Life cycle assessment on environmental feasibility of microalgae-based wastewater treatment for shrimp recirculating aquaculture systems.

This life cycle assessment (LCA) study analyzed the environmental consequences of integrating microalgae-based wastewater treatment into a shrimp farm with recirculating aquaculture systems (RAS). Microalgae treatment produced <10 % of the system's freshwater eutrophication potential (FEP), marine eutrophication potential (MEP) and global warming potential, which was dominantly contributed by electricity use. Microalgae treatment performed comparably to activated sludge treatment for FEP reduction, and was more effective in remediating marine eutrophication. Replacing coal in electricity mix, particularly with renewables, reduced the system's impacts by up to 90-99 %. Performing the LCA based on system expansion generally obtained higher impacts compared to allocation. Utilizing algal biomass for biogas production reduced the MEP; however, production of feed ingredient and biodiesel were not environmentally beneficial. This study proved the use of microalgae for aquaculture wastewater treatment to be environmentally feasible, the results can guide more sustainable RAS operations and design of full-scale microalgae treatment.

Algae and indigenous bacteria consortium in treatment of shrimp wastewater: A study for resource recovery in sustainable aquaculture system.

Shrimp production facilities produce large quantities of wastewater, which consists of organic and inorganic pollutants. High concentrations of these pollutants in shrimp wastewater cause serious environmental problems and, therefore, a method of treating this wastewater is an important research topic. This study investigated the impact of algae and indigenous bacteria on treating shrimp wastewater. A total of four different microalgae cultures, including Chlorococcum minutus, Porphyridum cruentum, Chlorella vulgaris and Chlorella reinhardtii along with two cyanobacterial cultures, Microcystis aeruginosa and Fishcherella muscicola were used with indigenous bacterial cultures to treat shrimp wastewater. The highest soluble chemical oxygen demand (sCOD) removal rate (95%) was observed in the samples that were incubated using F. muscicola. Total dissolved nitrogen was degraded >90% in the C. vulgaris, M. aeruginosa, and C. reinhardtii seeded samples. Dissolved organic nitrogen removal was significantly higher for C. vulgaris (93%) as compared to other treatments. Similarly, phosphate degradation was very successful for all the algae-bacteria consortium (>99%). Moreover, the degradation kinetics were calculated, and the lowest half-life (t1/2) for sCOD (5 days) was recorded for the samples seeded with M. aeruginosa. Similarly, treatment with F. muscicola and C. reinhardtii showed the lowest t1/2 of NH3-N (2.9 days) and phosphate (2.7 days) values. Overall, the results from this study suggest that the symbiotic relationship between indigenous bacteria and algae significantly enhanced the process of shrimp wastewater treatment within 21 days of incubation. The outcome of this study supports resource recovery in the aquaculture sector and could be beneficial to treat a large-scale shrimp facility's wastewater worldwide.

Life cycle assessment on marine aquaponic production of shrimp, red orache, minutina and okahajiki.

Aquaponics is an integrated food production system that intensively produces a diverse array of seafood and specialty crops in one closed-loop system, which is a potential solution to global challenges of food security. While current aquaponics systems are commonly operated with freshwater, marine aquaponics is an emerging opportunity to grow saltwater animals and plants. Although marine aquaponics can reduce the dependence on freshwater for food production, its environmental sustainability has not been systematically studied. This paper presents the first life cycle assessment (LCA) on a marine aquaponic production system growing shrimp and three halophytes. The system assessed covered from shrimp larvae nursery to grow-out. The effects of salinity, carbon/nitrogen (C/N) ratio and shrimp-to-plant stocking density ratio of aquaponics on its midpoint and endpoint environmental impacts were evaluated using a functional unit based on the economic value of the four products. Electricity use for aquaponic operation was the environmental hotspot, contributing ∼90 % to all the midpoint impacts. The system produced higher environmental impacts when operated at higher salinity, but lower C/N ratio and stocking density. Replacing fossil fuel with wind power for electricity generation can decrease the environmental impacts by 95-99 %. Variation in the shrimp price can change the impacts by up to 62 %. This study provides a useful tool to help marine aquaponic farmers improve their production from an environmental perspective, and can serve as groundwork for further assessing more marine aquaponic systems with different animal-plant combinations.