# Microalgal Biomass Generation via Electroflotation: A Cost-Effective Dewaring Technology
## 7 Cost Analysis of Dewatering Approaches for Microalgal Biomass Production
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Modified Electroflotation** & **Microalgal Species** & **Characteristics** & **References** \\ \hline Graphite electrode, flocculation via chitosan & & 90\% of total recovery efficiency with & \\ and sequential bubbling flotation facilitated electroflotation & _Chorella_ species & 23.7 g of chitosan and 0.43 kWh of & [99] \\ electricity to harvest 1 kg of biomass & & & \\ \hline Combination of oxidation, biofoculation and electroflotation with boron-doped diamond and aluminum electrodes & Green _Scenablesums quadricuala_ microalgae & Sequential anodic oxidation to & \\  & & & \\  & & & \\ \hline Stainless steel electrode- mediated electroflotation & Various microalgal species & 100\% biomass recovery influenced by current density, initial stage pH, and the electrode distance & [91] \\ Iron or aluminum plate rectangle electrode & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline Aluminum, steel, iron, and copper electrode mediated electroflotation method & _Chorella vulgaris_ UTEX 1803 & Aluminum electrode mediated & [77] \\  & & & \\  & & & electrode/nication leads to 95\% of & \\  & & & biomass recovery efficiency with 50 V & \\  & & & of voltage and reaction time to 25 min & \\ \hline \hline \end{tabular}
\begin{tabular}{c c} \hline \hline  & \multicolumn{1}{c}{Microalgal lipid yield (28.6 \(\pm\) 1.2,} \\  & & wt.\%), chlorophyll a (8.3 \(\pm\) 0.3 \(\mu\)g/mL), and enhanced fatty acid methyl ester composition with 2.65 kWh/kg of energy utilization and USD 2.09/kg of operation cost. & [93] \\ Electro-coagulation-floculation approach & _Scenablesmus_ microalgal species & & \\  & & & \\  & & \\  & & & \\  & & \\  & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Modified electroflotation approach for the efficient recovery of microalgal biomass. biomass production system will be evaluated by the respective currency (USD or \(\xi\)) per year using the initial mass balance Equation of algal biomass in each step as mentioned in Equation (3). \[F_{\text{in}}C_{\text{in}}=F_{\text{out}}\ C_{\text{out}}+F_{\text{co, out}}\ C_{\text{co, out}} \tag{3}\]  
where, \(F\) represents the in or out volumetric flow rates for algal biomass streams (m\({}^{3}\)/h), \(\infty\) is the costream with water and a small lost algal biomass fraction and C is the algal biomass concentration (kg/m\({}^{3}\)) in each stream. Later, the yearly costs of harvesting and dewatering can be calculated by the formula given by [PERSON] et al. (2010) as mentioned in Equation (4) [98]. \[P_{\text{C}}=(0.5I+M)\times C_{\text{I}}+C_{\text{I}}/A+C_{\text{e}}+C_{\text {c}}+C_{\text{I}}+C_{\text{loss}} \tag{4}\]  
where, the production costs per kilogram of algal biomass produced are represented by:  
\[P_{\text{c, algae}}=P_{\text{e}}/Y_{\text{total}} \tag{5}\]  
In this Equation, \(C_{\text{I}}\) is the total investment cost in the, respective country's currency, \(I\) is the rate of interest in %, \(M\) is the % of maintenance cost, \(C_{\text{I}}/A\) is the yearly depreciation in currency per year over \(A\) as the depreciation time (year), \(C_{\text{e}}\) is the energy cost, \(C_{\text{c}}\) is the consumable costs, \(C_{\text{I}}\) is the labor cost, mentioned in currency per year, and \(Y_{\text{total}}\) is the total kilogram of biomass produced in a year. Further, an optional term, \(C_{\text{loss}}\), can also be included in the Equation to represent the loss of algae in terms of cost per year. In general, the investment cost will be calculated for each scenario from the total costs of equipment purchased, that are multiplied with Lang factor, which is a purchase cost multiplier to cover the costs for electrical facilities, piping, instrumentation, construction, buildings, electrical facilities, engineering, and contractors fee [99]. In addition, the scaling factor rule can be used for extrapolation of purchase costs to other capacities as mentioned in Equation (6).