Nutrients in the form of commercial fertilisers are an expensive input for mass production of microalgae biomass (Collet et al. 2010), particularly nitrogen and phosphorous (Fenton and Ohuallachain 2012; Lyovo et al. 2010; Vaccari 2009). Large nutrient requirement can increase cost of microalgae biofuel production and compete with agricultural demand (Erkelens et al. 2014; Fenton and Ohuallachain 2012). Fertiliser prices are highly dependent on fossil fuels price’s (Fenton and Ohuallachain 2012; Vaccari 2009). Increase in fossil fuel price coupled with the higher worldwide agricultural demand resulted in increased fertiliser costs (Fenton and Ohuallachain 2012; Stephans et al. 2010; Vaccari 2009; Ward et al. 2014). Therefore, nutrient recovery from residual and waste products from the microalgae production is essential to allow sustainable product development (Erkelens et al. 2014; Sialve et al. 2009; Stephans et al. 2010). Anaerobic digestion can offer a solution to the fertilisers input problem by recycling extracted biomass and any by­products (Erkelens et al. 2014). Anaerobic digestion of algal biomass produces a clear liquid digestate that is nutrient rich containing both nitrogen and phosphorous (Stephans et al. 2010). Anaerobic digestion digestate nutrient content of 546­2940 mg/L ammonia nitrogen and 141-390 mg/L phosphorous have been reported from anaerobically digested microalgae (Collet et al. 2010; Erkelens et al. 2014; Ward et al. 2014; Zamalloa 2012). A further benefit of the integration of anaerobic digestion into microalgae production is the ability to utilise the microalgae cultures to purify the biogas produced from anaerobic digestion (Converti et al. 2009; Green et al. 1995a). The concentration of methane in biogas produced from microalgae is in the range of 30-50 % (Sialve et al. 2009); generally too low to utilise in its current form, and purification of the biogas is needed before utilisation (Vergara-Fernandez et al. 2008). Due to the low solubility of methane and high solubility of CO2, the uptake of CO2 in microalgae cultures is able to purify the biogas to a higher energy density, with the added benefit of stripping other gasses such as sulphur and ammonia (Green et al. 1995a; Ward et al. 2014). As methane has been shown to be non­detrimental to microalgae growth, the dual purification of biogas as a consequence of supplying microalgae cultures with additional nutrient in the form of CO2 achieves multiple productivity benefits (Green et al. 1995a; Sialve et al. 2009).