# Advances in Bio-Hydrogen Production: A Critical Review of Pyrolysis Gas Reforming
## 3 Hydrogen Production by Catalytic Reforming of Pyrolysis Volatiles
### Intermediate and Fast Pyrolysis  
Other types of pyrolysis used in the two-stage catalytic process of reforming pyrolysis volatiles are intermediate and fast pyrolysis. The assessment of different routes to produce hydrogen and biocarbon using the intermediate pyrolysis process of the Envigas plant in Sweden was performed by [PERSON] et al. [82]. An electrically heated screw reactor was used \begin{table}
\begin{tabular}{c c c c} \hline
**Feedstock** & **Catalyst** & **H\({}_{2}\) Yield (mmol/g)** & **Ref.** \\ \hline Corncob & Ni/Al\({}_{2}\)O\({}_{3}\) & 51 & [72] \\ \hline Sewage sludge & Ni/Al\({}_{2}\)O\({}_{3}\) & 53 & [75] \\ \hline Wood sawdust & Ni/Al\({}_{2}\)O\({}_{3}\) & 11.01 & [67] \\ \hline Corncob & Ni/Al\({}_{2}\)O\({}_{3}\) & 21.2 & [76] \\ \hline Rice husk & & 23.71 & \\ \hline Sugar cane & Ni-dolomite & 21.18 & [63] \\ \hline Wheat straw & & 21.59 & \\ \hline Corncob & Ni-exchanged resin char & 25 & [77] \\ \hline Poplar wood & Poplar char & 14.4 & \\ \hline Catalpa wood & Catalpa char & 17.1 & \\ \hline Elm wood & Elm char & 15.7 & \\ \hline Pine wood & Pine char & 14.4 & \\ \hline Poplar wood & 5\% Ni/poplar char & 21.4 & \\ \hline Poplar wood & 10\% Ni/poplar char & 27.2 & \\ \hline Poplar wood & 15\% Ni/poplar char & 18.9 & \\ \hline Comcob & Natural limonite ore & 50.2 & [72] \\ \hline \end{tabular}
\end{table} 
Table 4: The effect of using different catalysts on hydrogen yield. for the intermediate pyrolysis process, and an electrically heated reformer was considered for the reforming process. It is worth noting that two possible configurations were considered to produce biochar and hydrogen. While pyrolysis volatiles were used as feedstocks for the reforming process in the first scheme, a condenser was used in the second suggested configuration to separate condensable materials from the pyrolysis volatiles, and these processes were modeled in Aspen Plus software version 9.0. The flow rate of forest waste biomass as a feedstock was 1000 kg/h, and the pyrolysis and reforming temperatures were set to 550-650 \({}^{\circ}\)C and 850 \({}^{\circ}\)C, respectively. Ni-based catalysts were also used in the reforming process. Another important point that should be mentioned is the requirement to use a water-gas shift reactor after the reforming process because of high carbon monoxide production. Implementing a water-gas shift reactor is vital in increasing hydrogen yield. The final results of first suggested configuration showed a hydrogen yield of 93.5 kg/h, equal to 10 wt% of the dry biomass input. However, the hydrogen production was 43.8 kg/h in the second suggested configuration. The main reason for this difference was using a condenser in the second configuration to collect the bio-oil as a product. The results of this study should be considered important since the feedstock flow rate of this study was on the industrial scale, and it reflects the merits and energy efficiency of this process in large-scale capacities [82]. Fast pyrolysis was also considered a process for the first step of reforming pyrolysis volatiles, and the impacts of using this were examined in a research study. The experimental results of reforming pyrolysis volatiles produced by the fast pyrolysis of pine wood sawdust showed hydrogen yields with different reforming temperatures. Hydrogen production at 550 \({}^{\circ}\)C was 64 g/kg of biomass, which was enhanced up to 110 g/kg at a reforming temperature between 600 \({}^{\circ}\)C and 700 \({}^{\circ}\)C [83]. Waste wood was used as a feedstock in a two-stage fast pyrolysis and steam reforming process to produce syngas, and four different Ni-based catalysts were used in this experiment. The pyrolysis temperature, heating rate, and reforming temperature of this experimental study were set to 500 \({}^{\circ}\)C, 40 \({}^{\circ}\)C/s, and 760 \({}^{\circ}\)C, respectively. Product distribution results showed that using a NiO/SiO\({}_{2}\) catalyst maximized the gas product yield by increasing this amount up to 54 wt%.