Three Key Issues with Conventional Farming and How Aquaponics Can Help

Conventional agricultural practices have made it possible for us to provide over seven billion people with food. This is a great achievement, however, there are more than a few problems associated with the current system. Not only does it have direct negative environmental impacts, it is also unsustainable in the long term. Thus, in order to secure the future of  coming generations we must find alternative solutions.

So how does aquaponics come in the picture? Surely, we are not suggesting that we should stop using agricultural land and grow all our food in aquaponic systems. But we do believe that this technology can play an important role in producing more food sustainably, and that together with changes in the way we use land, transport, store and – perhaps most importantly – think of our food, it could help us achieve food security in the future.

So, what’s wrong with conventional farming and how is aquaponics different? Here are my top three reasons why we should come up with a new strategy for producing food and what role aqaponics could play in it.

1. Takes up lots of space

We have already converted around 50% of habitable land on Earth to farmland, which has significantly contributed to the loss of species and natural habitats. In order to meet the increasing demands of a growing population more and more land is being put to food production at the expense of biodiversity. In addition to putting many species in danger, conversion of natural areas like tropical rainforests also speeds up climate change, which in turn poses a threat to agriculture itself. Ironically, since more people will need not only more food but also more living space, this vicious circle will result in competition for land from urbanization and agriculture.

Aquaponics offers a means to producing more food without using up more land by spreading vertically instead, using “spare” urban spaces in and around buildings, or even below ground. As long as light (artificial light is just fine) is available, these systems can function perfectly well anywhere from the edge of a parking lot to a corner in the office on the 10th floor.

2. Inefficient and wasteful

Plants grown in the fields can only take up a portion of water and fertilizers applied. A simple reasons for this is that roots can only access a limited volume of soil and are therefore only able to absorb what is in their immediate surroundings. Although some nutrients are delivered to them by the mass flow of water, a lot will get washed away before they could be absorbed. Many ions, especially phosphates, also get bound to soil particles and become immobile, with the bulk of them remaining out of the plants’ reach. Since plant productivity is positively correlated with nutrient and water availability, in order to maximize yields we dump large amounts of fertilizers on fields and flood them with water. This is unsustainable for several reasons. On the one hand, production of nitrogen fertilizers is costly and consumes lots of energy, mainly from burning fossil fuels (I don’t need to explain why that’s a bad thing, do I?). On the other, phosphorus, the second most important nutrient for plants, is a finite resource: we get it from mining rock phosphates, which are running out at an alarming rate. As regards water use, irrigation messes up with the natural water cycle, threatening drinking water supplies and likely causing unpredictable changes in climate. To make things worse, intensive farming practices also lead to loss of soil productivity and erosion, rendering fields barren and unusable in the long run.

As opposed to conventional farming, aquaponics uses no fertilizer or, as a matter of fact, soil. Instead, plants are grown in a special medium consisting of clay balls infiltrated with water rich in nutrients. These are supplied by bacteria that convert fish waste into nitrates, an ideal source of nitrogen for most plants. This nutrient-rich solution is circulated throughout the system (i.e. fish tank + units containing plants), which means that all of it is freely accessible to the plants. Excessive watering is not necessary either, only the volume taken up by plants and losses due to evaporation need to be replaced. To put it short: no fertilizer, minimal water input, no nutrients wasted and maximum uptake efficiency resulting in high yields. If that wasn’t enough, aquaponic systems are also quite cheap to install and cost close to nothing to maintain, their sole expenses being those of the fish food, some low power water and air pumps, and the occasional bucket of water. Sounds like a fair deal, huh?

3. Polluting

Another issue with agriculture is its huge carbon footprint that results from the burning of fossil fuels for industrial fertilizer production and use in various machinery, not to mention long-distance transport of produce. High CO2 emissions, which contribute to global climate change, are only part of the problem, though. Chemicals applied to fields can get into the environment, polluting rivers and freshwater supplies and damaging natural habitats, poisoning animals or even humans. Pesticides and herbicides can leak into the groundwater and rivers and may eventually end up in the oceans, causing harm to ecosystems far away from the original source. Moreover, in the same way that antibiotics can’t make a difference and also kill “friendly bacteria” in our system, pesticides can often have negative effects on mutualistic fungi and bacteria living in the soil that, under normal circumstances, would help plants acquire nutrients or become more resistant to pathogens and harsh environments. Although fertilizers are not directly toxic, if they get into the environment they can disrupt ecosystems, which may have serious consequences.

In aquaponics a closed system is used, so normally nothing can get out into the environment. For the same reason, it is also unlikely that anything gets into the system, meaning that there is less need for disease and pest control. As mentioned earlier, this technology doesn’t rely on fertilizers and so does not add to the carbon footprint of the industry. Growing vegetables in the city also helps remove CO2 from the air, as well as contribute to lowering emissions from transportation of food (there is no need for it if it’s all grown on your doorstep!).

So, what are we waiting for? Let’s grow a sustainable future with aquaponics!

And where are the bacteria..?

This is one of the most frequently asked questions we get from people about our recently installed aquaponic system opposite the Students’ Union of the University of Sheffield.

aquaponics

And the answer is usually something like this: “Well, you know, in the water. Probably everywhere – we think so, at least.” And that is about as much as we could say. The truth is, we don’t know much about where they are, what they are doing, how many of them there are or what exact strains we have got in the system. (In our defence, it’s not easy to tell with microscopic organisms without the necessary lab equipment!) All we know for sure is that they are there and are doing a pretty good job.

But wait a minute. If they are invisible, how can we be sure they really are there? That is a fair question – but one we have a fair answer for, too.

Despite their minute size, nitrifying bacteria are key players in aquaponics. They are responsible for converting nitrogenous waste produced by fish into readily available nutrients that can then be absorbed by plants. To be more exact, ammonia is first turned into nitrites by a certain type of bacteria, which is then further metabolised into nitrates by another, providing a form of nitrogen suitable for plant uptake. Measuring the concentrations of these compounds in the water using some basic equipment can give an idea of whether and how much conversion is taking place.

ammonia-test

If there were no bacteria present, we would find virtually no nitrites or nitrates and an ever increasing level of ammonia from fish waste (not to mention far-from-healthy-looking plants as a result of nutrient deprivation). In contrast, in our system we get constant, low levels of ammonia, no nitrites and slightly variable, but usually fairly high concentrations of nitrates, as well as healthy, fast-growing vegetables. As far as we know, this can only be explained by simultaneous removal of ammonia and production of nitrates, something that neither fish nor plants are capable of doing, which clearly suggests the involvement of an invisible third party.

OK. So they are there, doing whatever it is that nitrifying bacteria do, supplying nutrients for our plants in the process. But how did they get there in the first place? First of all we created a welcoming environment, using expanded clay balls for our grow media:

clay-balls

These balls have a very high surface area, so there’s lots of space for the bacteria to take hold (if they want to, that is – they might prefer floating around, we are not sure). Then we added a little powdered fish food (before there were any fish in the system) to create some ammonia for the bacteria to feed on, and finally a little vermicompost we hoped would contain some suitable bacterial populations. Yes, we know it is not exactly what you would call a reliable way of introducing the right microorganisms to the system, but as they don’t sell nitrifying bacteria in little test tubes in garden centres (yet…), this seemed to be the most workable solution. And then all we had to do was add some fish and seedlings and wait for the bacteria to start doing their job. And… hey presto! There they were 🙂  At least we think so!