# Biomass and Cellulose Dissolution--The Important Issue in Renewable Materials Treatment
## 4. Conclusions  
The effective dissolution of biomass or its fractions is still a challenge in lignocellulosic waste processing. The wide variety of plant materials and differences in chemical compo \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Biomass Type**} & \multicolumn{2}{c}{**DES**} & \multirow{2}{*}{**Temperature [\({}^{\circ}\)C]**} & \multirow{2}{*}{**Dissolution Technique**} & \multirow{2}{*}{**Time [h]**} & \multirow{2}{*}{**Delignification Level [\%]**} & \multirow{2}{*}{**References**} \\  & **(HBA:HBD & & & & & \\  & **Molar Ratio)** & & & & & \\ \hline \multirow{2}{*}{Rice straw} & ChCl:Lac (1:5) & \multirow{2}{*}{60} & Stirring and & \multirow{2}{*}{12} & 60.0 & [138] \\  & BetLac (1:5) & & & heating & 53.0 & & \\ \hline \multirow{2}{*}{Miscanthus} & ChCl:Fa (1:2) & \multirow{2}{*}{60} & \multirow{2}{*}{Microwave} & \multirow{2}{*}{1} & 4.8 & \multirow{2}{*}{[135]} \\  & & 130 & & & & & \\ \hline \multirow{2}{*}{Birchwood} & ChCl:Ox (1:1) & \multirow{2}{*}{130} & 60 & \multirow{2}{*}{Microwave} & \multirow{2}{*}{1} & 43.0 & \multirow{2}{*}{[135]} \\  & & 130 & & & & & \\ \hline \multirow{2}{*}{Bamboo stem} & ChCl:U (1:2) & \multirow{2}{*}{120} & Stirring and & \multirow{2}{*}{10} & 19.4 & \multirow{2}{*}{[139]} \\  & ChCl:Ox (1:2) & & heating & & & & \\ \hline \multirow{2}{*}{\begin{tabular}{c} Wheat straw \\ Corn stalk \\ Rapeseed stem \\ \end{tabular} } & ChCl:Lac (1:5) & \multirow{2}{*}{100} & Stirring and & \multirow{2}{*}{16} & 8.5 & \multirow{2}{*}{[140]} \\  & & & heating & & & \\ \hline \multirow{2}{*}{Sorghum straw} & ChCl:Lac & \multirow{2}{*}{150} & Stirring and & \multirow{2}{*}{0.5} & 49.0 & [141] \\  & & & heating & & & \\ \hline \multirow{2}{*}{\begin{tabular}{c} Bamboo \\ residues \\ \end{tabular} } & ChCl:Lac (1:4) & \multirow{2}{*}{110} & Stirring and & \multirow{2}{*}{1.5} & 42.3 & \multirow{2}{*}{[142]} \\  & & 130 & & heating & & & \\ \cline{2-2} \cline{5-5}  & ChCl:Lac (1:8) & \multirow{2}{*}{110} & 130 & & & & \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Masson pine \\ \end{tabular} } & ChCl:Lac (1:10) & \multirow{2}{*}{110} & 140 & Stirring and & \multirow{2}{*}{6} & 58.1 & \multirow{2}{*}{[143]} \\  & & 140 & heating & & & & \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Bagasse \\ \end{tabular} } & ChCl:Ox (1:1) & \multirow{2}{*}{100} & Stirring and & \multirow{2}{*}{4} & 47.9 & \multirow{2}{*}{[144]} \\  & ChCl:Et (1:2) & & heating & & & & \\ \hline \end{tabular}
\end{table} 
Table 4. Delignification of plant biomass with DESs. sition makes the selection of an appropriate solvent even more difficult. The key step in making the process more efficient is to understand the mechanisms of biomass dissolution, which is generally based on the breakage of hydrogen bonds existing in lignocellulosic and the creation of new ones between solvent and biomass components. Nowadays, the rules of the sustainable development strategy and green chemistry should be followed in the selection of appropriate solvents. Classic acidic and alkaline solutions, known for their ability to dissolve biomass fractions, should be replaced by more ecological solvents. Ionic liquids and deep eutectic solvents are promising groups of solvents. Ionic liquids are especially effective in cellulose dissolving. This ability mostly depends on the solvent's anion--the higher the hydrogen bond basicity of the anion, the better the biomass dissolution properties. Moreover, in many works, a substituted imidazolium cation is presented as the best one. However, the length of alkyl chains in cation substituents has a significant impact on the effectiveness of the process. Shorter chains are more suitable for dissolving cellulose (e.g., [emim]\({}^{+}\)). If the process is devoted to lignin dissolution, it is recommended to use deep eutectic solvents, especially those with an acidic hydrogen bond donor. They are more effective than alkaline solutions.