Practical strategies to improve harvestable biomass energy yield in microalgal culture: A review

Pursuing research on renewable energy is a key challenge in this century due to worldwide increase in energy demand and environmental issues associated with fossil fuel consumption. In this sense, microalgae have received considerable renewed attention to become a feedstock for large-scale biofuel production. However, high cost of large algal cultivation systems precludes it from currently being an economically viable option. In other words, to lower the cost, the harvestable biomass energy yield, which is a function of productivity, energy content and harvestability of biomass, must be maximized. Therefore, any practical method that could improve these parameters would be beneficial and contribute to enhancement of the biomass energy yield and is interesting for further consideration. Hence, this study aims to review parameters influencing the harvestable biomass energy yield in microalgal cultures particularly wastewater-fed cultures and to discuss the advantages and limitations of different practical strategies in order to promote low-cost energy production from microalgal cultures. Five practical strategies were considered: CO2 addition, variation of hydraulic retention time, cultivation and dominance of colonial species, zooplankton control and algal recycling. Advantages and drawbacks of these parameters were assessed, and it is concluded that of these parameters, CO2 addition and its combination with algal recycling have the higher impact on the enhancement of the harvestable biomass energy yield. [Display omitted] •Harvestable biomass energy yield is a function of productivity, energy content and harvestability of biomass.•CO2, HRT, colonial species, grazer control and algal recycling have impact on harvestable biomass energy yield.•CO2 addition and algal recycling have the most impact on the enhancement of harvestable biomass energy yield.