After reflecting on my experiences at the Maker Faire, it seems like the biofilter experiment had generated the most questions. A lot of you liked it because it looked like a cost-effective project for science fairs or classrooms, and I’d have to agree. One of my biggest goals is to inspire younger generations to developing an appreciation for the sciences. Making a simple how-to seems like a good starting point :)
For most of us, we probably haven’t put much thought towards what measures that vegetables had to go through to make its way to our dinner table. Advances in agricultural technology over the last 100 years have sustained the explosion of growth in human population. Agriculture has shifted towards a monoculture means of farming, where square miles of land are used to grow the exact same crop – much like a factory. In order to provide the required nutrition to the plants, the farm is blanketed with modified fertilizer. This concentrated man-made plant food is much easier for the crops to process. This is inorganic fertilizer, and it supports half of the human population. With so many people relying on this type of farming practice, very few are aware of the implications that follow.
Inorganic fertilizer is designed to increase a farm’s productivity, and nothing more. It skips the biological processes that occur naturally and provides the plants with usable nitrates, ammonia, and phosphorus that they can stuff their faces with – kind of like if McDonald’s ever delivered. Needless to say, they fatten up pretty quick. Inorganic fertilizers like this very easily dissolves in water as well. Whatever isn’t utilized by the plants could drain into groundwater supplies or runoff into bodies of water, and this is where the untold story begins.
According to the EPA, 52% of public wells and 57% of private wells contain nitrates. Drinking water contaminated with these compounds can have health implications, especially with infants and pregnant women. Excessive nitrate consumption can lead to cyanosis (chocolate brown blood and bluish skin) and hypoxia (low oxygen count). Imagine always trying to catch your breath, and that’s hypoxia. In nature, fertilizer runoff can lead to algae blooms, high levels of biotoxins, hypoxic water, and fish kills. Inorganic fertilizer may yield large amounts of crops, but at what cost?
Nature, in its pristine state, never needed inorganic fertilizers. There are no farmers around to spray plants with super concentrated plant food. Instead, these nutrients are broken down from other biological cycles, and everything reaches a point where it’s happily balanced. At the risk of sounding distasteful, you could say that it all starts with poop. Bacteria and microorganisms see this as a food source, and they leave behind their own sort of waste. Plants chow down on this stuff, animals move in and eat the plants, and the cycle continues. Everything is full circle like this. The water cycle is an example that many of us are familiar with, but there are many other cycles. In our particular case, we’re especially interested in water, carbon, nitrogen, and phosphorous cycles.
Using aquaponics, it is possible to regulate these cycles. Aquaponics is farming with the help of fish. The fish make their own waste, and our biological cycles begin.
The big huge enormous advantage to aquaponics is that you don’t need supplemental fertilizers like traditional farming does, and thus, don’t have to worry about the implications of traditional farming. Your water (that you recycle) is already nutritious to the plants. Aquaponics also means that you’re cultivating fish and algae, which are excellent sources of nutrition. The challenge in a system like this is regulating that delicate balance.
Modern swimming pools use plants and bacteria to clean the water. No chlorine necessary!
If we’re interested in using fish to grow our plants, we have to be confident that we’re getting the bacteria growth that we want. This is where the scientific method come in. The scientific method, when executed properly, is how researchers can make arguments about scientific discoveries. It gives you something to base an argument off of. For example, if I wanted to prove to you that water boils at 100 degrees Celsius, I’d throw some water on the stove, stick a thermometer in it, and hopefully I’m right. The test must be controlled, though. Maybe I’m on top of a mountain when I perform this experiment. Will my water boil at 100 degrees Celsius? Probably not.
The scientific method consists of 5 real steps towards approaching a conclusion. First, you identify your problem. I need to know at what temperature water boils. Second, you research as much as you can. If I keep on heating water up, it will eventually start to bubble. Third, you create a hypothesis. You take knowledge from prior knowledge and formulate an educated guess. I think water will boil at 100 degrees Celsius because that’s what I’ve observed in the past. Fourth, you test. At this point, you need to identify any factors that could change your experiment. Do you think salt could affect your boiling point? Is there a difference between using a gas or an electric stove? Test it and find out! The last step to the scientific method is making an analysis. How does the outcome compare to your hypothesis? It’s okay if it’s wrong! It could even lead to discoveries that you never thought of. Look at your data and try to pick out anything that seems strange to you. My water boiled at 95 degrees Celsius, but I’m conveniently on top of a mountain. Therefore, I think boiling point has something to do with elevation. Now you have a new hypothesis, and can test further into it. How does your boiling point differ from 500 meters above sea level to 1000 meters above sea level? Keep on asking questions, keep refining your tests.
So, here’s my own scientific method:
- Problem – I need to convert fish waste into usable plant food.
- Background – Bacteria tend to cling onto things and like to be in oxygenated water.
- Hypothesis – If I provide a lot of surface area, a large amount of bacteria will develop.
- Test – (see below). I’m trying to change one variable with each bottle. The first has no stones for bacteria to cling onto, the second has just stones for the bacteria to cling onto, and the last has stones and a plant.
- Analysis – I don’t think I got the bacteria growth going on that I wanted, but my water definitely looks different. In fact, I’m pretty sure I have a lot of algae growth. Therefore, I think the presence of expanded clay is preventing my algae population from growing.
I wasn’t able to get the proof that I wanted for bacteria growth, but I was very surprised to see the algae differ so much. It’s led to some interesting thoughts and I’ll have to refine my tests further.
Without further adieu, here’s how you can make your own biofilter experiment:
The Biofilter Experiment
- 3x 2 liter bottles, nontinted
- 3x 4” net pots, found at any garden (or hydroponic) store
- Expanded clay puffs (hydroton), found at any garden (or hydroponic) store
- A plant with a developed root system, I used lettuce and fennel
- 1x aquarium bubbler
- About 6 feet of tubing for the bubbler
- 2x T air hose splitters
- 3x air stones
- 3x goldfish
- Fish flakes
- About 2 gallons of water from a natural source
- Acquire your bubbler materials. Cut three sections of tubing that are about a foot long. Cut a smaller section to a few inches in length. Using the T splitters and air stones, assemble your tubing so you have three ends to submerge into the water and one end to plug into the bubbler. The air stones break very easily if you pull on them, so make sure you have your tubing correct!
- Acquire your water and fish. Without removing the fish from the original bag that they came in, dilute their water to about 50% by adding pond water. You are trying to gently introduce your fish to a new environment so they don’t suffer from shock and die. Aerate both your pond water and bag of fish overnight.
- The next day, add your fish and diluted water to your original pond water. They should be able to handle the environmental change.
- With a pair of scissors, cut the tops of the soda bottles off. Make small cuts, check to see how the net pot fits, and make adjustments. You want the net pot to sit comfortably on the rim of the bottle.
- In one net pot, fill to the top with expanded clay.
- Carefully remove your plant from its soil and shake loose any dirt that may be caught in the roots. Carefully position your plant in another net pot and add the puffs. This may be easier with two people.
- Fill each soda bottle with enough pond water to submerge the net pot by about 1 inch. Throw a fish in each bottle and insert an air stone. Place a net pot on each bottle.
- Place near a sunny window and enjoy!
A few tips:
- Try testing for something that interests you! Perhaps sand will give better results than large pebbles.
- Number your bottles so you can more easily identify them. For me, #1 was my empty net pot, #2 was my net pot with just puffs, and #3 was my net pot with a plant.
- Take pictures and record your observatons!
As always, shoot us some questions if you have them. We love to hear the feedback :)