Would you like to compost properly at home and find out how to make your own compost? We will explain everything you need to know about composting.
Compost is a compilation (Latin compositum = “the compiled”) of a wide variety of starting materials. However, the path from waste to valuable soil improver is not only wonderful and practical but also mysterious: the processes that lead to the formation of new humus after rotting are still not completely unravelled. However, humans have been taking advantage of the special properties of humus for centuries by allowing organic material to rot and transform in compost piles. Nevertheless, even today many gardeners ask themselves the question: What can go on the compost heap? And what is the right way to compost?
- Composting: how to do it properly
- How does composting work?
- What belongs in the compost?
- Which compost is the best?
- Small composters for balcony and indoors
- The right location for composters
- Composting tips for successful rotting
- Creating compost
- Filling composters correctly: six golden rules for layering
- How long does the compost need?
- Sifting compost
Composting: how to do it properly
In this article, you too will learn everything necessary to properly compost in the compost pile or composter. The tools needed range from choosing the right composter, to knowing the microorganisms involved, to deciding when a compost is ready for use. But let’s first start with the basics.
How does composting work?
During composting, organic materials are transformed into new humus by billions of small and tiny organisms. The first step is decomposition, which is quite tumultuous: The environment is noticeably warmed up by the increased activity of the microorganisms, which try to get at the nutrients inside. This phase is called the “main rotting” or “intensive rotting” – the result of which is the so-called fresh compost.
After the decomposition, which lasts for several weeks, the “post-rotting” phase follows. Now, substances that were formed during the main rot are newly linked to form large biomolecules. These biomolecules are the humic acids that later give the compost its special properties. Their structure is extremely variable, which is why no scientist has yet been able to develop a universally valid model of such a humic acid. The new humus molecules are relatively stable – much more stable and less prone to degradation than the product of the main rot. The compost is now called “finished compost”. Up to this point, composting has taken at least five months under the best conditions. If composting is still not completed, the so-called mature compost is formed. Many a patient gardener swears by the exceedingly soil-improving properties of two- to three-year old mature compost. Anyone who has quickly reached this level of rotting has really done everything right in composting.
Tip: The “stability” of compost means that it can no longer be easily broken down by microorganisms in the soil. Because it consists largely of carbon, this would be possible: soil organisms would be only too happy to use this carbon to feed themselves and continue to reproduce. The rule of thumb is therefore: the more nitrogen the compost still contains, the more unstable it is. For this reason, the question of what is allowed on the compost is also crucial, because the balance of carbon and nitrogen in the rotting material is also significant.
Hot and cold rotting
Proper composting can be done in several ways and compost can be created in two different processes: cold rotting or hot rotting. In private gardens, in fact, cold rotting always occurs: when a compost heap is gradually piled up slowly, the rotting processes do not occur all at once, but one after the other, layer by layer.
The top layer in each case develops the most heat through the decomposition processes, but loses it quickly to the environment because it is not insulated. Therefore, there are no particularly high temperatures and pathogens and weed seeds thus unfortunately survive the rotting without any problems. For this reason, when composting in your private garden, make sure that no pathogens or seed-bearing plants end up in the compost.
Tip: If composting is done properly and professionally at recycling centres and composting plants, a whole pile is always put on at once for hot rotting. As a result, the intensive rotting and self-isolation of the pile leads to high temperatures of 50 to 80 °C, which hardly any pathogen or weed seed survives.
- Composting converts organic materials into compost or humus.
- The decomposition phase is called main rotting, and the build-up phase is called post-rotting.
- The product of the main rotting is fresh compost, which is rich in nutrients and unstable.
- The product of post-rotting is finished compost or mature compost, which is less nutrient-rich but much more stable.
- In the vast majority of cases, composting in private gardens proceeds in the cold rotting process.
- Pathogens and weed seeds are not killed in the cold rotting process – so the material to be composted should not come from diseased plants or carry unwanted seeds.
You can also read more about the properties and uses of the different types of compost in this dedicated article.
What belongs in the compost?
For convenience, in the table below you will find a list of the most important suitable types of waste and contrasted them with the those that are unsuitable. As a general rule, shredded material composts faster. Chipping branches and hedge trimmings can therefore be worthwhile.
|Compostable kitchen waste||Compostable garden waste||Not to be composted|
|Fruit and vegetable scraps||Lawn clippings||Glass|
|Coffee and tea residue||Leaves||Metal|
|Meatless leftovers||Hedge / wood clippings||Root spreading weeds|
|Citrus fruit and banana peels (in low quantities)||Sawdust||Meat left overs, bones, large quantities of dairy products|
|Shells from cooked eggs||Roots and soil from old planters||Shells from raw eggs|
Which compost is the best?
Before you start composting, you need to choose a suitable composter. We will here present some models and concepts for this purpose. Which composter is the most suitable for you always depends on the amount composted and the space available to you.
In a sheltered, semi-shaded location and on a healthy garden soil, you can create a compost heap – also called a compost pile. It is basically a pile that gets a little bigger layer by layer.
You can also create this heap in a frame made of metal, wood or plastic. These should, of course, be open at the bottom to let in microorganisms from the soil. The enclosure itself should also have a sufficient number of slits or air holes to ensure aeration. A two-chamber or two-tier system is useful in any case. You can use one space to collect material that you don’t want to put on the compost yet due to optimal mixing, or use the second chamber when turning. In any case, think about covering the pile, for example, with straw or mulch film. The compost heap generally requires a bit more space than a composter, and in its simplest form – as a plain pile – is probably the least expensive way to compost even large amounts of waste. If you love the flair of old farms, a compost heap is probably the only true way to compost properly.
Quick composters are basically open-bottom boxes with vents, a flap for loading and one for removing finished compost. They are designed to optimise moisture and temperature for microorganisms and enable proper composting of smaller amounts of waste by holding the material together. However, because mixing and rearrangement are difficult or even impossible in such a container, a good layering of various materials must be done from the beginning when operating a quick composter. Also, the compost material must not be compacted under any circumstances to avoid a lack of oxygen inside. Quick composters are usually dark in colour, so that they warm up faster. When choosing one, be sure to look for adequate aeration and a convenient removal flap. The space required by quick composters – depending on the volume – is usually limited to about one square metre of soil. The commercially available capacities range from 300 to 1600 litres.
Thermal composters are a special form of the quick composters described above, with the only added benefit of good thermal insulation. This ensures a constant temperature inside the composter that is as high as possible. Thermal composters are thus an improvement on quick composters, because even small amounts of material can be strongly composted in them. Their size is slightly more expansive than the rapid composters because of the insulation, and they are also usually more expensive. The available capacities here range from 180 to 900 litres.
Rolling composters are a relatively new idea. A rollable container – usually plastic – has the great advantage that you can easily move it to where the compost material is. For stationary storage, the rolling composter usually comes with a frame in which it can also be stored in a rotating position. In addition, rolling the material around inside mixes and aerates it, eliminating the need for layering and repositioning the material. The disadvantage is the often only small capacity of 70 to 180 litres. A solution to this can be achieved, if necessary, with the purchase of several rolling composters.
Small composters for balcony and indoors
Even on the very smallest scale and without a garden, composting or recycling is possible. With the worm box and the Bokashi bucket, we would like to introduce you to two working options for this purpose, To give away the product of Bokashi or worm bin, if you should ever have a surplus, is probably not even a problem, as you are bound to find someone in your circle of acquaintances will be happy to receive some organic fertiliser.
This compost trend from Japan does not actually involve composting at all, but rather fermentation. With a Bokashi bucket, you not only get an organic liquid fertiliser after a very short time, but also an organic fertiliser for potted plants or beds after two to six weeks (depending on conditions). Basically, the material comes “predigested”, and subsequent decomposition proceeds very quickly. Unlike composting, fermentation takes place in the total absence of air and is carried out by lactic acid bacteria, which are added specifically for this purpose. Incidentally, the same bacteria turn white cabbage into delicious sauerkraut. A bokashi bucket takes up only as much space as a standard organic waste bin and has a capacity of 15 to 20 litres.
A wormery makes use of the incredible abilities of various relatives of the earthworm to achieve odour-free composting, even indoors. In the meantime, however, many instructions for do-it-yourself construction can be found on the Internet. The principle of worm farms is simple: hundreds of worms live in a well-ventilated container, feeding on the organic waste you put inside. Wormeries are always divided into at least two chambers. Once a chamber is filled with composted material, the worms move through slits or holes to the next area where there is fresh food for them. They multiply in the box and usually need to be purchased only once. Users of worm bins often report that a strange odour is formed at the beginning, but it disappears with good ventilation and after a certain period of use. The worm boxes can be used in an area with a temperature of 15 to 25 °C, so it should be possible to find a place in every home. Available capacities start at about 70 litres and are expandable on some models. Because compost worms eat many things, but not everything, it is also important here to deal with the question in advance: What can go on the compost heap?
By the way: As mentioned above, a compost heap set up at one time can heat up strongly in the hot rotting process – to between 50 and 80 °C. This effect makes use of the organic pile, also referred to as the “compost heater”. Water pipes are laid through the pile, which constantly dissipate heat from the pile. The warm water can be stored in insulated tanks and also used later. In this way, it is possible to use a compost heap to power a heating system and the hot water system. However, as mentioned, this requires a hot rot and this is limited to only a few weeks. Therefore, having your own compost heating system is only worthwhile if extremely large quantities of compostable material are produced.
Summary: Which composter is the best?
- Composting in a compost heap is inexpensive, but takes up a lot of space; to allow adequate aeration, the pile should not be too wide or too high
- Quick and thermal composters are suitable for quick composting of smaller quantities of waste and are space-saving, but must be filled carefully in layers
- Rolling composters do not need to be layered or moved, but have a very limited capacity
- In the bokashi bucket, strictly speaking, fermentation takes place, but plant fertilisers are also produced from waste; they are the size of organic waste buckets
- The worm bin makes use of the properties of dung worms and composts kitchen waste on the space of a stool, for example
The right location for composters
To ensure the mildest and most consistent temperatures possible, you should also consider a few things when choosing a location. A semi-shaded location is optimal to ensure adequate, but not excessive, heating. If the site is protected, the compost can maintain the temperature longer. Humidity regulation is also easiest in such a location. Under the compost, there should also be a healthy garden soil, preferably broken up. In this way, the living organisms involved in composting can migrate into the compost and also migrate out once they have completed their task. If you want to run a compost heap, you should consider the subsequent width of the heap: A pile about 150 cm high should be about 250 cm wide at the base to ensure adequate aeration. The reason why the above factors are important for proper composting, you can read a little further down.
Summary: Composter location
- The site should be in a partial shady and sheltered position
- A healthy and loose garden soil allows the immigration of microorganisms
- Note the size of the finished heap or the space you may need for sorting or turning the compost
Composting tips for successful rotting
The processes taking place in the heap are controlled by microorganisms. In order to promote the rotting and perhaps even to accelerate the process, it is important to optimise the living conditions of these microorganisms. You can tackle them with a few adjusting screws:
The bacteria and fungi involved in the rotting process require a sufficiently humid environment. This is made possible by a semi-shaded location, a cover for the compost or the use of a composter. During hot, dry periods, you should water a compost pile.
High temperatures allow the microorganisms to reach peak performance, and the rotting process is accelerated. Thermal or quick composters are based on this principle. Insulating and covering the compost can also go a long way, as can a sheltered, location that occasionally gets some sun.
Oxygen inside the composter
The microorganisms involved are aerobic, which means they require oxygen to breathe. A compost heap that is too dense or too wet makes their work more difficult or even causes them to die. The use of sufficiently coarse, structurally stable material and frequent repositioning, on the other hand, ensures a good supply of important air for breathing. If the oxygen supply is insufficient, there will be an increased proliferation of anaerobic (i.e., non-air breathing) microorganisms. The products of their activity are, for example, unpleasant-smelling sulphur or methane compounds. So if your compost smells bad, you should provide aeration by turning the compost, for example.
Nutrients in the composter
In order to multiply and be active, microorganisms need not only carbon-rich but also nutrient-rich substrate. Therefore, in order to be sufficiently supplied with nitrogen, it may be useful to mix in some nitrogen fertiliser. However, if there is sufficient nutrient-rich material – that is, material with a small C/N ratio – this is not necessary. A colourful mixture of different materials provides an optimal breeding ground. The C/N ratio indicates the ratio of carbon (C) and nitrogen (N) in a material. Materials with a small C/N ratio (for example, manure, C:N = 5:1) decompose quickly, but little humus is subsequently produced. Materials with a large C/N ratio (such as wood chips, C:N = 120:1) decompose very slowly and the microorganisms even extract nitrogen from the environment for this purpose. To influence this, it is also important to know what is allowed on the compost.
pH value inside the composter
The activity of microorganisms increases with a rising pH – at least up to a certain point. Conversely, they are inhibited in their activity at low pH values. If a lot of “acidic” material (such as lawn clippings and leaves) ends up in the compost, you should powder it with a little lime. Algal lime is well suited, for example.
In the past, the layering of the compost was considered an irrevocable condition for the success of composting. However, you will notice that you have more than just this one option.
Create compost properly: should I layer or turn the compost?
Turning the compost, by introducing oxygen and mixing the material, should improve the living conditions of the unseen working microorganisms.
Basically, you have two options: You can build up your compost in perfect layers – or turn it over regularly. If you layer your compost conscientiously and with enough coarse material to avoid waterlogging, low-oxygen zones, or otherwise suboptimal rotting conditions, you can save yourself the trouble of turning it. Quick composters and thermal composters require this, because they are difficult to mix. However, this necessitates the careful sorting of all compostable waste. If you dislike this regular discipline, you can layer a compost more carelessly, but then you should keep an eye out for possible rot or dry spots. In this case, turning over is a must once a year and if you notice a slowed down rotting and stench, you should also grab the garden fork quickly and turn the lowest upwards and the innermost outwards. On this occasion, you should also moisten dry material and remove any rotten areas. If you are using a rolling composter, there is of course no need to mix the waste – only with reduced rolling around should you move the bin a little from time to time. Also, to avoid rotting from the wrong rotting material, such as dairy products or meat, it’s better to deal with what can go on the compost in advance.
Summary: How to create compost properly – in layers or by turning?
- Turning is intended to introduce oxygen into the rotting material and thus promote the conversion process
- If you layer your compost very carefully and ensure aeration, turning won’t be necessary
- If the rotting material is not sorted so carefully, it must be turned once a year or as required
- A rolling composter eliminates the need for both turning and layering if it is moved occasionally
Filling composters correctly: six golden rules for layering
- At the bottom of the compost, place some sawdust, bark mulch or wood chips
- On top of this, alternate layers of structurally stable material (for example, branch cuttings, firm, dry shrub cuttings, and leaves) and softer waste from the kitchen and garden
- Between the layers, if necessary, you can spread a very thin layer of lime or nitrogen fertiliser
- If you use other compost for inoculation, you can also add a layer of this occasionally
- Material that is too dry should be moistened, material that is too wet should be dried before it is put on the compost
- If you are using an open compost heap, it should be covered at the end with a thick layer of straw, hay, leaves or climbing plants
How long does the compost need?
If you set up your compost correctly, it will go through different stages: the initial fresh compost becomes finished compost and finally mature compost. Fresh compost is ready for use after about four to eight weeks, finished compost after five to six months. Prolonged composting does not harm the final product either; the newly built humus compounds become more resistant to decomposition and act more and more as soil conditioners the older they get. In general, the more nutrient-rich the starting material was, the faster composting will proceed and the lower the yield of stable “permanent humus”.
When is the compost ready?
The times given above are, of course, guidelines: depending on the working conditions of the microorganisms, the rotting time may change. It is best to trust what you can see, smell and feel: When your waste has turned into fragrant, fragrant, crumbly material that reminds you of forest soil and that you can hardly see its origin – then you can congratulate yourself on a successful compost!
Summary: How long does compost need?
- All times given are only guidelines, depending on the living conditions of the microorganisms involved, the rotting times will change
- Fresh compost can be used after four to eight weeks.
- A finished compost can be used after five to six months; it is then friable, smells pleasant and the starting materials are hardly recognisable
- The longer a finished compost continues to be composted, the more likely it is to become a very stable, low-nutrient mature compost that is ideally suited for soil improvement
- Compost is ready when it smells good, is dark and friable and you can no longer recognise the starting materials
Compost starters or compost accelerators and even compost worms are offered to optimise composting. You don’t need all these additives if you put a well-mixed compost on a piece of healthy soil. All the micro-organisms and worms will enter your compost from below and multiply there. Nitrogen or lime, as present in compost accelerators, are only necessary to a limited extent, as you learned above (in the section “Promoting composting”). If you are setting up a completely new compost, a simple trick can help you: Inoculate your new pile at the beginning with mature compost from another compost owner, if you can. This provides a base of microorganisms that can continue to multiply. The next compost is then always inoculated with the previous one. If you set up your new compost under the most unfavourable conditions (poor subsoil, no compost available for inoculation), you can of course use offered compost worms and compost starters as a last resort. You can find everything about worm composting in our special article on compost worms. If composting is to proceed quickly, optimising the living conditions of the microorganisms involved is of course the most effective approach.
Summary: Accelerating compost
- If you pile your compost on a healthy soil in a varied way, mix it and set up the conditions to suit the needs of the working organisms, you won’t need any other aids
- Inoculating a new compost with finished compost from another pile is an effective trick to get the rotting processes going quickly
- If conditions are too poor, using compost starters or accelerators won’t help either – but if there is just a lack of some compost to inoculate, there is nothing to stop you using such products
Sifting of the compost is common for fresh and finished compost. This separates coarse, undecomposed material from finished compost. Fresh compost is generally sieved more coarsely than finished compost, because it still contains many coarse pieces that are further decomposed in the bed. Mature compost does not necessarily need to be screened; at this rotting stage none of the initial organic structures should be present. Compost used for mixing planting soils should be particularly fine. The corresponding mesh sizes for further use can be found in the following table.
Tip: Compost produced at recycling yards has either been cleared of germinable seeds and pathogens by running off the hot rotting process or has been sterilised by treatment with hot steam. Since your private compost runs the risk of carrying diseases and seed weeds around the garden by running off the cold rot, sterilisation may also be an option for you. Small amounts of compost can be sterilised in about 20 minutes in a 200 °C oven. This is useful if you want to use your compost in pots indoors or for growing delicate plants. However, bear in mind that sterilisation also kills off any beneficial soil inhabitants that have helped you compost properly and continue to perform important tasks in the soil. Therefore, sterilise only if you consider it absolutely necessary.</div>Tip: Compost produced at recycling yards has either been cleared of germinable seeds and pathogens by running off the hot rotting process or has been sterilised by treatment with hot steam. Since your private compost runs the risk of carrying diseases and seed weeds around the garden by running off the cold rot, sterilisation may also be an option for you. Small amounts of compost can be sterilised in about 20 minutes in a 200 °C oven. This is useful if you want to use your compost in pots indoors or for growing delicate plants. However, bear in mind that sterilisation also kills off any beneficial soil inhabitants that have helped you compost properly and continue to perform important tasks in the soil. Therefore, sterilise only if you consider it absolutely necessary.