Ham's introduction to composting

    Composting is a natural process where insects, worms, fungi, and microbes cause plant matter to break down into plant-usable forms that look (ideally) like dark soil. Whether this is happening on a remote forest floor after the great autumnal leaf drop, on the underside of your mulch layer in your back yard, everything breaks down... eventually. However, that's not to say that you should put anything and everything into a compost bin and expect miracles. In fact, many people start composting, but fail to achieve usable results, and often end up getting frustrated and fed up with the whole idea.

    Why compost?

    • You take what is effectively waste (usually free) and turn it into something productive.
    • You reduce the burden on landfill while you reduce nutrient loss for your property.
    • You reduce the need for soil amendments, fertilizers, and potting mix.
    • Some people use the heat generated by compost heap to heat their hot water system.
    • You can restore poor soils, or improve good ones to produce higher yields and healthier plants, which reduces the need for pesticides and herbicides.

    If you have the absolute worst soil, whether it's rocky, brick-filled, sandy, or clay-ridden. The solution to making it fertile, productive, soil is the same:

    1. Add organic matter (compost).
    2. Mix it in.
    3. Keep it suitably moist. (Perhaps reduce water loss by mulching, which is again, more organic matter)

    So whether you have flowers, grass, a veggie patch, an orchard or a whole forest. Plants take nutrients out of their surrounding soil via the roots and re-purpose them for making all the plant parts you're familiar with, such as more roots, stems, branches, leaves, flowers, fruit, seeds, etc. That means that there's nutrients locked up in your kitchen and garden waste, but they might not be accessible to plants until they're broken down. To do that effectively... you need to compost.

    Mixing compost the right way, the Carbon (C)- Nitrogen (N) ratio:

    I don't know if you ever did Chemistry and/or Biology at school (or beyond) but not all kitchen scraps, or garden waste is the same. Your common green plant matter is high in nitrogen but comparatively low in carbon. Conversely your common brown plant matter, is usually high in carbon, but low in nitrogen. (The exception to this is coffee grounds, which is brown-yet-high-in-nitrogen). This underlying chemistry lesson is important because the microbes responsible for doing most of the decomposition (in your average "aerobic" compost bin) prefer certain mixes of Carbon to Nitrogen for efficient decomposition. Ideally, somewhere between 25 and 32 parts of carbon, to one of nitrogen. If you prefer percentages, that's 3-4% nitrogen, and the rest carbon.

    Think about that for a minute... your 100g of kitchen scraps are nitrogen sources... and you need to add 3Kg of straw (or some other carbon source) to balance that out. Got a kilogram of salad left over from a company party? That needs a whole hay bale or two to balance that out. Suddenly, the reason most people fail in their compost activities becomes clear... not enough carbon! Composting this without adding carbon, results in a wet, slimy, smelly compost bin. Adding carbon is relatively simple, and comes in many forms. Try adding hay, pea straw, shredded cardboard, wood chips (as long as it's real wood without paint, chemicals, glues, etc), wood ash, sawdust, corn stalks, peanut shells, pine needles, even newspaper.

    I generally avoid putting pet droppings, meats, oils and dairy products into my compost, as they will attract pests and potentially, add some really unpleasant smells. If you generate a lot of these waste materials, you might want to look into anaerobic (non-aerobic) composting like the Bokashi method. But this uses a completely different bunch of organisms, in an air-tight environment... and is more expensive to implement.

    Ways to speed up the process even further:

    • Shred (use a blender) your materials: Physically breaking the material down will speed up the composting process.
    • Mix your carbon and nitrogen ingredients well: Some people put a sprinkling of nitrogen-rich ingredients, and then layer carbon-rich stuff on top. The thinner the layers, the greater the integration, and the faster the process occurs.
    • Maintain a moist pile, not a soaked pile. Water is essential for life (including the compost microbes), and as such, giving your pile some water occasionally will speed things up. Too much water, and you drown the pile, reducing airflow, and temperature alike.
    • Aerate your pile. Whether that's turning the pile over every second day (it's a lot of work, but should allow you to break everything down in 2-3 weeks during warmer months) or running pipes riddled with holes into numerous layers of your pile, some even use aquarium air pumps to accelerate the process.
    • Maintain temperatures. A hot pile is an active pile. The location of the pile (whether it's in direct sunlight) will help to maintain temperatures. Also, the overall size of the pile will determine the heat retention rates. Numerous studies have shown that piles of roughly 1 metre cubed are the most efficient.
    • Culture your microbes: Like fermented foods, it's entirely possible to introduce microbes from one compost bin/pile to another if you have a fantastic starter culture. If you have one compost bin that is breaking things down really well, but aren't having so much success with another. Take some of the compost from the one working well, and put it into slow-composting one. Give it the air, water, and the right carbon to nitrogen mix, and you should see things improve.


    Compost designs:

    Ranging from the simplest... in-situ composting, and working our way up from there.

    Let's look at your average lawn. I call them uninspired, high-maintenance, spaces of unused potential. Who in Canberra actually sits on the lawn with their family? The answer: almost no one. So people grow lawns, and have to irrigate them, and feed them, and then they mow them. Often, the nutrients used to make those grass clippings are then often lost because they're thrown out. So, the lawn does ok for a while, until the nutrients start running out, then the grass looks a little patchy... so out come the fertilizers, and excessive watering to restore the lawn to a neighbour-impressing green again, only to mow it and throw more leaves away... does anyone see the point? I don't. I have a war on grass in my yard, and have replaced it with raised garden beds, strawberries, or clover, which puts nitrogen in the soil, and doesn't grow tall enough for me to worry about mowing. It's also a bee-attracting ground cover, which helps with the pollination rates for my food forest.

    I mention this to make two points. One, is the concept of nutrient loss, and how far too many people waste their plant matter by "chucking it out" into "green bins". The second point is that recycling those nutrients is achievable via composting, and thus stopping nutrient loss, it benefits the environment, you save some money on fertilizers and potting mix, and you have far more control over what goes into your soil. Back to the lawn....

    In situ-composting:

    Ok, so you could just take the mower's catcher off and leave the clippings on the lawn... and sure enough, the clippings will break down and fertilize the soil again. So this is bar none, the simplest form of composting... but in truth, birds take some, wind takes some, so the nutrient loop isn't exactly closed. So external nutrients are still going to be needed eventually. Also, if you have kids, pets, etc, you can be sure that clippings will make their way into your home.

    In situ composting includes just simply leaving the autumnal leaf drop and literally leave the leaves where they fell.

    Trench composting:

    The next step up, is "trench composting". In short, take your kitchen scraps, and simply bury it. This was common in my grandparents day. They'd grow their vegetables in rows, and between them, a trench would be dug to bury scraps and other plant matter. It works, but most people don't feel like burying their kitchen scraps the same way cats bury their droppings every day. Also, I have seen my grandparents run-ins with possums digging up food scraps when this method was used.

    Compost pile:

    It might seem odd, but this doesn't scatter the scraps and plant matter around the garden in drips and drabs, but gathers them into a concentrated space. You don't even really need a compost bin. Some people just make a pile, mix the right amount of carbon to nitrogen, wet it down, and cover it with a tarp. My mother wasn't even that fancy, she skipped the tarp, and just made a pile. This had some down sides because my mother didn't know the right C-N mix, and had a tendency to pour things like spent cooking oils into it. I'd normally say that we would have had a pest problem, but we had a dog problem. Our dog, would go and lick all the fat, drippings, and oil up.. and got horrifically fat. So in short, don't put meat, oils, or dairy into your compost.

    The ideal size of a compost pile is 1 metre cubed. This apparently has the right amount of surface area on the outside and short-material distances for aeration, while having enough material to insulate the active core's ideal temperature.

    Compost bins:

    This is where most people who make their weekend trips to the local hardware store will look for compost inspiration. Compost bins can be made from metal mesh or sheeting, plastic, and some are even made of wood. They can come in all sorts of shapes and sizes, so it's important to make sure the one you choose actually fits in your space.

    Compost bins can be both a benefit, and a hindrance. Very few have adequate ventilation. Others are bright colours which fail to absorb enough heat from the sun to maintain ideal temperatures during cooler months. Some make the process of turning your piles over far more difficult than if you'd merely had a pile.. so please consider these things when buying them. Having said that, I have four bins in multiple styles.

    Compost drums:

    These are basically compost bins which can rotate on a stand. The theory goes that the drum lays on its side, and is supported by an axle or wheels. By turning the drum, the compost inside is both aerated and mixed, and then you have a much easier time making compost. Some of these work well, but many do not handle much compost at all. Some are heavily insulated so temperatures are maintained in winter, and some even have multiple sections so you can stagger your compost production. However, these can run into hundreds of dollars.

    Compost stations:

    This is where serious gardeners get into larger scale compost production. In short, they build dedicated zone, with three sections, side by side. It's usually helpful to have the ability to empty a wheelbarrow, truck, trailer, forklift, or other machinery able to dump loads of manure and green waste on one side (the nitrogen), and the hay, wood, straw, etc (the carbon) on the other side. That way you have a really convenient location in the middle to make a huge amount of well mixed compost. Some people even make a four section station, so they can toss the mix from one central area over to the other, or just make two piles simultaneously and stir them a little every now and then for aeration.

    At the extreme end, higher-end compost stations have concrete or brick walls, but some people make them out of sleepers, corrugated iron, frame-supported mesh, or even wooden pallets. (See below)

    Wood compost station
    This has a mesh backing for aeration, and removable boards at the front.


    The next step up from there is what's called "OSCA" or On-site composting apparatus. This puts an industrial spin on the whole composting thing.

    There's a small one at the Canberra Environment Centre (where I did my Permaculture course) It can process up to 100kg of waste per day. To put this into context, the average household generates between 0.5-2.5kg per day. Here's the picture of it:

    There are even bigger units, capable of doing tonnes a day... but that's getting into a scale most people and even most institutions wouldn't possibly use.

    I've intentionally skipped worm farms, as I believe that's worthy of it's own article.

    The risks of composting:

    Like everything, there are certain risks in composting, especially when dealing with microbial-rich materials, manure, airborne dust, insects, occasional spiders, reptiles attracted to the warmth of the compost pile, heavy loads, and potentially back breaking work. These risks can easily be mitigated or entirely avoided by wearing gloves, sturdy shoes/boots and a dust mask. Similarly, choosing the right composting method for you can vastly reduce the physical risks and make the act of composting easier. Finally, making informed decisions about what goes into your pile can help you to avoid spreading pest problems, weed seeds, and avoid potential health risks.

    However, there are more subtle risks to worry about, particularly when you don't know where the ingredients have come from, and may have been sprayed, contain pests, and so spreading the resulting compost around can cause a number of problems, even if they're reasonably well composted. Some plants themselves can be quite toxic, to humans and animals alike.

    What sort of compost method should you choose?

    Well that will come down to a variety of factors. But here is a surprisingly good flow diagram that I found online:

    Good luck, and happy composting!


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