The stand for the region of Liguria at the Milan 2015 Expo features a project as bizarre-sounding as it is intriguing: an attempt to grow crops underwater, inside air-filled biospheres. It's part of an effort that could prove a low-cost, low-energy solution to grow food in parts of the world where this was not previously possible.
Though of fascinating beauty, the land in the region of Liguria in Northern Italy is known to be especially poor for farming. Between the crowded population, rocky terrain, steep hills that often give way to landslides, and the periodic floods, the locals have had to resort to energy-inefficient terrace farming.
This is not an isolated problem: lack of fertile land and adverse climate conditions around the world means we've seen several projects involving growing crops creatively, including underground, inside a skyscraper, in a tiny greenhouse and even in the cloud, to try and deal with the issue.
For their project, however, scuba diving company owner Sergio Gamberini and his son Luca have picked an even more unusual spot: under the sea, inside biospheres 6 to 9 meters (20 to 30 ft) below the surface, just off the Ligurian tourist beaches of the town of Noli, near Savona.
As bizarre as this solution may sound, there is method to this madness. A few feet below the surface, plenty of sunlight still filters in, the temperature is kept at a stable 25° C (77 °F) by the sea, and the crops are well out of the reach of parasites.
The evaporating sea water condenses on the inner walls of the biosphere, creating a high-humidity environment (up to 85 percent) that favors crop growth. All in all, according to its proponents, the system is sustainable and requires very little energy.
The Nemo's Garden project started in 2012 and continued through the next two summers. The three (now five) underwater biospheres were anchored to the seafloor and filled with air. Then, shelves were installed along with cameras and sensors that monitor the plants – bunches of basil (used to make Liguria's iconic pesto sauce) growing either in hydroponics or in soil.
About 50 days later, the basil is harvested and laboratories are tasked with analyzing the results. According to the company, there has been no significant difference compared to land-grown basil, except the underwater variety appears to be noticeably stronger in flavor.
The planting for this year started in late June. Live streaming for the underwater garden project is available via Ustream, 24/7. Four cameras will monitor the stretch of sea containing the garden and the inside of the biggest biosphere. Each week will also see a live underwater broadcast to describe the latest progress.
The video below further illustrates the project.
Source: Nemo's Garden via New Scientist
Harvesting the produce, & protection from rough water & storm surge may pose some challenges, but not that difficult to overcome.
Possibly use the natural buoyancy, and gentle swaying to harvest some energy as well while resupplying the carbon dioxide that the plants need from the humans breathing in the fresh oxygen during the harvest & tending, etc.
Concerned about the clouding of the outer membrane due to marine growth that may form.
One, scaling up to agricultural levels would be near impossible due to the size constraints a floating bubble would have. Additionally, the ocean IS real estate used for fishing, which means even if you overcame the materials end of the problem, vast farms of bubbles would still cut off fishing.
Two, as Bob Flint pointed out, the outer membrane would rapidly become clouded due to marine growth. You'd have to make a serious materials development to not have your bubble practically opaque in a couple years.
Three, their gas exchange has me puzzled. Plants can, essentially, suffocate from lack of carbon dioxide. They need animal life the way we need plant life for oxygen. Now, this could easily be solved by an air pump, but that raises the complexity of this system by an order of magnitude. Which means money and higher chance of failure.
2. This would obviously only work in very warm climates with very high ocean temperatures. There are several reasons that I see why it would not work well in colder climates. - The natural evaporation won't produce enough humidity to water a lot of plants. - The temperatures in the biosphere will be too low without heating. - The water will be too murky thus filtering out too much sunlight (colder water is usually murkier than warmer water due to the higher plankton content ).
3. I guess for large industrial size plantations, you would need a direct connection to the land near by (some sort of tunnel system) to allow for access of large machinery for harvesting, etc. This and the fact that you need to remain relatively close to the water surface, puts several technical and architectural limitations on those biospheres, which I fear will restrict them to areas close to the coast. How much water area is there available close to coasts that is not polluted and used otherwise. Most coastal areas are relatively densely populated.
4. Since you cant be too deep under water, your biospheres are a shipping hazard. Not sure how that would go.
Marine growth could be an issue though, although considering it's been going for three years I reckon they must have solved that problem by now as well.
For the location, I can see this working on a small scale, and if nothing else could inspire some ideas for larger scale farming.
Their website seems to be still under construction so there are still quite a few details missing.
My thoughts on possible issues that were mentioned:
1. Shipping Hazard As the biospheres are in a depth of 6-9m they will pose little to no hazard to small ships but will be a problem for container ships and other large vessels. When combined with an offshore wind park the space could at least have a double use. Otherwise there should also still be enough coastal sea area outside of shipping lanes.
2. Competition to Fishing As we already have a huge over-fishing problem I see it more as a positive than a negative to exclude some sea areas from fishing.
3. CO2 Also curious how they will solve the CO2 supply problem. Perhaps just empty some gas bottles with CO2 inside the biospheres during maintenance and harvesting.
4. Clouding of outer Membrane Could be a real issue. A small cleaning submarine robot might help.
5. Large Machinery Don't really think we need them even for large scale application. After all we also don't use tractors in greenhouses. I guess large scale Nemo's Gardens will involve long tube shaped gardens and not small spheres like the current prototypes.
Another interesting question is how they plan to apply fertilizers for the soil and hydroponics version.
I think you are right with the CO2. So one less problem.
As to costs of pressurized air tanks. The biospheres are situated in a depth of less than 10m. I guess it should be possible to dive without any air tanks. At least at those times where you don't need to stay outside the biospheres for a long time. So setting up the gardens will probably still need air tanks but normal harvest operations will not.
Another problem might be that red light is more or less completely absorbed by the water at those depths. Did a quick google search. Blue light seems most important for plant growth while red light is important for the flowering phase. So leafy greens (lettuce, basil, etc.) should be ok but for flowering plants (strawberry, beans, tomatoes, etc) they might run into problems.