## 3 Results and Discussion
### Comparison of Two Different Raceway Configurations
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Raceway** & & & & \\
**Configuration/Process** & **Productivity (g m\({}^{-2}\) d\({}^{-1}\))** & & & \\
**Condition** & & & & \\ \hline  & **Global** & **Maximum** & **Global** & **Maximum** \\ \hline Modified/1 & 6.610 & 15.282 & 0.048 & 0.141 \\ Modified/2 & 7.691 & 16.364 & 0.069 & 0.175 \\ Standard/1 & 6.277 & 19.007 & 0.047 & 0.172 \\ Standard/2 & 7.089 & 18.102 & 0.065 & 0.166 \\ Standard/3 & 5.375 & 11.131 & 0.057 & 0.130 \\ \hline \hlineRegarding the fatty acid profile, C16 and C20 FAME were the most prevalent. Ma et al. (20) reported that C16, C18, and C20 FAME were the major fatty acids found in _Nannochloropsis_ strains, contrary to the present study on which C18 were detected in very small amounts. EPA content ranged from \(26.17\%\pm 3.32\%\) to \(29.45\%\pm 0.41\%\) of total FAME, which was lower than the values reported by Baohua et al. (20) for three different _N. oceanica_ strains cultivated in indoor raceways (\(35.58\%\pm 0.63\%\), \(38.78\%\pm 2.49\%\), \(40.13\%\pm 0.28\%\)). The higher relative content of PUFA and omega-3 PUFA (\(\omega\)-3) in comparison with saturated fatty acids (SFA) and omega-6 PUFA (\(\omega\)-6), respectively, are interesting indicators of the quality of biomass produced by the _N. oceanica_ strain used. Concerning energy consumption, the modified raceway consumed, at least, twice the energy consumed by standard configuration (Table 7). The non-uniform velocity pattern generated with a half channel width paddlewheel mixing was responsible for the discrepancy. The typical plug flow of raceways (Shen et al., 2016) was altered in the modified and zones wherein an inversion of flow direction occurred. Thus, a higher rotation frequency was needed to attain a given circulation velocity. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Raceway Configuration** & \multicolumn{2}{c}{**Modified**} & \multicolumn{2}{c}{**Standard**} \\ \hline
**Process Condition** & **1** & **2** & **1** & **2** & **3** \\ \hline C14:0 & 1.28 & 1.97 & 2.13 & 2.71 & 3.19 \\ C16:0 & 20.53 & 24.02 & 19.93 & 21.62 & 23.46 \\ C16:1 & 40.14 & 36.06 & 42.06 & 34.04 & 35.60 \\ C18:2n-6 & n.d. & 0.44 & 1.96 & 3.37 & 1.45 \\ C20:4n-6 & 8.61 & 9.61 & 8.20 & 8.98 & 10.13 \\ C20:5n-3 & 29.45 & 27.90 & 27.85 & 29.29 & 26.17 \\ SFA & 21.90 & 25.99 & 19.93 & 24.33 & 26.65 \\ MFA & 40.06 & 36.06 & 42.06 & 34.04 & 35.60 \\ PUFA & 38.04 & 37.95 & 38.01 & 41.63 & 37.75 \\ \(\omega\)-3 & 29.42 & 27.90 & 27.85 & 29.29 & 26.17 \\ \(\omega\)-6 & 8.63 & 10.05 & 10.16 & 12.35 & 11.58 \\ PUFA/SFA & 1.74 & 1.48 & 1.91 & 1.77 & 1.47 \\ \(\omega\)-6/\(\omega\)-3 & 0.29 & 0.36 & 0.36 & 0.42 & 0.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Fatty acid profile of the biomass produced (n.d., not detected). Values represent an average of two biological replicates. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Energy Consumption (W m\({}^{-3}\))**} & \multicolumn{2}{c}{**Mixing Speed (Rad s\({}^{-1}\))**} \\ \hline
**Process Condition/Raceway** & **1** & **2** & **3** & **1** & **2** & **3** \\
**Configuration** & & & & & & \\ \hline Modified & 10.9 & 20.9 & - & 1.29 & 1.68 & - \\ Standard & 5.2 & 8.0 & 4.0 & 0.67 & 0.67 & 0.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Paddlewheel rotation speed and associated energy consumption. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Raceway Configuration/Process Condition** & **Proteins (\%)** & **Lipids (\%)** & **Carbohydrates (\%)** & **Ashes (\%)** \\
**Condition** & & & & \\ \hline Modified/1 & 38.9 & 13.2 & 30.5 & 17.4 \\ Modified/2 & 44.2 & 17.4 & 28.7 & 9.7 \\ Standard/1 & 40.4 & 14.5 & 27.1 & 18.0 \\ Standard/2 & 41.7 & 19.0 & 25.1 & 14.2 \\ Standard/3 & 39.1 & 12.7 & 36.2 & 12.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Biomass proximate composition. Values are presented relative to dry weight. Values represent an average of two biological replicates.