## 3 Pretreatment Methods in the Chain of Biogas Production
### Other Pretreatments  
Several other pretreatments such as ozonolysis, microwave irradiation, and high voltage pulse discharge have also been reported recently to increase the methane yield from lignocellulosic biomass. Ozonolysis is one of the most promising chemical oxidative pretreatments for lignin degradation with minimal losses of hemicellulose and cellulose contents [163], but most of the reported literature is on \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Substrates** & \begin{tabular}{c} **Pretreatment** \\ **Conditions** \\ \end{tabular} & \begin{tabular}{c} **Methane Yield** \\ **(Untreated)** \\ \end{tabular} & \begin{tabular}{c} **Methane Yield** \\ **(After Treatment)** \\ \end{tabular} & \begin{tabular}{c} **Reaction** \\ **System** \\ \end{tabular} & **References** \\ \hline \multirow{4}{*}{Corn stover} & Fungi, _Pleurotus & \begin{tabular}{c} _c_erugia, \\ 30 days \\ \end{tabular} & 301.5 mL/g VS & 360.4 mL/g VS & \begin{tabular}{c} Bottle \\ 0.25 L \\ \end{tabular} & [148] \\ \cline{2-7}  & Fungi, _Pleurotus_ & \begin{tabular}{c} \(c\) \\ _ostreatus_, 30 days \\ \end{tabular} & 294.3 mL/g VS & 300.6 mL/g VS & \begin{tabular}{c} Bottle \\ 0.25 L \\ \end{tabular} & [148] \\ \cline{2-7}  & Fungi, _Tranetes_ & \begin{tabular}{c} \(c\) \\ _versicolor_, 30 days \\ \end{tabular} & 362.2 mL/g VS & 222.83 mL/g VS & \
\begin{tabular}{c} Bottle \\ 0.25 L \\ \end{tabular} & [148] \\ \hline \multirow{2}{*}{Rapeseed stems and leaves} & \multirow{2}{*}{Rumen fluid, 24 h} & \multirow{2}{*}{485.5 mL/g VS} & \multirow{2}{*}{507.9 mL/g VS} & Reactor & \multirow{2}{*}{[160]} \\ \cline{2-7}  & & & & & 1 L \\ \hline \multirow{2}{*}{Sawdust} & Microbial consortium, & \multirow{2}{*}{89.9 mL/g VS} & \multirow{2}{*}{155.2 mL/g VS} & Digester & \multirow{2}{*}{[33]} \\ \cline{2-7}  & & & & & 5 L \\ \hline \multirow{2}{*}{Water Hyacinth} & Microbial, _Citrobacter_ & \multirow{2}{*}{338 mL/g VS} & \multirow{2}{*}{373 mL/g VS} & Bottle & \multirow{2}{*}{[38]} \\  & & & & 1 L \\ \cline{2-7}  & & & & & 1 \\ \hline \multirow{4}{*}{Wheat straw} &
\begin{tabular}{c} Fungus culture, \\ 0.3 OD; 7 days \\ \end{tabular} & 78.1 mL/g VS & 396.1 mL/g VS & - & [118] \\ \cline{2-7}  & Microbial consortium, & \multirow{2}{*}{229.8 mL/g VS} & \multirow{2}{*}{314 mL/g VS} & Reactor & \multirow{2}{*}{[159]} \\  & TC-5, & 12 days & & & 0.18 L \\ \hline \multirow{4}{*}{Willow sawdust} & Fungal, _Leitartes_ & \multirow{2}{*}{95.5 mL/g VS} & \multirow{2}{*}{62.4 mL/g VS} & Serum & \multirow{2}{*}{[40]} \\  & _memezisii_, 30 days & & & 0.16 L & \\ \cline{1-1} \cline{2-7}  & Fungal, _Ahortiporus_ & & & & 1 \\ \cline{1-1} \cline{2-7}  & & & & 0.16 L & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Effect of different biological pretreatments on methane yield from different lignocellulosic biomass. its application related to pulp. [PERSON] et al. [164] reported a specific methane production of 291 LCH4/kg VS using ozonolysis pretreatment of rye straw with an ozone dose of 100 g O\({}_{3}\)/m\({}^{3}\) for 60 min. Microwave irradiation is known as an efficient technique in disrupting complex structures such as sludge and thereby increases the accessibility and bioavailability to enhance methane production [165]. [PERSON] et al. [166] reported a methane yield of 221 mL/g of water hyacinth after a pretreatment of 500 W for 14.6 min, which was about 38.3% more than the substrate pretreated with hot water. However, after an economic analysis, they reported that it is not economically viable. Previously, [PERSON] and [PERSON] [167] observed that pretreatment of winery waste, cotton gin waste, olive pomace, and juice industry waste by microwave did not show an increase in methane production. However, they observed that structural changes in cotton gin waste and olive pomace, whereas increased solubilization in the case of winery and juice industry waste. [PERSON] et al. [168] evaluated the microwave pretreatment at different temperatures and exposure time, the ranges were 130-230 \({}^{\circ}\)C and 2-5 min, respectively.