Community Articles
Go to Site Index See "Community Articles" main page
General News · 10th June 2020
Maureen Williams ND
How to Compose Your Compost – what goes in, what stays out, and how to keep things balanced.

Any organic material will compost! That includes fruit and veggie scraps, eggshells, coffee grounds, tea bags, paper towels and tissues, clean newspaper and cardboard, leaves-grass-weeds, meat scraps, and other food waste like moldy bread and too-old leftover grains. But what do you really want in your compost bin? It mostly depends on when you want your finished compost: some things slow it down, others heat it up. In addition, some things are kept out of ordinary compost systems because they are smelly and attract rodents.

Most compost instructions categorize organics as “green” or “brown”. ALL organic materials are mostly carbon, but:
• Green materials (which are not always green in color) are relatively rich in nitrogen, so are often referred to as “high nitrogen”
• Brown materials are relatively nitrogen-poor and are referred to as “high carbon”

Nitrogen provides the heat; carbon provides the structure to hold nutrients in the soil.

In general, your compost should include some high nitrogen and some high carbon materials. The optimal ratio of carbon to nitrogen (C:N) for composting is around 25–30 parts carbon to 1 part nitrogen. Manure, seaweed, and certain grasses are examples of good nitrogen sources to rev up the composting process; Paper, cardboard, and woodchips, on the other hand, are super carbon sources. Seaweed, a great green material we often have access to, can add lots of other minerals to your compost, as well as other compounds that enrich the soil. Things like vegetable scraps, garden waste, weeds, and wood ashes have close to the perfect balance inherently. Check out the list below.

Estimated Carbon-to-Nitrogen Ratios

Browns = High Carbon C:N
Ashes, wood 25:1
Cardboard, shredded 350:1
Corn stalks 75:1
Fruit waste 35:1
Leaves 60:1
Newspaper, shredded 175:1
Peanut shells 35:1
Pine needles 80:1
Sawdust 325:1
Straw 75:1
Wood chips 400:1

Greens = High Nitrogen C:N
Alfalfa 12:1
Clover 23:1
Coffee grounds 20:1
Food waste 20:1
Garden waste 30:1
Grass clippings 20:1
Hay 25:1
Manures 15:1
Seaweed 19:1
Vegetable scraps 25:1
Weeds 30:1

(Source: Planet Natural Resource Center: Carbon to Nitrogen Ratios. Available at )

In order to keep the right balance, you want to consider countering high-nitrogen items with high-carbon items. Most composting experts recommend adding layers of brown material as your compost pile of food and yard/garden trimmings grows. As you can see, you only need small amounts of wood chips, sawdust, cardboard, or newspaper to counter a lot of grass, fruit, and seaweed. Low-nitrogen materials slow down the decomposition, but have the benefit of keeping odors down and flies at bay. If your compost is entirely fruit, veggie, and garden waste, you may be able to achieve the same advantage by simply layering on a small amount of plain dirt after each addition.

Your compost pile should be decomposing into something that looks a lot like dirt! If it’s too smelly and sticky, you need more carbon; if it’s not breaking down and filling up too fast, you need more nitrogen.

Some things to leave out
There are some organics you may not want to include in your compost.

Meat and dairy. Most people don’t put meat scraps or dairy waste in above-ground compost systems because they small bad and attract rodents. There are other ways of dealing with meat and dairy – some people have told me they leave meat scraps for the ravens! Others feed them to chickens or use compost systems such as trenching to take care of meat scraps. That’s a future post.

Weeds. Most people want to harvest their compost for use in the garden and don’t want to spread nasty invasive weeds around. If this is you, be sure to avoid putting any weeds into the compost that have gone to seed or that spread via roots (like morning glory). If you have a very hot compost, you may not need to worry, but in general it’s probably best to dispose of weeds somewhere else – feed the deer? Another option would be to compost them separately in black plastic bags.

Cat and dog poo. Cat and dog feces can harbour pathogens that might contaminate your compost. They should never be added to compost that will be used on a food garden.

Wood ash and conifer needles. Wood ash, while balanced in terms of carbon and nitrogen, is highly alkaline. Conifer needles, on the other hand, are acidic. In small amounts, they won’t affect the pH of your soil much, but if, for example, you add a lot of wood ash in the winter, your compost may become overly alkaline.

Some things to add
Air: your compost needs to be in a ventilated container and will be healthier – and break down faster – if you aerate it. This can be done by turning it occasionally, or simply poking holes in the pile with something like a piece of rebar or a shovel. You should also make sure your compost bin has good ventilation built in.

Water: your compost will decompose faster if it stays moist. Material from fruits, veggies, and garden plants will contribute some water, but you may still find the compost pile dries out in summer, especially if you add a lot of nitrogen-poor materials. If this happens, you can dampen lightly with a hose, and keep your compost pile covered to reduce evaporation.

Remember: No matter what you do, organic matter will turn to compost! Faster if you tend to it, slower if you don’t.