# Advances in Bio-Hydrogen Production: A Critical Review of Pyrolysis Gas Reforming
## 1 Introduction
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multicolumn{2}{c}{**Process Type (Temperature)**} & \multicolumn{1}{p{56.9 pt}}{**Feedstock**} & \multicolumn{1}{p{56.9 pt}}{**H\({}_{2}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**CO (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**CO\({}_{2}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**CH\({}_{4}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**C\({}_{2+}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**N\({}_{2}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**O\({}_{2}\) (vol\%)**} & \multicolumn{1}{p{56.9 pt}}{**Ref.**} \\ \hline \multirow{4}{*}{Slow (650)} & Waste wood & 7 & 30.5 & 44.7 & 14.7 & 3.1 & & \\ \cline{2-9}  & Cardboard & 13.4 & 36.6 & 32.4 & 15.3 & 2.3 & & \\ \cline{2-9}  & Textile & 5.4 & 34.7 & 35.6 & 19.2 & 5.1 & & \\ \hline \multirow{4}{*}{Slow (500)} & Neem seed & 6.89 \(\pm\) 1 & 0.46 \(\pm\) 0.3 & \(7.16\pm\) 1 & \(15.87\pm\) 2 & & \(18.46\pm\) 2 \\ \cline{2-9}  & Pigeon pea & 4.66 \(\pm\) 1 & 1.60 \(\pm\) 1 & \(8.93\pm\) 1 & \(21.57\pm\) 2 & & \(14.58\pm\) 1 \\ \cline{2-9}  & Yellow pea & 0.15\(\pm\) 0.1 & 1.30 \(\pm\) 1 & \(11.23\pm\) 1 & \(24.77\pm\) 2 & & \(15.56\pm\) 2 \\ \cline{2-9}  & Ground nut shell & 5.02 \(\pm\) 1 & \(10.16\pm\) 1 & \(6.97\pm\) 1 & \(13.21\pm\) 1 & & \(10.93\pm\) 1 \\ \cline{2-9}  & Channa straw cicer & 4.36 \(\pm\) 1 & 14.02 \(\pm\) 1 & 6.94\(\pm\) 1 & \(19.93\pm\) 2 & & \(10.58\pm\) 1 \\ \cline{2-9}  & Soybean Straw Glycine & 8.29 \(\pm\) 1 & 13.85 \(\pm\) 1 & 7.80\(\pm\) 1 & \(18.53\pm\) 2 & & \(10.60\pm\) 1 \\ \cline{2-9}  & Wheat straw & 7.05 \(\pm\) 1 & 7.51 \(\pm\) 1 & \(5.62\pm\) 1 & \(18.70\pm\) 2 & & \(13.38\pm\) 1 \\ \cline{2-9}  & Sawdust & 7.11 \(\pm\) 1 & 6.26 \(\pm\) 1 & 4.93\(\pm\) 0.5 & \(22.25\pm\) 2 & & \(15.40\pm\) 2 \\ \hline Slow (600) & Olive stone & 29.47 & 31.48 & 14.1 & 20.5 & 3.65 & 0.8 & [40] \\ \hline Fast (550) & Sawdust & 4.54 & 34.49 & 16.8 & 4.41 & 35.55 & 4.25 & [41] \\ \hline Fast (550) & Wood biomass & 7.01 & 24.13 & 36.35 & 4.41 & 28.1 & [42] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Pyrogas composition in different studies. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multicolumn{2}{c}{**Process**} & \multicolumn{1}{p{56.9 pt}}{**Advantages**} & \multicolumn{1}{p{56.9 pt}}{**Disadvantages**} & \multicolumn{1}{p{56.9 pt}}{**Efficiency (\%)**} \\ \hline \multirow{2}{*}{Steam methane reforming} & \multicolumn{1}{p{56.9 pt}}{Mature technology, low production cost} & \multicolumn{1}{p{56.9 pt}}{GHG emissions, fossil fuel resource depletion} & \multicolumn{1}{p{56.9 pt}}{74–85} \\ \hline \multirow{2}{*}{Partial oxidation} & \multicolumn{1}{p{56.9 pt}}{Proven technology resource depletion} & \multicolumn{1}{p{56.9 pt}}{GHG emissions, fossil fuel resource depletion} & \multicolumn{1}{p{56.9 pt}}{60–75} \\ \hline \multirow{2}{*}{Electrolysis} & \multicolumn{1}{p{56.9 pt}}{Mature technology, no emissions, cheap and available feedstock, O\({}_{2}\) byproduct} & \multicolumn{1}{p{56.9 pt}}{Low overall efficiency, high capital cost, corrosion challenges} & \multicolumn{1}{p{56.9 pt}}{40–60} \\ \hline \multirow{2}{*}{Biomass pyrolysis} & \multicolumn{1}{p{56.9 pt}}{Cheap feedstock, CO\({}_{2}\)-neutral} & \multicolumn{1}{p{56.9 pt}}{Tar formation, seasonal availability of and impurities in feedstock} & \multicolumn{1}{p{56.9 pt}}{35–50} \\ \hline \multirow{2}{*}{Biomass gasification} & \multicolumn{1}{p{56.9 pt}}{Cheap feedstock, CO\({}_{2}\)-neutral} & \multicolumn{1}{p{56.9 pt}}{Tar formation, seasonal availability of and impurities in feedstock} & \multicolumn{1}{p{56.9 pt}}{35} \\ \cline{2-9}  & \multicolumn{1}{p{56.9 pt}}{Tar formation, seasonal availability of and impurities in feedstock} & \multicolumn{1}{p{56.9 pt}}{35} \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of different hydrogen production processes [43; 44; 45].