Recycled phosphorus fertilizer could be made from dairy wastewater and aluminium water treatment residue

An image of cows to illustrate the phosphorus fertilizer created with dairy wastewater
©iStock/FrankvandenBergh

Researchers are working on a method to make phosphorus fertilizer from dairy wastewater, to combat a potential future phosphorus shortage.

Plants require nutrients, particularly nitrogen and phosphorus, so phosphorus fertilizer is often put on crop fields. However, in just 100-250 years, we could face a shortage of phosphorus. Scientists at Tel Hai College and MIGAL Institute in Israel are developing a way to create phosphorus fertilizer by recycling dairy wastewater.

What is dairy wastewater?

Michael “Iggy” Litaor, who led this work, explained: “The material left after purification, called aluminium water treatment residue, is normally taken to a landfill to be buried. We changed this material by mixing it with dairy wastewater rich with phosphorus and organic matter. We then found it can be just as good as common fertilizers.”

Litaor and his team mixed the aluminium water treatment residue with dairy wastewater. This dairy wastewater comes from washing cows udders between milking and from cooling cows on hot summer days, and is high in phosphorus due to the detergents used to clean the sheds that the cows live in, and the runoff from cow urine.

Phosphorus

Litaor added: “Phosphorus is an important nutrient needed by most crops,” Litaor explains. “However, it is a non-renewable resource. If we continue with the current rate of use, what we have may be depleted in 100 to 250 years. There are also side effects of too much fertilizer. Hence, scientists around the world are searching for simple and affordable ways to recycle the element without lowering crop yield.”

Litaor said that the next part of the research will be to assess the use of water treatment residue containing iron, which is another element that is lacking in many soils. It is also necessary for the team to show that no unwanted hormones or antibiotics are left in the fertilizer.

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