Title: Evaluation of flocculation based harvesting processes for microalgae biomass production based on floc characteristics
Authors: Vandamme, Dries
Muylaert, Koenraad
Foubert, Imogen
Issue Date: 2013
Conference: FWO Kennismakers location:Gent date:17 December 2013
Abstract: The transition of a fossil fuel to a biobased economy in combination with the prospected increase in the
world’s population will lead to a growing demand for additional sources of biomass to complement
traditional agricultural biomass. Microalgae are such a promising new source of biomass. These aquatic
microorganisms receive much interest today as a potential source of biofuels. The most pressing
challenge, however, does not lie in the production, but in the energy-efficient separation and
downstream processing in a manner suitable for the production of bioproducts. Introducing a
flocculation-based bulk harvesting step in the process can lower the energy needs 10-fold. Recently a lot
of new studies were published evaluating novel flocculation methods for microalgae harvesting. Our
recently published review revealed that most of these studies have focused on a single evaluation
criterium, namely flocculation efficiency.

In this study, we evaluated 5 different flocculation modes for Chlorella vulgaris and their influence on
floc characteristics such as settling velocity, biomass compaction degree and floc size. Based on
previous studies, alum sulphate, chitosan, cationic starch, pH induced flocculation and electro-
coagulation-flocculation were selected. In addition, the effect of the presence of algal organic matter (AOM) was studied for
all flocculation modes.

Our result show that the floc characteristics were influenced by the flocculation mode, which depends
on the coagulation mechanism. Secondly, the influence of the presence of AOM was evaluated. The
presence of AOM led to an increase in needed flocculant dosage for all flocculation modes. This
resulted particularly in a decrease of the concentration factor. The floc characteristics upon flocculation
using cationic starch were least affected by the presence of AOM, while flocculation using chitosan was
most affected. This study demonstrated that the impact on floc characteristics is important to consider
next to flocculation efficiency in the assessment of flocculation-based harvesting of microalgae.
Publication status: published
KU Leuven publication type: AMa
Appears in Collections:Microbial and Molecular Systems, Campus Kulak Kortrijk
Biology, Campus Kulak Kortrijk
Department of Biology - miscellaneous
Microbial and Molecular Systems - miscellaneous

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