Table 3 Various parameters considered for study
Unit process | Assumptions | Refs. |
|---|---|---|
Algae cultivation Algae growth | Algae strains: Chlorococcum sp. and Desmodesmus F2 sp: 47% and 53.8% lipid content for Chlorococcum sp. and Desmodesmus sp. Velocity culture: 0.3 m s−1 for raceways and 0.25 m s−1 for inoculum ponds HRT: 10 days. Raceways: 110 units of 310 m long × 30 m weight x 0.3 m height (2184.3 m3 volume medium). Inoculum ponds: 40 units of raceways of 160 m long × 15 m weight × 0.35 m height (656 m3 volume medium) Facility: 145 ha area. Operating time facility: 330 days year−1 (90%) Paddlewheels: 0.11 W/m2, time functioning: 12 h day−1. One unit per raceways and inoculum pond Blower system: 22.2 Wh kg−1 CO2, time functioning: 12 h day−1. One unit per raceways and inoculum pond. 14% v/v CO2 concentration in flue gas Water loss (evaporation): daily variable (ranging between 0.01 and 0.34 cm day−1) Inoculum input pumping system: power: 10 kW, 22 units, time functioning: 0.8 h h day−1. Electricity consumption: around 0.07 kWh m−3 Nutrients/water loss pumping system: 24 units (22 for raceways and 2 for inoculum ponds), time functioning: 12 h day−1. Electricity consumption: negligible | |
Algae harvesting (dewatering) | Settlers ponds: 22 units, energy demand: negligible, efficiency: 90%, outlet concentration: 10 g/L. Capacity: 364.1 m3. Residence time: 4 h Membranes: 22 units, power: 2 kW, energy demand (variable): 0.03 to 0.2 kWh m−3, efficiency: 99.5%, outlet concentration: 130 g/L. Capacity: 2.3 m3 h−1, time functioning: 12 h day−1 Centrifuges: 22 units, power: 6 kW, energy demand (variable): 0.9 to 5.05 kWh m−3, efficiency: 97%, outlet concentration: 200 g/L. time functioning: 12 h day−1 Overall harvesting process: 20% wt outlet concentration. Efficiency: 86.9%. Percentage of water volume reduced: 99.9% Harvesting pumping system: 22 units, power: 7.7 kW, energy demand: 0.08 kWh m−3, time functioning: 12 h/day Recirculation pumping system: 22 units, power: 7.7 kW, energy demand: 0.08 kWh m−3, time functioning: 12 h/day | |
Oil extraction | Sonication: 2 units, power: 16 kW, energy demand: 0.013 kWh kg−1 algae-DW, capacity: 12 m3 h−1, time functioning (variable): 1.5 to 8.8 h/day Static mixer: 1 unit, power: 6 kW, energy demand: negligible, efficiency lipid extraction: 90%, capacity: 12 m3 h−1, time functioning: 1.5 to 8.8 h/day. Hexane input: 10:1 mass ratio, 0.05% hexane losses Biomass solvent separator: 1 unit, power: 6 kW, energy demand: 0.005 kWh kg−1 algae-DW, Efficiency: 99.9%. Capacity: 5.7 m3 h−1 time functioning (variable): 3 to 19 h/day Distillation column: 2 units, energy demand (variable): 0.09 to 0.55 kWh kg−1 oil, capacity: 15.2 m3 h−1 time functioning (variable): 2.7 to 16 h day−1 | [28] |
Oil conversion | Transesterification reactor: 1 unit, power: 15 kW, energy demand: 0.03 kWh kg−1 biodiesel, time functioning (variable): 2.7 to 16 h/day. Chemical consumption: methanol 1.1 kg kg−1 biodiesel, Sodium methoxide 0.11 kg kg−1 biodiesel, HCl 0.014 kg kg−1 biodiesel, NaOH 0.008 kg kg−1 biodiesel, natural gas 0.063 L kg−1 biodiesel | [35] |