## 5 Conclusions  
The study demonstrated that FW and WH are promising feedstocks for biogas production using cow dung as an inoculum. Co-digestion in small reactors under controlled temperature conditions showed a higher biogas production potential as compared to mono-digestion. The current research showed that WH:FW (1:1) and WH:FW (1:2) could be an important co-digestion pair for significant biogas production. This research also showed that COD varied significantly among all reactors, which suggested that it is a good predictive variable for biogas production assessment. The fitted Gompertz model indicates a high degree of conformity between the experimental findings and simulated values for both mono- and co-digestion. The model also predicted that the reduction in lag phase depends critically on increasing the quantity of FW. The current study was conducted on a small scale with reactors using limited factors to access biogas production. Further study on the co-digestion of FW and WH needs to be carried out in larger reactors to determine the operational condition, scale effect, and economic criteria to prove its applicability for large-scale implementation. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app14219880/s1](https://www.mdpi.com/article/10.3390/app14219880/s1)]([https://www.mdpi.com/article/10.3390/app14219880/s1](https://www.mdpi.com/article/10.3390/app14219880/s1)), Table S1: Variation of production of biogas between Co-digestion, mono-digestion and overall (both Co-digestion and mono-digestion) digestion; Table S2: Pair sample _t_-test of biogas production between different co-digestions; Table S3: The kinetics parameters of the fitted model; Table S4: Analysis of overall variation of reduction of Chemical Oxygen Demand. Conceptualization, methodology, formal analysis, visualization, writing--original draft, G.N. and A.K. ; software, validation, visualization, A.K. and S.G.; project administration, funding acquisition, writing--review and editing, investigation, supervision, A.B.R. and S.B. All authors have read and agreed to the published version of the manuscript. This research was funded by the BEFWAM project: Bioenergy, Fertilizer, and Clean Water from Invasive Aquatic Macrophytes, grant number BB/S011439/1. Not applicable. Data Availability Statement: Data will be available on request. \begin{table}
\begin{tabular}{p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt}} \hline \hline
**Time** **(Day)** & **WH:FW (1:1)**: **CD** & **WH:FW (2:1)**: **CD** & **WH:FW (1:2)**: **CD** & **CD:WH (1:1)** & **CD:WH (2:1)** & **CD:WH (1:2)** & **CD:FW (1:1)** & **CD:FW (2:1)** & **CD:FW (1:2)** & **Blank** \\ \hline
0 & 0.76 & 1.06 & 0.83 & 1.02 & 0.95 & 0.70 & 0.49 & 1.21 & 1.04 & 0.63 \\ \hline
3 & 0.95 & 1.30 & 1.17 & 0.93 & 1.11 & 0.89 & 1.06 & 0.98 & 1.02 & 0.34 \\ \hline
6 & 0.24 & 0.24 & 0.22 & 0.26 & 0.23 & 0.26 & 0.21 & 0.23 & 0.20 & 0.28 \\ \hline
9 & 0.41 & 0.46 & 0.35 & 0.61 & 0.52 & 0.53 & 0.31 & 0.43 & 0.32 & 0.35 \\ \hline
12 & 2.67 & 5.00 & 2.56 & 6.19 & 4.56 & 3.87 & 2.99 & 7.16 & 2.26 & 1.58 \\ \hline
15 & 4.43 & 3.32 & 3.26 & 2.84 & 2.14 & 3.78 & 5.49 & 2.91 & 2.64 & 4.62 \\ \hline
18 & 0.31 & 0.00 & 0.14 & 0.16 & 0.00 & 0.41 & 3.04 & 0.32 & 0.56 & 1.58 \\ \hline
21 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.56 & 0.00 & 0.00 & 0.17 \\ \hline
24 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Ratio of acetic acid and propionic acid. **Acknowledgments:** The authors are thankful to [PERSON], Department of Environmental Science, Amity School of Life Sciences, Amity University, Madhya Pradesh, Gwalior, 474005, India, for his valuable assistance with the statistical analysis. **Conflicts of Interest:** [PERSON] was employed by the company Defiant Renewables Pvt Ltd.