Day to day, tiny bits of household food waste — potatoes that have sprouted in the pantry, a head of broccoli that went soft at the back of the fridge, leftovers no one wanted — don’t seem like much. Off they go into the garbage. We measure the success of yard clean-ups by the number of bags of grass, leaves, branches and tree trimmings we proudly place at the curb. Yet, each spring, we go to buy bags of soil for our flowerpots and compost for the veggie beds. We buy mulch and fertilizer to spread around our trees and our yard. We toss out organic matter into the garbage on one hand, and then essentially buy it back at $5 a bag in the form of compost from the hardware and garden stores on the other hand. To paraphrase Wendell Berry, we’ve taken an elegant solution and created two separate problems – having to dispose of household waste and then purchase nutrients and organic material to replenish our gardens and yards.
There is an alternative. We could hang onto all that organic material and use it as the raw material to create nutrient-packed compost for our soil right at home.
This would go a long way in stemming our garbage problem. Canadians have the dubious distinction of being among the most prolific producers of garbage in the world. Per person, we produce 2.2 kg of waste per day. That amounts to 30 million tonnes of garbage per year, as a nation. According to a 2013 study by the Government of Alberta, household food and yard waste alone accounts for 30 per cent of the municipal trash collected in the province.
And it’s not just potato peels and grass clippings that can be transformed into compost. Those boxes of outdated paper files, the cardboard tubes at the end of toilet paper and paper towel rolls, even that pea-green 100 per cent wool cardigan —minus the plastic buttons—languishing in the closet, can all, with the proper preparation, be composted.
In other words, we could keep almost one-third of what a typical family throws away out of the municipal waste stream while saving time and money, and have a steady, free supply of organic fertilizer to keep us in everything from arugula to azaleas, and radishes to roses whenever we need it.
The good news is that composting is a natural decay process, so it’s mostly about creating the conditions for what comes naturally to organic biomass. The bad news is, however, that it’s not as passive as many would like to think.
“People will say that composting is simply what goes on, on the forest floor. And that’s just not true,” says Jerry Leonard, PhD PEng, now a Professor Emeritus in the Faculty of Agricultural, Life & Environmental Sciences. “It’s a managed process,” he says, stressing “managed” in his affable Kenyan-Australian-British-Canadian accent.
Leonard knows a lot about the science and practice of creating compost. As an agricultural engineer, his teaching and research spanned control systems for machinery and intensive animal production systems to compost and waste management. Through his knowledge of composting, he became involved with the City of Edmonton’s Waste Management Branch in 1996. From 2002 to 2010, Leonard was seconded from the University of Alberta in order to set up the Edmonton Waste Management Centre of Excellence (EWMCE) and was its long-standing executive manager.
Technically speaking, composting is “an aerobic, thermophilic process in which microorganisms break down organic material into a stable humus-like material,” says Leonard, pausing to let the densely packed definition sink in. Given the right environment, raw materials, enough moisture and oxygen, he elaborates, the beneficial microorganisms — bacteria, fungi and actinomyctes, which create those threadlike filamentous colonies of mycelium in soil and compost — will feed on and reproduce in the organic materials, breaking it down into its simplest, smallest parts. In other words, a healthy compost is a living, breathing colony of microorganisms. When they have enough food, warmth and water, they continue to reproduce and go about breaking down solid matter into smaller, more basic units, ready for the garden.
It sounds simple on paper, but Leonard admits that it can be tricky to get “the recipe right,” he chuckles. The wetter “greens” and colourful organic kitchen peelings provide the high nitrogen source important in compost. Bacteria go to work on this material right away, feasting on the sugars and starches of the simpler carbohydrates. The drier materials like woody and tough yard waste, paper, straw and cardboard—often referred to as “browns”—provide the high carbon source that is necessary for the microbial oxidation (which produces the heat, which helps keep the composting activity going, especially in cooler weather). The fungi and actinomyctes tackle the tougher job of breaking down the complex carbohydrates of cellulose and lignins of the harder, denser woodier stuff like wood chips or even paper. For every part of dry nitrogen-rich materials, Leonard advises 25 parts dry carbon-rich organic matter. However, without a laboratory to weigh these materials out at home, some rules of thumb are useful. If there’s too much nitrogen in the mix, your compost will smell of ammonia. If there’s too much carbon in the pile, despite keeping it moist, it will not generate the required heat.
“Start off by chopping and shredding,” he advises, especially the drier “browns” to increase their surface area. But don’t go overboard. The “browns” create and maintain the oxygen pockets essential to the biological activity. A too-fine shred will not allow for enough oxygen, and “you’ll end up with a stinky pile,” due to anaerobic activity rather than an aerobic process.
When asked about the stranger stuff that some people are now adding to their compost piles, like old clothing, hair, pet fur and even meat, Leonard wrinkles his nose somewhat. “I suppose,” he says mulling the thought of an old pair of 100 per cent wool socks or a cotton t-shirt going into the mix. “Most clothing these days contain some synthetics,” he warns, which wouldn’t break down. Wool, fur and hair, essentially being a keratin protein, need to be finely chopped to speed their decay. He notes that you can compost meat, fish and animal fats, but you run the risk of having “all sorts of critters like coyotes or cats” rummaging in the pile. You also increase the odds of generating off smells with meats and fats. In the end, he doesn’t recommend getting too creative with what goes into the compost pile, especially in urban areas.
The most common mistake, says Leonard, is to maintain too small of a compost pile. You’ll need at least one large 100-litre yard waste trash bin worth of material. The mass will assist in keeping the centre of the compost warm enough for optimal biological activity. “If you get the recipe right,” he says, “the inside of the pile will reach 50 to 60o C within a day or two.” Warm compost is a sign of lots of activity, and the heat should inactivate any undesirable organisms, as well as weed seeds. The larger mass will keep the middle of the compost warm enough—above 10o C and you’ll still have some activity taking place—allowing you to keep your compost going year-round.
Making a mound out of the the raw compost materials is simplest and makes for easy turning, but some of the commercially available compost containers and elevated drum containers are useful as long as they have a large enough capacity.
Adequate airflow is another key to keeping the compost optimally active. Manual turnings to mix and maintain the absorbency of the pile are important, but Leonard suggests elevating your compost on wooden palettes or planks to allow even more fresh air to circulate through the pile.
It’s especially important to make sure there’s enough moisture. It’s a delicate balance to maintain the moisture content of the compost. In a relatively dry climate like Edmonton’s, compost can dry out quickly, effectively stopping the biological processes in their tracks. Ideally, about 50 per cent of the total weight of the compost should be water. For those of us without a laboratory to weigh this out, Leonard advises to keep the pile moist, but not wet. Given the right moisture level, and a quick turn of the materials to aerate and redistribute the “food” for the microorganisms, compost will heat up again.
Once the food source of degradable materials is exhausted, the compost cools, signaling that the microorganisms have either run out of air, food or the pile has dried out. “You have to get in there and stir it up,” Leonard says, excitedly. Regular checks for moisture and turning will keep the activity going strong through a number of cycles. When you don’t get any more heat and activity from the pile, then your compost is ‘done.’ At this point, you may also get earthworms and other insects churning through the compost, eating, digesting and excreting the last bits of waste material.
In three to six months, you should have finished compost -- moist dark brown and black, humus-like material that smells earthy, almost sweet, and which crumbles nicely in your hands.
Leonard warns to resist the temptation of planting directly into the compost. “There might be too much ammonia-type nitrogen in there for the plants to handle. Or, if there was a lot of (processed) food waste in the raw materials, it could be too salty.” Both conditions are going to make the compost toxic to your greenery. You absolutely need to dilute the finished compost with topsoil. A three-to-five-centimeter layer on top should be mixed into existing soil to a depth of about 10 centimetres.
However, once you produce your first compost, Leonard says, you can just “stand back and admire the results.” If for no other reason, creating a source of compost at home will turn your garden into a thing of envy in your neighbourhood.