Algae Harvesting

Collecting, concentrating, and processing algae consists of separating algae from the growth medium, drying, and processing it to obtain the desired product. Separating algae from its growth medium is generally referred to as algae harvesting. The term algae harvesting technologically refers to the activity of concentration of a fairly diluted (ca. 0.02-0.06% total suspended solids, TSS) algae suspension until a slurry or paste containing 5-25% TSS or greater is obtained. Specific harvesting methods depend primarily on the type of algae and growth media. The high water content of algae must be removed to enable further processing. The most common harvesting processes include: (1) microscreening, (2) flocculation, and (3) centrifuga­tion [20, 21]. The three methods represent different unit operations of filtra­tion, flotation, and centrifugation, respectively. Therefore, these harvesting steps must be energy-efficient and relatively inexpensive; as such, selecting easy-to-harvest algae strains becomes quite important. Macroalgae har­vesting requires substantial manpower, whereas microalgae can be har­vested more easily using microscreens, centrifugation, flocculation, or by froth flotation.