If you read my last post, you know that I’ve had quite a bit of time to refine my plans before carrying on with construction. Well, construction resumes next week, now that the rains have mostly stopped. I’ll certainly make refinements as I proceed, but I’ve finally settled on a concept that suits me.
The Aquaponic Component
I’ve begun to shy away from a commercial operation, at least right from the beginning. There’s plenty of land around if I’m inclined to expand in the future. I’ll still sell the produce, of course, but I’m not going to push the system to any limits to prove a point to myself. I’m going to go at it sort of the same way I cook– haphazardly.
If you look at the sketch to the left, you will see that I’ve reduced the number of hydroponic troughs growing lettuce and other leafy stuff from 3 to 1. When the “farm stay” component of my project kicks in, the system will just barely support the gastronomic needs of my guests, so I want to broaden their choices a bit. No, duckweed isn’t going to be on the menu. It’s there to discourage algae, and to become a high-protein additive to my mostly grain-based fish feed. The freshwater prawns can nibble on it, too.
I originally intended to stock only a few freshwater prawns in the hydroponic troughs. They don’t mind being in the dark, and they eat detritus (fecal matter from the fish, leftover fish feed, etc.). They also frequently eat each other. The males don’t grow at the same rate (they have 3 “morphotypes”), and the presence of the dominant BC (blue claw) males will inhibit the growth of the unfortunate, smaller fellows. That’s an easy problem to solve, though– eat ’em! It would be kind of hard to get at them for collection and eating of the larger males if they were under the rafts, though, so I’m going to raise some in the other 2 hydroponic troughs, about 20 per square meter. They will be easy to net underneath the bed of duckweed, as they won’t be able to see me coming. I’ll stock 10 per square meter in the trough with rafts just to see what happens.
I also don’t want to have to make too many rafts until they are needed. I can always increase the raft area, but my rafts are, well, going to be a bit unconventional. For a long time I thought I’d go with standard Styrofoam boards with holes cut in them for the net pots. That’s what people in the West seemed to be doing, until I learned that UV light makes them disintegrate. The cheap stuff will absorb water, too, and hence cease to float. So what people are using is special, expensive foam boards (blue, I believe) used in construction, but there are issues about the fire-retardant chemicals leaching out of them. And I don’t know where to buy them, either, so following a common theme in my project, I have decided to go all natural. Bamboo is the obvious choice. It floats (sort of) and doesn’t rot (for quite a while) in water. It’s also free, if you go and get it yourself. So after some trial and error, I came up with what you see to the right. Ugly, I know, but the bacteria will love the extra surface area.It is weighted down with 3 kg of junk that was laying around, as that’s about what 10 or so fully grown lettuce heads will weigh. But, what you don’t see, are the PET bottles I had to put, one each, on both ends. It works fine without the weight– seedling roots, for instance, would just be touching the surface of the water. At some point, however, the rafts will need a boost to their buoyancy. On the bright side, by adjusting the volume of air in the PET bottles (by adding water), it will be possible to maintain the raft depth of your heart’s desire. On the other hand, what a pain in the ass. . .
Another advantage to this revised design is that I now only need to make one filter contraption. I’m not handy when it comes to fashioning things. Designing things, well, I’m okay at that, I think. The two troughs with the prawns and duckweed should not need the filters as the solids that I’d otherwise be filtering out will be their source of food. There will undoubtedly be some kind of waste coming out the other end, but I think I can deal with that. It will also be possible to drain and clean the troughs individually while keeping the rest of the system going. So, I think I’ll be able to raise the prawns without any added feed. As it is designed now, I think the system will produce the following annually given an input of 3 to 4 kg of feed per day:
- 1 ton tilapia
- 40 kg prawns (2,000 at 20 g each)
- 5,200 heads of lettuce (a little over 1 ton)
- 300 kg tomatoes (grown upside down, utilizing vertical space, not shown)
- 230 kg bell peppers (grown upside down, utilizing vertical space, not shown)
I’ve also added a solar tunnel dryer/water heater into the design. The basic design is shown on the right. Coffee can generally be dried in the sun because it is harvested during the dry season, but I learned the hard way last year that this doesn’t always happen, especially when you’ve contracted the process out (and your contractor’s own coffee takes precedence). But the main use for the solar dryer will be to dry wheat and barley which I’ve malted, and also dry the spent grains after making beer with the malt. To obtain 3 to 4 kg of spent grain a day to feed my fish, I need to brew about 5,000 liters of beer every year, which is only about 200 liters every 2 weeks. That’s only about 22 big bottles (630 ml) a day. Hell, I can drink about half of that. Once the beer is brewed, the spent grains will deteriorate quickly if they are not rinsed and dried. It will come in handy for drying other fish feed supplements such as composting worms and duckweed, too. After scratching my head for some time about how I could use that heated air to heat my system water, I decided that I’d just lay down some black LDPE on the black surface and trickle feed ground water to the sump during the day. An aquaponics system loses about 1 to 1.5% of its system water daily, which is actually a fraction of what other aquaculture systems use, so I need to replace about 500 liters a day. That’s about 1 liter a minute over 8 hours. I’m hoping that this, plus painting the south-side of the fish tank black, will keep the water at around 25 to 26 degrees C.
There is a lot to be said for polyculture. An aquaponic system, raising fish with plants, is already a polyculture, but the addition of freshwater prawns expands the biodiversity. The prawns will make use of detritus that would otherwise be taken out of the system. Eron Martan wrote in the Aquaponics Journal:
Why even bother with polycultures in aquaponics or recirculating systems? There are many possible benefits, but one outweighs the rest and is of significant ecological importance. Polycultures are a form of agrobiodiversity that extend into ancient times and are a key to sustainable agriculture. According to a report by Lori Ann Thrupp (2000) from the Special Biodiversity Issue of the International Affairs Journal, “The homogenization of species and of farming systems increases vulnerability to insect pests and diseases. Purely monocultural systems are highly susceptible to attack, which can devastate a uniform crop, especially on large plantations.” Monocultures are an unnatural and unsustainable form of agriculture that has caused many disasters across the world, especially after the green revolution. Aquaponics is a step in the right direction, but with further integration and agrobiodiversity would be even closer to truly sustainable and eco-friendly agriculture. With more species, and more phyla, you will have a simulated ecosystem which will have more complete cycling of nutrients and more effective biological controls.
The Farm Stay Component
In the next 3 or 4 months I hope to not only complete the aquaponics component of my project, but get one “model” farm stay unit completed (which I intend to test thoroughly by living in it myself for a while). It will be located right next to the greenhouse on the upper tier, but the others to follow will be down by the stream and waterfall, in more picturesque locations. The goal is at least 3 units suited to families, with a bedroom on the ground floor plus a loft. I’d also like to build 3 or 4 smaller units for single guests and couples. The sketch here shows sort of what I want the family size units to look like, without the roof, loft, and a few other bits and pieces (such as windows and doors). The inside diameter is 7 meters. As you can see, I’ve added a Japanese twist in the form of an outdoor bath and garden. At 1,200 meters above sea level, most evenings a hot bath would be irresistible.
The units are based on some of the designs and concepts of Owen Geiger, former director of Builders Without Borders. The unit shown to the right was built by Mr. Geiger in Thailand. Details about how it was built can be found here. For more information, check out the Natural Building Blog. These buildings can be built for a fraction of what it would cost using conventional practices. They are as green as you can get, and will last forever.
Guests are going to be encouraged to make the most of their sojourn on a sustainable farm and admire lots of neat examples of ways we can live without ruining the planet, and this includes preparing their own meals. The way I look at it, what a relief it would be for a family or couple traveling together to be able to relax and make their own dinner using the excellent ingredients I can offer, especially after a succession of crappy restaurants. While the composting toilet will doubtless be the most memorable sustainable contraption one encounters at my farm stay, guests will also have the opportunity to prepare their own Japanese style bath. They can then drain the bath through their floor to take the edge off the nighttime cold (it drops easily below 19 C at night, and those floor tiles will be cold).
You usually wouldn’t think there is anything sustainable about quickly heating 200 liters of water from 19 C to about 40 C. Sustainable or not, this can be done thanks to a more robust version of the rice husk gasifier shown here. There are a lot of gasifiers out there which burn various types of biomass, but rice husks are tricky. In my search for DIY plans in cyberspace, I had the pleasure of corresponding with Dr. Paul Olivier. Paul heads ESR (Engineering, Separation and Recycling LLC) in Vietnam. Their motto is “Making Waste our Greatest Resource.” Not only have Paul and others refined the design, he is having them manufactured locally and has offered them to me at cost. What’s so special about a stove that burns rice husks, you may ask. First of all, it doesn’t just “burn” the rice husks, it “gasifies” them. Gasification is used in industry and such but not where it’s needed, in the kitchens of the rural poor. There are tremendous health issues caused by cooking with firewood and charcoal. And what the stove produces, other than heat, is biochar. Biochar is great for the soil. Paul offers an excellent presentation about biomass gasification on his website. He also suggests that you look at this, which puts gasification into a much larger context.
In the evening, after a hard day of trekking around the other waterfalls in the area, guests will be encouraged to go into the garden, fill a more robust version of this rice husk stove with rice husks, light it, and push it back under the 200 liter steel barrel full of water in the corner. They can then consume a bottle or two of my Beer Bolaven while the stove quickly heats the water in the barrel from about 19 C to 40 C. Having accomplished this, they then turn a valve which fills the bath. Instructions for Japanese bathing will be provided. After the bath, turn the valve which drains the bathwater to the radiant floor. Go back inside and, after a couple of hours, begin to enjoy the closest thing to central heating you will find in Laos.
Okay, so I’m not sure it will work. But it would be quite a novelty if it did. My idea for the radiant floor is shown to the right. The sand and vapor barrier are pretty straight forward, but what are those rice husks doing there? Well, rice husks make a great, free insulation. Won’t they rot, compact, or be eaten by all sorts of critters? I don’t think so. First of all, they should stay dry. They will initially compact, when the slab is poured, but they won’t compact any further. In other words, they shouldn’t compact over time, leaving voids. Rice husks can only absorb something like 7% moisture. This is not enough to become a home for mold and such, and anything that wants to eat them (and I can’t think of anything that does) will have to penetrate a 40cm thick wall. The cardboard is simply there to provide a solid base on an otherwise somewhat liquid material. The LDPE tubing goes down. It is tied in place to rebar mesh (not shown) on top of it, and then the slab is poured. The floor only supports a small amount of non-bearing wall and the people who wander about, so it doesn’t need to be thick.
And heating with bathwater? Okay, its a bit of a grey area (grey water, get it?). First of all, not a lot of heat is needed, just enough to take the edge off. At 15 cm spacing I should be able to get about 340 linear meters of 19 mm tubing in. That tubing will hold approximately 100 liters of water. Assuming that the bathwater is heated from 19 C, the same ambient temperature as the floor, to 40 C, and then cools down to, say, 35 C before it is run through the floor, that’s 16 degrees that the water has in residual heat. To heat 100 liters of water from 19 C to 35 C, about 6,400 Btu are required. That means there are that many Btu to go into my floor. But the bath will contain 200 liters, so if it is covered afterwards, and allowed to trickle through the floor, that’s some more Btu that can eke their way into the floor. So, if the total Btu were, say, 10,000, that’s the equivalent of running a 1,500 watt space heater for 2 hours.