Cultivation System Sizing

The sizes of both photobioreactors (HTR and ELR) and the raceway pond are esti­mated based on the capacity to produce 50,000 tonnes of dry weight biomass annu­ally. The volume and area of the horizontal photobioreactor were scaled up from the data presented by Chisti [6], the external loop bioreactor was scaled up from the design by Acien Fernandez et al. [1] , and the raceway pond was scaled up from the Outdoor Test Facility design in Roswell, NM [31]. Table 1 contains the annual production of biomass for each cultivation system and the biomass produced and harvested per batch.

1.5 Dewatering

Methods such as centrifugation, pressure filtration, vacuum filtration and tangential flow filtration (TFF) are used unaided to dewater microalgal biomass. This section explores the use of different dewatering methods either alone or as a preceding step to the aforementioned unit operations for microalgae dewatering.

Table 1 Annual microalgal biomass production design data for different cultivation systems

Variable

HTR

ELR

RP

Annual biomass production (tonnes)

50,000

50,000

50,000

Biomass required per BATCH (tonnes)

757.5

568.75

947.5

Biomass extracted per batch (tonnes)

606

455

758

Biomass concentration (kg/m3)

4.525

3.8

0.585

Dilution rate (1/d)

0.25

0.33

0.2

Area required per cultivation unit (m2)

947

12

1,050

Area per unit (m2)

1,263

16

1,400

Total cultivation area (m2)

5,284,365

8,980,263

8,098,291

Total area (m2)

7,047,680

11,973,684

10,797,721

Total cultivation area (ha)

528

898

810

Total area (ha)

705

1,197

1,080

No. of units required

5,580

748,355

7,713

Total tubing length (m)

58,925,967

59,868,421

N/A

Cultivation areal productivity (kg/m2 x d)

0.036

0.021

0.023

Total areal productivity (kg/m2 x d)

0.027

0.016

0.018

Volumetric productivity (kg/m3 x d)

1.131

1.267

0.117

Volume per cultivation unit (m3)

30

0.2

210

Total volume (m3)

167,403

149,671

1,619,658

Approximate annual CO2 consumption (tonnes)

92,000

92,000

92,000

Energy dissipation (W/m3)

60-170

60-170

Energy dissipation (kWh/per unit)

3.24~