Students will use the Engineering Design Process to develop and construct an aeroponic garden to grow a food crop. Students will develop and apply an understanding of plant anatomy and physiology related to plant growth and ultimately discuss the possibilities and limitations of using vertical farming to produce our food. Grades 9-12

aeroponics: a technique for growing plants without soil or sunlight in which the roots of the plant are suspended in the air and misted periodically with nutrient-rich water and light is provided by specialized grow lights

aquaponics: a system of aquaculture in which the waste produced by farmed fish or other aquatic animals supplies nutrients for plants grown hydroponically, which in turn purify the water

carbon dioxide: a gas consisting of one carbon atom bonded to two oxygen atoms; the byproduct of cellular respiration in animal cells and combustion of organic materials; essential to the process of photosynthesis in plant cells

hydroponics: the method of cultivating plants using a mineral nutrient solution in a water solvent without the use of soil

photosynthesis: the process by which plants convert carbon dioxide, water, and light energy into sugars and oxygen in order to store energy; the opposite of cell respiration

stomata: small openings in the leaves and stems of plants which can open and close to exchange oxygen and water vapor for carbon dioxide

transpiration: the process by which plants release water vapor back into the atmosphere through their stomata

water cycle: the series of conditions through which water naturally passes from water vapor in the air to being deposited (as by rain or snow) on earth’s surface and finally back into the air through evaporation and transpiration

Factors in Plant Growth
There are six major factors that contribute to plant growth—carbon dioxide, light, nutrients, temperature, and water.  Photosynthesis is the process by which plants store energy by converting carbon dioxide, water, and light energy into carbohydrates (sugars), oxygen, and water. This process requires carbon dioxide, water, and light energy, particularly blue and red light. In addition, plants need nutrients such as nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur, along with seven other trace elements (iron, boron, chlorine, manganese, zinc, copper, molybdenum) as reagents for other processes or cellular structure. Temperature is also important, because different species have different tolerances when it comes to the environmental temperature in which they grow.

Aeroponics
Aeroponics is the technique of growing plants in the air with no soil or other growth medium (a.k.a., "geoponics"). This is done by suspending the roots of the plant in a closed or semi-closed container, and misting them periodically with nutrient-rich water. Aeroponics is similar to hydroponics, without the need to artificially oxygenate the roots, since the roots are suspended in oxygen-rich air instead of water. Aeroponics has found popularity in the form of home gardening as well as in some major commercial farming operations, due to it's very low water use and the ability to grow crops year-round in a tightly controlled, often automated environment that some say leads to greater yields. In addition, aeroponics makes use of vertical as well as horizontal space. It is easy to stack grow beds on top of one another, thus maximizing the crop yield while minimizing the environmental footprint. 

Aeroponic Farming/Gardening at Home
Aeroponics can easily be done at home and even on a small space such as a countertop. When pursued as a hobby, not a livelihood, the term "farming" is changed to "gardening." Desktop and home garden units are sold commercially or can be constructed from readily available materials.

Commercial Aeroponics
Aeroponic farming has seen mixed results in the commercial arena. Though several large-scale aquaponic farms have been started, many have fallen on hard times and closed their doors, in part due to relatively high operating costs compared to traditional farming methods. However, some small-scale operations have seen success, especially in areas where there is a demand for fresh, local, high-value produce in urban areas where land is very limited. Interestingly, the legalization of cannabis in several states may lead to a boom in aeroponic farming, as many of these states require cannabis plants to be grown indoors under tightly controlled conditions.

Successful Aeroponic Gardening
Successful aeroponic gardening depends on a number of factors. In addition to meeting the general needs of the plants (correct lighting, nutrient levels, etc.), it is important that the drop sizes of the mist be of the optimum size for root absorption. Although some success will be had with traditional sprinklers, a serious aquaponic operation should use misters that produce drop sizes of approximately 50 microns. Optimizing the drop sizes may not be cost effective for the purposes of this classroom design challenge, but the systems produced by the students should still work reasonably well. Getting the timing right for the mist cycle is also crucial—water too often and the roots suffocate from too much water, too little and they will dry out. A general rule of thumb is approximately 3-5 seconds every 5 minutes; however, with a much larger drop size, it may be desirable to significantly increase the wait time between mistings to prevent roots from becoming waterlogged and drying out. It may be beneficial to experiment with misting intervals and duration to obtain the optimum cycle.

Temperature is also critical. The temperature of the root zone should be cooler than the leaf zone, as this optimizes nutrient uptake and photosynthesis.  Root zone temperatures should be between 17° and 22°C (62° - 71°F). 

1. Ask students where their food comes from. (farms) Follow up by asking them to describe what they think a farm looks like. If needed, provide prompts to lead students to think about the need for open space, availability of water, adequate climate for plant growth, etc. Most likely, students will begin describing a traditional farm with acres of open space.
2. Ask students if this type of farm land is abundantly available or if it is limited. (limited and growing more limited as population increases)
3. Explain to students that you are going to give them a list of criteria for a "Farm of the Future." Instruct them to think about each criteria as you read it and raise their hand IF they think it can be done.
   • The farm can be located in any climate and still produce food year-round.
   • The farm can be located in a large, urban city with very little open space.
   • No soil is used for plant growth.
   • The farm will use 95% less water than a traditional farm.
4. Show the video Farm of the Future on the projector or view screen. 

Activity 1: What do Plants Need?

1. Open the attached Aeroponic Farming PowerPoint presentation on the screen or projector. Use the presentation to guide a discussion on the needs of plants, addressing common misconceptions about what plants really need to survive and grow.
2. Take 2 minutes and ask students to use their prior knowledge to list everything plants really need to survive and grow. (Slide 3)
3. Before moving to the next slide, ask several students to share at least one item they wrote down.
4. Explain that most people probably wrote things like water, soil, air, sunlight, and heat, but there's more to the story. (Slide 4)
5. Explain that air, water, and heat are definitely things that plants need. Carbon dioxide is obtained from the air, water is taken up by plant roots, and all plants need to be in a temperature that they have adapted to. Ask students about sunlight and soil—do plants really need these? (Slide 5)
6. Explain that plants do not actually need sunlight or soil to thrive. However, plants do need light and nutrients. These can be provided in ways other than traditional soil and sunlight. (Slide 6)
7. Describe how plants can be grown without soil in a variety of ways, including hydroponics, aquaponics, and aeroponics. Explain a little about what each of these terms mean. Explain that special lights called "grow lights" emit certain colors of light that can be used to provide the optimum light for growing plants indoors. (Slide 7)
8. Review the five things that plants need for healthy growth—air, water, heat, nutrients, and light. Explain how each of these essential components for plant life can be provided. (Slide 8)

Three Dimensional Learning Proficiency: Disciplinary Core Ideas Engineering, Technology and the Application of Science: Defining and Delimiting Engineering Problems.

Activity 2: Aeroponic Garden Design Challenge

1. Once your students have completed Activity 1 and can identify all the factors impacting plant growth, project the Aeroponic Farming PowerPoint beginning with slide 9. Introduce the design challenge by explaining the problem (slide 10) and a possible solution (slide 11). Explain your students' role (slide 12) and the steps they will take for their assignment (slide 13).
2. Students will proceed by using the Engineering Design Process to guide their steps in designing their aeroponic garden. Choose one of the following options to guide students through the process. Option 1 is more simple, outlining each step of the process and allowing students to make all of their notes in their handout. Option 2 requires students to create a design notebook and use it throughout the entire process. This option requires more thought and organization, but allows students more creative liberty. Choose the option that fits your class best.
   • Option 1: Give each student one copy of the Aeroponic Garden Design Challenge handout. Inform students that they will follow each step precisely and keep all their notes and observations in this handout.
   • Option 2: Give each student a design notebook (or use existing notebooks) and explain your expectations using the Aeroponic Garden Design Notebook Rubric. You may also provide a good example of a design notebook for students to model.
3. Now that students understand their goal (to create an aeroponic garden) and that they will be keeping all of their notes on their handout (option 1) or in the design notebook (option 2), teach the Engineering Design Process in greater depth.
4. Discuss the career of an engineer as well as the process of engineering. Discuss how science and engineering are connected. Referring to the aeroponic garden students will soon be designing, ask, "Could an engineer successfully design an aeroponic garden if he/she did not understand the science of plant growth?" (No, knowledge of both plant science and technology/engineering are required for success.)
5. Show the Engineering Design Process video.
6. Using the Aeroponic Garden Design Challenge handout, review the entire Engineering Design Process in the context of an aeroponic garden. Inform students they will be following each of these steps shortly. Encourage students to ask questions as you go.
7. Divide students into small groups. 3-4 students is ideal, but larger groups may be necessary depending on budget and availability of supplies.
8. Assign students to complete steps 1-4 of the design process. To save on materials and cutting mistakes on the buckets, require students to have their plans signed off before they begin construction.
9. Once students have their design plans signed off, provide students with the materials and allow them to begin building their prototype. Once students have completed step 5, they should have their bucket constructed, water should be flowing, plants will be in place, and they will have taken all of their beginning measurements and pictures. Remind students of the importance of this step to accurately document the starting point of their aeroponic garden. This step is crucial to accurately evaluate the success of their design.
   • The watering system in each bucket will need to be programmed and controlled so that the water is on for 30 minutes and off for 30 minutes. This can be accomplished using an electric timer with 30 minute increments. However, to expose students to computer programming, complete the Optional Programming Activity below to allow students to build and program their own timers.
   • Review Tips for Classroom Aeroponics for a list of tips and best practices for success in the classroom. 
10. Over the next 3 or more weeks, students should monitor their aeroponic gardens. They should add nutrient solution as needed and record regular measurements and observations.
11. Once the time period has lapsed, have students complete steps 6 and 7 of the Engineering Design Process on their handout or in their notebook.
12. Discuss with students the results and what innovations may have led to the best results. Discuss how the various solutions (including the best solutions) might be improved to result in more plant growth.
13. Once optimal conditions have been discussed, return to the original introduction to the problem and ask your students, "Would it be feasible to grow large quantities of food using aeroponics to conserve land and water?"
14. Have students turn in their completed handout or their Design Notebook for grading.

Three Dimensional Learning Proficiency: Crosscutting Concepts Connections to Engineering, Technology, and Applications of Science: Influence of Science, Engineering, and Technology on Society and the Natural World

Optional Programming Activity (50-60 minutes)
This activity will enable students to program the watering cycle in the aeroponic system they designed in Activity 2. This activity is a great candidate for the "Hour of Code" or other initiatives to expose students to computer programming.

1. Give each team one copy of the Aeroponic Garden Programming Activity instructions and PowerPoint (or make it available electronically). Explain to students that this activity will help them learn how to program a microcontroller to manage the watering cycle of their vertical garden.
2. Pass out the supplies listed in the Materials section of the lesson plan and pictured below. Be advised that students do not actually need the water pump to complete the coding assignment. They should complete the programming and then they can test it with the actual pump later during the design challenge. 
3. Allow students time to work on the activity, and provide help where needed. If you need additional resources to troubleshoot, check out these resources:
   • https://www.arduino.cc/reference/en/
   • https://forum.arduino.cc/
   • https://www.arduino.cc/en/Tutorial/Foundations
4. Some students who have been exposed to coding may finish much earlier than the time allotted. Have these students assist their peers.
5. At the end of this activity, students should have produced a program that will enable them to control the water pump in their own vertical garden and set the spray timing and duration.

After conducting these activities, review and summarize the following key concepts:

• Plants need air, water, light, and heat to grow. Nutrients can be provided in soil or in the water. Light can be provided by the sun or grow lights.
• Aeroponics is the practice of growing plants suspended in the air and providing nutrients by misting the roots with a nutrient-rich solution.
• Aeroponics uses significantly less water than traditional land-based farming methods. It can also conserve space by utilizing vertical space.
• To conserve water and land, aeroponics can prove to be beneficial for the production of some food crops.

Ag Facts:

1. http://www.worldometers.info/water/
2. Bugbee, B. (2013, November 19). Turning water into food. Retrieved from https://www.youtube.com/watch?v=qEbdv3bFKww

Background Sources:

• http://aeroponicsdiy.com/aeroponics-misting-frequency-for-root-growth/
• http://www.aeroponics.com/siteindex2010-12.htm
• https://gardenpool.org/online-classes/how-to-make-a-simple-aeroponics-system
• The following link provides an example of a "5-gallon bucket Aeroponics system" that is the basis of the design challenge for this unit. https://gardenpool.org/online-classes/how-to-make-a-simple-5-gallon-bucket-aeroponics-system
• Garden Pool (n.d.) How to make a simple 5 gallon bucket aeroponics system. Retrieved from https://gardenpool.org/online-classes/how-to-make-a-simple-5-gallon-bucket-aeroponics-system
• Khokhar, T. (2017, March 22). Chart: Globally, 70% of fresh water is used for agriculture [Weblog comment]. Retrieved from https://blogs.worldbank.org/opendata/chart-globally-70-freshwater-used-agriculture
• Massie, L. (n.d.) Aeroponics misting frequency for root growth [Weblog comment]. Retrieved from http://aeroponicsdiy.com/aeroponics-misting-frequency-for-root-growth/

• Aeroponic Garden Kit
• Arduino Controlled Relay
• This High-Tech Farm Grows Kale in a Factory
• Vertical Farming video
• Vertical Farming video and activities