1. Introduction

1.1       Engineering Problem:

As the world population increases exponentially, more space is used for residential as well as for the means of production. As agriculture and aquaculture takes up a lot of space, it becomes a constraint for the urban living, and thus, located far away from the urban centers. The agriculture and aquaculture production becomes more expensive as the produce requires heavy transport and preservation infrastructure to deliver them into the urban areas where most of the consumers are. This project aims to solve this problem on a small scale. 

1.2       Engineering Goal:

To develop a system for the production of fish meat and vegetables in an urban setting.

1.3       Specific Requirements

Our design must meet the following requirements: 
  • Must be in urban areas
  • Lack of direct sunlight due to dense built up in urban areas
  • Must be space saving
  • Must be time saving
  • Must be cost saving  

1.4      Alternative Solutions:

1.4.1    Aeroponics
Aeroponics is a method of growing plants whereby the roots of the plants are suspended in the air in a partially closed environment. The plants are anchored in holes, atop a panel of polystyrene foam. This process is very useful as it does not require soil.

Water is used in aeroponics to transmit nutrients, and aeroponics is sometimes considered a type of hydroponics. The basic principle of aeroponics is to grow plants suspended in air and spraying the roots of the plants (that are dangling) with a nutrient rich solution. It is very important that the root zone (also known as the rhizosphere) has enough oxygen. Many plants can grow well with the use of aeroponics as aeroponics is conducted in air combined with micro-droplets of water. (Hydroponics1, 2011)


1. Reduce threats
Aeroponics reduces threats to the plants such as diseases and pests as it is in a partially closed, soilless environment. As the nutrients in the soil attracts pests, there will not be any pests. It can even eliminate pests completely when it is in a totally closed environment.

2. Conserve water
Aeroponics can help conserve a lot of water and also reduces the amount of human labour needed. Normal planting would cause massive water wastage as the plants have to be watered frequently. Using Aeroponics, we only have to spray the roots with a nutrient rich solution. Aeroponics is also typically 100% safe. 

3. More oxygen
Due to the plants being suspended in air, the roots (rhizosphere) is able to get more air. Getting more air for the roots help in mitigating the growth of harmful pathogens (diseases).

4. Require lesser nutrient solution
Compared to hydroponics, aeroponics require lesser nutrients. In aeroponics, the plants can be sustained through maturity with as little as micro-droplets of nutrient solution water.

5. Energy saving 
Since the plants do not receive sunlight, they utilize the carbon-dioxide-rich oxygen in the air to perform photosynthesis. We do not have to provide much light for the plants, only using low-energy lamps to supplement photosynthesis.


1. Pump failure
Pump failure can result in the death of plants within a few hours as the system is very dependant on the pumps.

2. High setup cost
The setup cost of an aeroponics system is not very cheap while the more affordable ones are only for smaller scale systems.

3. Clean root chamber regularly
It is very important to clean the root chamber regularly to prevent diseases to strike the roots, so we have to disinfect the root chamber every so often.

Types of aeroponics systems

Low pressure systems
They are easy to setup and maintain, but are not as effective. This system requires nutrient-infused water reservoirs and small pumps to deliver the nutrients to the plant. The disadvantage of low pressure systems is that it is only limited to small scale systems as the dangerous pathogens and debris tend to collect in the water reservoir. 

High pressure systems
Unlike the low pressure systems, they use a high pressure pump to deliver the nutrient rich solutions to the roots. This system is also structured to include air or water purification devices, special polymers and nutrient sterilization methods. High pressure systems are much more sustainable than low pressure systems for either home-based or commercial purposes. 

Commercial systems
They also use high pressure pumps, but they also use a more complex system of biological matrices. The system contains of technologically pressurized pumps, anti-pathogen/disease systems, heating and cooling apparatuses, photon-flux lamps, along with other automated, continuous processes and devices. 

It is usually recommended to start from a low pressure system and slowly upgrade systems.

1.4.2   Hydroponics

Hydroponics is the method of cultivating plants without soil. Instead of using soil, the plants are grown in a medium and the roots are submerged in a nutrient solution that provides the plants with the essential nutrients. There are many advantages of hydroponics and also disadvantages. 

Types of Hydroponics 

Drip System 
It is the most widely used type of hydroponic systems.There is a timer that controls a submersed pump that releases a nutrient solution, directly to the growing media, to the base of the plants, resulting in an efficient method of irrigating. The water is only applied to a specific place where needed, to the plants’ roots. Less water will be used as the water soaks into the growing media before it evaporates or run off and the water can be reused again.  It also has other benefits which make it useful almost anywhere. It is easy to install, easy to design and is inexpensive. It can also reduce the the chances of disease problems associated with high levels of moisture on some plants. 

Ebb and Flow System
The plants are grown in a plastic tray above the reservoir of nutrient solution as this method requires gravity to do the work. It works by temporarily flooding the tray with nutrient solution and when the water level reaches a certain height, through the use of the overflow method, the water flows back into the reservoir, which then the timer will be switched off. The disadvantage of this system is the possibility of a pump timer failures. This method allows high density planting and also provide a well oxygenated root systems with two ways. When the tray is flooded with nutrient solution, carbon dioxide rich air is pushed out from around the root system. When the pump is turned off, the tray is drained and oxygen rich air is drawn down to the roots. 

N.F.T (Nutrient Film Technique)
N.F.T systems have a constant flow of nutrient solution within the tray. The nutrient solution is pumped into the tank using a hose, flows over the roots of the plants and then drains back into the reservoir. Basically, to have a constant flow of water within this system, the amount of water flowing in and flowing out must be the same. 

Wick System
The wick system is the basic form of a hydroponics system. It is passive and there are four main components: grow tray, reservoir, aeration system and wick. The reservoir is a large container of fertilized water that sits below the grow tray and supplies water and nutrients to the plants. The water in the reservoir must be refreshed every week or so, because the strength of the nutrients diminishes as the plants absorb them. The reservoir is connected to the grow tray by two or more wicks. The wicks transport nutrient solution into the growing medium and to the roots of the plants.

Water Culture
The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants. The biggest drawback is that it doesn't work well with large plants or with long term plants.

1. Fast and easy
Hydroponics is an fast and easy way to grow a wide variety of healthy plants, as we are able to control the water parameters, to suit the plants, easily, providing it with the best environment to grow in. 

2. No soil required
Rather than worrying about getting the correct soil with enough minerals, the plants can absorb nutrients directly from the solution and you can also control the kind of nutrient your plant receive for optimum growth. As the roots are soaked in water at all times, the plants maintain a constant moisture level, not having to worry about it wilting. 

3. Lesser land used
More plants can be grown at a smaller area, as roots can grow without being root bound and no overcrowding occurs. It does not have to be in an open space, exposed to sunlight, as artificial lighting can be used. 

4. Lesser work for gardeners
It is also quite of an independent system, as often watering, weeding, digging are not needed. The gardeners do not have to check the plants very regularly.

5. No pesticides and diseases
These plants grown are more resistant to pests and diseases as no soil means no weeds and insects, therefore no pesticides are needed. 

6. Higher yield rate
Plants grown via hydroponics are healthier and more vigorous, because all the necessary growth elements are readily available. The plants can mature faster compared to those that are normally planted in soil and the harvest/yield rate will be higher. 

1. High setup cost
Although it is very easy to setup and to maintain, the setup cost is not a small amount. There are a lot of things needed but it is relatively long-lasting.

2. Easy spread of diseases can occur if not taken care of well enough
As all the plants in the hydroponics system share the same nutrient rich solution, once the water has the disease bacteria, it can affect all the plants in the system.

Hydroponics for commercial agriculture
There are many advantages towards hydroponics for commercial agriculture. Cultivating plants without soil eliminates the use of bigger land space, and it even allows plants to thrive well in desert areas. The water in the system can be reused and lesser water will be lost through evaporation.

1.4.3    Aquaculture
Fishing is one of mankind’s oldest professions, and seafood has long been a staple of the human diet. But nowadays the seafood you eat at your favorite restaurant is nearly as likely to have been raised on a farm as caught wild. Already almost half the seafood produced for human consumption is farm raised, and that percentage is expected to continue to climb. Our ability to catch fish has simply exceeded the capacity of marine ecosystems to produce them. Yet demand for seafood continues to grow. To fill this gap, governments and the seafood industry look increasingly to aquaculture. 

Aquaculture is the cultivation of both marine and freshwater species and can range from land based to open-ocean production. Some species spend their entire lives on the farm, while others are captured and 

1. Sustainable fishing
Aquaculture is one of the fastest growing food production sectors in the world. As the stocks of wild fish began to diminish, and even before the catastrophic decline of such species as cod, sea bass, and red snapper, aquaculture was seen as a way to satisfy the world’s growing appetite for healthful fish and at the same time a means of sparing wild fish populations and allowing their numbers to rebound. Today, over 70 percent of world fish stocks are fully exploited or are already overfished.

2. Provide a living
It provides a living for farmers and fishermen who witness their usual crops losing value in the markets and their catches disappearing.

As the graph below have shown, the value for aquaculture have been increasing over the years.

3. Produce protein efficiently
Aquaculture is one of the most resource-efficient ways to produce protein. Fish come out well because, in general, they convert more of the food they eat into body mass than land animals.  “Feed Conversion Ratios” indicate how many pounds of feed it takes to produce a pound of protein.  As can be seen in the table below, salmon – the most feed-intensive farmed fish – is still far more efficient than other forms of protein production


1. Spread of diseases
Most farms are put into natural lakes or saltwater coastal regions where local fish exist. The problem occurs when these farmed fish negatively impact the area by introducing toxic micro organisms which then infect local fish and put them at risk of being killed off. Pests such as sea lice proliferate in fish farms and spread out to afflict wild fish.

2. Water Pollution
Wastes from marine aquaculture, which include dissolved (inorganic) nutrients, particulate (organic) wastes (feces, uneaten food and animal carcasses), and chemicals, are flushed (often untreated) into the surrounding waters where they add to the contamination of the water supply. In many areas, notably China, waters are already heavily polluted from sewage, industry, and agricultural runoff. There are also serious questions about the advisability to consume the fish raised in such environments.

1.4.4    Final choice (Aquaponics):
We choose aquaponics as this system can work independently, and produce high quality vegetables and fresh fishes in a sustainable way. It is also a combination of aquaculture and hydroponics. There are many advantages over disadvantages.

Aquaponics is the method of growing crops and fish together in a recirculating system, to maximise the use of energy and nutrients in the system in order to harvest a large amount of vegetation and fish proteins from the system. Nutrient-rich waste water from fish tanks is provided to the plants to be grown hydroponically in grow beds. Beneficial bacteria in the grow beds convert ammonia to an available form of nutrients, nitrates to be taken up by the plants. The removal of nutrients from the water allows the freshly cleaned water to be recirculated back into the fish tank. 


1. Less water usage
Less water is needed for aquaponics as the water is being recycled through the system. It is not necessary to discard or change the water. Only 10% of the amount of water used for soil gardening is required for aquaponics. Thus, aquaponics can benefit poor countries or countries which are prone to droughts.

2. 100% Chemical free
Plants grown in aquaponic system are natural produce. Using the fish’s waste as a natural fertilizer, artificial fertilizers, like nutrient solution, are not needed. Aquaponics does not harbour soil pests which destroys the plants. The most effective way to eliminate soil pest is by using pesticides. This method of eliminating soil pests isn’t favourable because pesticide toxins can be absorbed easily by plants. The chemicals found in the fertilizers and pesticides are hazardous to human health. Thus by using the aquaponics system, consumers can be sure of the health quality and freshness of the fish and vegetables that are chemical and pesticide free. 

3. Less work
The owner can have ready and immediate access to fresh vegetables and live fish when required. They do not need to go the nearest market which might be very far.
Unlike traditional gardening, where straining of muscles are common by bending down to tend to the plants, the aquaponics structure are built around the waist level, thus farmers does not have to bend down. The disabled and elderly people can also work at the comfortable height of the plants and less energy is needed.
Once the system is set up successfully, it requires little effort and time to run it. There is no need to do any hard follow up tasks such as weeding and pest control.

4. Save space
Aquaponics system allows plants to be planted closer together. This is possible because plant roots are constantly submerged in water which is rich in nutrients thus there is no overcrowding.

5. Cost effective
Even though it can be costly to start an aquaponic system and to get it working as a unit, very little money is needed to be invested once it is started and functioning. This is because the plants, which do not require soil, are fed by the nutrients converted from the ammonia produced by the fish. Not having to rely on soil also reduces costs since there is no need to prepare or purchase soil, buy gardening tools like shovels or remove weeds by hand or chemicals. Water is recycled throughout an aquaponics system so only very little has to be added now and then after some is lost through natural evaporation. Very little maintenance is required to keep an aquaponic system running smoothly. 

6. Energy saving
Aquaponics energy usage is from 70% to 92% less than a conventional or organic farm which use fuel and/or petrochemical-intensive fertilizers. All energy used is electrical, so alternate energy systems such as solar, wind, and hydroelectric can be used to power an aquaponic farm. 

7. Sustainable
It is able to maintain a certain level of reproduction without depleting natural resources and hindering the ecological balance because aquaponics is based on a natural process of the correlation between aquatic animals and plants. It is low in irrigation and energy footprint and no fertilizers, pesticides, herbicides is needed.

8. Fast growth
Plants grown in an aquaponic system grow faster. This is mostly due to the abundant and constant supply of nutrients. The fish in the tank supplying the nutrient rich water to the plants also thrive with little effort, because the plants use up the nitrates in the water therefore only clean, fresh water is returned to the tank.

9. Food security                                                                                                                             
Plants grown in an aquaponics system can reach maturity in less time, grow year-round and can be planted more densely. Therefore, constant amount of food provided can be ensured.

10. Environmentally-friendly
Aquaponics reduces water-usage. There is no pollution as chemicals will not be used as the use of chemicals in an aquaponics system can be harmful to the fish, and can disrupt the natural interactions of the fish and their environment. The nutrients, essential for plants’ growth, are made available to them by the fish waste. There is no erosion of soil as there is no need to plough the soil.


1. High setup cost
The system can be expensive to set up as it requires pumping and tubing and tanks.


Why Lettuce?
Lettuce Hydroponics is the culture of plants in a soilless medium. It is a common plant used in hydroponic systems. It is a hardy plant that has a fast growth rate. Lettuce is the first salad crop to be cultivated commercially, worldwide. 

Butterhead Lettuce
It is known to be the most heat tolerant and bolt resistant among all the lettuce types. (Ly, 2012) It has a loose forming crown, with a silky texture to the lettuce leafs. It is known for its sweet flavor and tender texture and goes well with any type of meal. There is moderate amount of vitamin C. It takes around 50 to 70 days to mature. 

Hydroponics System
The water used has to be around 6 to 7 pH. The temperature of the water has to be around 21 to 25 degrees celsius. The lettuce will bolt (flower) in temperatures above 27, which is not desired as it slows down the rate of growth. 

Nitrifying bacteria takes place better at pH lower than 7.5. Removal of ammonia can be done by denitrifying bacteria. Ammonium is oxidised to nitrate (No2). Nitrites (No2) will then be converted to Nitrates (No3). Denitrification increases pH of the water.  

Tilapia fishes are under the cichlids family. They live in water around pH 5-10 and temperatures of 24 to 28 degrees celsius. They live in brackish water, of 5-10 ppm, which is also categorised  as fresh water. They are bottom feeders and requires food that sink to the bottom. The dissolved oxygen level has to be above 5 mg/L, nitrate levels must be below 5 mg/L, ammonia levels must be below 3 mg/L. Ammonia levels should rise up to very high around 1 to 5 hours after feeding.

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