Every week, tons of fruit peels, coffee grounds, wilted leaves, and vegetable scraps end up in common trash — and then in landfills, where they decompose improperly, releasing methane, a greenhouse gas dozens of times more potent than carbon dioxide. But what if these same “wastes” could transform into a rich fertilizer capable of revitalizing pots, gardens, and home gardens?
Home composting is one of the simplest, most accessible, and impactful practices anyone can adopt — and you don’t need a huge backyard or expensive equipment to start. With a bit of organization and the right information, you can close a natural cycle within your own home, returning to the earth what it should never have lost.
In this article, you’ll understand why this practice matters, how the science behind composting works, and — most importantly — how to set up your own system today, even if you live in an apartment.
Why Organic Waste Is an Urgent Problem
Organic waste represents a significant portion of everything we discard in Brazil. According to data from the Panorama of Solid Waste in Brazil, published by the Brazilian Association of Public Cleaning and Special Waste Companies (Abrelpe), organic waste accounts for about 50% of household waste generated in the country. This means that half of what goes into the trash bag could, in theory, be composted.
When this material goes to landfills without proper treatment, it doesn’t decompose in the same way it would in contact with the soil. The lack of oxygen inside the piles of trash favors anaerobic decomposition, which generates biogas with a high concentration of methane (CH₄). Methane has a significantly higher global warming potential than CO₂ over a 20-year horizon — a fact recognized by the IPCC in its assessment reports.
By composting at home, you interrupt this cycle. Organic material decomposes aerobically (with oxygen), generating much fewer emissions and producing, in the end, a stable and nutritious compound. It’s the principle of circular economy applied to everyday kitchen waste.
What Is Composting and How Does the Science Behind It Work
Composting is a controlled biological process where microorganisms (bacteria, fungi) and macro-organisms (worms, mites, beetles) decompose organic matter and transform it into humus — a dark, nutrient-rich substance with a granular structure similar to fertile soil.
The Four Pillars of Home Composting
For a home composter to work well, it needs a balance between four elements:
- “Green” materials (rich in nitrogen): fruit and vegetable peels, salad leftovers, coffee grounds, tea bags, fresh grass clippings.
- “Brown” materials (rich in carbon): shredded dry cardboard, dry leaves, untreated sawdust, non-plasticized paper napkins.
- Moisture: the mixture should have the consistency of a slightly squeezed sponge — neither soaked nor dried out.
- Aeration: oxygen is essential for the aerobic microorganisms that do the heavy lifting. Mixing the composter periodically speeds up the process and prevents unpleasant odors.
The ideal ratio between “green” and “brown” materials is usually indicated around 1 part green to 2 or 3 parts brown (by volume), but it doesn’t need to be exact. The important thing is to observe and adjust: if it smells bad, add more dry material; if it’s too dry and takes too long, add more moist material.
Types of Composting: Choose What Fits Your Life
There isn’t a single composting model. There are options for different spaces, routines, and waste generation profiles.
Aerobic Composting in a Worm Bin (Vermicomposting)
Ideal for apartments and small spaces. Uses worms of the species Eisenia fetida (red wiggler worms) to accelerate decomposition. Produces two valuable by-products:
- Solid humus: excellent fertilizer for pots and gardens.
- Leachate (or liquid biofertilizer): the dark liquid that drains from the worm bin, diluted in water (usually at a ratio of 1:10), acts as a potent foliar fertilizer.
Three-Bin Composter (Traditional Method)
Commonly used in homes with yards. Three plastic (or wooden) boxes are used in rotation: while one is being “fed”, another is maturing, and the third already has ready compost. This system ensures continuous production.
Bokashi (Anaerobic Fermentation)
A Japanese-origin method that uses bran inoculated with effective microorganisms (EM) to ferment organic waste instead of decomposing it. It’s faster, almost odorless (the smell is acidic, like vinegar), and accepts some waste that traditional composting doesn’t easily accept, such as small amounts of meat and dairy. The fermented material needs to be buried in soil or mixed with a conventional composter to complete the cycle.
How to Set Up Your Home Composter: Step by Step
Below is the method for a worm bin in stackable boxes — one of the most popular and recommended for apartment dwellers.
What you will need:
- 3 plastic boxes with lids (can be toolboxes or similar, about 50 liters)
- Drill or heated nail to make holes
- Red wiggler worms (available at nurseries, fishing stores, and community composting groups)
- Initial “brown” material (dry leaves or shredded cardboard)
Step by step:
- Prepare the boxes: make small holes (about 5 mm) in the bottom of the top two boxes (for drainage and worm passage) and smaller holes in the lids and sides (for ventilation). The bottom box has no holes — it collects the leachate.
- Set up the structure: stack the boxes. The bottom one remains without holes to collect the liquid. Place the other two on top, one inside the other.
- Prepare the worm bed: in the middle box, place a layer of 10 to 15 cm of moist “brown” material (shredded and moistened cardboard, for example). This is the worms’ “bed”.
- Add the worms: place the worms on the bed and let them settle for a few days before starting to feed.
- Start feeding: add small amounts of organic waste (peels, coffee grounds, salad leftovers) always covering with a thin layer of “brown” material. Never leave waste exposed.
- Monitor and adjust: check moisture and smell weekly. Stir or add dry material if necessary.
- Harvest the compost: after a few weeks, when the middle box is full, start feeding the top box. The worms will migrate to where there is food. The content of the middle box can be removed when the worms leave.
- Use the leachate: drain the liquid from the bottom box regularly. Dilute in water and apply to plants.
What Can and Cannot Go into the Composter
✅ Can compost:
- Fruit and vegetable peels and stems
- Coffee grounds and paper filters
- Tea bags (without the metal tag)
- Eggshells (help control acidity)
- Wilted leaves and flowers
- Non-plasticized napkins and papers
- Hair and nail clippings
- Straw, sawdust, and hay without pesticides
❌ Avoid in conventional composting:
- Meats, fish, and dairy (attract pests and generate odors — use bokashi for these)
- Very greasy or salty foods
- Feces of carnivorous pets
- Wood treated with varnish or paint
- Plastic-coated paper, carbon paper, or fax paper
- Plants with severe fungal diseases
How to Use Organic Fertilizer on Your Plants
The ready compost looks like dark soil and has a pleasant forest-like smell. It can be used in various ways:
- As base fertilization: mix the compost with the substrate when planting (proportion of about 20 to 30% compost in the total volume).
- As mulch: spread a thin layer over the soil of pots or beds to retain moisture and gradually release nutrients.
- As maintenance fertilization: add small amounts around plants every 30 to 60 days during the growing period.
- Compost tea: dissolve compost in water, strain, and use the liquid for watering — a way to apply nutrients more quickly.
Embrapa, a reference in agricultural research in Brazil, recommends the use of organic composts as a way to improve the physical structure of the soil, increase water retention, and stimulate biological activity — benefits that conventional chemical fertilizers do not offer in the same way.
Collective Composting: When Sharing is the Solution
Not everyone has the space or time to maintain an individual composter. The good news is that collective composting has grown significantly in Brazil in recent years. Condominiums, schools, markets, and even squares in some cities already have community composting points.
If you want to start separating your organic waste but don’t yet have the structure to compost at home, a good first step is to learn to separate waste correctly and find a voluntary organic waste drop-off point in your city. Many Brazilian municipalities have expanded these programs, especially after the revision of the solid waste regulatory framework.
Another possibility is to propose the implementation of a collective composter in your condominium — an initiative that reduces the volume of waste generated, can lower the cost of waste collection, and still generates compost that can be donated to community gardens.
Conclusion: Your Waste is More Valuable Than You Think
Home composting is one of the most concrete and accessible gestures a person can make to contribute to the planet’s health — and there’s an immediate bonus: more beautiful plants, livelier soil, and the satisfaction of closing a cycle with your own hands.
You don’t need to do everything at once. Start small: separate the peels, set up a simple box, experiment. Over time, the process becomes natural, almost automatic. And what was once “waste” becomes seen as a resource — a change in perspective that transforms not only your relationship with waste but with nature as a whole.
Start today. The earth thanks you — and so do your plants.
- As mulch: spread a thin layer over the soil of pots or beds to retain moisture and gradually release nutrients.
- As base fertilization: mix the compost with the substrate when planting (proportion of about 20 to 30% compost in the total volume).
- Set up the structure: stack the boxes. The bottom one remains without holes to collect the liquid. Place the other two on top, one inside the other.
- Prepare the boxes: make small holes (about 5 mm) in the bottom of the top two boxes (for drainage and worm passage) and smaller holes in the lids and sides (for ventilation). The bottom box has no holes — it collects the leachate.
- Leachate (or liquid biofertilizer): the dark liquid that drains from the worm bin, diluted in water (usually at a ratio of 1:10), acts as a potent foliar fertilizer.
- “Brown” materials (rich in carbon): shredded dry cardboard, dry leaves, untreated sawdust, non-plasticized paper napkins.
