If you are lucky enough to own an allotment, big garden or a piece of land, you can make your own compost. This is a substance which works as a fertilizer and is made from the biochemical decomposition of prevalently organic waste.
The following advice is taken from the "Practical guide to domestic composting" by the Valle d'Aosta Region and Monza College of Agriculture.
In nature, the organic substances produced and no longer "useful" (dry leaves, faeces, animal spoils, etc) are decomposed by the microorganisms present in the soil which restore the matter produced into the natural cycle.
The composter
The less degradable elements left make up the humus, which is important for the growth of other vegetable organisms. Humus can be considered a real nutritional reserve for plants since it releases the nutritional elements (nitrogen, phosphorus and potassium are the most important) slowly and steadily, therefore ensuring that the soil is constantly fertilized.
Composting imitates the processes (by reproducing them in a controlled and accelerated form) which in nature return the organic substances to the life cycle, by perfectly recycling organic waste.
In other words, the process used for making compost is copied from nature.
