Direct measurements of CO2 capture are essential to assess the technical and economic potential of algal-CCUS

Abstract

Power stations and industrial factories contribute a significant fraction of total anthropogenic CO2 emissions, which need to be mitigated to reduce their effect on the climate. Commercially available methods of CCUS (Carbon capture and utilisation or storage) rely on toxic chemicals for the capture processes as well as the long-term storage of CO2 gas. The use of photosynthetic microalgae for CCUS offers the potential for a sustainable capture system, which can both reduce emissions and produce renewable products. Previous studies have focused largely on the products (particularly biofuels) from microalgae, rather than their ability to capture CO2. In this study, Chlorella sp. was cultivated with CO2 concentrations similar to those present in power-station flue gases. 5 % CO2 was found to be the optimal concentration for growth of the microalgae. The CO2 removal efficiency of the cultures was then monitored in real-time with a nondispersive infrared sensor. The average CO2 removal efficiency was 17.5 % over 14 days, considerably higher than results reported within the literature which do not use a direct real-time monitoring system. A techno-economic assessment of algal-CCUS was performed using the experimental results and a range of different financial and operational scenarios. The assessment highlights that whilst microalgal CCUS is currently not competitive, it has potential to become so with advances in strain CO2 removal efficiency. This, alongside the reduction of capital expenditure and increasing government incentives for reducing emissions will make algal-carbon capture economically feasible.