"Sustainability" and "sustainable" are popular words these days, but often misused. We understand it as producing food while sustaining natural resources and achieving it only through production systems with minimal ecological impact.

The most common relation is linking environment with sustainability. If something does not impact the environment or has a positive impact on it, it is considered sustainable. However, there are other factors that might come into play when considering a product or production system's sustainability.

RAS as case study
We conducted a survey among different stakeholders whose opinions are critical for the advancement of the aquaculture industry. One of the questions we asked was why RAS is considered "environmentally friendly" fish production methods. Responses were received from all over the world and the main reasons given were: less water usage from the environment compared to other culture technologies, such as ?ow through systems; decrease of the eutrophication potential of the outgoing water; elimination of potential disease transfer and genetic contamination of wild stocks; use of no or very little vaccines or antibiotics because of a biosecure culture environment; and the possibility of re-using discharged nutrients in agriculture.

Nonetheless, in practice, sustainability of RAS was considered uncertain and the use of energy and its environmental impact was of little concern to the respondents. In fact, concerns identi?ed by the stakeholders included (Fig. 1): identifying alternatives to ?shmeal (35%); enhancing animal welfare (i.e. increased biomass production, increased survivals and reduced maturation with the subsequent reduction of product downgrades) (26%); decreasing the feed conversion ratio (23%); decreasing the use of chemicals (11%); and decreasing the use of energy and thus, created environmental impacts (5%).

Energy plays an important role when considering the sustainability of RAS. Respondents were also asked about techniques or strategies applied in relation to energy recovery systems designed/applied. Examples included exchanging heat between the incoming (i.e. make-up water) and outgoing water through a heat-exchanger; retaining heat based on the system's operation/water use; controlling the energy use of CO2 stripping through pH/CO2 set-points for on/off control of blowers for energy saving and; increasing the recirculation rate through the use of denitri?cation technologies which resulted in energy use reduction and cost savings. Using system sludge for local farming purposes and producing energy for other nearby companies through a bioreactor supplied by sludge, guts from the processing stage and mortalities, were also mentioned.

Environmental sustainability
Typical environmental benefits of RAS are less water and land use, greater control over the environmental and water quality parameters enabling optimal conditions for fish culture, and high biosecurity standards. However, there is something else beyond this. There are many other reasons to consider such systems as environmentally sustainable. RAS are located where consumers are, decreasing the transportation and thus the carbon footprint of each of the marketed products. RAS producers are committed to promote site-specific energy sources such as renewable energies and zero or near-zero impact initiatives within the local community. The recapture and reuse of waste from the system, included in a lifecycle assessment throughout the whole production cycle, make it possible to consider such systems within circular economy business models.

Social sustainability
Aquaculture is the production of fish, the industry of the future, the (potential) engine of many communities in developing countries and the promising farming method to meet the seafood demand in technological and economically advanced areas. Society needs aquaculture as aquaculture needs society.

RAS produces absolutely fresh products, possibly and potentially certified, available all year round. Moreover, these systems allow full traceability of the product, from egg to the table, giving consumers the confidence of purchasing a trustworthy product. The site selection by investors and/or company managers also guarantees local employment and economic development. This positively contributes to local job creation and generates ripple effects in the local supply and service sectors. RAS can promote aquaculture (and related areas) through schools, universities and research companies as well as investing in R&D with continuous feedback from stakeholders.

However, society and consumers need to be educated. The understating of what fish production is and the implications of the industry in the near and further future is crucial. RAS companies need to educate fish eaters about the benefits of sustainable choices. The importance and awareness relies on the information strategies to adopt sustainable seafood choices.

Should technology and the economy also be considered when defining the sustainability of RAS? Learn about sustainability and the circular economy,  which radically limits the extraction of raw materials and the production of waste, recovers and reuses as many of the products and materials as possible, in a systemic way, over and over again.

The prevailing model of production and management of resources that promote short-term consumption is leading the planet to an unsustainable outcome. In contrast, the circular economy is a "make/remake - use/reuse" economy that offers substantial improvement.

Repoduced From Hatchery International, by Maddi Badiola, PhD, is a RAS engineer and co-founder of HTH aquaMetrics LLC, (www.hthaqua.com) based in Getco, Biscaye, Basque Country, Spain. Her specialty is energy conservation, life cycle assessments and RAS global sustainability asessments.