What is composting, and how does it work?

Composting is one of the oldest ways of recycling based on the biological breakdown of organic material by microorganisms in the presence of air and moisture. The bio-organic waste decomposes during the composting process to produce a soil-like material. The end product of composting can then be used as a natural fertilizer, rich in carbon, nitrogen, and other nutrients, for the soil to improve plant growth while also serving as a natural pesticide.

What can and can't be composted?

YES: Kitchen scraps of fruit peels and vegetable cuttings, coffee grounds, tea bags, peanut shells, eggshells, decaying leaves, garden trimmings, grass clippings, straw, hay, soil...

NO: Seeds, weeds, diseased plants, animal products except eggshells (meat, fish, cheese, bones), animal waste (because of possible spread of E. coli), oil, grease, plastic, metals...

Composting Process:

  • Gather organic waste and make sure peelings and plant material are small in length, so that they can break down and decompose faster.

  • Store in a composting bin or out in the open contained by metal chicken wire or wood fencing, ensuring 1 metre in diameter and height.

  • Mix dried "browns" (decaying leaves, straw, dry organic material) with moist "greens" (grass clippings, fruit peels, vegetable cuttings) in a 1:2 or 1:3 ratio and pour some soil

  • Turn the compost twice a month to increase the amount of air. Keep the compost pile damp by adding water (if severely dry) or "greens".

  • The temperature of the pile should be around 54°C. (Can go up to 63°C if composting to destroy weed seeds.)

  • The compost is ready when it appears dark and has an earthy smell and appearance.

Destroying Weed Seeds by Composting

If the composting pile accidentally contains weeds that produce seeds, there is a way to destroy the weeds and the seeds. By turning the compost to make sure that the weeds are on top of the pile, the seeds will dry out as they are left out in the sun - a process called solarization. The heating of the compost will help to eliminate the seeds. An effective way to increase the temperature of the compost is to create "a greenhouse effect" by spreading out the pile and placing a plastic sheet on top. A compost pile temperature of 63°C will be enough to destroy even the most resistant seeds after one month.

What to do if the compost pile temperature is not increasing?

This can be due to a lack of "greens" and moisture.

Make sure the compost pile is damp by increasing more nitrogen-rich "greens". Then, move the pile to a location that provides enough of both sunlight and shade to maintain optimal water drainage. Otherwise, if placed in an overly sunny location, the compost will become too dry to reach the required temperature.

What to do if the compost pile has an odour?

The compost pile should not have an odour other than an earthy soil-like smell, and when done correctly, will not attract insects or rodents.

When the composting process is done incorrectly, the compost pile might have a rotten egg smell. However, there are ways to fix this! If an odour is present, that indicates that materials from the DO NOT compost list or too many "greens" were added, contributing to an increase in moisture and low pH. Fix this by adding more "browns" and turning the compost pile more frequently. Also, consider moving the pile to a sunnier spot to improve water drainage. If the pH is below 6, add limestone to increase the pH back to the optimal range of 6-8.

What pH should the compost pile have? How to measure and adjust the pH?

The compost pile should generally have a neutral pH, meaning that the pH should be between 6 and 8.

The pH can be measured using pH indicator paper, a soil test kit, or a calibrated pH metre. When using pH paper or a calibrated pH metre, dissolve the compost sample into distilled water before measuring the pH, and this will give the pH of compost in water (pHw).

If too acidic (pH below 6), then the pH of the compost can be increased using limestone, mixing the pile more frequently to improve air circulation, and by adding more "browns". If too alkaline (pH above 8), then the pH of the compost can be lowered by adding pine needles, oak leaves, and letting the pile sit without mixing to reduce airflow.

Where can I find compost and mulch in Waterloo Region?

From April to October at Cambridge (201 Savage Drive) and Waterloo (925 Erb Street West, Gate 2) Waste Management sites.

Due to COVID-19, compost and mulch cannot be currently picked up.

Visit the Region of Waterloo Waste Management website for more information.

Is KW Urban Harvester composting?

We want to start composting at our garden located at the Northdale site soon but are not composting at the moment.