Turn your kitchen waste into plant food

In nature, the concept of waste as we understand it is unheard of. One species' waste is another species' food. What we term as waste is an integral part of the food cycle – living things grow, die and release nutrients which in turn serves as sustenance for other living beings.

But modern man has abandoned this circular method for a linear approach. We take, use and dispose. In this way, we eat up non-renewable resources and often produce toxic waste. Even when the apparently harmless, perfectly bio-degradable kitchen waste ends up in landfills, it produces methane – a greenhouse gas that contributes to global warming and climate change.

There is an easy way to utilise kitchen waste at home, though. A way that mimics nature's technique of recycling resources and does more good than harm.

Many rooftop gardeners start off with perfect, nutrient rich potting soil, but the soil becomes depleted of nutrients and organic matter after a year or two. A gardener actually needs to amend and replenish the soil on a regular basis.

Biodegradable kitchen waste can be used as a source of various macro and micro nutrients essential for plant growth. For example, used tea leaves contain all the main three nutrients – nitrogen, phosphorus and potassium – as well as some trace minerals. Egg shells are rich in calcium, while onion skin is a source of magnesium, copper, iron, calcium and potassium. Banana peels have potassium and a small amount of nitrogen, phosphorus and magnesium. Green leaves and vegetable scraps are full of nitrogen, and so on.

Adding organic matter to soil leads to the rise in organic carbon in it, which is essential for microorganisms living in the soil. These microorganisms convert nutrients to plant-available minerals. Organic matter amends the soil, increases porosity, promotes aeration and helps hold moisture.

The simplest and most commonly practiced way to use kitchen waste is to bury them under the soil. Within a month or two, if you dig again, you will probably not find any trace of it.

If you do not want to do the digging, you can also just create a layer of mulch with the kitchen scraps on top of the soil and let it be. This method is advisable only for rooftop gardens where there is plenty of sunlight. This may end up being a little smelly in sunlight deprived areas, like balconies, especially if the layer is thick. The scraps will turn grey and slowly disappear into the soil. Also, this should not be done in a pot with young plants.
In both cases, if the soil has earthworms in it, no worries. The worms will eat the decomposing organic matter, and the worm manure will enrich the soil. Also, numerous isopods will appear beneath the mulch, who feed on decaying plant matter and help break down the scraps. They are beneficial to the garden "system," and harmless to the plants.

Many people prefer plants to be the only tenant in their gardens and try to get rid of anything else that appears there. But nature is much more complex than what we can see with our naked eyes. Whether we like it or not, the soil is already full of microbes and without them, the plants simply will not grow. The soil in a garden that mimics nature is more alive and you will start to love all organisms, large or microscopic, living in it.

kitchen wastes can be a good source of organic matter for soil. Photo: Ashraful Haque

Vermicomposting 101

A more advanced method of turning your kitchen waste to a high-quality product is vermicomposting. In this method, kitchen scraps are combined with dry leaves, paper, etc., and fed to earthworms. Earthworms then breakdown the organic matter and make worm castings that are nutrient rich and contain less contaminants. Vermicompost is dubbed black gold by many gardening enthusiasts because of its value in improving garden soil.

There is a certain amount of "ewww factor" involved in vermicomposting, but if one can get over it, it is even possible to do vermicomposting inside an apartment. Worms like the dark, moist conditions inside the compost bin, and do not come out unless something is terribly wrong.

The Business Standard spoke to Ariful Hasan, an avid rooftop gardener who has been making extensive use of kitchen scraps at his Kafrul residence for 20 years. Asked how he prefers to do it, Ariful said, "First, I started composting in a large barrel. I used to put all kitchen scraps into it, then applied a layer of soil and repeated the process until the barrel was full. I would collect the compost after a few months.

"But nowadays, I collect banana peels and other vegetable skins separately because they decompose fast. I use a blender to chop the scraps into finer particles and put it into the worm bin. Usually, worms take up to a week to start processing a new batch of scraps, but when chopped, they can start their work within a day. This way, I can produce my vermicompost faster."

Ariful also uses the leachate that drains out of the compost bin. He collects the leachate, adds a little molasses, mustard oil cake, etc., and leaves the liquid for weeks. Then he dilutes the compound with water at a 1:20 ratio and applies it to matured plants. Simply soaking banana peels and onion skins in water for few days and then using the water to water plants is also very effective, Ariful added.

The gardener prepares his potting soil by mixing various composts that he makes at home, pots the plant and lets it grow. When the plant is ready to fruit, he adds his homemade liquid fertilizer at regular intervals – every 4 days to a week – depending on the plant and pot sizes.

So how effective is his kitchen waste turned fertilizer recipe? Ariful gave an example, "This winter, I planted banana tomatoes in 4 litter pots. The plants grew 5-7 feet high and produced 4-5kg of tomatoes in each pot. In a same sized pot, I was able to yield 3kg of cherry tomatoes – a very good produce compared to the pot size."

Ariful advised gardeners to not throw away a single banana peel or used tea leaves. A simple mixture of crushed egg shells and tea leaves does amazing things to potted plants. If someone has enough space for planting, she can use all her kitchen waste in that garden. However, success in turning kitchen waste into black gold requires a little patience, a lot of experimentation and experience. Ariful mentioned that there are many resources on the web, and the number of gardeners using advanced techniques of utilising kitchen waste is on the rise.

Using kitchen scraps to grow a garden has multiple benefits. While it enriches the soil and grows healthier plants, it also helps in disposing garbage.

Besides, it can be an educational project for younger generations who will get to know a bit more about how the natural world recycles everything.

If you have not already, you may start this project right away before the Covid-19 shutdown is lifted.