Sewage can provide a new way to help consumers with rising food bills and reduce pollution in our waterways – if sewage plants release phosphorus, a vital component of fertilizer, according to a new report.
Phosphorus, found naturally in all plants, is essential for growing plants, but its use as a fertilizer creates widespread pollution in developed countries, as much of it is wasted. Phosphorus is a leading cause of water pollution, as runoff from the use of fertilizers in fields produces excess nutrients that upset the natural balance of rivers and lakes, leading to algae blooms that harm fish and plants.
Most of the phosphorus used to make manure is extracted from rock and not recycled from sources such as sewage. Only about 15% of sewage phosphorus is currently being recovered worldwide, but rising fertilizer costs mean it is now much more economical to do so.
Brian Spears, a professor at the UK’s Center for Ecology and Hydrology (UKCEH) and lead author of the most detailed report on the phosphorus problem to date, said: “Phosphorus could push us to the brink of a food security crisis. This is a limited resource and is overused in developed countries, while developing countries do not have enough. This is the main cause of pollution, as it disturbs the ecological balance [in waterways]. Phosphorus pollution also threatens drinking water supplies.
He said phosphorus supplies were rising sharply in price, which would jeopardize food security if governments did not take action to reduce phosphorus waste in our agricultural systems and encourage recycling from sewage and other sources.
The report, written by 40 international experts led by UKCEH and the University of Edinburgh, shows that much more can be done at a low cost to restore phosphorus.
Prices have jumped from about $ 240 (£ 192) per tonne to more than $ 900 per tonne for some forms of phosphorus-containing rocks as the war in Ukraine disrupted fertilizer production. Phosphorus rock comes from only a few countries, mainly Morocco. Most fertilizers use a mixture of phosphorus, nitrogen and potassium (NPK), and Ukraine and Russia are the main suppliers of fertilizers.
High fertilizer prices have forced farmers to suffer heavy losses, to be unable to plant crops or to face lower yields. As a result, food prices for consumers who are already affected by supply problems and the effects of high energy prices are rising further.
CEH researchers said farmers can also save money and reduce phosphorus waste by using fertilizer more efficiently, as most of the phosphorus in fertilizer is now lost in runoff. This can be as simple as directing the fertilizer to the crops and injecting them into the soil and avoiding using them just before heavy rain is expected.
The report, which is the most detailed study to date on the global phosphorus problem, recommends a 50:50:50 target of a 50% reduction in global phosphorus pollution due to a 50% increase in phosphorus recycling by 2050.
To achieve this, scientists call on governments to improve wastewater treatment to remove and reuse phosphorus from sewage; to help farmers use more targeted fertilizer techniques; to encourage more animal manure to become manure as an alternative to chemical fertilizers; and people eat less meat, which would reduce the amount of phosphorus currently used to raise animal feed.
A spokesman for the UK’s Department of the Environment, Food and Rural Affairs said the government was acting: “Phosphorus pollution in our rivers has decreased by 67% in the last two decades. We have proposed setting long-term goals in our Environmental Act to further reduce phosphorus pollution from agriculture by 40% and wastewater by 80% by 2037.
CEH researchers estimate that the capital investment needed in the UK to recover phosphorus from sewage is around £ 1.6 billion, which could easily be outweighed by the benefits of reusing the recovered mineral as fertilizer.
A small but significant use of phosphorus is in beverages such as Coca-Cola, in which it is used as a preservative. Removing it can lead to changes in taste, but an alternative would be to obtain phosphorus from recycling – which would make consumers effectively drink urine by-products.
Will Brownlee, a freshwater scientist at the University of Edinburgh who co-ordinated the report, said: “I would be happy if Coca-Cola could develop an alternative, use recycled phosphorus – remove pollution from our rivers and lakes and turn it into a beverage ”
Coca-Cola did not respond to the Guardian’s request for comment.
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