Background: Algaculture, like any form of agriculture, is highly sensitive to fertilizer
or nutrient costs. A major roadblock to commercial algaculture is efficiently utilizing
volatile nutrients, specifically carbon dioxide and ammonia, to feed microalgal
cultures. These nutrients are typically plentiful in multiple agricultural and industrial
waste streams and can potentially provide fertilizer or nutrients for large-scale
microalgal cultivation. However, individual methodologies need to be developed for
each type of waste stream to remove uncertainty in the assumption of yield and cost of
production in microalgae cultivation systems.
Methods: This review focused on the use of waste nutrients used for cultivation of
microalgae, specifically nutrients that are currently being underutilized or wasted. Those nutrients, carbon dioxide and
ammonia, require special capture and/or handling steps in order for them to be used for microalgae cultivation. A variety
of techniques, using carbon dioxide for pH control, mixing sumps, sparging, controlled dosing techniques and pond covers
represent approaches used for handling and maximizing the use of available carbon dioxide and ammonia for microalgae
Results: Efficient nutrient recycling has been shown to reduce fertilizer input costs, although this is highly dependent on
the specific processes being employed, and the nutrient utilization efficiency. This review summarizes efforts to quantify
and improve carbon dioxide and ammonia utilization in microalgal cultivation and to reduce overall volatilization and loss
of these valuable nutrients. Practical methods of preventing volatilization and increasing gas transfer to the microalgae
crop included: pH control, nutrient dosing and improving gas transfer efficiency.
Conclusion: Finding an economical nutrient source to drive microalgal biofuel production remains a key challenge.
Wastewaters represent a relatively untapped source of nutrients for microalgae cultivation. Key nutrients in wastewaters
are volatile (carbon dioxide and ammonia), potentially toxic, and require special handling approaches such as balancing
pH, temperature, contact time, and contact surface area. Preliminary results suggest that these volatile nutrients can be
effectively utilized for microalgal cultivation.