Sustainable Sourcing of Nutrients


Hi All,

I’m thinking about building the Food Computer (and potentially a Food server if all goes well) with the kids at our school, I became interested in the OpenAg project after hearing of it as a potential solution to producing food sustainably and at scale.

However, after looking into the hydroponic systems a bit further, I understand that the sources of nutrients used in the growing medium is a) non-renewable, meaning i have to continuously buy more and b) produced using energy (from oil and gas) and water intensive methods. As such, I’m concerned that this method of growing is, in fact, highly unsustainable when scaled up and over long periods of time.

As the sustainability aspect of the method is key to how we plan to use the Food Computer at the school as an educational resource, does anybody out there know of a genuinely sustainable way of getting the nutrients into the water/growing medium?

At school we’re looking at cycles, and so the Food Computer seems great at solving problems when water is scarce, but given how critical the nutrients are to growing food, I’m hoping theres an answer out there that could also do this sustainably.



Hi Tom,

I’m still rather new to a lot of this, but i do gardening and unusual plant breeding for my climate as a hobby. So i’ll bite and throw in my two cents.

Sustainable and/or low-tech methods of obtaining the key nutrients that plants need is one area i’m keenly interested in. Some of it may take a little experimentation, but i have a few ideas. The main idea i have is that plants need certain nutrients in certain quantities and sometimes that’s hard to find (other than petroleum based fertilizers and the like). Especially Nitrogen. So, why not use plants to feed plants. What i mean by that is something similar to combining “green manure” and “compost teas”. Ground up weeds and green leaves off of trees mixed with water in my mind should make an excellent liquid that plants can use in theory.

A few years back i attempted my first hydroponic system which consisted of a tomato plant, a home depot bucket, a fish tank heater, a aeration pump, and some homemade compost tea (ground up weeds and sugar, and molasses). It kinda worked for awhile, but i think in the long run i put too much sugar and molasses and it all got gross. So i’m thinking skip the compost tea ideas of sugar / carbon sources. The sugar (carbon source) and molasses was meant more to try and form symbiotic relationships with fungi and bacteria to help break down the micro nutrients into forms that the plants could readily absorb. So if that is indeed a step that is needed perhaps one could do that in a separate tank or something. I don’t even know if that is needed. The use of green leaves should have a good amount of nitrogen before it goes back into the atmosphere. Around my house i have access to plenty of field bindweed, maple leaves, and apple leaves so those would be the first i would experiment with.

Another year i was working on my Watermelon landrace breeding project. I live here in Northern Colorado and it would be mild to say that Watermelons don’t grow here. In fact prior to that year i had attempted 4 times and failed miserably all 4 years. But that year i was determined to get a watermelon breeding project off the ground. The spot i chose was horrible, it had dry cracked earth, it was nutrient deficient from growing corn in that spot several years in a row. So the single best thing i ever did (which was the first time i did it) was i noticed that the ground around our apple trees was in similar shape. I hypothesized that since we raked up the leaves every year and hauled them to the landfill that the nutrients from the soil was being robbed and was not being replenished. Many of those leaves had already been gathered and were in a trash can next to me while i was observing this. Many of those leaves had been mowed up and were in tiny little pieces. I decided to grab as much of those mowed up leaves as possible and spread them on the spot for my watermelons the following spring. Boy oh boy did that soil improve. I don’t even think it had even been three weeks, but when i had come back the soil was so lush and smooth as butter. I literally could have planted my seeds with a butter knife. When the soil had been so dry, cracked, and compacted a few weeks before. The leaves did a number of things. They helped preserve moisture, which in my dry climate is critical. They also provided a cover where, insects, fungi, and bacteria could work to break down the leaf litter and release those nutrients back into the soil. The watermelon project that year was a success, and i am still planting seeds descended from that mass cross today. I didn’t have as much luck this year as i did not do the same things as i did that year, but i still have a watermelon variety that at least grows to maturity here in my climate where few other watermelons grow and where no one in there right mind would ever try, and don’t.

Some have also mentioned trying fish aquaponics where there is a symbiotic relationship with the fish. I don’t know much about that, but it doesn’t sound like a bad idea.

My two cents,


Hi @tomfff

This also concerns me, and I am searching the web for options.

It is hard to emulate the natures own system, using mycelium and microbes to convert plant materials to useful substances in the soil, as the processes involved are not totally understood, and it will be hard to aquafy the nutritions from the earth.
Andrews suggestion of using leaves is interesting, but the question is if the useful materials will leave the leaves in a form that is useful.

Other approaches.

  1. Organic fertilizers are available. I do not know if it has been tried with the FC, but it has been used with success in other aeroponic systems.
    It seems like Kelp also can be a good alternative.

  2. Re-use of the fertilizers.
    Without practical experience with the FC, it is a bit difficult to see what could be done on the system side. I assume the vapor is waterized, and ends in a tank. Maybe it could be possible to re-use this.

kind regards


Øyvind, you make a good point. The question is whether ground up green leaves are in a form that plants can directly use or not. I don’t really know the answer to that right now, but i hope to experiment with it later on. The logic in my head went like this “that since plants need certain ratios of nutrients, then why can’t i feed a plant other ground up plants”. Sounds a little cannibalistic, but i do wonder if it will work.

You are right though that most of the time in nature it seems microorganisms like bacteria and fungi make a huge impact on breaking down more complex nutrients (like chemical fertilizers) and putting them into a form that is more easily absorbed by plants. Whether they are needed at all or whether some sort of organic composting method using fungi could work i don’t know, but planning to actively research and experiment.

Watching old Paul Stamets videos has me really all excited about mushrooms and mycology right now. His talk about how Oyster mushrooms can break down black oil spill contaminated soil and restore clean ecosystems is amazing and inspiring. If they do so much in nature why can’t we cultivate them ourselves and put them to work in our own controlled systems?


Two directions I’d like to point you in.

  1. Aquaponics is the same as Hydroponics but the reservoir contains fish. The fish waste is then circulated through the plants, this method works well for NFT, but is difficult to use with Aeroponics due to the organic matter.

  2. Compost Teas are useful to not only boost your microbial activity but can be used with some crops as the entire nutrient recipe. There are many types, I suggest watching some YouTube videos and getting a feel for what the ingredients are and then you can idealize your own.

I will say that both of these methods will not provide you with enough nutrients go take many crops to harvest, the majority of aquaponics and tea crops are leafy greens.

I hope that helps,
Peter Webb.


Hi Bio
Yes Stamens work is amazing!
Have you also seen this?

I am trying to figure out if we can make the base and side plate of mycelium instead of plastic.

Regarding plant leaves… Many chemical substances in the leaves are probably so bound that water cannot dissolve them. But that does not mean that some nutritions may be released. It might be difficult to directly measure whats in it, but as all other factors are controllable, it might be possible to measure the effect.
@Webb.Peter : Thanks - I will also check it out. Everything that can reduce cost is important.

kind reagards


The answer is no. The plants root system can’t absorb the elements until their broken down into the single raw chemical element. Pouring water alone on a plants leaf (or any organic mater) won’t break it down into the raw chemical elements.

Not just broken down into the raw chemical elements, but into the single element form. As an example hydroponic nutrients use chelated iron, as well as separate iron and calcium in their nutrient concentrates. The reason they keep them separate is so they don’t bond with each other, when they do bond they become unusable to the plants, leading to both iron and calcium deficiencies. Chelated iron has a resistance to bonding with calcium as well, and is why it’s the preferred iron source for hydroponic nutrients.

Most people hear the words “Chemical” and get scared, but everything on the planet is made up of chemicals called the periodic table of elements. Whether their derived naturally or by synthetic means, the chemicals/elements are still the same. Plants cant tell the difference, and nor do they care how they were derived, they only care if their usable. This is the most misunderstood aspect of the term “Growing Organic” that most people just don’t know. The see the words “grown organically” so they automatically think it’s healthier or better for you, but that’s simply not true. The plants absorb the exact same chemicals/elements regardless of how they were derived, theirs no difference.

Theirs no benefit to the plants, taste, or nutritional value of the plants growing organically. With that said there is a benefit to the health of the soil ecosystem growing organically. But hydroponics is growing without soil, so organics has no benefit for hydroponically grown plants.

Yes, hydroponics and aquaponics are essentially the same thing. The difference is simply that aquaponics is a method of making your own nutrients from fish waste. These nutrients can be used in any of the 6 types of hydroponic growing methods. The most common used being Drip and NFT systems. But can easily be used with the Aeroponics method as well, and both low and high pressure systems. Sure there can be small particles of organic mater in the water, but it can easily be filtered out before the misters. Fact is even using synthetic nutrients the mister heads still tend to clog up from the dissolved mineral salts (nutrients) in the water, so clogging is a regular issue with aeroponic methods.

While some manufactures will bill their compost teas as a replacement nutrient solution and/or organic nutrients, and some people do try and use compost teas as the entire nutrient source. Trying to do so is not only complicated to get the balance of nutrients correct, but not very efficient either. Compost teas are really just an additive source for inoculating beneficial microbes. Beneficial microbes cant live long suspended in water, and there isn’t a constant supply of organic mater for the microbes to convert into nutrients even if the microbes could live forever suspended in water.

While I agree with you about trying to use compost teas as a complete nutrient solution, aquaponics is vastly different. While the concept of aquaponics is simple, it’s actually complicated to get nutrient balance consistently correct. It also takes lots of bio filter space, the right fish to plant ratio, more organic mater than just fish waste, and a lot of time and dedication. But for those that invest the space, time and effort into their aquaponics systems, reap the rewards of a divers productive garden.

In a world where perfection and constancy is what sells at the market, the inconstancy of the quality of the fruit using aquaponic methods is a huge issue, and why the method isn’t more widely used. Where for home growers who aren’t selling the produce will use it even if they all aren’t the same size or have blemishes, consistency and perfection aren’t as important. For commercial growers it’s simply easier, more efficient, and more cost effective to grow hydroponic crops using synthetic nutrients. After all, if you can reduce costs and make more money, that’s what maters in a world where money is king.


Good to know. Compost teas still interest me though as the idea is to take advantage of bacteria (and maybe fungi, though i have my doubts, maybe yeasts?) to help break down plant matter and complex chemicals back into something plants can use. I personally have had more success of using compost teas to bioboost my normal compost pile rather than directly using it in the garden.

To me the word organic also includes not using pesticides, though that is my personal view. Legally it is a different matter entirely and i believe pestices and herbicides can be used and something still be called “organic” so the term organic is a bit misleading and ambiguous at best. Though i dont think pesticides are really relevant for this discussion.

I think the OP was more interested in sustainability, maximizing recyclable nutrients, and eco-friendly long term. Since synthetic Nitrogen fertilizers are made from natural gas, and natural gas is a finite resource i think investigating other ways to obtain adaquate nitrogen to be worth while. Though at this point your right synthetic is much easier to use right now. Not sure whether that will always be the case.

What about combining these ideas together. For example, using compost teas to speed up normal compost to then use in your aeroponic system. Or to use compost tea and to add it to your aquaponic system with the fish which then later the fish waste makes it to your plants. Or cultivating algae in DIY Bioreactors which then you feed to bottom feeding fish like catfish and use that in an aquaponic system.

Maybe even use mycology and mushrooms and molds in normal compost intelligently as well.

Just throwing ideas around.


Hello BioLumo,
Every micro organisms (and by microbes that means every micro organism both plant and animal) can fall into one of two categories, either beneficial or a Pathogen (helpful or harmful). In either case their life cycle is to feed and break down organic mater. Beneficial microbes wont harm plants, Pathogens cause disease and harm plants. But both beneficial microbes and Pathogen break down all organic mater to it’s raw elements. In the case of plants we try not to introduce pathogens to our plants so we only try and use beneficial microbes. However you will always have pathogens present, you cant avoid them.

Think of it like a war. The side with the most soldiers wins. By increasing the numbers of the beneficial microbes, you kill the enemy and keep them from taking over. There will always be survivors and more ready to take over, but as long as the beneficial microbes outnumber the pathogens they will never be able to gain a foothold and take over.

While beneficial microbes will feed on pathogens, when there isn’t enough pathogens for them to feed on so they can breed and multiply, they need an alternate food source to survive. Namely the organic mater. Compost is far richer in organic mater than most typical soils. That’s why they call it compost tea, not soil tea. Combine that with the fact that commercial synthetic fertilizers kill the microbes in the soil, over time that can even render the soils ecosystem baron of microbiology (or close to it). Depending on how heavily used the fertilizers were, the effects can last decades. It can take many years for enough of the synthetic fertilizers and pesticides to leach out of the soil and start rebuilding the soils ecosystem of microbial life again.

[quote=“BioLumo, post:8, topic:703”]
To me the word organic also includes not using pesticides, though that is my personal view. Legally it is a different matter entirely and i believe pestices and herbicides can be used and something still be called “organic” so the term organic is a bit misleading and ambiguous at best. Though i dont think pesticides are really relevant for this discussion.

Your right, the term “organic” means different things to different people, But by law to get a “certified organic” certification, it requires using organic pesticides, or better yet beneficial insects to combat pests. It can take as long as three years for a grower to get a certification because the soil has to be tested for microbial life as well as traces of pesticides and synthetic fertilizer levels. so it can take years to get the soil in a condition to fall within certification levels.

However the terminology of each level of certification, and their the legal definition can be ambiguous like you said because it varies from state to state, and even county to county. I forget the actual wording used, but many states and areas even allow farms to sell their produce as organic while in the process of getting the organic certification, even though they haven’t gotten it yet. They just change the terminology of the certification slightly to make the legal distinction. However it’s very misleading and ambiguous to consumers that not only don’t understand the levels of certification, but don’t understand that it changes from area to area depending on where the produce was grown and came from.

While the legal definition of certified organic includes using both organic fertilizers as well as pesticides. I personally think of them separately for the very reason I mentioned earlier. That is plants cant absorb elements unless their in their raw chemical single molecule state. Since I grow everything hydroponically (withough’t soil) I don’t have to worry about maintaining the microbial ecosystem of the soil in my hydroponic systems. So there is no benefit to trying to use organic nutrients for hydroponically grown plants. But I do prefer to use beneficial insects or organic pesticides like neom oil to combat pests. I didn’t really mention pesticides since like you, I didn’t think it was really an issue or concern. But from a legal standpoint, both fertilizers and pesticides need to be addressed for certification.

As far as I know there is no such thing as free energy. That is being able to use and replace the amount of energy used without using more energy. In that scene nothing is sustainable. Plants consume nutrients as energy, the only way to recycle those nutrients is decomposition. Decomposition takes energy itself in the form of heat energy, microbial life, and acids. That’s what aquaponics is all about. Naturally decomposing organic mater and recycling those decomposed raw chemical elements for the plants to use. But again it’s a complicated posses to get the balance of the entire ecosystem just right.

Given the right conditions, compost is already a breading ground for microbial life, and decomposes quickly. Can you speed up the decomposition by making compost teas out of the compost and reintroducing it back into the compost? In theory yes, but how much will it really speed up the decomposition? Is it worth the effort? With enough trial and error under controlled conditions those questions may be able to be answered. .

Regardless again it’s about balance, and getting the balance right. Just because the compost has decomposed doesn’t mean the raw chemical elements are within balance for a specific plant. That’s like saying if you poured every liquid in your refrigerator into one pitcher it will make a good drink. What comes out of the compost is only as good as what goes into it. Not only do you need to control the amount of each specific material going into the compost, but you need to know the rate of decomposition of each as well to even get close to a balanced nutrient coming out of it. Essentially you would be trying to use compost tea as a complete nutrient solution, so you have to control the balance of nutrients in it. Now can you do trial and error and testing to determine those values to come up with workable recipes? In theory yes, I don’t see why not. Is it worth the effort and practicable? That’s yet to be determined, and I don’t know of anyone working on such a project. But even if so it won’t replenish itself, you’ll have to continue brewing more compost to replenish what the plants consume.

I believe many people are already doing that very thing. However as I keep mentioning, maintaining the balance of the ecosystem is important. You don’t want to just add things willy nilly to your fish ponds, doing so can kill your fish. That’s all part of what makes aquaponics complicated, maintaining a balanced ecosystem with the right amount of fish that provides all the nutrients the plants need in a balanced formula, while not harming the fish and other living plants or animals in the ecosystems either. Theoretically if you have a balanced ecosystem there isn’t a need to to add any new microbes to the ecosystem since they would be feeding and breeding in healthy numbers to begin with.

I have known one person who wanted to grow algae in hydroponic systems, but for use as medicine. That’s easily done, but again it’s all about balance in the ecosystem. Diversity is important for balance, but you have keep the balance under control or things can go very wrong. Like with everything in nature, everything is connected and affects everything else. Again, while the concept of aquaponics is simple, the practice of getting it right is far more complicated.

Compost is chocked full of fungal spores. Fungi is a major part of decomposition. you can’t avoid fungi. Fungal spores are all around you, even in the air you breath as well. But not all fungi is beneficial to plants. Soil manufactures often sanitize the final product to kill fungi before they sell it. You can inoculate compost with beneficial fungi, and many people do. I often use Trichoderma and Mycorrhizal fungi myself. Not just in soil, but I sometimes inoculate the growing medium with them before I use it, or add them to the nutrient reservoir. While these fungi are both good for killing pathogens and protecting the plants root systems from disease, they also attach themselves to the plants roots and help the plant absorb nutrients and aid root development. The use of beneficial fungi is already widely used. Some soil manufactures even add them to their potting soils and planting mixes.


I just joined the group today after hearing Caleb Harper on TED. The talk peaked my curiosity which brought me to this forum. Wow! This particular forum is truly amazing, full of information and I am anxious to continue reading more posts/information. Ok, onto my comment:

I just want to add an addition piece of information after I read your post. I moved to the ‘organic’ lifestyle many years ago and I agree with much of your comment regarding “grown organically”, with one exception. Growing organically also encompasses foods grown without herbicides and pesticides which is, to many, the key component to eating organically. Does Roundup ring a bell? Those two toxins are what is dangerous to the soil microbes with much of it affecting the symbiotic relationships in the soil and in effect the nutritional basis, with a by-product to effect the cells in our bodies when we eat from foods sprayed with these chemicals.
I know this is not what this forum is about but felt I needed to add to the definition of growing organically.
Thank you for your time.


Apparently I skipped by the comments about pesticides/herbicides from Nov 3. So my concern was already discussed. Disregard my comment.
Lessons learned :blush: