Research has shown that people with various healthy eating patterns were less likely to die from cardiovascular diseases, cancer, or respiratory disease compared to other participants in the same study (Shan et al., 2023). Despite the numerous health benefits, a healthy diet is not accessible in all places of the world or even in many urban areas of the United States. Food deserts are geographic locations where an absence of grocery stores within convenient traveling distance makes it difficult or impossible to access healthy food options. Most residents routinely resort to consuming highly processed fast food that lacks important nutritional qualities. The USDA estimates that about 19 million residents live in these low-access areas, demonstrating how prevalent urban food deserts are (USDA, 2022). Since many people living in food deserts would also not have access to a backyard, an indoor garden that waters itself via hydroponics presents a reasonable solution.
The benefits of hydroponic growth methods are demonstrated beyond the ability to cultivate food indoors. Traditional soil agriculture requires steady weather patterns, large labor costs, and immense land usage, all of which are threatened by climate change on Earth today. In addition to being heavily impacted by the erratic weather patterns caused by global warming, conventional outdoor agriculture contributes to as much as 20% of all greenhouse gas emissions, especially as a result of its low land efficiency and high reliance on fertilizers (Ahmed et al.). These issues with conventional agriculture stress the need for the adoption of a farming method that can be more land-efficient and require fewer fertilizers.
These issues stress the need for hydroponics-based farming. A hydroponics system works by using water infused with nutrients found in soil to create a body for crops to grow in to save on space and allow farming in a more controlled environment. According to Sharma et al. (2023), soilless culture conserves both water and land, using up to 90% less water and up to 80% less land than traditional agriculture. Controlled environment plant growth systems also deliver more accurate nutrient ions to the plant than soil-based agriculture, resulting in more efficient nutrient use, and reducing the use of excess fertilizers that contribute to climate change (Manthiram and Gribkoff). This technique allows for precise control over the plant's environment, including the nutrients, pH levels, and water content, producing biochemically and nutritionally enriched, high-yielding crops (Goh et al., 2023; Sharma et al., 2023).
There are seven main methods of hydroponic farming. Of these seven, the two most common are Nutrient Film Technique (NFT) and Deep Water Culture (DWC) farming. In NFT systems, a thin film of nutrient-rich water flows over the plant roots, which are supported by a sloping trough or channel. The roots are exposed to the nutrient solution, and any excess solution is recirculated. NFT is suitable for crops with relatively small root systems, such as lettuce and herbs. DWC systems suspend plant roots in a nutrient solution, usually in a reservoir. An air pump is used to oxygenate the solution, and the roots are suspended in the nutrient-rich water. This method is often used for growing larger plants like tomatoes and cucumbers. A study that compared the efficiency of both methods concluded that the NFT system outperformed the DWC system in terms of energy-use efficiency, indicating higher growth and better energy savings associated with NFT systems (Gillani et al., 2023). By weighing this conclusion along with the fact that NFT systems are more suitable for growing our preferred plant, lettuce, we chose to use an NFT design for our research project.
When comparing the NFT system to a traditional agricultural system, a study found that the hydroponic yield of romaine lettuce outperformed the yield from the substrate (soil) method of cultivation (Dutta et al., 2023). In addition, another study using aggregate data for already existing hydroponic designs in Arizona in 2015 showed that using artificial lighting allowed lettuce plants to be able to be harvested multiple times in a year – as much as 10 times compared to conventional farming which usually includes just one harvest (Barbosa et al., 2015). The study further demonstrated that hydroponics produced 11 times as much food per square meter and used 13 times less water (Barbosa et al., 2015). However, the three studies also observed that hydroponic systems consumed more electricity due to the operation of sensors, microcontrollers, and actuators. For this reason, our design focuses on using gravity as much as possible to transport water, limiting energy usage. While our initial design does not include renewable energy, a main goal of future alterations is to attach the system to a solar power source to reduce energy waste. One other concern we hope to address is the price associated with building a hydroponics system. According to a 2022 study that compared the cost of building and maintaining a similar-sized hydroponics garden and conventional farm, the hydroponics garden costs 1.5 times as much to build and maintain (Gumisiriza et al., 2022). The study found that the main reason for this price difference was the need for expensive custom parts used in hydroponics (Gumisiriza et al., 2022). In order to address this issue, our main goal was to limit the use of expensive parts in this design, relying on PVC pipes and cheaper, smaller UV lights to reduce costs and to keep the total design below a cost of 500 US dollars.
In planning what the design would look like, existing research offered several facets to focus on in creating a successful design. Our main requirement was to demonstrate lettuce growth through a design using commonly available materials. We then compared this lettuce growth to lettuce grown at home in standard conventional farming conditions. In order to build the design, we created 4 different working gaps in each level of PVC pipe and secured the system to a wooden board along with artificial lighting to allow for greater compartmentalization. A successful design will provide regular water flow, will demonstrate nutrients successfully reaching the plants, and will be able to grow at least 4 different lettuce plants at a time.
Recognizing these requirements and issues to address, if this type of hydroponics-based design is further improved, we can improve food security for those in urban areas, saving on both space and water. This could allow individuals and community organizations to store hydroponic farms in community gardens, buildings, and roof-tops to produce even more fresh, accessible food even with limited space. An improved design will need to use less energy to be sustainable, but past precedent has demonstrated the space efficiency of hydroponics and the potential for future growth when used in conjunction with more renewable energy. For this reason, we will be initially focusing on using gravity as much as possible to transport water, in order to limit energy usage. In future research, we also hope to attach the system to solar-powered systems to reduce climate change impacts. If both of these are done properly, hydroponics may be able to replace conventional farming and provide a more efficient alternative to conventional farming, which is important as the US and global population continues to rise, increasing food demand, especially in rapidly growing urban areas. Thus, with this research, our goal is to demonstrate how compared to the conventional methods of farming that draw the nutrients out of the soil, hydroponics-based solutions offer a viable and effective alternative.
Procedures
To create the hydroponics system, the first step was to create and secure a wooden backboard. This acts as the mainframe to attach the rest of the structures to and should be secure. We chose a 4-foot by 6-foot wooden board with 0.5-inch thickness as that was what was available, however, a board as small as 3.5-by 3-foot would have been sufficiently sized. The next step was to put the PVC piping together in a configuration shown in Appendix C. We used 4-inch PVC pipe parts as those were available, but any PVC with at least a 2.5-inch diameter and 6 feet of total length should work. To set up the PVC piping, we used a 90-degree and 45-degree elbow to keep both PVC lengths closer to horizontal as shown in Appendix A and modeled in Appendix B. Along the side of the PVC, we drilled a 1.5-inch diameter hole every 6.25 inches to provide space for the lettuce to grow. We then filled these gaps with planting cups containing Long fibered sphagnum moss (a moss that acts as a growth medium to retain water), as well as string coming out of the bottom so that water reaches the plant through capillary action. At the top of the piping, we drilled a half-inch diameter hole to allow our plastic tubing to pump water into the system. At the bottom, we drilled and tapped 2 holes to allow for the insertion of two taps (with half-inch outer diameters and ⅜-inch inner diameters). We then used metal PVC straps to attach the PVC to the board. Following this, we screwed in 20-watt plant growth lights one foot above where each of the lettuce plants would grow, which can be plugged into a wall outlet. We then set up a 40-gallon tank at the bottom (although future designs could use as little as a 5-gallon tank, and ran the piping intake and outtake to it. We then connected the piping to a sea-water pump that already existed in the lab and connected it to a wall outlet using a 5-volt, 5-amp AC to DC power adapter. We also added an ¼-inch restrictor into the piping coming out of the pump to further reduce water flow. In addition, we added an Arduino connected to a relayer to keep the pump on for two minutes at a time and then to turn it off, to prevent the pump from burning out. Following the completion of the main design, we then added a pre-mixed Nutrient Solution at a ratio of one teaspoon per quart of water. Appendix D provides images showing the design as a whole as well as some of the more specific designs. Appendix E includes the materials used to create the Hydroponics design.