Phosphate fertilizers: a strategic and economic issue
Phosphorus – an economic challenge
The exploitation of phosphate rock deposits has become both a major economic and strategic issue. Indeed, these mineral resources represent important global assets and generate a complex economic dynamic between producer and user states, some of these states being both producers, through mining, and users, notably in agriculture, such as the United States.
The phosphorus supply chain is fragile, as this element cannot be substituted, and its natural reserves are limited in time. According to several studies, such as that of Dana Cordell of the University of Linköping in Sweden, the world’s phosphate reserves will be exhausted within 50 to 100 years. The United States Geological Survey and the International Fertilizer Industry Association predict that phosphate reserves will be depleted within 100 to 125 years. However, it is estimated that from the years 2040-50, phosphorus production will enter a period of deficiency. In other words, its demand will be higher than its availability.
The term phosphorus is frequently used to designate different formulations (phosphates, phosphorus, polyphosphates). Phosphorus naturally present in soils is not very accessible to plants, it is frequently fixed on metals such as iron or aluminum. Phosphorus is most often found in rocks, in completely unusable forms. Sulfuric acid is generally used to generate the phosphate known as P2O5.
The main phosphate deposits are located in Morocco and China and this element is nowadays indispensable for the manufacture of fertilizers for the world agriculture, whose needs in fertilizers are growing in a significant way to allow an agricultural production able to meet the needs of a world population in exponential growth.
|Country||Yearly production in thousands of tons||Reserves|
|China||140 000||3 200 000|
|Morocco + Western
|33 000||50 000 000|
|United States||27 000||1 000 000|
|Russia||13 000||600 000|
|Jordania||8 800||1 000 000|
|Saudi Arabia||5 200||1 400 000|
|World total||270 000||70 000 000|
Virtually 90% of phosphate rock mined is used to produce fertilizer. In Canada, the fertilizer industry plays an important role in the national economy with $23 billion in annual economic activity and 76,000 jobs (source: Fertilizer Canada)
Phosphorus and agriculture
In order for a plant to grow, it needs water and 13 nutrients, including macronutrients such as nitrogen, phosphorus and potassium. One of these nutrients, phosphorus, is in danger of disappearing in the next few decades. Phosphorus is essential for plant development. Among other things, it contributes to the transport of energy in the cells. Phosphorus stimulates root development, flowering and fruiting. It also allows plants to better resist the effects of frost. Without it, agricultural production would not be possible.
Agriculture requires 90% of the phosphate produced. This is mainly in the form of inorganic phosphate fertilizers and phosphate feed for livestock. Manure and slurry are natural fertilizers rich in phosphorus, but livestock farms are not always in the direct vicinity of crop land. Worldwide agriculture uses some 40 million tons of this chemical fertilizer per year.
In Canada, the annual consumption of phosphate fertilizers has increased from 887,000 tons in 2013 to 1,133,000 tons in 2018 (source: International Fertilizer Association).
As for fertilizers in general, the quantity used in the world is also increasing.
Source : Statista
Phosphorus and manure
Phosphorus is one of the fertilizing elements present in manure. It is largely derived from the faeces and is therefore closely related to the solid fraction, whereas in the liquid fraction (largely urine) the element is available as dissolved phosphates. In the solid fraction, phosphorus is essentially in mineral form. Organic phosphorus in food that is not perfectly digested is of little fertilizing interest because it is not available to plants.
On the other hand, about 80% of total phosphorus is mineral and therefore has a fertilizing value for crops. Its fertilizer equivalence coefficient is estimated at 0.85 (Ziegler and Héduit, 1991).
Phosphorus potential of pig manure.
The availability of phosphorus in pig manure is comparable to that of cattle manure. This availability is higher than that of poultry manure because, for the latter, mineral phosphorus represents only 60% of total phosphorus. Hog manure, once its liquid fraction is removed, which represents a significant percentage of volume (over 90%) and therefore constitutes the main cost of transporting manure for spreading, is therefore an interesting source of phosphorus for agriculture.
A study performed by the CRAAQ (Centre de Référence en Agriculture et Agroalimentaire du Québec), highlights the following quantities of phosphorus (P2O5) present in various types of pig manure.
|Type of manure||P2O5 quantity in kg /t|
If we consider that after separation of the solid and liquid fractions ( with the Solugen process), the result is a solid bio which represents 10% of the initial volume of manure (for maternity manure) and that 85% of the phosphorus initially contained in the manure is concentrated in the solid fraction, we theoretically obtain:
|Type of manure||P2O5 quantity in kg / 100kg of not dehydrated bio solid|
|Nursery||1.7 kg, of which 1.36 kg is mineral phosphorus available for crops|
An interesting potential, therefore, and to be considered in view of the evolving situation of phosphate rock mining and the growth of organic agriculture.
From left to right: liquid fraction and solid fraction resulting form Solugen’s process