Last weekend I finally took a trip to Granja San Patricio, owned by progressive-minded brothers Rafael and Rodolfo Castillo. They have built the first commercial sized integrated aquaculture-hydroponic system in El Salvador, known as aquaponics. Their system is modeled after the oft-replicated system of Dr. James Rakocy, of the University of St. Croix. Rafael Castillo and I had both met Dr. Rakocy a few years ago – while we were attending the same aquaponics congress in Guadalajara, Mexico! There were many attendees, and since he speaks only Spanish and at the time my Spanish was deplorable, it is not surprising we never chatted. However, it was a wonderful example of what a small world this is! Not that the aquaponics world is very big. In the U.S., thanks to Will Allen, founder of Growing Power – a Milwaukee based organization that develops and promotes urban food systems, including the use of vermiculture and aquaponics – aquaponics is on the rise. Since Allen was granted the MacArthur Genius Award in 2008, he and his organization have been highlighted and replicated across the U.S. The past three years has seen a tremendous growth in aquaponics systems across the U.S., and if you are interested in setting up a system, the leaders in that arena are undoubtedly Rebecca Nelson and John Pade. The fact that they own the www.aquaponics.com domain should give you insight into how long they have been around!
But back to El Salvador. Rodolfo Castillo first contacted me through LinkedIn. I imagine a quick search for “aquaponics” and “El Salvador” doesn’t bring up a very long list, and so that’s how he found me. He wanted me to come visit his system and give him some advice on how to move forward. Well, naturally I was a little hesitant at first, but after several months of emails and talking to mutual acquaintances, and determining that this guy was legit and not a cyber-stalker, I enlisted my neighbor and her Salvadoran boyfriend to accompany me to the farm. And I was glad I went. The system was clearly new, and the hydroponic part clearly struggling. Rafael gave me the tour, and confessed that while knowledgeable people in aquaculture were easy to come by (there are several tilapia aquaculture facilities in the country), finding someone who knew anything about hydroponic growing was next to impossible. The lettuce in the raceways looked good, but the eggplant, sweet peppers, and even basil appeared to be under a great deal of stress.
The system consisted of four fiberglass fish tanks, and each tank contained fish in different stages of growth. Right now, they buy the tilapia fingerling from a nearby hatchery, but they intend on building their own hatchery within the year in order to supply their system and start selling the fingerling. (As I said, tilapia aquaculture is very common here.) From the fish tanks, the water flows into a large conical tank that settles out much of the solid waste (leftover food and feces), then the water flows into a pair of rectangular tanks that are stuffed
with bird netting. This also helps trap solid waste, but also allows the beneficial nitrogen-converting bacteria to break down the ammonia into nitrites and then into nitrates – the form of nitrogen that the plants can absorb. The bird netting gives this bacteria a place to live. From these tanks, the water flows into yet another rectangular tank, flowing through a screen – a final measure to ensure no solid material (little fish included) will be sent into the plant raceways. This tank is heavily aerated to increase the dissolved oxygen (DO) content of the water. Both the fish and the plants need relatively high levels of DO – the fish so they can breathe, and the plants so they can absorb nutrients. The water leaves this final aerated tank in large pipes that run underneath the plant raceways and then enter the plant raceways. These raceways are also aerated with several air stones; if that was not done, the DO levels would decline steadily from the inflow to the outflow. The outflow brings the water to a sunken tank, where the only pump of the system pumps the water back into the fish tanks. And the cycle begins again. Throughout this system, the plants are designed to remove the nutrients generated by the fish, and the fish provide nutrients for the plants to grow. Inputs include the fish feed and additional fertilizer for the plants (phosphorous and calcium, which are typically very low in the system). Of course, the fertilizer has to be natural, otherwise it would be dangerous for the fish. This is also why pesticides cannot be used on the plants; many pesticides are toxic to fish.
The farm is located relatively close to La Libertad, and the beaches around there are lined with restaurants who would probably be very interested in purchasing his product, as long as Rafael can bring the system under consistent production. No chef wants to purchase sporadically; they need to be able to rely on a product. My opinion was that they need to focus on just one or two crops (such as lettuce, or basil), and then establish a relationship with
a few restaurants or supermarkets to buy their produce as well as their fish. As was the case with the system I operated in the Bahamas, the most un-sustainable aspect is the fish feed that is imported and composed of decidedly not natural ingredients. In fact, I would not be surprised if the feed contained genetically modified soybeans. The Castillos are eager to triple the size of their existing system, add the hatchery, and also manage their entire property in a style not common around here. They have planted hundreds of fruit trees on terraces, trees that are watered by a gravity irrigation system that begins at the tank on top of the hill, which is fed by their well pump. They compost all of the waste produced from the plants and the fish, and have a vermicomposting system with California Red Worms. They use the effluent from the worm system as a nutrient-rich fertilizer for their growing fruit trees. In ten years time, their property will be a wonderful, shady oasis in the middle of an otherwise parched, overgrazed valley several kilometers from the coast. The brothers wish to be a model that works to reverse the typical land management styles, and a model for sustainable food production. But until they can reduce their input costs (and imports in general), then it seems unlikely their ideas will spread to their impoverished neighbors. However, that being said, they definitely need to be commended for their desire to bring change to their country.