A Beginner’s Guide to Composting — What You Can and Can’t Compost

Happy National Learn About Composting Day!! Yes, it turns out they really do have a holiday for everything. Composting is getting more and more popular, and as quarantine has led to more people gardening, this is a great time to start! Let’s be honest though, it can be a little bit confusing to keep track of what can and can’t be composted. I don’t know how many times I have googled if tea bags are compostable (FYI, it depends on the teabag, some have plastic and some are completely compostable- read more about it here).

So first off, here are the things you can’t compost. The most common reason something shouldn’t be composted is to avoid pests and critters being attracted to your compost.

- Meat scraps, eggs, and dairy– they can really smell, and it can also attract pests

- Oils and fats, including grease foods or baked goods — the smell also attracts pests

- Coal and charcoal — they are bad for plants

- Sawdust and scraps of wood that have been treated (untreated is fine)- the chemicals can be damaging to any plants

- Really acidic foods like citrus or anything pickled — this can kill the bacteria needed for the composting process

- Pet wastes — this can cause parasites or harmful germs to get in your compost

- Weeds — while these can go in the compost, just be cautious because they could start growing in your pile and ruin the composting process

- Yard trimmings and plant remains that are treated with pesticides or diseased — these are harmful to any plants you use the soil on

Also, all of these are still fine to go into the green bin except actual pieces of wood!

So, what can you compost? Well, to start off there are two kinds of materials needed for good compost- “green” material” and “brown” materials.

Green materials are rich in nitrogen and break down faster than the brown materials. While these high nitrogen items are often green or colourful, some things (like coffee grounds) are brown but still count as green materials because they’re high in nitrogen! Another rule of them is that green materials are often “wet”, and by that, I just mean not dried up like most brown materials yet.

- Grass clippings

- Fruit and vegetable scraps

- Coffee grounds and tea bags (just check the tea bags aren’t plastic)

- Plant trimmings and weeds that haven’t set seed yet

- Eggshells

- Animal manures (just not from dogs or cats!)

- Seaweed

Brown materials provide the carbon, and they feed the creatures that help you break down your food waste. They also help the airflow through your pile. If your compost is smelling really bad, try adding some more brown materials!

- dried leaves, hay, or cornstalks

- twigs, pine needles, and sawdust

- paper, napkins, coffee filters, even cardboard as long as it isn’t waxy or coated in plastic

- dryer lint or cotton fabric

- egg cartons and toilet rolls

If you are composting, you should make sure you have a good ratio of green to brown. Generally, for a good ratio, you would have a quarter green material and 3 quarters brown materials, but you can adjust this depending on your soil. The ratio is by no means the “be all, end all” of composting. If the ratio is off, decomposition will still take place, it just may take longer. You can use a container or even just a pile, as long it’s at least 1 cubic metre and has good airflow.

The timeline depends on the kind of composting you are doing, if you just leave it to do its thing, it can take 3 months to a year for decomposition. Hot composting can take only 30 days. It depends on a lot of factors besides just the method of compost, like temperature, the amount of material you are adding to the pile, and how often you are adding it.

Best of luck with your composting adventures!


Busch System. (2016, September 19). 7 Things You Shouldn’t Compost. Retrieved May 25, 2020, from https://www.buschsystems.com/resource-center/page/7-things-you-shouldn-t-compost

City of Toronto. (2019, October 22). What Goes in the Green Bin? Retrieved May 25, 2020, from https://www.toronto.ca/services-payments/recycling-organics-garbage/houses/what-goes-in-my-green-bin/

Lallanilla, M. (2019, October 07). Here’s a List of What to Compost and What’s Not Safe to Compost. Retrieved May 25, 2020, from https://www.thespruce.com/what-to-compost-1709069

Networx Systems. (2017, May 31). Composting: A timetable. Retrieved May 26, 2020, from https://www.mnn.com/your-home/organic-farming-gardening/stories/composting-a-timetable

Vanderlinden, C. (2019, November 30). 50 Items to Add to Your Compost. Retrieved May 25, 2020, from https://www.thespruce.com/things-you-can-compost-2539612

Vanderlinden, C. (2019, February 02). Which Items Are “Greens” and Which Are “Browns” for Composting? Retrieved May 25, 2020, from https://www.thespruce.com/composting-greens-and-browns-2539485




A student-run club that operates a small-scale composting service, while also promoting sustainability through proper waste management and Zero Waste lifestyle.

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UW Campus Compost

UW Campus Compost

A student-run club that operates a small-scale composting service, while also promoting sustainability through proper waste management and Zero Waste lifestyle.

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