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Early research on commercial aquaponics focused on evaluation and the development of specific, mostly research institute-led case studies. These first results were highly positive and optimistic about the future of commercial aquaponics. Bailey et al. (1997) concluded that, at least in the case of Virgin Islands, aquaponic farms can be profitable. Savidov and Brooks (2004) reported that the yields of cucumbers and tomatoes calculated on an annual basis exceeded the average values for commercial greenhouse production based on conventional hydroponics technology in Alberta. Adler et al. (2000) performed an economic analysis of a 20-year expected scenario of producing lettuce and rainbow trout and argued that the integration of the fish and plant production systems produces economic costs savings over either system alone. They concluded that an approx. \$300.000 investment would have a 7.5-year payback period.
Technologically based dynamic optimization models are commonly used to represent production engineering relationships in aquaponics systems (Karimanzira et al. 2016; Körner et al. 2017). It is noticeable that so far hardly any different scales are considered, and previous studies like Tokunaga et al. (2015) and Bosma et al. (2017) are limited to small-scale aquaponics for the local production of food or are performed on data from research facilities, such as University of Virgin Islands' aquaponics systems (Bailey and Ferrarezi 2017). Furthermore, as Engle (2015) points out, the literature on the economics of aquaponics is sparse, with much of the early literature based primarily on model aquaponics. Without realistic farm data, such projections often are overly optimistic because they lack details on expenses beyond the obvious ones of fingerlings, feed and utilities and do not include the everyday risks involved in farming. In this research on the economics of aquaponics, production functions are only partially reproduced and questions of process-based optimization addressed only to some extent. Leyer and Hüttel (2017) demonstrated the potential for investment accounting as part of an initial analysis to capture various parameters of an aquaponics facility. Furthermore, Engle (2015) points to the difficulties of estimating annual costs to operate in aquaponics farms since many of these systems are quite new. She also points out that modelling is based on hypothetical situations and that more realistic farm data is needed, whereby the unexpected expenses are incurred daily, "from screens that clog, pumps that fail, or storms that cause damage".
As aquaponics started to grow both as a do-it-yourself (DIY) activity (Love et al. 2014) and as an industry (Love et al. 2015), research on real commercial farm case studies emerged. Specific case studies of aquaponics production were performed on commercial attempts, for example, in Puerto Rico (Bunyaviroch 2013) and Hawaii (Tokunaga et al. 2015), including also the case study of a small-scale aquaponics social enterprise (Laidlaw 2013) (see Chap. 24).
With the continuous rise in the number of aquaponics growers, the first in-depth analyses of the state of the art of the industry emerged, focused primarily on the USA. These studies showed a less optimistic picture of the emerging industry. Love et al. (2015) performed an international survey amongst 257 participants, who in the last 12 months sold aquaponics-related food or non-food products and services. Only 37% of these participants could be named as solely commercial producers who gained their revenue from selling only fish or plants. Thirty-six percent of the respondents combined the sales of produce with aquaponics-related material or services: Sale of supplies and equipment, consulting fees for design or construction of aquaponics facilities and fees associated with workshops, classes, public speaking or agro-tourism. Finally, approximately one third (27%) were organisations that sold only aquaponics-related materials or services and no produce. The average aquaponics production site of 143 US-based producers was 0,01 ha. By comparing this to the overall hydroponic production in Florida (29,8 ha), Love et al. (2015) concluded that the size of aquaponics producers is significantly smaller than hydroponic production and is to a large extent still more of a hobby activity than successful commercial enterprises. In terms of water volume, the aquaponics farms reported comparable sizes as typical RAS aquaculture farms in the USA. Yet nearly a quarter of respondents (24%) did not harvest any fish in the last 12 months, and the estimated overall size of fish production was 86t of fish, which is less than 1% of the farmed Tilapia industry in the USA.
According to the same study, aquaponics was the primary source of income for only 30% of respondents, and only 31% of respondents reported that their operation was profitable in the last 12 months. For example, the median respondent received only \$1000 to \$4999 in the last 12 months, and only 10% of respondents received more than \$50,000 in the last 12 months. This led Love et al. (2015) to conclude that aquaponic farms were small-scale farms, which is comparable to agriculture in general, since farms with gross revenues of less than \$ 50,000 made up approximately 75% of all farms in the USA and farms with less than \$50,000 typically sold only around \$7800 in local food sales — making it thus necessary to combine farming income with other sources of income. It is therefore not surprising that aquaponics, like small-scale farming, relies heavily on volunteer work. Typically, there were a large number of unpaid workers, family members and volunteers working on these small units, with an average of six unpaid workers per facility.
Similarly, Engle (2015) addresses the 2012 census where 71 aquaponics farms across the USA were reported which represented 2% of all aquaculture farms. Of these, only 11% had sales of $ 50,000 or more, compared to 60% of pond-based aquaculture operations that had sales of $ 50,000 or more. Additionally, Engle (2015) points out to the difficulties of obtaining data from these farms, for example, estimating annual costs to operate in aquaponics farms, since many of these systems are quite new.
In summary, from an economic point of view, there is a research gap in so far that there are no records and analysis available which include statements about economically viable systems. Further research is needed that would take into account (a) the production possibility curves (normative), (b) the combined analysis of fish and plants including feedback between both, (c) the economic efficiency in combination with optimising the business processes and feedback (simultaneous optimization production process and economic efficiency) and (d) the consideration of different scales (scale efficiency) against the background of the environmental sustainability of this agricultural system. In addition, there are no comprehensive and reliable data that combine key factors such as production volumes, factor entitlements and cost structures, scaling and sales strategies derived from existing real investments. Further profitability analyses should consider temporal aspects and risk whilst formulating normative benchmarks that in turn can serve as the basis for investment decisions.