Table 1 Comprehensive comparison of common microalgal biomass production systems

Open ponds

 Natural/artificial ponds

Arthrospira sp.; D. salina

• Low construction and operation costs

• Easy to maintain and clean

• Large capacity

• Mature cultivation technology

• Low light utilization

• Sensitive to biological contaminants

• Suitable for few species

• Evaporation losses and CO₂ losses

• High harvesting costs

• Climatic dependence

• Larger area requirements

 Raceway ponds

Arthrospira sp.; Chlorella sp.; D. salina; H. pluvialis; E. gracilis

 Circular ponds

Chlorella sp.; E. gracilis

 Circulation cascades

–

Enclosed photobioreactors (PBRs)

 Tubular PBRs

Arthrospira sp.; Chlorella sp.; D. salina; H. pluvialis

• Larger surface-to-volume ratio

• Low CO₂ losses

• Reduced risk of contamination

• Smaller area requirements

• Prevention of evaporation

• Higher cell productivities

• High species applicability

• Higher construction and operation costs

• Overheating and fouling

• Difficult to maintain and clean

• High concentration O₂ accumulation

• Cell damage by shear stress

• Difficulty in scaling up

 Vertical-column PBRs

–

 Flat panel PBRs

–

Fermenters

 Fermenters

Chlorella sp.; E. gracilis; H. pluvialis

• High growth rate and high productivity

• Low or none requirement for light

• Cost effectiveness

• Suitable for few species

• High organic carbon costs

• Sensitive to bacterial contamination

• Reduction of intracellular photosynthetically derived compounds