What is phosphorus and why is it important to care about?

What is phosphours?

Phosphorus (P) is an element and essential for all life on earth since all living cells contain phosphorus. Phosphorus is necessary for the growth of new cells, which leads to phosphorus biggest application today, mineral fertilisers for the agriculture and as feed supplements for animals.

The world’s food production would be halved without the addition of phosphate fertilisers. With a growing population demanding an increased food production, the phosphorus supply is and will be even more important in the future since phosphorus as an element can’t be replaced.

Today there is only one phosphate deposit in Europe. It is located in Finland and produces only 10 percent of Europe's phosphorus needs. Phosphorus is listed on the EU's Critical Raw Materials (CRM) list.

Where does the phosphorus come from?

Phosphorus is a highly reactive element and is therefore never found as a free element in the nature. Most of earth’s phosphorus are therefore contained as minerals in the earth’s crust and rocks with high accumulation of phosphorus minerals, called phosphate rocks. The phosphate rock is mined and used to produce fertilisers for farming, feed stock, and other applications that needs phosphorus. The world’s phosphate rock resources are not equally distributed, and the largest deposits are in Morocco (West Sahara), China, and Algeria.

Can we avoid Peak Phosphorus?

A key difference between Peak Oil and Peak Phosphorus is that oil can be replaced with other forms of energy or materials when it gets to scarce while there isn’t substitute for phosphorus. A different approach must therefore be used to avoid Peak Phosphorus; effective management through recirculation of mined phosphorus and efficiency in production and use to extend its life cycle.

Not removing the phosphorus before sending the processed water to the recipient causes massive over-fertilisation of the WWTP’s surrounding environment.

How can phosphorus be recirculated?

The phosphorus is accumulated in plants and animals when it’s used as fertilisers and feed supplements by the agricultural industry. Humans eats the food and send most of the phosphorus to waste water treatment plants (WWTP). Most of the phosphorus is through the WWTP’s water cleaning processes accumulated in the sewage sludge. Not removing the phosphorus before sending the processed water to the recipient causes massive over-fertilisation of the WWTP’s surrounding environment.

The Peak Phosphorus scenario can be avoided or substantially delayed by extracting phosphorus from the sludge and recirculating it to the agricultural industry. For example, Sweden is using approx. 10 000 tons’ phosphorus in agricultural fertilising, while Sweden’s sewage sludge together with feed industry wastes (mainly slaughterhouse wastes) contains approx. 8 000 tons of phosphorus.

Are we recirculating any phosphorus from sewage sludge today?

Yes. Sweden and EU are respectively recirculating 25% and 48% of the phosphorus from the sewage sludge production through distribution of sludge on agricultural land. Unfortunately, it doesn’t come without risks since untreated sewage sludge contains heavy metals, pathogens, and medical residues. Heavy metals, such as, cadmium are absorbed by plants and constitutes a serious health risk to humans by increasing the risk of developing bone, kidney, and heart diseases.

The pathogens and medical residues effect on agriculture have in recent years being studied extensively and gained higher importance since it is suggested that medical residues possibly can increase antibiotic resistance and pathogens can reach out to drinking water areas.

Why are we spreading sewage sludge on farmland if it can be harmful to humans and the environment?

Distributing sewage sludge on farmland is today considered as ”good enough” since it is seen as the easiest way to recirculate phosphorus and increase our sustainability. Sweden have a rigorous control system for sludge from WWTP that is allowed to be spread on farmland, but new content limit legislation that require WWTPs to invest in upstream cleanness and other purification investments are causing them to look for other alternatives for disposal of their sewage sludge .

There are two main ways of extracting phosphorus from sewage sludge

How can we increase the recirculation of phosphorus to the agricultural industry?

There are some competing technologies for recirculating phosphorus to the agricultural industry in addition to distributing sewage sludge to the farmland. There are two main ways of extracting phosphorus from sewage sludge. The first way is to extract phosphorus directly from the sludge. The other way is to first heat or incinerate the sludge and thereafter extract the phosphorus from the residue (such as ash). Both ways have their advantages and disadvantages.

Direct extraction from sewage sludge

• Advantages: Few process steps and relatively small capital investments. Mature technology and a simple infrastructure.
• Disadvantages: The sludge are expensive to transport and manage since since the sludge contain large amounts of water. Technologies that extract phosphorus from the sludge have low extraction ratios of phosphorus and therefore also have high operative costs P/ton.

Extraction from ash of incinerated sewage sludge

• Advantages: Incineration decreases the weight of the sewage sludge with 90% consequently making the transport considerably cheaper. In addition to concentrating the phosphorus, incineration kills all pathogens and evaporates all medical residues. The higher concentration of phosphorus (P/ton) makes the operative cost of extracting phosphorus lower.
• Disadvantages: The incineration itself is expensive and requires relatively high capital costs. The technology of extracting phosphorus from ash is less mature and the infrastructure is more complex.

Phosphorus needs to be recirculated in agricultural production and stay in the recirculating cycle

What do EasyMining think about the future of phosphorus recirculation?

The most important thing for a sustainable phosphorus management is that phosphorus is recirculated to the agricultural production and stays in the recirculating cycle. We believe that the future of sustainable phosphorus management requires phosphorus products that:

• The agricultural industry accepts and are as good or better than today’s products
• Are pure and safe to use
• Have high plant availability
• Can be used for precision fertilisation
• Mainly are based on recirculated phosphorus

How can EasyMining contribute?

EasyMining’s process for recirculating phosphorus from sewage sludge ash is called Ash2Phos and is a wet chemical process that uses ash from incinerated sewage sludge. The main advantage of Ash2Phos is that the process can produce pure commercial phosphorus products called mono-ammonium phosphate (MAP) or di-calcium phosphate (DCP) and at the same time separate heavy metals, such as, cadmium from the sludge.