## 3 Results and Discussion  
### Bio-Delignification and Chemical Delignification Processes  
The raw characterization of the fresh biomasses used in this study for biogas production are reported in Table 1. Typically, OFMSW is a highly heterogeneous material with high moisture content that makes it highly biodegradable due to the large fraction of food scraps and fresh food waste. On average, the TS content is about 20%, in a range between 9% and 30% [67], depending on region, waste collection, and management by authorities. The heterogeneity of GW is caused by various factors, including the place where it is collected, the composition, and seasonal variations. It is very difficult to refer to average values because TS an vary from 5-8% in the case of a prevalence of flowers, grass, and leaves to 35-40% with woody materials [68]. In order to evaluate the performance of bio-delignification in comparison with chemical treatments, GW was submitted to four different treatments with different characteristics, as summarized in Table 2.  
Bio-delignification showed a yield of about 40% after 7 days of treatment, which is a very long time in comparison with the time for chemical delignification, but it is worth noting the total absence of toxic chemicals and the working temperature of room value. The yield obtained is comparable to values reported in the literature for bio-delignification, in the range 20-42% [69; 70]. As expected, treatment based on sodium hydroxide had the highest yield, due to the strong effect of caustic degradation on lignocellulosic materials [23], provoking relevant damage on cellulose fibrils [60]. Chemical treatments with sulfuric acid \begin{table}
\begin{tabular}{c c c} \hline \hline
**Substrate** & **OFMSW** & **GW** \\ \hline TS (\%) & 18.1 \(\pm\) 1.8 & 98.3 \(\pm\) 3.9 \\ VS (\%) & 16.8 \(\pm\) 1.7 & 84.5 \(\pm\) 3.8 \\ COD (\%) & 17.6 \(\pm\) 1.9 & 89.1 \(\pm\) 3.7 \\ TKN (\%) & 0.8 \(\pm\) 0.1 & 2.05 \(\pm\) 0.3 \\ P tot (\%) & 0.0 \(\pm\) 0.0 & NA \\ C/N & 20.7 & 43.5 \\ VS/TS & 92.8 & 86.0 \\ Lignin & NA & 23.8 \(\pm\) 0.57 \\ \hline \hline \end{tabular} TS = total solids; VS = volatile solids; COD = chemical oxygen demand; TKN = total Kjeldhal nitrogen; P = phosphorows; C/N = carbon/nitrogen ratio.  
\end{table} 
Table 1: Chemical compositions and characteristics of fresh biomasses (OFMSW and untreated GW) (OFMSW = organic fraction of municipal solid waste; GW = green waste). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatment** & **Residual** & **Yield of** & **Time of** & **Temperature** & **Use of** & **Rinsing** \\  & **Lignin (\%)** & **Delignification (\%)** & **Exposition** & **(\({}^{\circ}\)C)** & **Chemicals** & **Water (l)** \\ \hline BA & 13.7 \(\pm\) 0.28 & 42\% & 7 days & 24 \({}^{\circ}\)C & no & 0 \\ Chlorine & 17.1 \(\pm\) 0.31 & 28\% & 60 min & 25 \({}^{\circ}\)C & yes & 5 \\ Dil. sulfuric acid & 17.9 \(\pm\) 0.32 & 25\% & 45 min & 121 \({}^{\circ}\)C & yes & up to pH = 7 \\ Sodium hydroxide & 5.2 \(\pm\) 0.25 & 78\% & 60 min & 121 \({}^{\circ}\)C & yes & up to pH = 7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of delignification and bio-delignification treatments carried out on GW samples (BA = _Bjerkandera_ _adusta_). and sodium hydroxide need some distilled water for biomass washing until reaching a neutral pH (pH = 7 \(\pm\) 0.1), and 5 liters of distilled water is required for chlorine treatments. This is different from bio-delignification, which does not alter the pH of the solution. For residual rinsing water from chlorine treatments, an evaluation of the amount of reducing (fermentable) sugars lost in water was carried out, showing a value of 926.7 \(\pm\) 55.6 mg/L.