# Slow Pyrolysis as a Method of Treating Household Biowaste for Biochar Production
## 3 Results and Discussion
### Properties of Biochar
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline  & \multicolumn{4}{c}{**Kitchen Biochar**} & \multicolumn{4}{c}{**Spring Garden Biochar**} & \multicolumn{4}{c}{**Autumn Garden Biochar**} \\ \cline{2-11}  & **400 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **600 \({}^{\circ}\)C** & **400 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **600 \({}^{\circ}\)C** & **400 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **600 \({}^{\circ}\)C** \\ \hline Y\({}_{\text{m}}\) (mass yield of biochar) & \multirow{2}{*}{36.64} & \multirow{2}{*}{32.02} & \multirow{2}{*}{28.71} & \multirow{2}{*}{66.53} & \multirow{2}{*}{58.13} & \multirow{2}{*}{60.07} & \multirow{2}{*}{66.99} & \multirow{2}{*}{63.15} & \multirow{2}{*}{60.68} \\ (\% wt.) (dry basis) & & & & & & & & & & \\ \hline \multicolumn{11}{c}{Proximate analysis (\% wt.) (dry basis)} \\ \hline VM (volatile matter content) & 20.49 & 14.88 & 11.14 & 12.59 & 11.65 & 5.89 & 15.42 & 12.10 & 5.76 \\ A (ash content) & 18.57 & 21.81 & 21.09 & 64.69 & 65.38 & 72.57 & 61.71 & 64.38 & 71.32 \\ FC (fixed carbon) * & 60.94 & 63.31 & 67.77 & 22.73 & 22.96 & 21.54 & 22.87 & 23.52 & 22.93 \\ \hline \multicolumn{11}{c}{Ultimate analysis (\% wt.) (dry basis)} \\ \hline C (carbon content) & 58.02 & 54.81 & 55.55 & 25.34 & 26.60 & 21.00 & 27.84 & 27.45 & 25.62 \\ H (hydrogen content) & 4.00 & 3.02 & 2.67 & 2.41 & 1.71 & 1.41 & 2.80 & 2.54 & 1.47 \\ N (nitrogen content) & 3.64 & 3.46 & 3.01 & 1.44 & 1.52 & 1.05 & 1.15 & 1.00 & 1.02 \\ O (oxygen content) ** & 15.77 & 16.90 & 17.68 & 6.12 & 4.79 & 3.97 & 6.50 & 4.63 & 0.57 \\ \hline \multicolumn{11}{c}{Other measurements (dry basis)} \\ \hline HHV (higher heating value), & \multirow{2}{*}{22.68} & \multirow{2}{*}{20.84} & \multirow{2}{*}{21.90} & \multirow{2}{*}{9.04} & \multirow{2}{*}{8.95} & \multirow{2}{*}{7.51} & \multirow{2}{*}{9.96} & \multirow{2}{*}{9.02} & \multirow{2}{*}{8.40} \\ MJ/kg & & & & & & & & & \\ LHV (lower heating value), & \multirow{2}{*}{21.80} & \multirow{2}{*}{20.17} & \multirow{2}{*}{21.31} & \multirow{2}{*}{8.51} & \multirow{2}{*}{8.58} & \multirow{2}{*}{7.20} & \multirow{2}{*}{9.35} & \multirow{2}{*}{8.46} & \multirow{2}{*}{8.07} \\ MJ/kg & & & & & & & & & & \\ CCs (combustible & \multirow{2}{*}{81.43} & \multirow{2}{*}{78.19} & \multirow{2}{*}{78.91} & \multirow{2}{*}{35.31} & \multirow{2}{*}{34.62} & \multirow{2}{*}{27.43} & \multirow{2}{*}{38.29} & \multirow{2}{*}{35.62} & \multirow{2}{*}{28.68} \\ compounds), (\% wt.) & & & & & & & & & \\ \hline \end{tabular}  
* by difference. ** by difference (without considering the sulfur and chlorine content).  
\end{table} 
Table 2: Yield and properties of biochar obtained from slow pyrolysis of biowaste. 20-36 MJ/kg [17], these results suggest that the analyzed garden biowastes are not suitable feedstocks for energy-oriented biochar production through slow pyrolysis. Nevertheless, due to their high ash content, garden biochars could potentially be repurposed as soil amendments to enhance soil fertility, depending on the mineral composition of the ash. It is also likely that contamination from soil, rocks, and other inorganic matter during the collection process--since garden waste is typically raked directly from the ground--negatively affected the quality of the resulting biochar. While such contamination is a known issue, it remains uncertain whether it can be entirely avoided.