Expanding the microalgal industry – continuing controversy or compelling case? Evan Stephens, Ian L Ross and Ben Hankamer Herein we examine the potential role that microalgae might play in the approaching challenges of energy and fuel security, and food and water supply. Microalgal production systems remain the subject of controversy however, generally consisting of arguments about the economic and environment sustainability of these systems. We discuss these aspects and draw some parallels with other systems to highlight real advantages and obstacles to expanding the modern microalgal industry. Emerging alternative production models and the relatively early developmental state of the microalgal biofuels industry provide room for extensive innovation that has the potential to bring the technology to a highly productive maturity. Addresses The University of Queensland, Institute for Molecular Bioscience, St Lucia, Qld 4072, Australia Corresponding author: Stephens, Evan (e.stephens@imb.uq.edu.au) Current Opinion in Chemical Biology 2013, 17:444–452 This review comes from a themed issue on Energy Edited by Michael D Burkart and Stephen P Mayfield For a complete overview see the Issue and the Editorial Available online 12th April 2013 1367-5931/$ – see front matter, # 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cbpa.2013.03.030 Introduction Human society faces challenges in the management of food and water resources, energy and fuel production, and climate change impacts – but how these issues will be addressed and prioritized is a highly charged and political debate. These issues are all connected to economic stability and sustainable development, and cannot be solved separately. The balancing of production, resource, and climate concerns is central to issues like the ‘food versus fuel’ debate [1,2] which has been the subject of considerable controversy. Currently, this issue is promi- nent in both the US and the EU as a result of global grain price increases. Graziano da Silva, the Director-General of the UN’s Food and Agriculture Organization (FAO) has highlighted rising food prices, particularly corn in the US due to extended drought, asserting that ‘risks are high’ and suggesting a suspension of biofuel mandates [3]. His view is that potential complications from climate change and extreme weather events could further destabilize food security. At the same time in the EU, the real concerns over food versus fuels are moving the European Commis- sion to curtail the diversion of food crops to biofuels, with a proposal for caps on crop-based fuels [4]. Given that total EU biofuel targets are being maintained, microalgae are being investigated as an alternative biofuel feedstock that does not compete with food production. Applied phycology and the modern microalgal industry Long utilized for wastewater applications, aquaculture and the production of high value products, microalgal mass cultivation is increasingly being touted as a potential solution to aid in addressing food and fuel challenges with benefits such as siting on non-arable land, increased nutri- ent efficiency, use of saline or waste water inputs, scal- ability, and use for waste treatment and bioremediation applications. The general productivity of basic microalgal high-rate pond (HRP) production systems are currently up to 70 T ha 1 yr 1 [5] of dry microalgal biomass when cultivated in climatically favourable regions. This is very high relative to corn yields (up to 10 T ha 1 yr 1 ) or soybean yields (up to 3.5 T ha 1 yr 1 ) [6], and while the global mean for sugarcane productivity of 70 T ha 1 yr 1 [6] may seem comparable to microalgal productivities, these crops are not measured in dry weight (e.g. harvested sugarcane can be 70% moisture) so embo- died chemical energy as carbonaceous biomass is lower. The high productivity of basic microalgal production sys- tems, and the potential for future improvements (given the relatively early stage of technology development), are promising. Although advanced systems can achieve even higher productivities, input requirements are greater than conventional agriculture and achieving economic viability in microalgal production has remained elusive for low value biocommodity products (e.g. fuels) [7  ]. A positive energy balance has been difficult to achieve with microalgal bio- fuels, though the potential energy return on investment (EROI) is sufficiently high. Recently, a renewed interest in microalgal biofuels [8  ] has generated a charged debate with everything from overzealous cheerleaders overstating production capacity to staunch critics citing figures from inappropriate technology configurations to argue that the technology will never work. Recent estimates by Wigmosta et al. [9] that the US could potentially satisfy 17% of its oil imports with microalgal oil were drawn into mainstream media approaching the US election, resulting in a polariz- ation at the community level of what is already a conten- tious discussion in the scientific literature. Recently the US Department of Energy’s (DOE’s) com- missioned report from the National Research Council on Sustainable Development of Algal Biofuels was released Available online at www.sciencedirect.com Current Opinion in Chemical Biology 2013, 17:444–452 www.sciencedirect.com