Hydroponics With Recycled Materials: Plastic Egg Tray, Ice Cream Box & Pet Bottle

The recession made everything more expensive. I looked for ways to save on essentials. Since I love cooking pizza and pasta, which are always better with fresh herbs, I decided to grow my own. To keep costs as low as possible, I took a budget-friendly approach by repurposing reusable materials and upcycling items that would otherwise go to waste. This also supports the Sustainable Development Goals (SDGs) by promoting responsible consumption and production, as well as reducing waste.

I used to spend about 50 USD a year on basil, Italian parsley, and dill. Now, I grow more than that each year, without the waste of packaging or the use of chemical pesticides. Although I initially started growing herbs to cut food expenses, it has become a joy watching the plants grow.

1. Plastic egg tray
2. Ice cream box
3. PET bottle (plastic bottle)
4. Sponge
5. Plastic cup
6. Seeds (choose your preferred herbs)
7. Powder nutrients
8. Water

Some plants are not suitable for hydroponics, so it's important to select herbs or small vegetables that thrive in water-based systems. Additionally, temperature and humidity play a key role in determining what can grow well in your environment. Using this method, I have successfully grown basil, Italian parsley, dill, chive, thyme, oregano, lemon balm, sage, and tomato.

I wrap my seed packets in aluminum foil, place them in a ziplock bag, and store them in the fridge. Even seeds I bought four years ago still germinate.

I use 25x20mm sponges. In the past, I cut old kitchen sponges, which also worked well. If making your own sponge, cut it vertically halfway. The sponge should be 25-30mm wide and at least 10mm deep to fit securely into the neck of a PET bottle. You can adjust the size to fit your setup. Make sure the sponge is not too tight or too loose in the neck of a PET bottle, allowing proper growth.

I’ve also used makeup cotton for germination. It works well, but once the roots grow through the cotton, it becomes difficult to transfer the plant to a sponge later. If you don’t mind leaving the cotton attached, you can try using it for germination as well.

Soak the sponges to ensure they have enough water before sowing. It is easier to sow seeds into sponges using a wet toothpick. I usually plant seeds in 2-3mm deep.

When sowing seeds, it's a good idea to plant at least two or three per sponge to account for any that might not germinate.

Once the seeds are sown, make sure they don’t dry out, as dried seeds may fail to germinate. Additionally, you don’t need to add water mixed with powder nutrients at this stage, as the seeds have enough nutrients to germinate on their own. Adding nutrients at this point isn’t necessary and could even harm the delicate new plant if the concentration is too high.

Place the sponge in a plastic egg tray, add water to keep the seeds wet, and ensure it stays damp but not soaked. Add water every day or two to maintain moisture, being careful not to overwater and risk seed rot. I use tape to keep the egg tray closed.

Keep the setup in a warm, well-lit area until the seeds sprout. I place it in a room near a window to ensure it gets plenty of natural light. Note that some seeds require darkness to germinate, so check the specific requirements of the seeds you choose. For seeds that need darkness, cover them with a light-blocking material like aluminum foil until they sprout.

Once you see sprouts and roots starting to emerge through the sponge, it’s time to transfer them to an intermediate setup. I use a compass circle cutter to make holes in the ice cream box lid, then place plastic cups into the holes with the sponge securely inside.

At this stage, I use water mixed with powder nutrients to speed up the growing process. However, I only use about half the amount recommended for fully grown plants, as too many nutrients can promote algae growth.

As long as the roots are in contact with the water, the plants will be fine.

If preferred, skip the intermediate step and place the sponge into the neck of a PET bottle. Results may vary depending on your setup and the plants you're growing.

Once the plant has grown about 4 leaves, I move the sponge with the plant into the PET bottle. I cut off the top of the PET bottle and flip the top part inside, which makes it easier to add water later on. I usually use a 1500ml bottle, but 500ml works if you're okay with growing smaller plants. Larger volumes are better for root growth, allowing plants to grow larger.

Except for the best-grown one, I recommend discarding the others to maximize yield and improve maintenance. One sponge, one plant. I know it’s very sad, but thinning out the weaker plants ensures the strongest one gets all the nutrients and space it needs to thrive. I never get used to this task, but I’ve found it leads to better results (I used to keep them all). However, some plants, like oregano and thyme, are quite tiny and take time to grow, so it might be worth keeping them all until they fully mature.

I use the Kratky hydroponics method, which is a passive method where the plant roots are suspended in the nutrient solution, allowing the roots to absorb water and nutrients as needed. During the summer, when plants generally need more water than in other seasons, I add water about once a week to keep the plants hydrated.

To provide a more controlled environment for the plants, I created a simple greenhouse using clothes drying racks, leftover DIY wood, and an old clear vinyl tablecloth that I no longer use. I use an insect net not to completely close the environment sometime greenhouse became too humid. This setup helps maintain the right humidity and temperature, promoting healthy plant growth. The transparent cloth allows sunlight to filter through while protecting the plants from harsh conditions.

Of course, you can grow plants without a greenhouse!

Once your plants have grown to a suitable size and are ready for harvesting, it's time to enjoy the fruits of your labor! Carefully cut the herbs or small vegetables, and they’re ready to use in your favorite recipes. Whether you're making pizza, pasta, or any dish that calls for fresh herbs, you’ll have a steady supply right at home. Enjoy the fresh, home-grown taste of your work!