Modeling and environmental evaluation of a system linking a fishmeal facility with a microalgae plant within a circular economy context

Abstract

Microalgae cultivation has been proposed as a strategy to capture CO2 from industries. Besides that, feeding microalgae cultures with flue gas could improve their growth and environmental performance. Nevertheless, the potential of microalgae cultivation as a CO2 capture strategy should be contrasted against real volumes of emissions from industries. In view of this fact, we modeled an integrated system in which microalgae capture CO2 from flue gas of a fishmeal and fish oil facility. A cogeneration turbine system provides heat and electricity for fishmeal production and microalgae cultivation. Further requirements of electricity are fulfilled from the grid, considering different mixes. We constructed a baseline scenario and six alternative scenarios, where the capacity of microalgae plant matches the amount of CO2 released by the cogeneration system. Moreover, we assumed that microalgae biomass could partially replace fishmeal, which allows attaining an additional reduction of emissions. We carried out a carbon balance with and without a life cycle approach to evaluate the environmental performance of the proposed system. Results showed that the integrated system released less CO2 compared to the traditional one during the operation phase. However, from a life cycle perspective, environmental benefits were only achieved when low carbon electricity was consumed. Otherwise, the integrated system entailed harmful burdens to the environment. Moreover, considering the maximum achievable absorption of CO2 (8.92% reduction of greenhouse gas emission), it would require 3.16 ha to cultivate microalgae. These results highlight the importance of including land-use among the life cycle impacts categories when microalgae system are proposed for providing environmental services, such as CO2 capture.