## 3 Results and Discussion
### Energy Evaluation by Process Scenarios  
The combination of the various technologies involved in the dry biomass production process generated 24 scenarios (Figure 1 and Table 2). One of the main parameters to  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **Case D1** & **Case D2** & **Case D3** & **Case D4** \\ \hline Biomass Production (tons/year) & 69.957 & 69.957 & 69.957 & 69.957 \\ Energy Consumption (kWh/year) & 16,777 & 9027 & 941 & 1399 \\ Operating Cost & 76,000 & 15,000 & 71,000 & 15,000 \\ Unit Production Cost (US 5/kg) & 1.08 & 0.21 & 1.01 & 0.21 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary of Results for Secondary Harvest (Centrifugation and Filtering).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Case E1** & **Case E2** \\ \hline Biomass Production (tons/year) & 69.957 & 69.957 \\ Energy Consumption (kWh/year) & 2,816 & 2,177 \\ Operating Cost (US 5/year) & 37,000 & 19,000 \\ Unit Production Cost (US 5/kg) & 0.53 & 0.28 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Summary of Results for the Drying stage (Spray Dryer and Drum Dryer).  
consider in process design is energy consumption. This is mainly associated with the need for continuous feeding of water, nutrients, the circulation and mixing of the growing medium, and the energy requirement for harvesting and drying the biomass. Many authors report that energy consumption is high or low for the different technologies involved in the process, but they do not indicate the amount or under what criteria they are compared. In this study, for all scenarios the biomass feed produced in tubular photobioreactor from the cultivation stage is contemplated, this being a constant value, 875,053 kWh/year. The cultivation stage to produce biomass in photobioreactors consumes between 96% and 98% of the total energy consumption, depending on the scenario analyzed. The energy consumption for the primary harvest shows minimal variations, compared to the later stages of the process. The secondary harvest and the drying are the stages that cause the variation in energy consumption in the scenarios. Figure 6 shows the individual contribution of energy consumption by technology in each process stage, not including the preculture and cultivation stage. Based on what is observed in Figure 6, scenario 6 is the one with the lowest energy consumption, with a total consumption of 858,567 kWh/year, it considers NaOH as flocculant, belt filter press and drum dryer for drying. Scenario 17 with a total consumption of 875,192 kWh/year is the one with the highest energy consumption and considers Chitosan as flocculant, centrifugation, and spray drying. Evaluation of each of these technologies individually showed that centrifugation and the spray dryer are the technologies with the highest energy consumption in this stage. We can see in Figure 6 that scenarios that consider these two technologies (scenarios 1, 9 and 17) are those with the highest energy consumption. The scenarios with a behavior similar to these only change the technology from spray dryer to drum dryer (scenarios 2, 10 and 18). Scenarios 3, 4, 11, 12, 19 and 20 have a slightly lower energy consumption than the scenarios that consider centrifugation. Scenarios 3, 4, 11, 12, 19 and 20 consider vacuum filter for secondary harvest. In the remaining scenarios, a similar energy consumption is observed. However, those scenarios that consider belt filter press (5, 6, 13, 14, 21 and 22) have a slightly lower energy consumption than those that consider pressure filter (7, 8, 15, 16, 23 and 24).