India is running out of phosphorus. Does the solution lie in our sewage?

Subject :Geography

Section: Economic geography

Phosphorus fertilizer:

Phosphorus is scarce fertilizer and exists only in limited quantities, in certain geological formations.
- Rock phosphate is the raw material used to manufacture most commercial phosphate fertilizers on the market.
It also pollutes the environment. It doesn’t exist as a gas and can only move from land to water, where it leads to algal blooms and eutrophication. Due to the algal bloom water bodies become oxygen-starved, leading to fish deaths. The algal blooms are also toxic, causing respiratory issues, nausea, and other ailments to people exposed to them.

Geopolitics and the phosphorus game:

Phosphorus as a fertilizer recognised by Guano (bird) droppings.
The world’s largest reserves of phosphorus are in Morocco and the Western Sahara region. But here phosphorus coexists with cadmium, a heavy metal that can accumulate in animal and human kidneys when ingested. Removing cadmium is also an expensive process.
- Countries with phosphorus reserves: Morocco, Egypt, Tunisia, Algeria and China.
Only six countries have substantial cadmium-free phosphorous reserves. Of them, China restricted exports in 2020 and many EU countries no longer buy from Russia.

Cadmium absorption by crops:

Crops absorb cadmium at different rates. But paddy crops are more susceptible to absorbing the cadmium from phosphorus fertilizer.
Other grains, such as wheat, barley, and maize also absorb cadmium.
The cadmium-laden fertilizers (as removing cadmium from phosphorus will make it expensive) when applied to the soil leads to bioaccumulation in our bodies. This accelerates heart disease.
The uptake of cadmium by crops varies based on soil quality, climatic conditions, and the type and variety of crops grown.
In 2018, the EU passed new legislation to regulate cadmium levels in fertilizers.

Indian scenario:

India is the world’s largest importer of phosphorus followed by Germany, most of it from the cadmium-laden deposits of West Africa.
- India imported over 87.7 thousand metric tons of the element, with a value of nearly 161.34 million U.S. dollars.
- Vietnam is the largest exporter of phosphorus in the world.
Di ammonium Phosphate (DAP):
- DAP is used as a fertilizer. When applied as plant food, it temporarily increases the soil pH, but over a long term the treated ground becomes more acidic than before, upon nitrification of the ammonium.
- It is incompatible with alkaline chemicals because its ammonium ion is more likely to convert to ammonia in a high-pH environment.
- DAP can be used as a fire retardant.
- Nano-DAP (Di-ammonium Phosphate) is an agri-input developed by the Indian Farmers Fertilizer Cooperative Limited (IFFCO).
- Composition: It comprises 8% nitrogen and 16% phosphorus, whereas the conventional granular bag contains 18% nitrogen and 46% phosphorus.

The phosphorus disposal problem:

Only about a fifth of the phosphorus mined is actually consumed through food. Much of it is lost directly to water bodies as agricultural run-off, due to the excessive application of fertilizers.
Most of the phosphorus that people consume ends up in the sewage along with nitrates. Most sewage in India is still not treated or treated only up to the secondary level.
Nitrates can be digested by denitrifying bacteria and released safely as nitrogen gas into the atmosphere, while phosphorus remains trapped in the sediments and water column.

Finding phosphorus elsewhere:

One solution is to reduce the use of chemical fertilizers through precision agriculture.
Low-input agro-ecological approaches
Mining urban sewage to produce high quality phosphorus.
Almost two thirds of the phosphorus we consume leaves in our urine and the rest in faeces. Source-separating toilets can be a viable solution to produce phosphorus and other fertilizers like nitrogen and potassium.
Recycling the nutrient-rich wastewater and sludge.
Sludge-mining from STPs to recover nutrients.

Problems in producing phosphorus from sewages and waste waters:

Creating a circular water economy:

Setting up STPs with phosphorus mining plants.
Innovators need to lower the costs of sewage mining to be financially viable in India; regulators need to allow the use of urban-mined phosphorus in agriculture; and STPs need to be paid not based on discharge standards but on nutrient recovery.