The complete guide to composting

Composting is one of the most rewarding and impactful practices in organic gardening. It not only reduces waste but also helps nourish your plants and builds healthy, living soil. Whether you have a small balcony or a large garden, there’s a composting method that fits your space and needs. 

What is compost?

Compost is organic matter that has decomposed into a nutrient-rich, dark, crumbly substance called humus. When added to the soil, it improves soil structure, boosts water retention and supports beneficial microorganisms, which are essential for a healthy living soil. 

Benefits of composting:

Composting has many benefits: 

1. Diverts food waste from landfill: Helps reduce the amount of organic waste that ends up in landfills.
2. Builds living soil biology: Encourages healthy soil organisms that improve plant health.
3. Reduces the need for synthetic fertilisers: Compost naturally adds nutrients to the soil, reducing the need for chemical additives.
4. Improves moisture retention: Helps retain water in the soil, making it easier to grow healthier plants.

What Can Go in Your Compost

The key to good composting is balancing two main components: greens (which are nitrogen-rich) and browns (which are carbon-rich).

Greens (Nitrogen-rich):

These provide protein for microbes and help heat up the compost pile. These include:

• Vegetable and fruit scraps (avoid citrus peels in large amounts)
• Coffee grounds and tea leaves
• Fresh grass clippings
• Garden trimmings
• Manure (from herbivores only)

Browns (Carbon-rich):

These give compost its structure and provide energy for decomposition. These include:

• Dried leaves
• Shredded paper and cardboard
• Straw or hay
• Sawdust (from untreated wood)
• Wood chips (in moderation)

What not to compost

Some materials hinder the composting process or attract pests. Avoid placing the following in your compost pile:

• Meat, bones, and dairy
• Oily or cooked food
• Pet waste (especially from carnivores)
• Diseased plants
• Weeds with seeds or persistent roots
• Synthetic materials or glossy paper

The Dos and Don’ts of composting

Do:

• Balance greens and browns (aim for a 1:2 ratio).
• Keep compost moist—it should feel like a wrung-out sponge.
• Turn it regularly to introduce oxygen (every 2 weeks).
• Chop large items up to speed up breakdown.
• Let it mature for 6–12 weeks before use.

Don’t:

• Let compost get soggy—this can cause anaerobic rot.
• Add plastics or non-organic materials—they don’t break down.
• Forget to cover exposed piles—protect from heavy rain or drying out.
• Expect composting to be “set and forget”—it’s a living system that requires attention.

Different Ways to Compost

Composting can be done in various ways, depending on your space, time, and effort. Here's a breakdown of popular methods.

1. Traditional compost heaps or bays

Great for larger gardens or anyone with space. Open piles allow for larger volumes, with compost usually placed in three bays. Layer greens and browns in each bay, turning every two weeks. Cover to improve composting.

2. Worm farms (Vermicomposting)

Perfect for small spaces. Worms, like red wrigglers, process food scraps into worm castings, which are a supercharged soil conditioner. Worm farms use a tiered system, where worms start at the base and work their way through layers of food scraps. Worm tea, a liquid byproduct, can be used as a plant tonic.

Note: In addition to the usual items that should be avoided in all composting systems, in worm composting you should also avoid onions, citrus and spicy foods.

3. Compost tumblers

Ideal for suburban gardeners. These enclosed systems reduce mess, deter pests, and make turning easy. Tumblers are best for smaller volumes and allow compost to finish in 4–6 weeks. Turn the drum every few days to aerate the materials.

Beyond traditional methods, here are some additional methods suitable for different climates, spaces and applications:

4. Hot Composting

• Method: High temperatures (55–65°C) decompose organic matter quickly.
• Time: Finished compost in 4–6 weeks.
• Best For: Larger gardens, experienced gardeners.
• Benefits: Kills pathogens and weed seeds, fast results.

5. Cold Composting

• Method: A slower, low-maintenance approach.
• Time: Can take 6 months to a year.
• Best For: Beginners or low-effort composting.
• Drawbacks: Doesn’t kill weed seeds or pathogens.

6. Bokashi Composting (Fermentation)

• Method: An anaerobic (no oxygen) process that uses special Bokashi bran to ferment food scraps.
• Time: Takes 2–3 weeks in airtight containers.
• Best For: Small spaces, kitchens, and indoor composting.
• Benefits: Can compost all food scraps, including meat and dairy.

7. Trench Composting

• Method: Dig a trench or hole, fill with food scraps, and cover with soil.
• Time: Breaks down over several months.
• Best For: Low-maintenance composting.
• Benefits: Ideal for preparing new garden beds and fertilizing directly in-situ.

8. Sheet Composting

• Method: Also known as lasagne gardening, lay alternating layers of organic materials directly on garden beds.
• Best For: Improving poor soils and suppressing weeds.
• Benefits: Great for soil health and garden prep.

9. Black Soldier Fly Composting

• Method: Uses larvae to break down food waste, especially high-protein scraps.
• Time: Fast breakdown.
• Best For: Rapid food waste processing.
• Benefits: Odourless and perfect for high-protein scraps.

10. Composting Toilets (Humanure)

• Method: Converts human waste into compost over time.
• Time: Requires 1–2 years for safe decomposition.
• Best For: Off-grid living.
• Caution: Requires careful management and long resting periods.

11. Indoor Electric Composters

• Method: Small countertop devices that dry and grind food waste into a pre-compost form.
• Time: Very fast (a few hours).
• Best For: Urban living and small spaces.
• Benefits: Fast and space-saving.