This experiment is to identify whether kitchen waste water is helpful for plants growth and determine the options of kitchen waste water for plant growth. It was conducted with 5 different types of water - 3 types of kitchen waste water, water with plant food and tap water.

Among the multiple cycles conducted, plants fed with the three kitchen waste water types grew comparatively better than the other 2 types of water. Particularly, 'Rice Rinsed Water - Second Wash' had some positively contributing factors when compared to the other types of water which helped the plant grow relatively better and survive for longer duration. The plants fed with vegetable washed water also seemed to have some unique factors that helped good growth of the plant.

Since the plants grew better with kitchen waste water I wanted to research further on why did the plant grow better fed with kitchen waste water compared to the other 2 non-kitchen waste waters and what were the components that helped the plant grow better with kitchen waste water 

According to my research, the positive part about kitchen waste water is, it helps the plant a lot for its growth because of factors mentioned herewith. The main factors that seemed to have helped the plant growth are the existence of the following nutrient due to the leaching process

• Phosphorus

• Potassium

• Calcium

The other nutrients are starch, iron, nitrogen, magnesium and sulphur.

The reason why rice rinsed water - first wash is not as beneficial as the second wash was that the concentration of the composition was too high that was detrimental to the plant growth. From this, we infer that even too much of natural fertilizers and chemicals can harm the plant and that is why the rice rinsed water - first wash did not do better than rice rinsed water - second wash. 

On further study on the plant food chemical composition versus mung bean plant growth requirements, the mung bean plant requires low nitrogen feed. However, the type of plant food used during this experiment has a 10% nitrogen composition which is considered high and hence could have some negative effect on the plant growth.

Variables Involved in this experiment:

• Types of water - 5 types

• Potting soil (Golfgreen Garden Soil)

• Planting pots - 5 

• Mung bean seeds

• Sunlight

• Controlled temperature

• Ruler

Types of Water

Why Mung Bean? 

Given the short duration of time available to complete multiple cycles of the experiment, it was required to identify a plant that grows in a short time. The mung bean is readily available and meets the criteria without any other specific requirements.

For this experiment, five identical pots of approximately 5 litre capacity were filled with the same quantity of garden soil in each of them.

The mung bean seeds were soaked in water allowing it to sprout for 2 to 3 days. Well sprouted seeds were selected & planted in equal quantity in each pot. All five pots with the same soil type were maintained under the same environmental conditions like sunlight, quantity of water fed, room temperature & other growing conditions. The key difference between the pots was the type of water used to feed the plants in each pot.

The plants were watered regularly with different types of water to each pot & their growth was observed. The details were recorded by observing the health, measuring the height and by taking photographs on their health. The details were collected over 4 to 5 weeks and were analyzed using a plant health score^[1] to arrive at the final observations. The same cycles of procedure were repeated and observations recorded.

Note: This experiment was conducted during the winter months of Canada, & hence the plans were maintained indoor for the entire duration

^[1]  A ten-point health score arrived at 2 points each for the following parameters: 1) New leaves, 2) Liveliness, 3) Survival count, 4) Sign of any disease, 5) Height of plants

Among the five pots, the plants in the one fed with Second Wash Rice Rinsed Water grew comparatively better than the other plants or survived longer.

At the end of 5 weeks, plants fed with First Wash Rice Rinsed Water also survived but it did not grow as healthy as the Second Wash. Meanwhile in the next cycles the vegetable wash water grew comparatively similar to the rice rinsed water - second wash and the rice rinsed water - first wash maintained it's health but still did not show any growth benefits. 

It was observed that the overall plant growth on all pots were relatively better during the second cycle possibly due to warmer weather conditions.

Since the experiment was conducted in multiple cycles, the concept of health score was introduced to get a consistent and accurate health measurement of the plant growth. 

To arrive at the health score reading, the plants were measured using the following 5 different parameters

• Liveliness - Fresh looks, juicy stems and green leaves, not dry and tilting

• Height - To measure the heigh of the plant, if the plant maintained the same height the same score as last time will be given. If the height of one plant grows 3 - 5cm taller in a pot, the score will be increased by 0.25. If the pot has 2 or more plants that grew 3 - 4 cm taller in a pot, the score will increase by 0.5. If the pot has one plant that grew 5cm or more taller than the last time measured, the score increases by 0.75. Lastly, if 2 or more plants height increase by 5cm or more the score was given 1 point more. If the score exceeded 2 points the score would remain 2.

• No infections - Dry leaves or stems, white spots on stem or leaf, holes developing on the leaf, fungal growth (white spots) on the soil, curly leaf tips, etc

• New leaves - Growth of new leaves from time to time 

• Survival count - Reccording the number of plants in the pot that are alive from the initial sprout and during the day of health measurement

On the first day of each cycle that is observed, all the parameters will be given 1 point as a base score, because the plants have not grown fully and hence I can not predict which plant will grow well so just to be fair 1 point was given to start the new cycle. Once a pot has 0 plants living the overall score will be given 0 because there is nothing to observe since the plant is dead. 

These parameters were used to measure the health score out of 10, and for each parameter the maximum points that were given was 2 (as explained in the height related point above). The plants were observed and given a health score using the parameters every 4 - 6 days. Lastly the health scores were populated in a tabular column and plotted as a bar graph.

Out of the 5 different pots taking different types of water, the plants fed with vegetable wash water and rice rinsed water - second wash grew better than the other three pots. In the first cycle, rice rinsed water - first wash grew decently well, but the tap water and the plant food with water did not stand out at all. At the end of the second cycle, the health score of plants in those 2 pots was decently high. 

It is clearly seen that using the vegetable wash water and rice rinsed second wash water helped the plants grow much better than normal tap water.

What Next?

• More research can be done on the chemical compositions of the different types of waste water

• Extend this experiment outdoor and during all seasons (especially spring and summer)

• Try the experiment with different plant seeds

• Experient with other types of waste water

1. Water conservation - Using a portion of the water used for washing organic produce for plants can save many litres of going into the drain. Typically, when Calgary had water scarcity during June 2024 re-using kitchen waste water for growing indoor and outdoor plants, could have been an option for the citizens.

2. Environment friendly - Using kitchen waste water is more friendly than chemical fertilizers like plant food for plants and according to the research that was done the kitchen waste waters have similar nutrients compared to the plant food 

3. Save on fertilizer cost - Since the plant food comes with a cost, everybody can just use kitchen waste water and still get the same or better benefit than using the plant food 

4. Reduce soil pollution - The soil can be affected by the manmade chemicals in the plant food compared to no cost, soil friendly, natural chemicals and it is much better for the soil

• Seed selection - Not all seeds will grow onto a plant. To avoid this error, only the well sprouted seeds were planted. Even then, each seed's potential to grow could be different

• Scoring method - The scoring method could have some error because of the way they were measured. If one pot had only one or fewer plants surviving, and the other pot that was fed a different type of water had many plants surviving but in bad health the pot with many plants gets a higher score for survival count. However, the other pot gets a higher score for the other parameters which could mislead the overall score.

• Winter weather -  As said in the procedure, this experiment was conducted in the winter months of Calgary and the plants were maintained indoor. The plants might not get enough sunlight because of unclear skies and the temperature was also colder than optimal for weather 

• Mung Bean, Britannica - https://www.britannica.com/plant/mung-bean

• Mung Bean, Wikipedia - https://en.m.wikipedia.org/wiki/Mung_bean#:~:text=Mung%20bean%20(Vigna%20radiata)%20is

• How to Grow Bean Sprouts in a Jar? https://www.seriouseats.com/how-to-grow-bean-sprouts-in-a-jar-slideshow#:~:text=Lentils%20and%20mung%20beans%20have,grow%20to%20about%20an%20inch

• Using Household Waste Water On Plants - https://vric.ucdavis.edu/pdf/fertilization_householdwastewater.pdf

• Is Rice Water Good for Plants? https://www.allrecipes.com/why-you-should-save-your-rice-water-8676338#:~:text=Nutrients%3A%20Rinsing%20rice%20makes%20a,a%20variety%20of%20B%20vitamins

• Learn How To Grow Mung Beans - https://www.gardeningknowhow.com/edible/vegetables/beans/how-to-grow-mung-beans.htm

• ​​Label Image of Schultz Liquid Plant Food (10-15-10) composition, https://i.ebayimg.com/images/g/5RAAAOSwY3BdaPYG/s-l1600.webp 

• Packaging Image of Golfgreen Garden Soil, https://media-www.canadiantire.ca/product/seasonal-gardening/gardening/soils-mulch-hardscaping/1590218/golfgreen-garden-soil-28-3l-03ac3c65-5fed-461a-900e-84749af98a1d-jpgrendition.jpg  

• Banner Image - Photo by Unknown Author is licensed under CC BY-SA-NC

I would like to thank Ms. Underdahl who was the coordinator for CYSF Science Fair 2025 for her guidance, encouragement and support whenever I reached out for help, as well as my class teacher Ms. St.Louis.

Also, I am thankful to my parents for their support in helping for the preparations of the experiment, teaching presentation and reporting techniques.