\({}^{-9}\) m/s for landfill class I and k \(\leq\) 5 \(\times\) 10\({}^{-10}\) m/s for class II [54]. The interim conclusion was that we could add the rice husk ash and milled brick as substitutive materials up to 40 % of the sealing mix to reach the required hydraulic conductivities. The following soil mechanical parameters have been determined:  
w (-) water content \begin{table}
\begin{tabular}{c c c} \hline \hline
**Unit Process** & \multicolumn{2}{c}{**Changes Made**} \\ \hline \multicolumn{3}{c}{Water, unspecified natural origin, VN} \\ Bentonite quarry operation & Electricity, medium voltage (VN) \(\mid\) & Water and Electricity input changed to Vietnam region \\ RoW\(\mid\)APOS, U & market for electricity, medium voltage \(\mid\)APOS, U & Water emission changed to \\  & & voltages \(\mid\)APOS, U \\  & Emissions—Water, VN & \\ \hline Claypit operation RoW\(\mid\)APOS, U & - & - \\ \hline \multicolumn{3}{c}{Water, unspecified natural origin, VN} \\ Sand quarry operation, extraction from river bed IN\(\mid\)APOS, U & Electricity, medium voltage (VN) \(\mid\) & Water and Electricity input changed to Vietnam region \\  & & market for electricity, medium voltage \(\mid\)APOS, \\  & & voltage \(\mid\)APOS, \\  & UEmissions—Water, VN & \\ \hline Treatment of waste brick, recycling & - & - \\ RoW\(\mid\)APOS, U & - & - \\ \hline \multicolumn{3}{c}{Market for transport, freight, lorry 16–32 metric ton, EURO4 RoW\(\mid\)APOS, U} \\ \hline \multicolumn{3}{c}{Water input changed to} \\ \multicolumn{3}{c}{Water, unspecified natural origin, VN} \\ \multicolumn{3}{c}{Heter emission changed to} \\ \multicolumn{3}{c}{Heter emission changed to} \\ \multicolumn{3}{c}{Emissions—Water, VN} \\ \multicolumn{3}{c}{Heter emission changed to} \\ \multicolumn{3}{c}{Emissions—Water, VN} \\ \hline \multicolumn{3}{c}{Agri FootPrint—5/zero allocation} \\ \multicolumn{3}{c}{Beoinvent—Water, unspecified natural origin, VN} \\ processing/CN Mass & natural origin, VN & Rice, at farm/VN Mass \\  & Ecoinvent—Emissions—Water, VN & Zero allocation for ash as waste \\ \hline \multicolumn{3}{c}{Market for transport, freight, lorry 16–32 metric ton, EURO4 RoW\(\mid\)APOS, U} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Unit Processes used for LCA from Ecoinvent. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category Group** & **Impact Category** & **Category Indicator** \\ \hline Climate Change & Global warming potential & kg CO\({}_{2}\) eq \\ \hline Depletion of Abiotic & Mineral Resource Scarcity & kg Cu eq \\ Resources & Fossil Resource Scarcity & kg oil eq \\ \hline Acidification & Terrestrial Acidification & kg SO\({}_{2}\) eq \\ Eutrophication & Freshwater Eutrophication & kg P eq \\ Particulate Matter & Fine Particulate Matter Formation & kg PM2.5 eq \\ \hline Ozone & Stratospheric Ozone Depletion & kg CFC11 eq \\ Ozone & Ozone Formation Terrestrial Ecosystem & kg NOx eq \\ \hline Cumulative energy demand & Cumulative energy consumption & KJ \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Different Impact categories selected from ReCiPe. \(\rho\)s (g/cm\({}^{3}\)) installation density  
\(\rho\)Pr (g/cm\({}^{3}\)) proctor density  
wPr (-) Water content at proctor density  
kf (m/s) hydraulic permeability  
FC (%) usable field capacity  
AC (%) air capacity  
The results in Table 8 show that mixes MB 2 and MB 3 were feasible material mixtures to reach the quality requirements for class II landfill mineral sealing systems. The mix MB 1 and MB 5 still reached the quality requirements for class I landfill mineral sealing systems. Meanwhile the mixes MB 4 and MB 6 did not comply with quality requirements and remained unsuitable for sealing applications.