Environmental performance for microalgae cultivation commercial systems: sustainability metrics and indicators / Desempenho ambiental para sistemas comerciais de cultivo de microalgas: métricas e indicadores de sustentabilidade

In this study, we evaluated metrics and sustainability indicators for cultivation commercial systems based on microalgae. Cultivation systems as a raceway pond, tubular photobioreactor, flat plate photobioreactor, and fermenter were evaluated under a standard functional unit of 1 m³. These cultivation systems were estimated by midpoint indicators through the nine impact categories and later submitted to the normalization phase. Among the results found, three impact categories were shown to be more expressive to contribute to environmental impacts for the four cultivation systems, which are ecotoxicity potential, energy resource, and global warming potential. The best environmental performance was identified for raceway pond, although the worst-case scenario for the water footprint category was identified. Besides, in a comparative analysis between closed systems, fermenters showed better environmental indicators, followed by tubular and flat plate photobioreactors. In this way, the life cycle assessment allowed to highlight the hot points of the process, identifying the energy requirements as the critical points of the whole performance of the cultivation systems. Finally, regardless of the impacts associated with different cultivation configurations, it is important to note that the choice of the system will be directly associated with the target product to be produced. Therefore, the results found about the environmental performance of cultivation systems can serve as basic information to reduce the global environmental impacts of microalgae-based processes and bioproducts.

Environmental assessment of the integrated bio-combustion process: A life cycle energy balance / Avaliação ambiental do processo integrado de bio-combustão: balanço energético do ciclo de vida

The aim of the present study was to evaluate the life cycle energy balance of the integrated bio-combustion process. The life cycle analysis tool was applied to assess the environmental performance of the system. The experiments were performed in a bubble column photobioreactor with a volume of 2L, photon flux density of 150 µmol/m²/s, continuous aeration of 1VVM, and injection air-enriched with 15% of CO2. The photobioreactor exhaust gases were integrated into the bio-combustion furnace, which was designed on a lab-scale. The operational conditions were: initial coke mass of 1g, total combustion reaction time of 20 min, and airflow rate of 1 L/min. The energy balance was determined by equating of the energy produced by the required energy, followed by the net energy ratio. The results obtained showed a net energy ratio for the integrated process of 0.69, indicating an energy efficiency improvement close to 70%. Thus, the system has the potential to boost the sustainability of industrial facilities.