The economic viability of the current microalgae to fuel (or chemical) processes (summarised in Fig. 1.1) is limited by the high cost and energy burdens for growth inputs, capital and operating costs for dewatering, and the operating and capital costs of the growth system (Clarens et al. 2010; Lardon et al. 2009; Stephenson et al. 2010). Advances in growth, harvesting and extraction systems provide incremental improvement to these systems. The persistence of companies/research institutions and governments in continuing to pursue these systems indicates that many believe that such incremental improvement over time will ultimately result in an economically viable process. Others believe that a step change is required and are pursuing an entirely different biofuel production model in which the product of interest is continually secreted by the microalgae. This novel method is generally referred to as ‘milking’, as the product of interest is ‘milked’ from the algae without the need to destroy it and subsequently regrow it.