The problem of garbage is deeper in urban centers, where the amount of waste generated is usually greater than 1 kg per day per inhabitant, which implies thousands of tons of garbage annually. In turn, of this kilogram, 50% is usually organic waste, 17% paper and cardboard, 14% plastic, 12% metals, 5% glass and the remaining 2% classified as "other", which includes dangerous elements such as batteries, solvents, etc.
Undoubtedly, each type of waste deserves a particular destination with a specific treatment and it is for this reason that the separation of waste at source is a fundamental issue.
In the specific case of organic waste, there are several possible treatments. One is the dumping in sanitary landfills where the waste can be revalued through methanization. Another is incineration, where it is burned to produce heat, electricity, ash and polluting gaseous emissions. A third option is composting, where the biodegradable matter is decomposed by the action of bacteria and fungi, through a natural fermentation process, to result in a quality organic compost called compost.
The compost production begins with the formation of the pile of organic matter to be treated. While any biodegradable material is potentially compostable, there are recommendations and restrictions, especially when the compost is homemade. The remains of vegetables, fruits, eggshells, dry leaves, branches, grass, hair, vegetable ash, natural fabrics, paper and cardboard are always usable, as long as they do not contain toxic inks. Likewise, it is recommended to avoid remains of animal origin (they contain pathogens that could later contaminate the compost), meats, dairy products and eggs, since they tend to produce bad odors and attract unwanted animals and insects. On the other hand, magazines, coal ash, synthetic fabrics, and, obviously, everything that is toxic or non-biodegradable should not be added.
With the pile assembled, the organic matter begins to oxidize, producing carbon dioxide, water, ammonia, sulfur oxides, more microorganisms, compost and heat. During the first days, microorganisms begin to reproduce and digest the most biodegradable compounds. In this phase, known as "latency and growth", mesophilic microorganisms predominate, the temperature of the pile increases to 40 ° C and its pH decreases, the medium becoming acidic (pH 5.5). As a consequence of this increase in temperature, a second phase begins, called “thermophilic” since the action of thermophilic microorganisms is triggered, the temperature rises even more (up to 70 ° C) and the degradation becomes more energetic during the 3 weeks of duration of this phase. After this time, the medium becomes alkaline (pH 8), most of the nutrients are depleted and cell activity decreases considerably. The pile is also sanitized as a result of the high temperatures that eliminated most of the microorganisms, including pathogens.
The next three months comprise the "ripening" phase, a stage where less biodegradable materials, such as cellulose and lignin, are digested by fungi. While this process is going on, a great variety of compounds are produced (humic colloids, hormones, antibiotics, vitamins), the temperature decreases to equal the ambient temperature, the pH becomes neutral and the battery is biologically stabilized, that is, significant biological activity ends. At that time the original waste is no longer recognized, the pile is a homogeneous dark color, spongy in consistency and emits a pleasant forest smell. The process is then terminated.
There are many factors that contribute to obtaining a good compost: temperature, humidity (50-60%), aeration, pH, Carbon / Nitrogen ratio (directly linked to raw materials), size of waste, degree of mixing, etc. For this reason, composting requires certain care such as mixing the pile periodically, adding water if it is very dry or additives such as lime to regulate acidity. All this makes it comparable to a kitchen recipe, where if the ingredients and the steps are respected, a good result is reached.
Once the compost has been obtained, either in a centralized industrial way or in a household or community scale, it can be used as compost if it is mixed together with soil or as a layer on the ground to control weeds, maintain humidity and protect against erosion. The main virtue of compost is that when it comes into contact with the earth, the cycle of many nutrients is closed, in the same way that occurs in nature.
Sources: Wikipedia | Manual for the elaboration of compost | ONGRSU
Newspaper of the Common Good