Given the fact that the site is called ‘Compost Guy’, I figured it was time that I actually put together a solid page about composting! This page will grow and evolve over time, and its primary purpose is to provide an overview of composting and how to get started.
What Is Composting?
Perhaps the best place to start is with a geeky, technical definition, followed by an explanation for the various key components.
Composting is a bio-oxidative decomposition of organic wastes under controlled conditions, which results in a stabilized, humus-rich material.
Ok, let’s look at each part of the definition in more detail…
Bio-oxidative – Composting involves countless aerobic (oxygen-dependent) microorganisms, including numerous species of fungi, bacteria, protozoans and actinomycetes – all contributing to the breakdown and stabilization of the waste materials. This ‘breakdown and stabilization’ of materials is what’s known as decomposition.
Organic Wastes – Not to be confused with a type of agriculture (or gardening), the term ‘organic’ generally refers to any material that was once part of a living organism, or is the waste product of a living organism – not a perfect definition (since likely some exceptions), but sufficient for our purposes. Basically anything that is ‘biodegradable’ is an organic material. Examples include: grass clippings, kitchen scraps, leaves, straw, shredded cardboard, manure, wood (although this is a very resistant material). Materials such as plastic, metal and glass are examples of non-organic materials. The term ‘waste’ gets thrown around a lot, but when it comes down to it there is no such thing as ‘wastes’ – only misplaced resources!
Controlled Conditions – While some may consider composting to be the exact same thing as decomposition or rotting, technically speaking it is really actually a human invention, and a human-mediated process. The saying about the tree falling in the woods comes to mind – i.e. “If a tree falls in the woods, but no one is there to hear it, does it really make a sound?”. Similarly – if a pile of leaves falls in the woods, but no one is there to turn it, is it really composting?
Ok, so I’m being a tad facetious here. When it comes down to it, composting means a lot of different things to a lot of different people, but for the most part there IS some sort of human involvement – whether it be the piling, watering, or turning of the material etc – so it is at least somewhat controlled. In the case of large-scale composting conducted by professionals, it can be a very precisely controlled process.
Stabilized – While you might not realize it, all living creatures (including ourselves) are in a constant state of flux. A great deal of energy and effort is dedicated to maintaining this complex arrangement of molecules, cells etc. When an organism dies, all these maintenance mechanism start to shut down and the materials that make up the organism naturally breakdown into smaller components – eventually you are left with materials that basically won’t break down any further.
Humus – Humus is a prime example of a very stable material that results from the breakdown of living organisms (and their wastes). It is made up of very large, complex carbon-based compounds that are very resistant to further breakdown. It has considerable surface area, and is electrically charged, thus attracting (and holding) mineral and nutrient molecules very readily. All this surface area provides excellent water holding capacity and habitat for a diverse array of beneficial microorganisms. This is a very dark, rich smelling material – just visit a forest in your area and scrape away the upper leaf litter and you find lots of humus down below.
So there you have it – a fairly ‘quick and dirty’ look at what composting is. One thing I didn’t add to my definition was a mention of a heating (thermophilic) phase – something that many composting professionals would likely see as an important part of any technical definition of composting. Given the fact that I’m focusing more on home/backyard composting, I don’t think it is quite so important to get nitpicky with our definition. Further down the page I will discuss some of the main types of ‘composting’, and related organic waste management approaches.
There are many good reasons to start composting. Aside from the fact that it is just a LOT of fun (ok, so I’m a little biased!), composting is of course very beneficial from an agricultural, horticultural and environmental standpoint as well.
Agricultural and Horticultural Benefits of Composting
The stabilized end product produced via composting (i.e. compost) has a wide range of properties, beneficial for both plants and soil. Here are a handful of the most significant benefits of this material.
- Improves soil structure – makes it more ‘friable’ – i.e. gives it crumbly texture, beneficial for root growth.
- Improves water-retention in soils, helping to keep plants healthier for longer in dry conditions
- Provides a source of slow-release, organic fertilizer for your plants
- Boosts the community of microorganisms and other creatures beneficial for enhancing nutrient uptake and fighting plant diseases
Environmental Benefits of Composting
I don’t have any hard statistics to wow you with, but I’ve heard that the organic (remember our definition up above) fraction of waste that ends up in the landfill can commonly make up as much as 20-40% of the total waste stream, or even considerably higher in some locations (and certain times of year, I would imagine). This ALONE is a fantastic reason for composting – why on earth would we sent these materials to the landfill when we can produce such an amazing end product (and have so much funny doing it)?!
Aside from taking up space, organic wastes dumped in the landfill aren’t provided with the optimal conditions for aerobic composting and will often undergo anaerobic decomposition, which can result in considerable amounts of methane gas (CH4) being produced. Methane is apparently 21 times more potent as a greenhouse gas than CO2, so composting can even be helpful on the global warming front.
As mentioned above, compost helps to improve soil structure – rich organic soils (such as that amended with compost) are much more resistance to erosion, which continues to have a serious impact on the agricultural soils in parts of North America. Compost amended soils can also lessen the impact of storm-water and fertilizer run-off, thus helping to preserve natural water bodies and reducing water usage requirements.
Compost has even been used to successfully bring back to life soils affected by toxic spills or industrial activities such as mining. The complex humic compounds in compost can help to bind a variety of heavy metals and other nasty molecules, and the rich microbial community in compost can help to re-populate the soil with ‘good guys’ – the microbes that can help to enhance nutrient uptake in plants and protect them from disease.
How Do I Get Started?
Many people wrongly assume that composting is a complex and challenging undertaking, and worry that if they try it they won’t do it “right”. While large-scale ‘professional’ composting facilities certainly do have the process down to an exact science, there is really no need for us mere mortals to be intimidated. By following a few basic guidelines, you can produce your very own beautiful compost – and do so with relative ease.
Here are the basic requirements for making compost – 1) Moisture (water) 2) Organic ‘waste’ 3) Warmth, and 4) Oxygen
Moisture – Composting is a biological process mediated by countless microorganisms. While you may not think about it when you pick up a handful of garden soil (which may only be slightly moist to the touch), in order for there to be life (or at least active life) in that soil, there needs to moisture spread throughout. You don’t want to have too much moisture however – when all the soil/compost pore spaces are filled with water, it is much more difficult for air (and thus oxygen) to permeate the material.
Organic Waste – You’re obviously going to need some sort of starting material – typically a ‘waste’ of some sort. For a typical home owner this could include fall leaves, grass clippings, yard and garden waste, kitchen scraps, paper, cardboard etc. Someone who lives on a farm may also have some sort of manure, which is an excellent starting material for composting. There are two very important elements that we need to consider when deciding on what materials to use – carbon and nitrogen. Specifically, it is important to consider the ratio of these two elements, known as (surprise, surprise) the ‘Carbon to Nitrogen Ratio’ (C:N). The ideal C:N ratio for composting is somewhere in the range of 20:1 to 40:1.
You definitely don’t need to let this fancy term intimidate you though – we can compost just fine (thank you very much) if we think in terms of ‘carbon-rich materials’ and ‘nitrogen-rich materials’ – or even ‘browns’ and ‘greens’. I prefer the former, simply because there are plenty of exceptions to the colour rule. For example, manure is a fantastic n-rich material for your composting system – but I have yet to see a green heap of manure (and would likely run away screaming if I did)!
Here are some common examples of carbon- and nitrogen-rich materials:
- Fall leaves
- Cardboard / Paper
- Peat moss
- Coir (coconut husk waste)
- Wood chips / Sawdust
- Fresh Grass Clippings
- Green Yard Waste
- Kitchen Waste (certainly some exceptions here, but in general not a bad idea to think of them as N-rich)
- Hair (yes, you can in fact compost hair!)
It is important to realize that even the n-rich materials can have lots of carbon (and c-rich materials will have some nitrogen as well), so you certainly won’t need 20-40 times more fall leaves than grass clippings for example. A reasonable rule of thumb would be to to use about twice as much c-rich material as n-rich – but as you’ll see, there are no hard and fast rules for composting. The best way to see what works best is simply to start experimenting yourself. I like to think of composting as part art form, part science – once you’ve done it enough you will start to get a ‘feel’ or it and will be able to create a perfect pile without even thinking about it! Just so you know, if your composting heap has too much nitrogen (the C:N is too low), excess nitrogen will tend to be lost in the form of ammonia gas. On the other end of the spectrum, if you C:N ratio is too high the composting process will slow down considerably. Find the sweet zone between these two extremes is the key – so long as you pay heed to the other important requirements, that is!
Warmth – The success of your composting efforts can be temperature dependent as well. If you compost heap is frozen solid you can be sure that the microorganisms needed to mediate the process won’t be very active, and thus it will come to a complete stand-still. If your aim is to create a ‘hot composting’ system, temperature will play an even more important role – but don’t worry, as long as you take care of a few requirements the microbes will do the rest!
We talked already about the C:N ratio – well aside from playing an important role in the decomposition process in general, it is particularly important when you want your heap to heat up. If you dump and big pile of saw dust on the ground for example, while it certainly may get somewhat warm in the middle thanks to the activities of microbes, it won’t generate the kind of heat a well balances compost heap can – and it will also take a LONG time to breakdown. That’s because saw dust is incredibly high in carbon, but not nitrogen.
The size of the heap (or container that holds the materials) is also an important consideration. You can set up an incredibly well-balanced compost heap in a margarine container if you like, but you certainly won’t have a mini hot composting pile on your hands. You need a certain “critical mass” in order for a heap of organic materials to generate enough heat for thermophilic (hot) composting to occur – generally this is in the range of 1 cubic yard, but using even more materials will likely produce better results.
There are of course ways to help the process along, should you not have the critical mass needed. Putting your materials in a dark container (backyard composter, tumbler etc) can help since the container will absorb a lot of heat from the sun (more so in warm weather) and reduce the amount lost to the surrounding environment. There are even systems that can artificially mimic the hot composting phase on a much smaller scale. Small home composters like the ‘NatureMill’ are an example of this.
And of course, there are other types of ‘composting’ that don’t require any heating at all – such as vermicomposting and bokashi, both of which will be discussed shortly.
Oxygen – As mentioned, composting is an aerobic process – that is to say that it requires oxygen in order to proceed properly. The community of microbes needed to help the process along require oxygen for respiration – and in fact it is via this respiration that heat is given off.
The challenge for a composter is to maintain adequate moisture while providing enough oxygen to the composting mass. Water cannot hold nearly the same amount of oxygen as air, so if your compost heap becomes waterlogged air will no longer be able to circulate through the pile. It is important to find a balance however, since a bone dry compost heap is about as effective one that is frozen solid – it will basically be held in suspended animation until some moisture is added.
When oxygen levels drop significantly in a compost heap aerobic processes start shifting to anaerobic processes, and the community of microorganisms changes with it. Anaerobic digestion can be a useful waste management strategy in its own right, but this is NOT what you want to have happen to your compost heap. Anaerobic pathways tend to produce a variety of undesirable compounds – some of which have bad odours and/or phytotoxic (plant harming) properties. One easy way to determine if your compost heap is staying aerobic is to use the good ol’ fashioned “smell test” – simply move some of the material around and take a good deep whiff. Does it have a nice, earthy aroma (or no smell at all), or does it have an unpleasant ‘rotten’ smell?
The type of materials you use in your compost pile can have a major impact on air flow. Bulky materials like shredded cardboard, straw and fall leaves are all great for encouraging air movement. If you are trying to compost wastes with really high moisture content, such as liquid manure or fruit/vegetable scraps, it will be vitally important to use these bulking agents. Often times (but not necessarily a hard and fast rule) the bulking agents are your carbon-rich materials.
You can also artificially aid the aeration of your pile by turning the materials, with a pitchfork or by placing them in some sort of tumbler. In fact turning is an important part of hot composting – as the composting mass heats up and more and more oxygen is consumed, concentrations of this gas within the pile can be depleted regardless of bulking agents etc, so a little help from you can be important.
Hot composting doesn’t always require active turning however – you can also try out various passive composting techniques. Apart from using bulky carbon-rich materials, you can situate your heap over top of a raised, vented floor, allowing air to be drawn up through the pile as hot air is released from the top. Another strategy is to insert perforated pipes into the composting mass, so air can be drawn in to the center of the pile where it is needed.
What About Other Kinds of Composting?
As I’ve mentioned above, there are other types of ‘composting’ that you can try out apart from ‘hot composting’. Two other significant ones are vermicomposting (aka worm composting) and bokashi.
Vermicomposting – In a nutshell, vermicomposting is a cooler composting process involving the joint action of earthworms and microorganism (with a few other helpers as well). It is my personal favourite composting method, given the versatility and benefits of this strategy. It is important to mention that only certain kinds of worms can be used effectively for vermicomposting – those specialized for a warm, crowded life in rich organic environments. These are what I refer to as the ‘composting worms’. Probably the most widely used and known worm for vermicomposting is the ‘Red Worm’ (also known as ‘Red Wigglers’), Eisenia fetida, but there are also others such as the European Nightcrawler (Eisenia hortensis), the African Nightcrawler (Eudrilus eugeniae), and the Blue Worm (Perionyx excavatus).
Worm composting is a great option since it can literally be done on any scale. No heating is required (in fact, you want to discourage any heating of your composting materials, since this can harm the worms), so you don’t need the ‘critical mass’ mentioned above. This is an ideal composting method for those who don’t have a lot of space, but still want to produce a nice compost for their plants.
Bokashi – Bokashi is another interesting composting alternative. Unlike hot composting and vermicomposting, it is primarily an anaerobic process, and it doesn’t produce a rich, stabilized end product the same way the other methods do. What I love about bokashi however is the sheer ease of it. You simply add your food waste to a bucket, along with a bokashi mix (wheat bran inoculated with special microbes) and then let it sit for a period of time once the bucket is full. Unlike some other anaerobic digestion processes, bokashi does not produce foul odours if done properly.
The only downside of this method is that you need some place to put your end material. You can’t simply start feeding it to your house plants. If you have worm bins or other compost bins you can add it to these and it will quickly be converted into an aerobic compost. Or, you can simply dig the material straight into your garden, where it will gradually be broken down and contribute to the health and nutrition of your garden.
For a complete overview of the topic of bokashi, be sure to check out my Bokashi Resource Page