An approaching global phosphorus crisis and microalgal biotechnology: A growing problem & strategies for effective use
Conference contribution, 2015
Phosphorus (P) is a critical element for life on Earth. However, readily extractable ores are being exhausted rapidly and a combination of increasing usage, rising costs and numerous geopolitical problems are expected to impact food security and industry sectors within the next few decades. This hence represents another great anthropogenic challenge and near-future issue. P is needed in the production of microalgal biomass; indeed the value of P in microalgae is similar or exceeds that of the potential biofuels, demanding a 100% recovery and recycling of P. However, unlike nitrogen (N) sources (that can be synthesised) for which the relationship of cell-contents and growth is linear, the need for P is less clearly understood. We have empirically explored the interaction between P supply and microalgal production and biochemical composition. P usage could be at least halved relative to the use of N, while maintaining adequate growth of Nannochloropsis. Indeed, by deploying certain strategies, the amount of P required to produce 1 kg of biomass can be decreased from 2.4 g to 0.85 g (65% reduction). The quantitative effects of dual N- and P-limitation on biochemical composition, fatty acid profile and biodiesel quality were also evaluated in a greater detail than has previously been reported. The replacement of inorganic nutrients with those obtained from waste nutrient streams was examined and also proved to be a successful strategy in decreasing resource consumption. P usage in the broader context of large-scale microalgal cultivation will be put into context with information critical for algal physiology, practitioners and LCA development.