Why compost matters more in the city

Good soil is the single biggest factor separating a thriving kitchen garden from a struggling one, and in Nairobi's often depleted urban soils, compost is how our members build fertility without spending on expensive fertilizer. Unlike rural plots that may have years of organic matter built into the soil, many urban plots and sack gardens start with soil that has been stripped of nutrients by construction, poor drainage, or years of continuous cropping without replenishment.

The three-bin method

We teach a simple three-bin method: one bin for fresh kitchen scraps and green waste, one for partially broken-down material that is turned weekly, and one for finished compost ready to use. Moving material through three stages rather than one large undifferentiated pile makes it far easier to manage smell, pests, and the pace of decomposition.

Layering 'greens' — vegetable peels, tea leaves, grass clippings — with 'browns' — dry leaves, shredded cardboard, sawdust — keeps the pile balanced. Too many greens and the pile turns slimy and smells; too many browns and it barely breaks down at all. A rough two-to-one ratio of browns to greens by volume is the starting point we recommend to new members.

Turning, moisture, and timing

Regular turning, roughly once a week, introduces oxygen that speeds up decomposition and keeps the pile from turning anaerobic, which is the usual cause of bad smells and pest problems. The pile should feel like a wrung-out sponge — damp but not soaking — and most members find that a light watering during Nairobi's dry months is needed to keep it active.

Most households following this method have usable compost within six to eight weeks, faster in the warmer months and somewhat slower during cooler periods of the year.

Beyond the garden

Composting also cuts the volume of household waste sent to informal dumping sites in Babadogo, which is part of why we have paired this training with our wider community waste-reduction efforts. A household that composts its kitchen scraps is, in a small way, also solving a local sanitation problem.

Troubleshooting a compost pile that isn't working

A pile that has stopped breaking down, smells persistently bad, or has attracted pests is usually signalling one of a small number of common problems rather than requiring a completely different approach. A pile that smells like ammonia or rotten eggs generally has too many wet greens and not enough dry browns, and needs a generous addition of dry material worked through it. A pile that seems dry and is barely decomposing at all usually needs both more moisture and more frequent turning to reintroduce oxygen.

Pest problems, particularly flies or rodents, are almost always traceable to specific materials that should not go into a household compost pile in the first place — cooked food, meat, dairy, or oily scraps — rather than a fundamental flaw in the composting method itself. Removing these materials from what goes into the bin resolves the great majority of pest complaints we hear from new composters.

Composting in a genuinely tiny space

Members with very little outdoor space sometimes assume composting is out of reach for them, but a scaled-down version of the three-bin method works even for a household with only a small balcony or a narrow strip beside a doorway. A set of three small, lidded containers rather than open bins achieves much of the same effect in less space, though smaller batches take slightly longer to reach a stable internal temperature and may need more careful moisture management than a larger pile.

For genuinely space-constrained households, we sometimes recommend a simplified two-bin version instead of the standard three-bin method, trading a small amount of processing speed for a meaningfully smaller footprint, which several of our most space-limited members have found a workable compromise.

Composting is also one of the few farming practices that genuinely improves with more people doing it. A single household's compost pile is limited by that household's own kitchen waste, but our wider waste-reduction effort, which pools organic waste from multiple households and market stalls, produces far more finished compost than any individual pile ever could — while also solving a genuine local waste problem at the same time. Starting your own three-bin system at home remains the best first step, whether or not you ever connect to the wider community effort.

Key takeaways

  • Urban soils in Nairobi are often depleted and benefit heavily from added organic matter.
  • The three-bin method separates fresh scraps, breaking-down material, and finished compost.
  • A rough two-to-one ratio of browns to greens keeps a pile balanced.
  • Most households get usable compost within six to eight weeks.

Frequently asked questions

What can I put in a compost bin?
Vegetable peels, tea leaves, and grass clippings as 'greens', balanced with dry leaves, shredded cardboard, or sawdust as 'browns' — avoid meat, dairy, and diseased plant material.

Why does my compost pile smell bad?
Usually too many wet greens and not enough dry browns, or a pile that has gone anaerobic from lack of turning — add browns and turn the pile weekly to fix it.

Do I need a special bin to start composting?
No — three simple containers, or even three marked sections of ground, are enough to run the method effectively.