aquaponics: the context

Below is an essay representing the cumulative research of an Independent Project conducted during the Fall Term of the 2015-2016 academic year. In three separate sections, it explores the context of aquaponics: the agricultural industry and sustainability, hydroponics, and aquaculture.

For details on the benefits of aquaponics itself, see ‘aquaponics: the benefits’


Agriculture: The Big Issue(s)

*ominous music*

Within the past half-century, food production has raced ahead of population growth, decreasing overall hunger despite a doubling population. The ‘Green Revolution’, an overarching initiative encompassing the concentrated development of industrial technologies and agricultural processes in developing regions, is credited with curbing a global catastrophe: without the surge of agricultural production, a great many people of the world would be starving.

However, in no sense are we hunky dory.

Within the next half-century, the population is projected to plateau at around nine billion people (Godfray). In response to both the increase in per capita income, which will shift dietary standards to be more resource intensive, and the increase in capita itself, food production is expected to have to more than double.

Why is that so bad?

Because we cannot have another Green Revolution.

To be more precise, we cannot afford another Green Revolution; industrial agriculture relies on a plethora of resources to function – nutrients, water, chemical fertilizers and pesticides – as well as tons and tons of space. Many of these resources are being rapidly depleted, at much faster rates than they can regenerate. We cannot afford another Green Revolution because we have run out of arable land, because we have depleted groundwater aquifers, and because we have used up all the nutrients in the soil from which we harvest our crops. On top of that, the application of pesticides, use of synthetic fertilizers, and practice of intensive irrigation, all damage the natural environment. On an even broader scale, monoculture eats (food pun!) away at biodiversity and natural ecosystems, predicating a future landscape of wheat and barley and more wheat and more barley. We cannot afford another Green Revolution because industrial agriculture, is, at its core, unsustainable.

Land: Consumption of and Competition for Space

Land use is one of the greatest limiting factors of industrial agriculture, especially in developed countries; according to estimates based on the linear continuation of the trends of the Green Revolution, in order for food production to double, an additional ten percent of land would have to be used to cultivate crops (Tilman). Such an estimate contradicts the trend of decreasing farmland in the United States, which has shrunk by over forty thousand acres since 1997. Factors contributing to this decrease are multifaceted – they collectively can be traced to rapid urban expansion and economic competition for land. In both developing and developed countries, arable land, loosely defined as land suitable for the cultivation of crops, is a precious resource; the same soil that facilitates crop growth is also apposite for construction, or often hosts valuable natural resources (Science Online).

In addition, many of the negative side effects of industrial agriculture can be held accountable for the hesitancy to simply dedicate more land to the cultivation of crops. Factors such as eutrophication and irrigation, two processes directly tied to the land used for commercial agriculture, carry with them serious consequences that few could consider lightly.

As it becomes increasingly clear that land is a resource that will not soon be made available to industrial agriculture, the focus shifts to alternative and more efficient processes that can increase food production through the capitalization on available space.

Water: Irrigation

Of the agricultural land currently in use, only around sixteen percent is irrigated (Tilman). That sixteen percent accounts for roughly forty percent of crop production (Tilman). A substantial amount of cultivation is dependent on irrigation; during the past half century, much of the increased food production can be traced to the introduction to or improvement of irrigation in developing agricultural systems. However, as beneficial as irrigation is to farms, it does draw upon a critical resource: water.

In order to increase agricultural production, irrigation must also be expanded, and short of technological advancements that imp roves, to a groundbreaking (groundwater pun!) degree of efficiency, usage of water resources by irrigation, it will also require a large increase in water consumption.

Water is already considered a regionally scarce resource. Entire geographic regions, such as the one occupied by China and India, will soon lack the water resources to maintain per capita food production from irrigated lands (Godfray). Many regions, including the United States and those aforementioned, have a significant portion of water used for irrigation pumped from aquifers, which are replenished at a much slower rate, rapidly depleting local water resources (Science Online).

As of today, urban water use, preservation and restoration of existing bodies of water, freshwater fisheries, and protection of natural resources all compete with irrigation for water resources. In addition, some of the negative impacts of irrigation hold communities back from devoting additional water resources to irrigation – excessive irrigation can cause soil degradation and eutrophication.

Nutrients: Nitrogen and Phosphorous

One of the largest and most widely known issues that industrial agriculture faces is eutrophication, a process in which run off with high concentrations of chemicals, largely nitrogen and phosphorous, have devastating impacts on local ecosystems.

Due to soil degradation, industrial agriculture relies heavily on synthetic fertilizers to provide nutrients for crops. Fertilizers are rich in nitrogen and phosphorous, which are critical to plant growth. However, due to the larger scale of commercial agriculture, crops are often saturated with such materials, with excess substance entering local ecosystems, carried by runoff water or spread through the air.

Eutrophication occurs when the nitrogen and phosphorous are absorbed into natural systems, for which the two substances are usually limiting nutrients (Tilman). The sudden influx of nitrogen and phosphorous disrupts the biochemical cycles of the ecosystem and damage the organisms that it supports.

Even as efforts are made to reduce eutrophication, projections show that following the same mechanisms of the Green Revolution, to meet the demand for double food production within the next half century, nitrogen fertilization would have to increase by almost 6.8 fold, and phosphorous fertilization by 3.5 fold (Tilman).

*ominous music climaxes*

            The Green Revolution was built on industrial agriculture, a system which, at its core, relies heavily on the elimination of ecological factors, and complete control over artificial processes. Such a philosophy encourages monoculture, nutrient saturation, and use of synthetic stimulants. It brought ‘advanced’ techniques and technology to underdeveloped regions of the world and immensely boosted local agricultural production. However, the problem we face now is not a question of where we farm, but how we farm. The pressure to find a solution to world hunger grows rapidly with our population, and industrial agriculture’s ravenous consumption of resources and disregard for the natural environmental bar another brute-force surge in industrial productivity from being a viable solution.

What’s Next?                        

            Significant efforts have been made to improve industrial agriculture – such efforts focus on systemic or technological improvements that streamline or increase the efficiency of various processes. Procedural developments such as the use of conservation tillage or the practice of contour plowing, and mechanical innovations such as the invention of genetically modified crops, are all geared towards increasing production. However, these methods, however effective, only build upon the existing system and principles of industrial agriculture, and can only carry it so far.

Emerging trends such as organic food, recently made into a national standard, which aim to reduce the use of harmful chemicals, and buy-local, which encourages smaller scale, localized production that is less harmful to the environment and beneficial to local economies, are indicative of a shifting view towards contemporary food production.

So how do we feed two billion yet unborn people within the next fifty years?

We need a Green Revolution.

Not the same Green Revolution that boosted agricultural production half a century ago, but a revolution green in an entirely different sense of the word; industrial agriculture is a system of food production that must change at a fundamental level to become viable as a means of providing sustenance in our resource-strained future.



Unearthing the Truth (behind by soilless horticulture)

            Hydroponics and industrial farming seem very similar; in fact, aside from the substitution of an active substrate for a more easily controlled nutrient solution, the two are, at a conceptual level, not that different. However, the development of hydroponics systems have diverged sharply from that of industrial agriculture. Hydroponics, the cultivation of vegetation without the use of soil, focuses on resource efficiency, especially nutrients, the waste of which is one of the largest drawbacks of industrial agriculture.

Hydroponics can be traced as far back as the ancient Egyptians, but was popularized in the 18th and 19th centuries; developments in two aspects of horticulture were made – first, the study of plants’ nutritional needs, and second, the control of disease organisms (Raviv). Such advancements allowed for more effective manipulation of growth substrate, the material in which plants were grown. Hydroponics were used largely in scientific experiments to analyze and study plant growth, but was later adapted for the cultivation specific plant types. In particular, floriculture and off season plants, both difficult to harvest at larger scales through traditional agriculture, proved much easier to produce due to the malleability of the hydroponics system (Raviv).

The same characteristics have pushed hydroponics to the forefront of modern agricultural development. The scalability and plasticity of the system is used to create space and resource efficient methods of food production. In the face of mounting issues presented by industrial agriculture, hydroponics presents interesting potential as a sustainable and economically viable form of food production.

The Root of it All: Nutrients

Hydroponics is based almost wholly on the function of the root systems of plants. Roots absorb a vast majority of the nutrients needed for plant growth; these elements include potassium, sodium, calcium, magnesium, sulfur, phosphorous, and nitrogen (Raviv). Nitrogen and phosphorous are two especially important nutrients in plant growth; they are both considered natural limiting nutrients, meaning that in most ecosystems, such elements are defecient. In other words, plant growth is directly limited by the amount of nitrogen and phosphorous available to them (Raviv).

In nature, root systems will actively seek out such nutrients within the soil, which are replenished by biological cycles of the ecosystem (Raviv). In grounded agriculture, synthetic fertilizers provide most of the nutrients for plant growth. In hydroponics systems, roots are instead immersed into a nutrient rich solution, allowing for direct absorption. The use of a nutrient solution in hydroponics carries two main benefits; first, it allows for greater control over the amount  and concentration of nutrients given to the plants, and second, it removes the energy invested by root systems to find the elements within the soil (Raviv).

In addition, external factors such as temperature and pH can affect the absorption of nutrients as well as the health of the plants (Raviv). In hydroponics systems, it is much easier to regulate such environmental conditions.

The System: Adaptability and Potential

There are several basic types of different hydroponics systems; substrate systems include some form of inert substrate that have structural or moisture retaining functions. Non-substrate systems directly expose the root systems to the nutrient solution. These includes systems such as nutrient film technique, in which water is constantly cycled throughout the system, or aeroponics, in which nutrient solution is regularly sprayed onto exposed roots as mist (Simply Hydroponics).

A nutrient-film-technique hydroponics system in which nutrient solution is continuously circulated through the grow bed by a pump, with water and excess nutrients returning to the reservoir via a drain tube.

Variability and flexibility are key characteristics of hydroponics systems that arise as an emergent property of their various components; the method of cycling water, structure of vegetation growth, and measuring of nutrient concentration, are three distinct aspects of every system that can be manipulated according to circumstance and adapted and improved individually to increase the efficiency of the system as a whole.



Fish as Food

            Although aquaculture, the cultivation of aquatic organisms as a form of food production, has existed long before the large industrial complexes we see today were developed; the first published work on the subject dates back as far as 475 BC, although historians speculate that it could have existed before (Tidwell).

Today, aquaculture plays a significant role in global food production. 15% of protein produced worldwide is attributed to aquaculture – in addition, aquaculture has the fastest growing rate of production, 6.6% since 1970, amongst other methods of food production such as terrestrial farmed meat and capture fisheries, which have grown 2.8% and 1.2% respectively (FAO). Additionally, the other two forms of protein production face serious shortcomings – terrestrial livestock require large tracts of land and agricultural production for grazing space and livestock feed. Marine fisheries are already exploited at unsustainable rates, with 53% fully exploited, 28% overexploited, and 3% completely depleted in the past year, with only 1% recovering from depletion (FAO). Aquaculture, given its relatively recent but rapid development, seems to hold great potential to become a primary form of protein production.

Fishy Business

Aquaculture systems differ from many other forms of food production due to the characteristics of most aquatic organisms; fish are all, to some degree, highly dependent on the conditions of their environment. Temperature, salinity, acidity, and levels of oxygen are just a few of the main aspects of every aquaculture system that must be considered. In many ways, aquatic organisms are more similar to crops than other livestock in the sense that they are directly products of their environmental conditions – aquaculture industries aren’t so much raising fish as they are growing them (Tidwell). The manipulation of these conditions allows aquaculture systems to exert a great degree of control over the productivity of the inhabiting aquatic organisms – specific conditions can be artificially created in order to accommodate particular species or to replicate certain environmental conditions.

In addition to environmental conditions, the management of biological waste is one of the most significant aspects of an aquaculture – the regulation of excrement is critically important for the health of the organisms, but the process for disposing waste water can be complicated and costly. The waste of aquatic organisms contain large amounts of ammonia, which is deadly in high concentrations. In addition, ammonia is often passively diffused from the gill systems of fish. In nature, this is a process which cuts the energy cost of metabolic processing and expulsion of the waste (Tidwell). In closed aquaculture systems, such a characteristic leaves the fishes’ vulnerable to ammonia concentration in environment.

The development of the aquaculture industry is focused on improving the ability of systems to regulate these factors – temperature, salinity, acidity, oxygen levels, and waste. The variety of these conditions also account for the great diversity in methods of cultivation – a number of types of systems have emerged which have advantages in specific aspects, but less so in others.

Open Systems

Open system aquaculture systems utilize natural ecological processes to address their three primary functions; temperature is regulated by the open environment. Waste management and oxygen production are both regulated by the local ecosystem, usually through bacteria and algae, but also through the physical circulation of water (Simpson). Algae produce oxygen through photosynthesis, and both heterotrophic bacteria and fungi break down fish waste as a part of their natural biological processes (Tidwell). The fish waste can be converted into less toxic forms and absorbed by other organisms within the environment, such as plant matter. In open systems, cultivation of aquaculture is almost entirely dependent on the environment. In addition, because they are reliant on natural processes, systems are initially low yield, and can only support biomass limited by the magnitude of the local ecosystem (Tidwell). Such systems usually involve some kind of container immersed within a body of water such as an ocean or lake.

Semi-Closed Systems

Semi-closed systems, too, rely on natural processes to drive basic aquaculture function. However, the aquaculture systems are usually isolated in manmade structures. Such structures can be more easily manipulated, and thus optimized for production – semi-closed systems can be a thousand times more productive than fully open systems (Tidwell). Semi-closed systems circulate water through adjacent natural water systems such as rivers or waterfalls, relying on natural processes to manage waste, oxygen, and temperature. A semi-closed system can be thought of as an open system which outsources biological functions to nearby ecosystems and sacrifices a stable local ecosystem for a greater degree of control over factors such as predation, water quality, and productivity. The cost of such control is a greater amount of energy required for regulation, and vulnerability of closed biological systems, which include susceptibility to water quality issues and disease (Tidwell).

Closed Systems

In closed systems, all of the basic functions are, to some degree, affected by human intervention. The greatest advantage of closed systems in that they grant the operator precise control over almost all aspects of the aquaculture system. As with semi-closed systems, such control comes at a cost– the operator assumes full responsibility for all of the ecological processes that would otherwise by accounted for by the natural environment. In order to alleviate such a burden, many closed aquaculture systems incorporate certain mechanics with some element of natural biological processes. The most prominent example is the use of biofilters – the colonization of heterotrophic bacteria to help regulate fish waste (Tidwell).

Hybrid Systems

Many recent aquaculture systems have developed to include characteristics of all three types of systems, mixing and matching various components to compensate for specific shortcomings, overcome environmental limitations, and streamline overall efficiency. Aquaculture holds enormous potential as a means of protein production – the industry is pushing towards sustainable but intensified production, incorporating natural processes to simultaneously reduce environmental impact and resource consumption.



“Overview: Major Trends and Issues.” Global Statistical Collections. Food and Agriculture Organization of the United Nations, n.d. Web. 05 Oct. 2015. <;.

Food and Agriculture Organization Overview Major Trends and Issues; very basic overview of current trends in aquaculture; shallow but broad information.

“FAO National Aquaculture Sector Overview (NASO).” FAO National Aquaculture Sector Overview (NASO). Food and Agriculture Organization of the United Nations, n.d. Web. 05 Oct. 2015. <;.

National Aquaculture Sector Overview United States; comprehensive summary of aquaculture in the United States – topics covered include history, economics, practices, and institutional framework.

Tidwell, James. Aquaculture Production Systems. Ames, IA: Wiley-Blackwell, 2012. Ebrary. Proquest. Web. 5 Oct. 2015. <;qtype=subject;locg=1&gt;.

Aquaculture Production Systems; emphasis on physical systems and technical components of aquaculture farms. First few chapters encompass conceptual factors – historical context and development as an industry, systemic characteristics that drive all aquaculture farms, and extensive examples of various types of aquaculture and how they differ depending on function and location.

The State of World Fisheries and Aquaculture, 2000. Rome: Food and Agriculture Organization of the United Nations, 2000. Ebrary. Proquest. Web. 5 Oct. 2015. <;qtype=subject;locg=1;page=1&gt;.

State of World Fisheries and Aquaculture 2000; comprehensive report that describes a broad range of topics, focusing mostly on empirical data and the statuses of various aspects of aquaculture. Includes the impact of fisheries on ecosystems and biodiversity, and outlines the policies and sociopolitical factors driving the industry forward.

Edwards, Peter. “Aquaculture Environment Interactions: Past, Present and Likely Future Trends.” Aquaculture 447 (2015): 2-14. Science Direct. Web. 5 Oct. 2015. <;.

Aquaculture Environment Interactions; Past, Present, and Likely Future Trends; analyzes the development of aquaculture systems and practices. Focuses on the relationship between aquaculture and the environment, stipulating how aquaculture systems both affect and are affected by factors such as location, industrial development, and technological development. Also discusses the benefits of improvements of efficiency and their potential in helping the aquaculture industry develop to meet rising demands.

Simpson, Sarah. “The Blue Food Revolution.” Scientific American 304.2 (2011): 54-61. Web. 5 Oct. 2015. <;.

The Blue Food Revolution; focuses on contemporary fish farms, the context of aquaculture in global food, and the most prevalent issues with the current aquaculture industry. Establishes the discrepant ratio of population growth and meat consumption to agriculture and food production. Describes current fish farming methods and the potential improvements of these systems.

Raviv, Michael, and Johann Heinrich Lieth. Soilless Culture: Theory and Practice. Amsterdam: Elsevier Science, 2008. Ebrary. Proquest, Dec. 2008. Web. <;.

Soilless Culture: Theory and Practice; Discusses six main topics applicable to hydroponics – first, the significance of soilless culture in agriculture (history and context), second, the functions of the root systems of plants (nutrient absorption and significance), third, the physical characteristics of soilless media (interaction between media and plant), fourth, irrigation in soilless production (flow/cycle of water), fifth, the technical equipment involved in soilless production (imposition of human process in biochemical cycle), and sixth, the chemical characteristics of soilless media (specific process of nutrient flow in soilless media).

Gold, Mary V. “Sustainable Agriculture: Definitions and Terms.” Sustainable Agriculture: Definitions and Terms. United States Department of Agriculture National Agriculture Library, Sept. 1999. Web. 05 Oct. 2015.

Sustainable Agriculture: Definitions and Terms; Discusses the theory and practice of sustainable farming. Provides historical development of sustainable agriculture as a contrasts it at a conceptual level with industrial farming. Briefly outlines the impact of agriculture on ecologic, economic, and social spheres. Includes various perspectives on the subject that outline various philosophies regarding sustainable agriculture, and stipulates a ‘future concept’ of farming.

“Commercial Horticulture.” Horticulture. 2007. Science Online. Web. 5 Oct. 2015. <;.

Commercial Horticulture; outlines some of the major issues that industrial agriculture faces, including but not limited to, unsustainable consumption of natural resources (water and soil), economic conflict (land use), and elimination of biodiversity (susceptibility to disease etc. ). Also discusses some of the benefits of greenhouse crops and hydroponics systems – lower water use, fewer fertilizers and pesticides, less labor, less damage to the environment, and higher yield. The system also allows increased regulation and adjustment of nutrient and pH levels. Additionally, the system can be (more) easily modified to meet a variety of specifications.

“Natural Systems Agriculture.” Encyclopedia of Biodiversity. 2012. Science Online. Web. 4 Oct. 2015. <;.

Natural Systems Agriculture; defines natural systems agriculture as an approach to food production that incorporates biodiversity and ecology in emulation of natural cycles and discusses the inherent flaws within industrial agriculture (unsustainable fuel and nutrients / harmful chemical components).

Despommier, Dickson. “The Rise of Vertical Farms.” Scientific American 301.5 (2009): 80-87. Web. 5 Oct. 2015. <;.

The Rise of Vertical Farms; addresses one of the major issues with industrial agriculture – land use and population (to feed). Proposes vertical farming as a potential solution, outlines it conceptually, and discusses practical applications of such systems. Establishes hydroponics as a viable basis for the development of prototypes, citing its structure (nutrient and water flow) as conjunctive with vertical farming.

El-Serehy, Hamed A., Magdy M. Bahgat, Khaled Al-Rasheid, Fahad Al-Misned, Golam Mortuza, and Hesham Shafik. “Cilioprotists as Biological Indicators for Estimating the Efficiency of Using Gravel Bed Hydroponics System in Domestic Wastewater Treatment.” Saudi Journal of Biological Sciences 21.3 (2014): 250-55. Science Direct. Web. 5 Oct. 2015. <;.

Cilioprotists as Biological Indicators for Estimating the Efficiency of Using Gravel Bed Hydroponics Systems in Domestic Wastewater Treatment; explores the potential of using waste water as a nutrient solution in a hydroponic system with the primary goal of treating the water (as opposed to food growth). Mimics a wetland ecosystem. Contains specific experimental procedures and data, as well as a discussion of the results and a conclusion to the experiment.

Adrover, Maria, Gabriel Moyà, and Jaume Vadell. “Use of Hydroponics Culture to Assess Nutrient Supply by Treated Wastewater.” Journal of Environmental Management 127 (2013): 162-65. Science Direct. Web. 5 Oct. 2015. <;.

Use of Hydroponics Culture to Assess Nutrient Supply by Treated Wastewater; an experiment conducted on the basis of reusing treated wastewater for crop irrigation. Primarily used for analysis of the nutrient/chemical composition of the two samples of wastewater used.

Godfray, H. C. J., J. R. Beddington, I. R. Crute, L. Haddad, D. Lawrence, J. F. Muir, J. Pretty, S. Robinson, S. M. Thomas, and C. Toulmin. “Food Security: The Challenge of Feeding 9 Billion People.” Science 327.5967 (2010): 812-18. Web. 21 Nov. 2015.

Food Security: The Challenge of Feeding 9 Billion People; article containing information about trends of agriculture, food production, and global hunger. Strong context of increased demand for food and analysis of current trends and projections of growth versus demand.

Tilman, D. “Global Environmental Impacts of Agricultural Expansion: The Need for Sustainable and Efficient Practices.” Proceedings of the National Academy of Sciences 96.11 (1999): 5995-6000. Web. 21 Nov. 2015.

Global Environmental Impacts of Agricultural Expansion: The Need for Sustainable and Efficient Practices; emphasis on current flaws of agricultural production and its failure to meet rising demand of production.

Tilman, David, Kenneth G. Cassman, Pamela A. Matson, Rosamond Naylor, and Stephen Polasky. “Agricultural Sustainability and Intensive Production Practices.” Nature 418.6898 (2002): 671-77. Web. 21 Nov. 2015.

Agricultural Sustainability and Intensive Production Practices; in depth analysis of current agriculture and major flaws. Explores potential improvements and areas most in need of redress in order to meet rising demands for both increased production and sustainable practices.

Despommier, Dickson. “The Vertical Essay.” Vertical Farm RSS. N.p., n.d. Web. 21 Nov. 2015.

The Vertical Essay; explores Despommier’s idea of the vertical farm comprehensively. Both explains vertical farming theory, describes potential benefits, outlines possible methods of integration and expansion, and highlights the need for centralized, sustainable methods of food production.

Steinfeld, Henning, Pierre Gerber, Tom Wassenaar, Vincent Castel, Mauricio Rosales, and Cees De Haan. “Livestock’s Long Shadow: Environmental Issues and Options.” Livestock’s Long Shadow: Environmental Issues and Options. Food and Agriculture Organization of the United Nations, 2006. Web. 21 Nov. 2015.

Livestock’s Long Shadow: Environmental Issues and Options; discusses terrestrial livestock – explores environmental impacts and economic and production trends. Places terrestrial livestock in the context of agriculture and food production.

“Basic Hydroponic Systems and How They Work.” Simply Hydroponics. Simply Hydro, n.d. Web. 21 Nov. 2015.

Basic Hydroponic Systems and How They Work; very basic overview of general types of hydroponics systems.

Naylor, Rosamond L., Rebecca J. Goldburg, Jurgenne Primavera, Nils Kautsky, Malcolm C. M. Beveridge, Jason Clay, Carl Folke, Jane Lubchencho, Harold Mooney, and Max Troell. “Effects of Aquaculture on World Fish Supplies.” Issues in Ecology 8 (2001): 1-12. Ecological Society of America. Web. 21 Nov. 2015.

Effects of Aquaculture on World Fish Supplies; comprehensive report measuring major trends within the aquaculture industry and their impacts on the environment. Explores food efficiency within various systems.