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The original was posted on /r/permaculture by /u/cologetmomo on 2024-11-26 06:09:55+00:00.
Original Title: Can you feed a family of 4 on an area the size of a parking space? No, but there's a group on Reddit and social media that would love to sell you a book about it! I reviewed their claim and figured you all might enjoy it and at the very least, stay protected from these kinds of scams.
The Integrated AquaVegeculture System (IAVS, sandponics) is an aquaponics system that uses sand as the growing medium and biological filter. Advertisers have made claims that yields from this system could feed a family of 4, year round, on a plot of land the size of an automobile parking spaceA.
1988 article
The noteworthy proclamation details that a parking space-sized IAVS system can produce 200 kg of fish and 1,400 kg of vegetables per year. The only caveat being year-round production in a ‘temperate’ climate or controlled environment. The fish weight is further clarified as being the live weight of the fish.
Official shop using claims as advertising.
The claims have been further amplified on social media platforms:
Social media post of research continuing 35 years after the 1988 article.
Note: The parking lot model (PLM) appears entirely conceptual. At no point is there an actual facility matching these dimensions linked or referenced, only that these figures are based on research conducted by Mark McMurtry, a graduate student at North Carolina State University in the 1980s.
The article cites that fish are harvested at 250 grams. To continuously feed a family, the system would be operated with sequential rearingB, where multiple sizes of fish are kept in the same tank and selectively harvested as needed. However, to evaluate the claim of no aeration, we can start simply with calculating a stocking density. If the tank were harvested all at once, we can assume 3 harvests per year based on the harvest weight. A total harvest of 200 kg per year yields, on average, 67 kg (150 lbs) live weight of tilapia. The article states a total tank volume of 3 m3 (about 800 gallons). The final stocking density is about 0.19 lb/gal. It is plausible juvenile fish at an extensive stocking density can forgo supplemental aeration between the flood and drain cycles the article illustrates.
However, 200 kg per year of live fish weight equates to only about 8.5 lb of fish per week. Further compounding this small harvest is that it’s referring to the live weight of fish. A tilapia may only contain 30 to 40% fillet yield or dress-out weight, meaning that family of four may have as little as 2.5 pounds per week, or 0.63 lbs per person per week.
Vegetable production is estimated at 1,400 kg per year on an area of approximately 19.5 m2 (200 ft2). However, that assumes the entire area is devoted to crops, ignoring the aisles require to access the system, as detailed below.
Diagram illustrates a total growing area of 19.5 square meters. With no indication the area lost to the access aisles is considered.
If the two access aisles measure only 0.4 m (about 1.5 ft), the total growing area is reduced to 14.7 m2 (150 ft2). This figure is an order of magnitude too small for even a single individual who, depending on crop variety, will need 1,000 to 2,000 square feetC. Therefore, a family of four could require as much as 8,000 square feet to sustain themselves.
The document itself, if written in 1988, represents one of the first instances of the term “Integrated AquaVegeculture System.” The document also illustrates the first instance where a profit motive emerges.
Dr. Mark R. McMurtry, is essential for start-up and propagation of new installations. We can envision a number of arrangements under which Dr. McMurtry’s services could be made available to first-time operators.
Additionally, if written in 1988, the document followed the very first experiments conducted by Mark McMurtry at North Carolina State University, prior to any large-scale system and on the heels of his graduate research, which was limited in scale, as discussed here. Additionally, this was written 4 years before the largest system to have ever been constructed in the United States, the Mora System, as discussed here.
The ‘parking lot model’ of the Integrated AquaVegeculture System (IAVS, sandponics) continues to serve as dishonest advertising. Luring potential customers into a sand trap, where they are misled into believing they are supporting something beyond a small group of people with a profit motive.
A Gross, H. Douglas. “The Aqua-Vegeculture System.” iAVS. 27 May 2024, https:// iavs.info/the-aqua-vegeculture-system/.
B SRAC 454
C
