Why Your Compost Isn’t Breaking Down and What to Do About It

If your compost looks exactly the same week after week, it can be frustrating. You’ve been adding food waste, you’re doing “the right thing, and yet nothing seems to be happening.

Slow compost doesn’t mean composting has failed. It usually means the conditions aren’t quite right.

In urban gardens and shared composting spaces in Bristol, slow composting is very common, especially during colder or wetter months. This guide explains why compost sometimes stalls, what’s going on biologically, and how to get things moving again.

How compost is supposed to break down

Composting is a biological process. Microorganisms, fungi, insects, and worms work together to break organic material down into soil.

For this to happen efficiently, compost needs:

• Oxygen

• Moisture

• A balance of materials

• Time

When one of these is missing, decomposition slows down.

Common reasons compost isn’t breaking down

Too much carbon or too much nitrogen

Compost works best when food waste (nitrogen-rich 'greens') is balanced with carbon-rich materials ('browns').

Too much food waste can make compost soggy and smelly.

Too much cardboard or woodchip can cause compost to dry out and stall.

The materials are too large

Whole vegetable stalks, thick cardboard, or large food scraps take much longer to break down.

Microorganisms work on surface area. The bigger the material, the slower the process.

Compost is too dry or too wet

Compost organisms need moisture, but not saturation.

• If compost is too dry, microbes slow down

• If it’s too wet, oxygen can’t circulate

In Bristol’s climate, compost is more likely to be too wet, especially in uncovered systems.

Lack of oxygen

Without oxygen, composting slows or shifts toward anaerobic processes.

This can happen if:

• Compost becomes compacted

• Food waste is layered without mixing

• The system doesn’t allow airflow

Temperature and seasonal slowdown

Composting slows naturally in autumn and winter.

Lower temperatures mean microorganisms work more slowly. This is normal and doesn’t mean your compost is broken.

How to speed up composting safely

Chop or tear materials smaller

Breaking food scraps and cardboard into smaller pieces speeds up decomposition dramatically.

Even tearing cardboard by hand makes a difference.

Rebalance greens and browns

Aim for a rough balance between food waste and carbon material by volume.

If compost looks dry and unchanged, add food waste.

If it looks wet and dense, add carbon material.

Check moisture levels

Compost should feel like a wrung-out sponge.

If it’s dry, add water gradually.

If it’s wet, add dry material and improve drainage or cover.

Introduce oxygen

If your system allows it:

• Gently turn or mix compost

• Loosen compacted layers

• Avoid compressing food waste

Even small increases in airflow help.

When slow compost is actually okay

Not all compost needs to be fast.

Cold composting, leaf composting, and low-maintenance systems all break down slowly but still produce valuable soil over time.

The goal isn’t speed. It’s healthy decomposition.

Signs your compost is starting to recover

As compost improves, you’ll notice:

• A more earthy smell

• Materials softening and darkening

• Fewer recognisable food scraps

• Increased insect or worm activity

These are signs biology is doing its work.

When to get extra support

If your compost hasn’t changed for months despite adjustments, the issue may be:

• System design

• Location (shade, drainage, space)

• Contamination

• Volume mismatch

At this point, general advice online often isn’t enough.

Practical composting support in Bristol

If you’re based in Bristol and struggling with slow compost, Generation Soil’s Compost Clinic offer practical, hands-on support.

The Compost Clinic help with:

• Diagnosing why compost isn’t breaking down

• Adjusting systems for urban conditions

• Building confidence with food waste composting

They’re ideal if you want help tailored to your space, not generic tips.

👉 Learn more about the Compost Clinic

👉 You can also explore our composting and soil workshops to learn the process from the ground up

Composting takes time, and that’s okay

Composting isn’t instant, and it isn’t about perfection.

It’s about creating the right conditions and letting biology do the rest.

With patience, balance, and the right support, even slow compost will eventually become living soil.