The drawback with the fertilisation of land is as previous as agriculture itself. When early people first started to have interaction in settled agriculture, they shortly realised that whereas crops require vitamins for his or her development, repeated cycles of cultivation and harvest depleted these vitamins, decreasing yield over time. Early agricultural societies started to note that sure areas produced higher crops and that soils could possibly be replenished.
This commentary led to practices to revive important vitamins in the soil essential for plant and crop development. Indigenous communities round the world developed strategies of fertilisation, for instance, utilizing fish remnants and chicken droppings (guano) as fertilisers.
This modified in the nineteenth century, which noticed important developments in chemistry, resulting in the creation of artificial fertilisers in addition to the identification of nitrogen, phosphorus, and potassium. They’re the basis of trendy artificial chemical fertilisers and have prompted agricultural productiveness to growth. The Green Revolution of the mid-Twentieth century accelerated the adoption of high-yield crop varieties and intensive use of these fertilisers, and at this time these substances are essential to maintain world meals manufacturing.
But we now have an issue. Phosphorus is scarce and exists solely in restricted portions, in sure geological formations. Not solely are we running out of it, it additionally pollutes the atmosphere. It doesn’t exist as a fuel, which suggests it may possibly solely transfer from land to water, the place it results in algal blooms and eutrophication.
Geopolitics and the phosphorus recreation
The historical past of phosphorus spans its discovery in guano to present world provide chains. Today, a handful of international locations management most of the world’s reserves of phosphorus. This is a significant geopolitical concern. The world’s largest reserves are in Morocco and the Western Sahara area. But right here, phosphorus coexists with cadmium, a heavy steel that may accumulate in animal and human kidneys when ingested. Removing cadmium is additionally an costly course of.
As a end result, cadmium-laden fertilisers are sometimes utilized to the soil, absorbed by crops, and consumed, bioaccumulating in our our bodies. Studies have discovered that this accelerates coronary heart illness. In 2018, the EU handed new laws to control cadmium ranges in fertilisers.
Only six international locations have substantial cadmium-free phosphorous reserves. Of them, China restricted exports in 2020 and lots of EU international locations now not purchase from Russia. So the marketplace for secure phosphorus has all of the sudden exploded. This is one cause why Sri Lanka banned the import of artificial fertilisers and went natural in 2021, later experiencing a sudden drop in crop yield that precipitated a political disaster.
Today, India is the world’s largest importer of phosphorus, most of it from the cadmium-laden deposits of West Africa. Not all crops soak up cadmium at the similar fee, however paddy, a staple crop in India, is notably prone; Indian farmers additionally apply loads of fertilisers to paddy. Other grains, comparable to wheat, barley, and maize additionally soak up cadmium, simply much less.
(The uptake of cadmium by crops varies based mostly on soil high quality, weather conditions, and the sort and selection of crops grown. Social and cultural elements additional have an effect on the consumption of cadmium into human our bodies and the severity of well being results.)
Thus, we could face a tough alternative down the line: if we don’t take away cadmium from the phosphorus, we could face a public well being disaster; if we do, fertilisers will turn out to be dearer.
The phosphorus disposal drawback
First, solely a couple of fifth of the phosphorus mined is truly consumed by way of meals. Much of it is misplaced on to water our bodies as agricultural run-off, attributable to the extreme software of fertilisers.
Second, most of the phosphorus that folks eat finally ends up in the sewage. Most sewage in India is nonetheless not handled or handled solely as much as the secondary degree. So even when the natural matter is digested, the effluent discharged from STPs nonetheless accommodates nitrates and phosphates. Of these, nitrates may be digested by denitrifying micro organism and launched safely as nitrogen fuel into the ambiance, whereas phosphorus stays trapped in the sediments and water column.
It is then absorbed by the algal blooms that develop in response to the excessive nutrient provide, and after they decompose, the micro organism that feed on them eat the dissolved oxygen. The end result: water our bodies turn out to be oxygen-starved, resulting in fish deaths. The algal blooms are additionally poisonous, inflicting respiratory points, nausea, and different illnesses to individuals uncovered to them.
Finding phosphorus elsewhere
Since a lot of the phosphorus is not truly taken up by crops, one option to ameliorate the phosphorus paucity is to cut back the use of chemical fertilisers by way of precision agriculture. Low-input agro-ecological approaches are more and more proving to be a viable various. If practised accurately, they are often achieved with little to no loss in yield, particularly in smallholder farmers that can’t afford the value of chemical fertilisers and pesticides.
But there is rising curiosity in closing the phosphorous loop by mining city sewage to supply prime quality phosphorus. Interest in ‘circular water economies’ has in truth prompted the European Union – which has nearly no phosphorus reserves of its personal – to rethink the city water cycle.
First, supply separating bogs – Almost two thirds of the phosphorus we eat leaves in our urine and the relaxation in faeces. Urine additionally accommodates massive quantities of nitrogen and potassium. If we will acquire this secure and concentrated waste stream, we may generate an area fertiliser supply. Source-separating bogs are designed to separate urine from faeces. If they’re to turn out to be mainstream, buildings and houses would require a group and storage system, resulting in a logistics system that collects and processes the urine centrally.
Second, recycling wastewater and sludge – Sewage recycling already happens in some kind in India at this time. Nutrient-rich wastewater is utilized on to agriculture as at the KC Valley-Kolar venture, which transports Bengaluru’s wastewater to the water-scarce areas of Kolar. But there are considerations that the amount of vitamins could also be too excessive and finally degrade the soil. Similarly, in many cities and cities, farmers already take away the sludge from STPs but it surely is cumbersome to move. So whereas farmers could also be keen to pay to move sludge, they can not afford to pay an STP for the sludge itself. Thus, sewage recycling at this time doesn’t assist render sewage therapy worthwhile.
There is potential right here for a game-changing innovation: sludge-mining from STPs to recuperate vitamins. Companies like StraightforwardMining in Europe are retrofitting STPs to recuperate vitamins from the sewage. The finish product seems to be precisely like standard fertiliser and is in truth of larger high quality and marketable at a comparable value.
Mining phosphorus from sewage permits international locations to manage their very own phosphorus manufacturing whereas additionally addressing the drawback of water-body eutrophication.
Trouble with the incentives
In concept, given the at the moment excessive fertiliser costs, these applied sciences are already economically viable. Why then have they not been realised?
One drawback is the incentives at the sourcing and the consumer ends of the phosphorus worth chain. In rural India, the strongest farmers in villages are sometimes additionally the pesticide and fertiliser sellers and prolong credit score to farmers with smaller holdings. As a end result, the latter are incentivised to over-apply fertilisers reasonably than to cut back them. This must be tackled individually, by way of higher extension companies and consciousness campaigns.
In city India, sewage is perceived to be an undignified exercise traditionally relegated to individuals belonging to the so-called ‘lower’ castes. The rules mirror this “get rid of it” mindset. Around the world, rules have been framed in phrases of discharge requirements. Companies have to make sure nitrate and phosphate ranges in effluent therapy crops are beneath a suitable degree. But when the rules are written this fashion, therapy plant operators in India usually dilute effluents with freshwater earlier than discharging it. Dilution is not likely a solution to air pollution as the similar amount of vitamins find yourself in water our bodies anyway.
Even if regulation and enforcement are tightened, the elementary drawback persists: wastewater therapy is a value centre, not a income centre, for many cities. No one needs to pay the excessive value, not even Bengaluru, a metropolis with a comparatively excessive GDP per capita. And whereas utilities receives a commission to provide water, they don’t achieve extra income from treating wastewater to requirements. In truth, from their perspective, it merely will increase the value of sewage therapy, additional burdening them. So they have an inclination to tug their toes till the National Green Tribunal imposes a superb.
Creating a round water economic system
This is why essentially rethinking our complete strategy may fit. If the expertise is low-cost sufficient, can we give a concession to arrange STPs with phosphorus mining crops and permit them to promote the fertiliser? To do that, we’d like systemic – not incremental – change.
This requires each single stakeholder to make small changes. Innovators must decrease the prices of sewage mining to be financially viable in India; regulators want to permit the use of urban-mined phosphorus in agriculture; and STPs have to be paid not based mostly on discharge requirements however on nutrient restoration.
And such adjustments, whereas difficult, may additionally clear up a number of issues. India can turn out to be much less depending on unsure geopolitical crises; farmers can procure fertilisers at inexpensive charges; water our bodies may have some hope of changing into swimmable (after eliminating legacy vitamins in lake beds); and public well being can achieve from the consumption of meals grown in cadmium-free soils.
Dr. Veena Srinivasan is the Executive Director of the Water, Environment, Land and Livelihoods (WELL) Labs, a brand new analysis centre based mostly at the Institute of Financial Management and Research (IFMR) Society and Krea University. Sneha Singh is a researcher in the Urban Water Programme at WELL Labs.
