Microalgae are an attractive feedstock for biofuel production, however the harvesting of algal biomass
from very large volumes of culture broth represents a major technological and economic challenge.
One low cost strategy for addressing this challenge involves the use of flocculation as an initial dewatering
step. In this study, flocculation of the green microalga Chlorella sorokiniana was explored in detail
using the natural compound, chitosan as flocculant. Results show that clarification efficiency of the process
can reach above 99% below pH 7. The optimal chitosan dosage (approximately 10 mg per gram algal
dry weight) is determined primarily by cell concentration rather than cell age, lipid content or composition
of the medium. Furthermore, the impact of flocculation on the subsequent dewatering process was
determined and it was shown to reduce the volume to be processed by 20–50 folds, and significantly
reduce energy input and material costs of centrifugation or filtration operations.