Compost

1. Compost builds healthy soil. The decomposed organic matter in finished compost is full of essential nutrients for plants including nitrogen, phosphorus, potassium, and more. Compost also improves the structure of soil so that it can soak up more water and stay damp longer. Finally, the beneficial microbes in compost help plants pull in more water and nutrients, as well as resist pests.

2. Compost significantly cuts down on garbage. While the exact proportion varies in different communities, a major chunk of the waste we make in Canada is composed of food scraps, soiled paper (like pizza boxes and napkins), grass, leaves, and other yard waste. Keeping this out of the trash means landfills fill up slower, saving money over time.

3. Compost rots cleanly, while organic waste in a landfill makes methane pollution. When decaying material rots in a place with fresh air / oxygen available, the beneficial microbes break it down in a few months and store carbon in the finished compost. But when the same material rots in a place starved of fresh air / oxygen, it takes decades to fully decompose, and releases byproducts like methane gas which contribute to climate change. Compost systems include air, but landfills need to be packed down tightly for safety reasons. So organic material packed into landfills rots slowly into methane instead of quickly into finished compost.

Almost anything made of organic matter (carbon-based material that came from something living like a plant, animal, or micro-organism) can be composted, as long as microbes like bacteria and fungus can break it down. However some materials are faster and easier to decompose than others. The most common things we compost are:

• Food scraps – Spoiled food as well as discarded pieces of food like egg shells, vegetable peels, fruit cores, coffee grounds, tea leaves, and bones can all be composted. However food scraps high in animal fat and protein (meat, bones, dairy products, and the inside of eggs) have a strong, unpleasant smell while they decompose that can also attract animals, so most people composting at home leave them out.
• Yard waste – Leaves, grass clippings, garden plants, and even trees can be composted. Wood decomposes slowly, so it should be chipped into smaller pieces to speed it up. Seeds and the roots of creeping weeds are cooked and killed in large, hot compost systems, but often live through smaller, cooler compost systems. So some composters choose to avoid adding seeds or roots from the worst weed species.
• Soiled paper – Pizza boxes, napkins, paper towel, paper bags, paper straws, and some takeout containers can be composted. Paper and cardboard are made almost entirely of plant fibre, and are easy for microbes to decompose. While the inks used on different paper are not entirely organic, they do not contain enough other chemicals to cause any harm. However paper food containers that have a waxy or plastic coating (like coffee cups) will leave the wax or plastic behind in the finished compost, so they should be left out.
• Manure – Manure (feces) contains high amounts of nitrogen and other nutrients plants need to grow, however it can also contain harmful bacteria or pathogens that can spread illness. To minimize risks, we typically only compost the manure of tame animals / livestock that eat primarily plants, such as manure from cows, horses, sheep, goats, pigs, rabbits, or chickens. Feces from wild animals, animals that eat more meat, and humans can be composted safely in hot compost systems, or as long as the compost is handled carefully and not applied to areas where we grow food.
• Compostable plastic – In recent decades food scientists have developed types of plastic that can fully break down into water, carbon dioxide, and biomass. However most compostable plastic items will only decompose in very hot compost systems, so they should not be added to smaller, cooler systems like backyard compost bins. There is also no benefit to using compostable plastic for materials that will end up in a landfill.

Compost bins keep food scraps, garden waste, soiled paper, and other material neat and tidy while they decompose. Almost any kind of large, sturdy container will do, as it is not actually the bin that makes the material break down – it is the basic recipe of nitrogen, carbon, oxygen, water, and microbes. (In fact, composting in a heap on the ground also works, as long as you have the space to do it without causing a nuisance.)

Most compost bins sit on the ground, but there are also tumbling compost bins. Tumbling compost bins are typically barrel-shaped and sit up on frame that lets them spin.

Tips:

• Compost bins work in any light conditions from full sun to full shade.
• Make sure the compost bin is on top of a permeable surface like dirt, grass, or mulch (not pavement or cement), for drainage.
• Put your compost bin somewhere that is easy to get to from your door to make it convenient to take out kitchen scraps. In winter you can also switch to putting food scraps in a secondary container kept just outside the door, and move these to the bin in spring.
• Having multiple bins, or a bin with multiple chambers, makes harvesting finished compost easier. You can make multiple batches at a time, so you do not have to separate out finished compost from fresher material when you harvest.
• Mice prefer dry, undisturbed compost bins. To keep them out, water and stir the compost every weekly during the spring, summer, and fall. (Or use a tumbling compost bin – most kinds are rodent-proof.)
• Large piles of compost that are very microbially active can generate enough heat to warm themselves up for a few weeks. However most backyard compost bins are too small for this to be noticeable.

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Trench composting is a very simple method, although it does require garden space. Dig a trench or hole at least 30 cm deep. Add food scraps or yard waste into the hole and then cover them with at least 15 cm of soil. The natural bugs and microbes in the soil will set to work decomposing the material into finished compost.

Tips:

• Mix a little bit of soil in to the material to kickstart decomposition.
• Many plants do not like growing directly on top of a trench compost for the first couple months, but they can grow beside it.
• Squash plants grow well directly on top of trench composts, even right away.

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Vermicompost is an indoor method in SK (although it can be done outdoors in warmer climates). It relies on earthworms, kept in a tub or other container, to eat food scraps and make compost. Earthworm droppings, also called castings, are already fully broken down and ready to be used as fertilizer. Vermicompost bins also use damp paper, cardboard, or other bedding to cover food scraps and keep the worms comfortable.

Tips:

• Native prairie earthworms do not thrive in vermicompost systems because prefer more vertical space. Vermicompost systems should use a surface feeding earthworm instead, such as red wigglers (Eisenia fetida).
• The most important factor for keeping the earthworms is keeping their compost or bedding damp but not soaked. Worms can easily dry out or drown.
• If there aren’t enough worms to keep up with the food waste in the bin, it will become moldy and smelly. This means the bin either needs less food waste or more earthworms.
• Making sure food scraps are always buried under bedding helps prevent attracting fruit flies or fungus gnats. However if these insects do end up living in the vermicompost, apply a predatory nematode blend meant for fungus gnats, aphids, and/or thrips. You can find them at garden stores.
• Harvesting finished compost can be done a bit at a time by hand, or by using the worms’ natural tendency to move toward food and away from light. To use food, bury all new food scraps on one side the tub for a few weeks to lure most of the worms, and then scoop out the other side. To use light, spread the worms and compost out under a bright light, wait a few minutes, and then skim compost off the top as the worms move downward to hide.

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Bokashi composting is a two-step process that starts by fermenting food waste in a sealed container with a microbe inoculant called bokashi bran. The second step is regular composting, either in a trench compost or outdoor compost bin. While bokashi is easiest with some access to outdoor garden space, fermented food waste can be stored up for several months at a time, making it a potential indoor option.

The fermentation step of bokashi composting helps break down fat and protein, allowing this method to work for meat, bones, and dairy scraps as well as the usual plant-based food waste. However because the first step uses a different kind of microbes than regular composting, while open the pail will have a noticeable odour ranging from a neutral vinegar smell (if the scraps are mainly plant-based) to a more unpleasant ammonia smell (if the scraps are mainly meat or dairy products).

Tips:

• It is best to have two or more buckets so that multiple batches of bokashi compost can be active at a time. Once a bucket is full, it will need at least two weeks to finish fermenting.
• Fermented bokashi waste breaks down quicker than normal food scraps when it is added to a regular compost bin or buried in a trench compost.

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This type of indoor, electric appliance for processing food waste is a relatively new addition to the world of composting. They use a combination of heat and grinding to pulverize and dehydrate food waste. They do not make finished compost, as the microbes that normally decompose scraps into compost need more time, and cannot handle the high temperatures of the appliances.

The dehydrated and pulverized food these appliances create will not rot until water is added again. This means the food powder can easily be stored in a secondary bag or container until it can be taken somewhere to finish composting – such as adding it to outdoor garden soil or putting it in a municipal green cart. The food powder should not be added to indoor plants it typically causes mold problems.

These appliances can handle mixed food waste including most bones and meat scraps, although larger bones may cause jams.

While the higher price tag and electricity use mean these appliances are not the best indoor solution for everyone, they can be useful in buildings where other compost methods are inconvenient or unappealing.

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Composting at home is simple, but not everyone wants to. In order to capture more organic waste out of the trash, many communities have a curbside collection program for food scraps, yard waste, and soiled paper.

Most communities compost the green cart material at a largescale compost site, where the compost piles are quite large and can hold on to more microbial heat than smaller backyard compost bins. This means that the municipal compost decomposes at a higher temperature that cooks and kills most weed seeds and harmful bacteria. The heat also helps break down protein and fat, so most green carts can typically accept mixed food waste including meat and bones. But make sure to check what your local green cart accepts!

Green carts are still useful to people with home compost bins for getting rid of difficult-to-decompose or excess compost material.

Under construction.

Collection / drop off

Windrows – flipping, ASP, bunkers, covers

In-vessel compost systems

Screening – testing – end use

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While composting is often the first option that comes to mind for organic waste, there are other options.

Food scraps can be fed to livestock such as chickens, goats, or pigs. (Their manure can then be composted.)

Organic waste can be used in an anaerobic digester to produce biogas for energy. (The leftover digestate can be composted.)

Wood waste can be used with pyrolysis to make biochar, a valuable charcoal-based soil amendment.

The important thing is keeping organic waste out of a landfill and putting it to good use.