## 3 Benefits of Biochar Amendment in Green Roofs
### Runoff Quality Improvement  
The reduction in pollutants in green roof discharge is another significant benefit of biochar that has been extensively studied. While nutrients are vital for plant survival, they can leach from green roof substrates due to rain and irrigation, potentially polluting aquatic environments. Although many runoff quality parameters were evaluated, Table 3 focuses only on the most significant nutrients and heavy metals. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Reference** & **Approach** & **Substrate** & **Biochar Setup** & **Pollutant** & \begin{tabular}{c} **Concentration** \\ **without Biochar** \\ **(mg/L)** \\ \end{tabular} & \begin{tabular}{c} **Concentration** \\ **with** \\ **Biochar (mg/L)** \\ \end{tabular} & \
\begin{tabular}{c} **Coactration** \\ **with** \\ **Biochar (mg/L)** \\ \end{tabular} &
\begin{tabular}{c} **Coactration** \\ **with** \\ **Biochar (mg)** \\ \end{tabular} \\ \hline
[58] & Pilot-scale & \begin{tabular}{c} Recycled brick, expanded day, \\ spagmite, and \\ peat \\ \end{tabular} & \begin{tabular}{c} Wood/swage \\ sludge/food \\ peat \\ \end{tabular} & TN & \begin{tabular}{c} 2.20 \(\pm\) 1.20 \\ \end{tabular} & \
\begin{tabular}{c} \(13.8\pm 21.2/\) \\ \(7.87\pm 9.03\) \\ \end{tabular} &
\begin{tabular}{c} \\ \(7.87\pm 9.03\) \\ \end{tabular} & NA & NA \\ \hline
[58] & Pilot-scale & \begin{tabular}{c} Recycled brick, expanded day, \\ spagmite, and \\ peat \\ \end{tabular} & \begin{tabular}{c} Wood/swage \\ sludge/food \\ peat \\ \end{tabular} & \
\begin{tabular}{c} \\ sludge/food \\ waste biochar \\ \end{tabular} & TP &
\begin{tabular}{c} 0.38 \(\pm\) 0.35 \\ \(0.38\pm 0.35\) \\ \(0.38\pm 0.35\) \\ \end{tabular} & NA & NA \\ \hline
[64] & Field-scale & \begin{tabular}{c} Recycled, crushed \\ brick, compost, \\ crushed bark, and \\ spagmum moss \\ \end{tabular} & \
\begin{tabular}{c} Surface biochar \\ crushed bark, and \\ Buried biochar \\ \end{tabular} & TP and TN & NA & NA &
\begin{tabular}{c} Sedum: 35 and 580; \\ meadow: 41 and \\ \(700\) (m\({}^{-2}\)) \\ \end{tabular} \\ \hline
[71] & Pilot-scale & \begin{tabular}{c} Gravel, sand, silt, \\ clay, pumice, Fiber \\ Life compost, and \\ paper fiber \\ \end{tabular} & NA & \
\begin{tabular}{c} Organic carbon \\ **(sedum and \\ vegetables)** \\ \end{tabular} & 78.8 and 73.6 & 257.0 and 21.6 &
\begin{tabular}{c} 1436-1521 and \\ 1024-1236 \\ \end{tabular} & 425-488 and 395-439 \\ \hline
[72] & Pilot-scale & \begin{tabular}{c} Gravel, sand, silt, \\ clay, pumice, Fiber \\ Life compost, and \\ paper fiber \\ \end{tabular} & NA & \begin{tabular}{c} Inorganic carbon \\ **(sedum and \\ vegetables)** \\ \end{tabular} & 13.3 and 18.6 & 12.7 and 17.2 & 233-288 and 257-322 & 223-242 and 335-345 \\ \hline \multirow{6}{*}{[71]} & \multirow{6}{*}{\begin{tabular}{c} Float-scale \\ sawdust \\ \end{tabular} } & TP & \
\begin{tabular}{c} (redum and \\ vegetables)** \\ \end{tabular} & 10.3 and 17.4 & 8.3 and 8.4 & 199–216 and 238-352 & 119-183 and 151–182 \\ \cline{1-1} \cline{3-6}  & &
\begin{tabular}{c} TN (sedum and \\ vegetables) \\ \end{tabular} & NA and 79.2 & NA and 10.1 & NA & NA \\ \hline
[72] & Pilot-scale & \begin{tabular}{c} Peat, vermiculite, \\ perfite, and \\ sawdust \\ \end{tabular} & NA & \begin{tabular}{c} TP \\ TN \\ \end{tabular} & 0.15 & 0.21 & \begin{tabular}{c} 0.002 \(\pm\) 0.001 (m\({}^{-2}\)) \\ \end{tabular} & 0.003 \(\pm\) 0.001 (m\({}^{-2}\)) \\ \cline{1-1} \cline{3-6}  & & \begin{tabular}{c} Peat, vermiculite, \\ perfite, and \\ sawdust \\ \end{tabular} & NA & \begin{tabular}{c} TP \\ TN \\ \end{tabular} & 16.14 & 9.85 & \
\begin{tabular}{c} 0.205 \(\pm\) 0.089 (m\({}^{-2}\)) \\ \end{tabular} & 0.096 \(\pm\) 0.042 (m\({}^{-2}\)) \\ \cline{1-1} \cline{3-6}  & &
\begin{tabular}{c} Zn \\ Fe \\ \end{tabular} & 0.03 & 0.02 & NA & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Quality of runoff from biochar-amended green roofs. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Reference** & **Approach** & **Substrate** & **Biochar Setup** & **Pollutant** &