What composting method should be used to make good compost?

Good compost is compost that promotes good activity of micro-organisms and bacteria. The ideal composting method varies according to the situation, but it always allows for a sufficient supply of water and air.

3 phases for good composting

Regardless of the method chosen, composting takes place in 3 phases.

The first is the decomposition phase. The organic matter breaks down rapidly, initially under the action of mesophilic micro-organisms, those that are active in degradation and that are also found in our intestines!

In the second stage, thermophilic micro-organisms, extremely resistant bacteria, which act at high temperatures, around 60-70°C, intervene. At this stage, the water evaporates and the nitrogen is mineralised. The pile loses mass.

The second phase is an intermediate phase. The material cools down, its temperature drops below 40°C. The nitrogen is incorporated into complex molecules.

The third phase is the maturation phase. The organic matter is transformed into stable humus by the action of fungi, which take over from the bacteria.

Cold composting

Cold composting methods are the most classic. The temperature rises naturally. Composting is therefore quite long: it takes between 6 and 12 months to obtain humus.

There are two main types of cold composting: in-bin composting and vermicomposting.

You're familiar with in-bin composting: this is the traditional method used by gardeners. It can also be done on a larger scale in houses, in large bins with a capacity of 10 to 15 tonnes per year. In both cases, the result is stable, good quality compost, rich in humus and fairly moist... but often poorly sanitised, unless regular stirring is carried out.

Vermicomposting is a technique based on the breeding of red worms that decompose organic matter. On an individual scale, vermicomposters take up little space and can easily be placed in a kitchen or on a balcony. Less well known, professional vermicomposting facilities can process several dozen tonnes of bio-waste per year.

Here again, the compost obtained is not hygienised. Above all, this method of composting is complex to use: it is necessary to maintain ideal conditions for the worms, and in particular to be very selective about the composition of the bio-waste that goes into the compost. On the other hand, the humus obtained is of very good quality, particularly fine and easy to spread. On a professional scale, vermicomposting is therefore often used for the maturation phase, after a hot decomposition phase.

Hot composting

With hot composting, the decomposition phase can be accelerated considerably: it takes only 2 to 3 weeks. How does it work? The temperature of the material is raised quickly to bring in thermophilic bacteria, which are the fastest to decompose.

Andean composting

A mixture of raw materials is placed in long narrow piles called andins. Thanks to their size, they quickly reach a high temperature of around 60 to 70°C.

The heaps are turned regularly to promote oxygenation and homogeneity of the compost. Another method is passive aeration. In this case, perforated pipes are installed in the windrow, open at the ends. The air circulates through the pipes and the windrow thanks to the draught effect created by the escaping hot gases. It is even possible to use a fan to better control the process and use larger piles.

The main difficulty is that the collection requirements are high and constant. In addition, odours are sometimes difficult to control. It is therefore best reserved for industrial livestock farms that produce slurry and for wastewater treatment plants!

Composting in crates

Here, the material is confined in a closed container or building. There are several different methods, all of which have in common that aeration is controlled and the material is regularly stirred.

The most successful technique is the stirred bed. The organic material is spread out in long corridors, called beds. A rail guides a machine that moves forward, turns the compost and places it back behind it. Some machines also have conveyor belts that move the compost automatically.

The resulting compost is of good quality and well homogenised. The investment costs are high, however, and bad odours are not completely eliminated.

Electro-mechanical composting

The material is stored in a tank where it is regularly stirred by paddles. The tank is insulated to maintain the temperature. The air flows are controlled to ensure that the compost breathes properly.

Electromechanical mixing is an extremely reliable solution:

It allows good oxygenation, and therefore optimises the work of the micro-organisms

It ensures very rapid composting: the decomposition phase lasts only 2 weeks

It guarantees an excellent homogeneity of the compost

It meets hygiene requirements

It allows for easy management of the odour problem.

The electromechanical composter can process all types of bio-waste, in small or large volumes: up to 1000 tons per year! Above all, it treats it on site. There is no need to collect biowaste by truck and bring it, as is sometimes the case, several hundred kilometres from the initial place of emission.

UpCycle's Démeterra composter is intelligent: it weighs the waste, ensures the traceability of the materials, controls the temperature, etc. Several programmes managed on site or remotely respond to different situations: holidays, peak activity, sensitive waste, etc.

This machine thus combines the advantages of local composting and industrial composting, which is fast and secure.