Recycling – What Happens When You Compost?
What is Composting All About?
It’s very simple but it seems like magic. You throw all your kitchen and garden rubbish onto a heap, add a bit of muck and maybe one or two extras, and tiny creatures convert it into crumbly sweet smelling stuff that plants can feed from as and when they need it.
What Happens When You Compost?
You don’t have to get too technical about, as decomposition of organic material is a perfectly natural process that will eventually happen whatever you do, but the more you know about what goes on when you compost, the easier it is to get the best results. You may find the processes at work quite fascinating, as your compost heap is not just a pile of old waste but a teeming pile of life and energy: macro-organisms and micro-organisms, chemical processes and physical ones, reproduction, death, new life … it’s a seething hotbed of activity.
As soon as you lay down some organic material into a compost pile organisms get to work. Allcontains substances that plants need to grow, but these remain locked up until transformed by decomposing organisms into forms that plants can use.
Macro-organisms include mites, centipedes, millipedes, spiders, springtails, beetles, ants, flies, nematodes and earthworms. They start the work of decomposing, dragging materials through the heap, and chewing, grinding, sucking and tearing them into smaller pieces. The smaller the pieces, the larger the surface area for the micro-organisms — bacteria and fungi — to get at. These then digest whatever they come across, liberating nutritious elements locked into the waste.
The bacteria in compost heaps depend on the material, the temperature, moisture and air content. Bacteria produce enzymes to digest whatever organic material is available to them. The most important bacteria are psychrophiles, mesophiles and thermophiles. As they feed on the waste they break down compounds, grow and multiply and release heat as a by-product. The problem for bacteria is that they kill themselves off — as they work and reproduce they make their environment too hot to live, so they die or move to cooler areas at the edge of the heap.
Psychrophiles, or low temperature bacteria, start things off in colder situations. They operate at cool temperatures, below 15°C. As they consume fibrous matter they oxidise carbon and raise the heat of the heap so the next level of bacteria can get to work. In very cool areas psychrophiles will do most of the work so theprocess can take over a year.
Mesophilic bacteria are medium temperature operators, content (like humans) at between 15°C-40°C. If you start a compost pile in summer, mesophiles will get straight in there. In most compost piles mesophiles do the bulk of the bacterial work, but if they generate too much heat their job is finished. In hotter temperatures, over 40°C, thermophiles or high-temperature operators take over. They can take the temperature right up to 75°C. They are the shortest lived of all the composting bacteria as a heap shouldn’t remain too hot for a long period.
Actinomycetes and fungi
Well-made compost has a characteristic earthy smell like newly turned, or freshly picked mushrooms. This is caused by actinomycetes at work. They are a higher form of bacteria that increase as decomposition gets under way. They liberate carbon, nitrogen, and ammonia from decomposing matter. Fungi also take over at the later stages of decomposition, breaking down complicated compounds and releasing further nutrients.
Continued Benefits of Composting
All these organisms working together transform compost into nutritious humus, and as it is a living substance the beneficial micro-organisms continue their work of liberating and transforming elements when the compost is added to your soil.