Composting is the result of the observation and learning of our great teacher “Nature”. In the natural world, composting occurs when the leaves accumulate in the forest floor like a cake, in layers, and begin to decompose thanks to a large number of microorganisms that live there. After a while, the nutrients from the decomposed leaves reach the roots of the plants around them. This completes the recycling process of nature.¹
A large part of the materials present in the municipal solid waste can be considered for composting. Those materials that escape this quality are plastics, metals, glass and leather. But regarding its representation in weight, the compostable materials (remains of food, paper and cardboard and remains of gardening) are strongly considerable.
It is also possible to compost waste coming from industries, taking into account, in particular, the potential presence of hazardous materials. This type of waste has the advantage that they are more easily separated from the rest of non-compostable waste compared to urban waste.
ADVANTAGES OF COMPOST
- It promotes the growth of plants and roots: it has been shown that plants planted in a growth medium containing compost are stronger and have a better yield. Compost not only adds organic matter to the soil but also trace elements such as iron, manganese, copper, zinc and boron, which are necessary for plant growth.
- It improves the rate of nutrient diffusion: nutrients are only released when the plant needs them: faster when the weather is hot and humid, and more slowly when it is cold. Compost returns nutrients to the soil, prolonging their presence in the soil to feed the plants for a long period of time. Adding fertilizer to the soil also prevents the loss of fertilizer by runoff into surface water.
- It improves soil porosity: microbial activity is essential for soil fertility. Microorganisms break down organic matter to make the nutrients contained in these materials accessible to plants. Compact soils do not allow water and air, essential for soil micro-organisms, to penetrate the soil surface. Compost is composed of particles of different sizes, it offers a porous structure that improves the porosity of the soil.
- It improves the water retention capacity: the organic matter contained in the compost can absorb the water, thus improving the water retention capacity of the soil. The soil is then able to absorb water when it is raining or during watering and to retain it so that the plants can draw on these reserves between rains and waterings.
- It increases resistance to erosion by wind and water: the addition of compost prevents erosion by water and wind by making water and nutrients more accessible to plants, allowing them to grow faster and stronger in places that are prone to erosion. It promotes the limitation of diseases in plants: research has shown that some compost reduces the incidence of certain diseases in plants.
- Compost attracts and feeds earthworms.
- Compost improves the pH (acidity / alkalinity) of the soil.
- Compost reduces the water demand of plants and trees.
- Compost helps control erosion.
- Compost reduces plant stress in periods of drought or frost.
- Compost can lengthen plant growth periods.
- Compost improves the content of minerals and vitamins in foods grown in soils rich in compost.
- Compost applied generously to the soil can completely replace petrochemical fertilizers.
- Composting is the recycling system of nature. It is a dynamic process, there is no possibility of failure in composting, the compost simply happens.
DISADVANTAGES OF COMPOST
- Some of the disadvantages associated with composting lie in the emissions generated during the process such as the generation of leachates, odors and dust.
- In those more advanced processes, the use of energy can be considerable, presenting important costs.
- In the case of composting green waste, it can happen that the presence of some herbicides do not disappear after the composting process, obtaining a product of lower quality and affecting the animal tract.
- Some problems have been detected due to the presence of impurities such as plastics and glasses that end up being ingested by animals and seriously damaging their condition. That is why a correct final sieving is essential, but a very good previous classification of the waste acquires even more importance.
- On the other hand, it is necessary to establish the mechanisms that guarantee that the quality and sanitary criteria of compost are adequate. These kinds of demands are not always easy to establish.
- Other problems associated with compost, is the possibility of finding a market capable of absorbing the generation of this material. There is competition with chemical fertilizers, since they occupy a much smaller volume for transport and have been installed in the market for several decades. It is necessary to transmit to the producer the environmental advantages that the compost presents in front of this type of material (and make it clear that the compost is not a fertilizer but a soil improver). Another competitor is mobs obtained from bathes or land illegally removed from abandoned or public land.