Soil fertility is understood as its ability to supply all the nutrients that plants need at all times, in the necessary quantity and in an assimilable form.
Fertilization is an irreplaceable agrarian practice whose main objective is to maintain soil fertility, and is not limited to restoring that extracted by the crop, but also those components lost by the soil due to washing, degradation and erosion.
Fertilizers restore these nutrients to the soil, and make them available for the crop.
NPK complex fertilizers are products that contain two or three primary nutrients (N, P, K) and possibly secondary nutrients (Ca, Mg, S) and micronutrients (e.g. Zn, Cu or B). They are applied to balance the soil content in nutrients according to their content, the needs of the crop to be planted and the expected yield. They can be solids (granular form) or liquid, with the latter being increasingly common.
However, the amount of fertilizers consumed annually is very high (over 200 million tons in 2018 according to the FAO) and increasing in recent years. This leads to a huge amount of waste, much of which has significant nutrient content (N/P/K), being produced and accumulating in landfill sites.
Thus, the circular economy in the production of fertilizers needs to be improved. This circular process is based on the recycling of products, optimizing the use of mineral resources, recovering and incorporating the by-products produced, minimizing emissions and reducing dependence on non-renewable energy sources.
Thus, the European Commission has adopted a new and ambitious package of measures on the reuse of products and the circular economy. More specifically, a draft regulation on the commercialization of fertilizer products is included within the package of measures, to incorporate the by-products of some industries into the production of fertilizers; thus reducing dependence on raw materials.
Depending on the chemical composition of the by-products, the processes necessary for their conversion into fertilizers varies. The by-products we have worked with mostly for recovery as fertilizers are the sludge from aerobic purification processes and the digestate produced in biomethanization plants.
To recover phosphorus in the form of a solid fertilizer, it can be crystallized in the form of struvite, a slow-release mineral fertilizer composed of magnesium, phosphorus and nitrogen, with a low metal content. This slowly provides nutrients to the soil, favoring its absorption by plants and reducing surface losses that can end up in water bodies.
In addition, the production of liquid fertilizers rich in ammonium can be viable through an adsorption-desorption process with zeolites and membrane contactors. Sometimes, to achieve a specific relationship between the main nutrients, surplus nitrogen needs to be removed. This can be done via a process under microaerophilic conditions with low energy consumption.
Another way of transforming waste into fertilizers is, firstly, to mix the waste with other organic waste and other mineral fertilizers to adjust the nutrient levels (N/P/K) to commercial values. Secondly, the resulting mixture undergoes vacuum evaporation to remove the water and transform the material into a stable and easy-to-use solid.
As in all our business, at Condorchem Envitech we work with the customer to evaluate the identified source of waste to determine the potential of the fertilizer. Samples can be sent to our laboratory for a complete analytical evaluation; after which, our technical team will work with the customer to establish a profitable program to obtain the maximum potential of the fertilizer produced.