21.7 Conclusions

There is an array of criteria that contribute to the performance of each farm and their number grows with the number of disciplines involved in this the interdisciplinary field of aquaponics. Of note is an earlier study that has provided a definition of aquaponics and a classification of the types of aquaponics based on size and system (Palm et al. 2018). Many criteria for the analysis of the enclosure type identified in this study stem from immediate farm context — local climate, the quality of the built environment context, energy sourcing practices, costs, market, and local regulatory frameworks. An aquaponic greenhouse in a rural context performs differently than one in a city, just as farms in arid climates do not share the same requirements as their counterparts in colder areas. In general, greenhouses classified as medium-tech and passive solar offer a lower cost, environmentally sustainable enclosure option, currently only used by smaller aquaponic operations. However, due to their intentionally limited level of technical environmental controls, they only perform well in specific climate zones. In comparison, high-tech and rooftop greenhouses can be technically implemented anywhere, though in extreme climate conditions they generate high operational costs and larger environmental footprints. Recent case studies show that indoor growing facilities can be financially feasible, but due to their exclusive reliance on electrical lighting, their resource use efficiency and environmental footprint are of concern. Further research is needed to establish the relationship of specific aquaponic farms and their enclosures to existing resource networks. This work can help connect aquaponics to research done on urban metabolism.

Other criteria determining farm typology and performance are internal. These include environmental control levels, crop and fish selection, aquaponic system type and scale and enclosure type and scale. Taking on an integrated LCA approach, the relationship between all factors have to be assessed throughout the lifespan of the farm, from cradle to grave. Life cycle assessment of aquaponic farms must include both building impacts and growing system impacts since there is overlap in the farm operation phase. A series of promising strategies in heating, cooling, lighting, and material design can improve overall farm efficiency throughout the entire lifespan of the farm. Beyond accounting for environmental impact, LCA can become a design framework for horticulture experts, aquaculture specialists, architects, and investors.

Continuing to survey existing commercial aquaponic farms is important to validate LCA models, identify strategies, and cataloguing aquaponic operations emerging on a larger scale. Combining modeling with case study research on controlled environment aquaponics has the potential to connect aquaponics to the larger scope of urban sustainability.

Acknowledgments The authors of this study acknowledge the financial support of the National Science Foundation (NSF) under the umbrella of the Sustainable Urbanization Global Initiative (SUGI) Food Water Energy Nexus and the support of all CITYFOOD project partners for providing ideas and inspiration.