Evaluating the available techno-economic studies for the production of biofuels from microalgae leads to the inventible conclusion that using existing technologies, the biofuel production is at least 2 but more likely 4-5 times more expensive than current fossil fuels and biofuels (final costs are dependent on the expected yields, growth system design and harvesting system employed). The major roadblocks to economic fuel production include:

1. High yields: Regardless of the system, it seems a minimum annual average productivity of 30 g/m2/day is required with at least 30 % lipid content. Although highly possible, this has yet to be demonstrated and will require continued strain development either through traditional methods or genetic modification.

2. Low Capital costs: At low productivities (<25 g/m2/day), growth system capital costs dominate and in the case of open ponds, liners are cost prohibitive. With this limitation, it is difficult to see how PBR’s could ever be cost effective, as they typically do not increase aerial productivity rates (Benemann et al. 2012) relative to open ponds. Furthermore, capital and operating costs for dewatering must be lowered through the use of innovative concentrating steps (self — or electro-flocculation followed by settling or DAF). Using centrifuges for com­plete harvesting is not viable (Klein-Marcuschamer et al. 2013).

3. Co-products: In production systems that produce a protein for animal feed, selling prices will typically need to be in excess of $350/tonne to compete with on-site anaerobic digestion of wastes (ANL et al. 2012).

In addition to these challenges, the climate in most locations causes significant seasonal variation in microalgae productivity (5-10 times in the American context), resulting in underutilised capital for significant periods of the year. Furthermore, assumptions associated with low-cost water availability and CO2 availability are very optimistic as very few sites around the world have these resources in com­bination with the correct climate.

With this in mind, two observations can be made as follows:

1. Biofuels from microalgae will be viable as long as significant (disruptive) improvements are made in the growth/harvesting stages.

2. There are a handful of sites around the world where climate, land availability, CO2 and water availability align to transform this potential viability into com­mercial reality.

Considering the current pace of development and intense interest in this space, the former is likely to occur in the next 10-20 years. In the meantime, microalgae will continue to be exploited commercially for high-value products.