*3.3. Total Capital Cost*

Based on the simulation results, economic analysis was conducted by Aspen PEA for each scenario. Total project investments are USD 51.69 million and USD 48.90 million for scenarios 1 and 2, respectively. The retention times for transesterification reactions in scenarios 1 and 2 are 3.64 and 1.5 h, respectively. The volume of equipment in scenario 1 is much higher than those in scenario 2, which results in the higher total capital cost of the plant in scenario 1 [31].

The most expensive units of plants are SSF and wastewater treatment (WWT) (Figure 7). SSF needs a long retention time (24 h) and a relatively high number of equipment, and the WWT unit needs filtration together with large anaerobic digesters with a long retention time [13].

**Figure 7.** Breakdown of capital investment in units. The empty and filled columns represent scenarios 1 and 2, respectively.
