## 5 Conclusions  
Experimental studies of two-phase anaerobic biodegradation of corn extract--a waste product from corn grain processing for starch extraction--were performed with mesophilic temperatures in both bioreactors. The obtained data will be used for calibration of the developed early mathematical models [29; 30]. For the first time, an automatic mode was implemented in continuous two-phase ABD with simultaneous production of hydrogen and methane using the developed computer system for monitoring and control. The best results for daily biogas yield were obtained at an organic load of 20 g/L for hydrogen-producing BR1, with a daily biohydrogen yield of 0.74 dm3/L at a hydrogen concentration in biogas of 32.6% volumetric, and the daily yield of biomethane is 0.587 dm3/L at a methane concentration in biogas of 69% volumetric. This \begin{table}
\begin{tabular}{c c c c} \hline \hline Hydraulic retention time for H2 reactor (days) & 0.25 & 1 & 1.5 \\ Dilution rate D1 (days\({}^{-1}\)) & 4 & 1 & 0.667 \\ Hydraulic retention time for CH4 reactor (days) & 2.5 & 10 & 15 \\ Dilution rate D2 (days\({}^{-1}\)) & 0.4 & 0.1 & 0.067 \\ Hydrogen production (NL L\({}^{-1}\)day\({}^{-1}\)) & 1.67 & 0.49 & 0.19 \\ Methane production (NL L\({}^{-1}\)day\({}^{-1}\)) & 4.52 & 1.31 & 0.99 \\ Total energy production (kWh/day) & 0.0004997 & 0.14472 & 0.108 \\ Efficiency \(\eta\) (\%) & 49 & 56 & 63 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Experimental conditions and results for the TPAD continuous tests (\(\gamma\) = 0.1). \begin{table}
\begin{tabular}{c c} \hline \hline Hydraulic retention time for H2 reactor (days) & 2.5 \\ Dilution rate D1 (days\({}^{-1}\)) & 0.4 \\ Hydraulic retention time for CH4 reactor (days) & 25 \\ Dilution rate D2 (days\({}^{-1}\)) & 0.04 \\ Hydrogen production (dm3 L\({}^{-1}\)day\({}^{-1}\)) & 0.241 \\ Methane production (dm3 L\({}^{-1}\)day\({}^{-1}\)) & 0.405 \\ Total energy production (kWh/day) & 0.005028 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Experimental results obtained during the TPAD continuous tests (\(\gamma\) = 0.1 and S0i = 50 g/L). means that the obtained energy is over 40% higher compared to the traditional single-stage CH\({}_{4}\) production process. Biohythane obtained from TPAD (hydrogen + methane = hythane) is a biofuel used in vehicles [31; 32]. Comparing TPAD with one-stage AD using different organic wastes, it was concluded that energy recovery was in the range of 9-19 MJ/kg VS\({}_{\text{added}}\); the overall energy was significantly higher (8-43%) for the TPAD than one-step AD in the large majority of the laboratory experimental conditions tested [4]. These preliminary results should evoke further research to better understand the conditions for achieving higher performance using TPAD. The temperature-phased anaerobic digestion biogas plants are an interesting and promising concept [33]. In our future work, the influence of a thermophilic temperature in the first bioreactor will be studied. A disadvantage is the need for additional purification from hydrogen sulphide (H\({}_{2}\)S) of both gases before obtaining electricity and/or heat. Our results are a good base for the transition to industrial two-phase biogas plants for simultaneous production of biohydrogen and biomethane, which have not yet been well studied due to the complexity of this biotechnology. Conceptualization, E.C. and I.S. ; methodology, I.S. ; software, E.C. ; validation, E.C., V.H., Y.G. and I.S. ; formal analysis, V.H., Y.G. and I.S. ; investigation, E.C., V.H. and I.S. ; resources, E.C., V.H., Y.G. and I.S. ; data curation, V.H. and Y.G. ; writing--original draft preparation, E.C., V.H., Y.G. and I.S. ; writing--review and editing, E.C., V.H. and I.S. ; visualization, E.C. and I.S. ; supervision, I.S. ; project administration, E.C. ; funding acquisition, E.C. All authors have read and agreed to the published version of the manuscript.