What is compost?
Compost is the final product of a process in which biowaste is broken down into nutrients and recycled back into the soil. Composting is one of the most environmentally friendly technologies for managing organic waste, also known as biowaste (Barrena et al. 2014). Biowaste includes organic material such as kitchen scraps and yard trimmings which are often referred to as “green compost”, as well as wood biowaste like paper, cardboard, fallen leaves and wood chips which are called “brown compost”. Brown compost is largely composed of carbon, whereas green compost is largely made up of nitrogen. Carbon and nitrogen are necessities to life and return to the soil when biowaste like green and brown compost breaks down.
Let’s start with the basics
A great place to start is understanding the difference between “green” and “brown” compost. Green compost includes most plant-based products from your kitchen like fruits and vegetables, as well as fresh grass clippings (Schwarz and Bonhotal 2011). Green compost is typically high in nitrogen, an essential nutrient for plant development. As green compost decomposes, water is released from the plant’s cell walls; this is why leafy greens like spinach get watery when they’re left in the fridge for too long. When green compost decomposes, the water will leave the plant tissue and be released into the soil and air. In comparison, brown compost is predominantly produced by trees, which are largely composed of carbon (Schwarz and Bonhotal 2011). Therefore, brown compost includes fallen leaves, twigs, sawdust and woodchips. Brown compost also includes cardboard and newspaper that isn’t glossy or dyed. A mixture of green and brown compost should be added into the same compost pile or bin at home to yield high-quality compost and avoid common problems such as excess-moisture or odour. But these problems are easy to avoid and there are many benefits to composting for those who persevere!
Benefits to composting:
- returns nutrients to the soil;
- reduces landfill waste (Schwarz and Bonhotal 2011);
- add compost to soil to increase carbon sequestration (Favoino and Hogg 2008);
- moisture retention (Favoino and Hogg 2008);
- reduces the requirements for water irrigation during drought (Favoino and Hogg 2008);
- decreases the need of chemical fertilizer and pesticide (Martínez-Blanco et al. 2011)
Compost Fact: Fallen leaves contain microbes that will start the decomposition process in your compost, so you do not need to purchase a “compost activator” from a garden store (Park Brown 2007).
What’s the difference between industrial versus at-home composting?
Aside from the difference in scale and technology, home composting and industrial composting can both yield high-quality compost.
Home composts are made on a much smaller scale than industrial facilities and do not usually have external heat sources and gas treatments. Therefore, home composting often requires a bin or building-up a pile of alternating layers of green and brown compost. This is most efficient when the pile is periodically turned over or mixed to keep the pile hot, allowing even aeration and moisture through-out the pile (Park Brown 2007). Home composts don’t have to be limited to a single dwelling in a backyard, but may be managed by a community of people or in larger settings like a school. A major benefit to composting at home is that it usually avoids the fossil fuels required to collect and transport biowaste from residential areas to an industrial compost facility. Plus, you get to reap the benefits and apply the compost to your own garden or share it with neighbours!
In comparison, industrial composting is a large-scale process in which the biowaste is heated, and greenhouse gas emissions are minimized, filtered and treated (Sánchez et al. 2015). Both home and industrial compost practices share similar strategies of minimizing greenhouse gasses that include optimizing the carbon to nitrogen ratio and maintaining good aeration and moisture levels during the decomposition process (Sánchez et al. 2015). The benefit of industrial composting is that biowaste can be treated year round, which can be challenging with composting at home during our cold Canadian winters.
For those who are fortunate to have the ability to compost from home and live in an area with access to a municipal composting program, how do you choose a composting method? You may wish to use both methods of composting as the seasons change or your ability to manage biowaste at home fluctuates. For example, you may compost at home during the spring, summer and fall, and utilize municipal compost in the winter months. Or you may use home compost for fruit and vegetables, and use the municipal compost program for biowaste that requires a higher temperature such as meat, bones or biodegradable plastics. Alternatively, your municipality may have a brown compost program in the autumn to collect fallen leaves. Look into your municipality's waste website for more information.
Compost fact: Globally, composting recycles 1 million tonnes of plant macronutrients, which is equivalent to CAD $1.1 billion a year. These annual benefits could be increased over 12-fold, if the world’s biowaste were collected separately and composted (The Compost Council of Canada).
Thinking about composting at home? Here’s what you need to consider:
First and foremost - composting does not replace food waste reduction at the source. The root cause of food waste in many Canadian households is a culture of accepting waste and no one (e.g. industry and consumers) internalizing the true costs of food waste (Gooch et al. 2019). While reducing food waste is the best option, there will always be a need to compost food scraps to recycle nutrients back into the soil.
Composting is simple! To start composting at home you will need:
- Compost location: The ideal location for a compost pile is on relatively flat ground with some sun exposure and within reach of a water source.
- Water: Access to a hose or watering can (if you’re up for the extra exercise) is helpful to maintain a good level of moisture in the compost pile during the dog days of summer!
- Shovel: Turning over the pile with a shovel or another garden tool will help to maintain aeration and moisture throughout the compost pile. Aeration and moisture is important to maintain microbial activity. Mixing the pile also speeds up the decomposition process by breaking up any biowaste that may clump together.
- Compost: Green and brown compost!
- Structure - bin or pile: Decide whether you (and your neighbours) would prefer the compost to remain in an enclosed compost bin, or whether you have the space for a well-structured compost pile. Municipalities often encourage their residents to compost at home by selling compost bins at a reduced cost. Alternatives to purchasing a compost bin include using a garbage can or building your own compost bin with wood.
Rule of thumb for layering your compost:
It’s good practice to start your compost with a layer of brown compost, and for every layer of green compost, add some more brown! Once you have about 3- to 4-inches of brown compost, a 3- to 4-inch layer of green compost can be added, and so on and so forth. If you are building a compost pile instead of using a bin, include some twigs or small branches to the first layer of brown compost that sits on the ground to provide a good foundation and space for air. Compost piles also need moisture, so use a hose or watering can to dampen each layer of dry brown compost (Park Brown 2007). Additionally, an important feature of a compost pile is that it’s a minimum of 3’ x 3’ x 3’ because this helps trap heat in the centre of the pile to encourage further microbial activities (Park Brown 2007). The final layer of any compost pile should be a layer of brown compost that completely covers all of the green compost which helps keep flies out of the pile and filters odours (Schwarz and Bonhotal 2011). Ideally, a compost pile should look like a large pile of brown compost from the outside, with layers of green and brown compost in the centre. As you add more green compost on top of your pile, cover it with more brown compost or soil.
Tips for your outdoor compost
- Keep your green compost covered with brown compost, (or soil or grass clippings, in a pinch) to aid in the decomposition process and to avoid attracting flying insects.
- Cover your compost with a tarp in the spring to reduce the amount of rain soaking into the pile. A water-logged compost pile will limit the air and oxygen throughout the pile, which will reduce microbial activity.
- Add more brown compost to reduce moisture if the compost pile is too soggy.
Tips for the kitchen
Creating high quality compost begins in the kitchen. For starters, lining an indoor compost bin with newspaper will help absorb excess moisture released from kitchen scraps. In order to speed up the composting process outside, it helps to make your kitchen scraps smaller. For example, cut large fruit and vegetables into smaller pieces and crush egg shells prior to adding them to your compost bin to help them decompose faster. Breaking your compost into smaller pieces also applies to your brown compost like wood and cardboard. It’s also important to know what to include and what to avoid adding to your compost.
Healthline has a great list of what to add to your compost bin, and what to avoid with explanations for why certain items can’t be composted at home. Generally, avoid adding animal based-products (e.g. meat and dairy) that may produce odours as they decompose and attract pests. Additionally, you should never try to compost materials that may contain harmful chemicals or bacteria. Check out our infographic about composting at home for more information about some do’s and don’ts.
Compost fact: A global estimate found that composting reduces greenhouse gas emissions by 9 million tonnes of carbon dioxide equivalents a year through storing carbon in soil and offsetting fertilizer use. This is equivalent to driving an average car for 36 billion kilometres; almost 95 thousand times the distance between the earth and the moon (The Compost Council of Canada)!
Composting in The Land Between
The Land Between not only contains a large proportion of Ontario’s cottage country, but we’re also a part of bear country. Tips from the Municipality of Hastings Highlands re-emphasize the importance of never putting meat, bones, fish or dairy products in a compost bin. If you have had bears in the past, then consider purchasing a compost bin that can be securely closed. Several jurisdictions offer compost bins at reduced cost. Contact your local waste facility to see if they offer any discounts on compost bins.
Written by Olyvia Foster, Conservation Communications Specialist
Barrena, R., Font, X., Gabarrell, X., & Sánchez, A. (2014). Home composting versus industrial composting: Influence of composting system on compost quality with focus on compost stability. Waste Management, 34, 1109–1116.
Favoino, & Hogg, D. (2008). The potential role of compost in reducing greenhouse gases. Waste Management & Research, 26, 61–69.
Gooch, M., Bucknell, D., LaPlain, D., Dent, B., Whitehead, P., Felfel, A., Nikkel, L., Maguire, M. (2019). The avoidable crisis of food waste: technical report. Value Chain Management International and Second Harvest; Ontario, Canada. Retrieved from: https://secondharvest.ca/wp-content/uploads/2019/01/Avoidable-Crisis-of-Food-Waste-Technical-Report-January-17-2019.pdf
Martínez-Blanco, J., Muñoz, P., Antón, A., & Rieradevall, J. (2011). Assessment of tomato Mediterranean production in open-field and standard multi-tunnel greenhouse, with compost or mineral fertilizers, from an agricultural and environmental standpoint. Journal of Cleaner Production, 19, 985–997.
Park Brown, S. (2007, August). Compost tips for the home gardener. Environmental Horticulture Department Florida Cooperative Extension Service, Retrieved from https://discover.pbcgov.org/coextension/horticulture/pdf/residential/CompostTips.pdf
Sánchez, A., Artola, A., Font, X., Gea, T., Barrena, R., Gabriel, D., Sánchez-Monedero, M. Á., Roig, A., Cayuela, M. L., & Mondini, C. (2015). Greenhouse gas emissions from organic waste composting. Environmental Chemistry Letters, 13, 223–238.
Schwarz, M., & Bonhotal, J. (2011). Composting at home - the green and brown alternative. Department of Crop and Soil Science Cornell Cooperative Extension, Retrieved from https://ecommons.cornell.edu/bitstream/handle/1813/29111/compostingathome.pdf?sequence=2&isAllowed=y
The Compost Council of Canada. (2021). Benefits of compost highlighted during International Compost Awareness Week 2021. The Compost Council of Canada, Retrieved from http://www.compost.org/compost_week/