Unlike for many other energy crops, the cost of harvesting microalgae could present a significant challenge to economic energy production from algae.

The reasons lie in the differences present between harvesting algae and other energy crops:

• The medium in which algae grow is different – the other oilseeds are land crops while algae grow in water
• Microalgae’s physical characteristics are significantly different from those of the primary oilseeds, the main difference being the size.
• Algae are harvested almost everyday, for most part or all through the year, whereas harvesting for most oilseeds is quite seasonal in nature

Owing to these reasons, harvesting algae, especially microalgae, could be a fairly expensive process. A number of methods could be potentially used for harvesting. These are discussed in detail in this chapter.

1. Some of the prominent methods currently used for harvesting microalgae are filtration, centrifugation, flocculation and flotation.
2. Harvesting microalgae is an expensive and energy intensive process and presents a key challenge, unique to the algae industry.
3. While centrifugation and flocculation/flotation are expensive harvesting methods, both these are expected to have the most potential in future for harvesting microalgae.
4. Methods suggested for efficient and cost effective harvesting are still in the research stage.