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When, in 1669, the German pharmacist and alchemist Henning Brand carried out an experiment on urine in an attempt to find the philosopher’s stone, he discovered a substance that glowed in the dark. He decided to call this powder 'phosphorus' from the Greek, meaning the ‘bringer of light’. Brand had unknowingly discovered one of the fundamental elements vital to all living organisms. Phosphorus compounds are a key part of our DNA, which carries our genetic code. Moreover, phosphorus is essential for both growth and energy metabolism. In other words: no phosphorus – no life. REMONDIS Aqua has joined forces with HAMBURG WASSER and built a pilot facility that is able to recover this precious substance from sewage sludge ash.
The bad news first: this substance is gradually running out. Whilst around 0.09 % of the Earth’s crust is made up of phosphorus compounds, it is only technically and/or economically practicable to mine just a fraction of this. Phosphorus occurs almost exclusively as a compound in nature, as phosphate or phosphoric acid, and can also, for example, be found in sewage sludge. For many years, therefore, farmers have been putting sewage sludge on their fields to improve their crops. The German government, however, wishes to put a stop to this practice as, unfortunately, the sewage sludge not only releases this valuable substance into the ground but many pollutants, too, such as heavy metals. The demand for high quality fertiliser is growing but phosphoric acid is needed to produce phosphate fertiliser and high quality animal feed – two products that are vital for the agricultural industry. For a long time now, scientists across the world have been looking to find cost-effective ways of recycling phosphorus – an essential nutrient for all living organisms – as reserves of this natural resource are gradually being used up. The demand for phosphoric acid in Europe alone lies at over 1 million tonnes a year.
Phosphorus is vital to all living organisms – and natural reserves of this substance are gradually being depleted.
Now for the good news: REMONDIS Aqua has developed a novel process that can provide established supply chains with phosphorus as a high quality secondary raw material – closing the material life cycle of this vital substance. It does this by recovering a pure form of phosphoric acid from the ash of incinerated sewage sludge.
This new process to recover phosphates was developed by chemists in the laboratory and now, thanks to the strong cooperation work between HAMBURG WASSER and REMONDIS, it is to be tested and optimised under ideal conditions at a pilot facility set up close to VERA Klärschlammverbrennung. VERA is a public private partnership owned by HAMBURG WASSER (60 %) and REMONDIS (40 %). For many years now, the two companies have been working together successfully in the area of sewage sludge incineration. The sewage sludge from Hamburg and neighbouring sewage treatment plants is thermally treated and used to generate energy. The leftover sewage sludge ash is now to be used as a valuable raw material for recovering phosphorus.
Tests will now be run over the coming months to work out the best configuration for the new facility. “If everything goes to plan, then REMONDIS and HAMBURG WASSER should be able to build a large-scale plant and recover several thousand tonnes of phosphoric acid every year,” commented Dr Martin Lebek during the official opening of the pilot facility in July 2015. Hamburg’s Senator for the Environment, Jens Kerstan, was really pleased to see that cost-effectiveness and environmental protection really can go hand in hand: “It’s great to see this process being tested out in Hamburg. Phosphorus recycling helps protect the environment – and makes good business sense as well."
(from left to right) Michael Beckereit, managing director of HAMBURG WASSER, Jens Kerstan, Senator for the Environment Hamburg, and Dr Martin Lebek, project manager and managing director of REMONDIS Aqua, show the materials produced by recycling the phosphoric acid during the official opening of the pilot plant
The RePacid® phosphoric acid recovered during this process is free of heavy metals making it a perfect source material for producing fertiliser and animal feed. However, this method not only generates phosphoric acid from the ash. It also creates gypsum for the building supplies trade and iron and aluminium salts which can be returned to sewage treatment plants to be used as a precipitating agent to treat wastewater and eliminate phosphorus. REMONDIS’ TetraPhos® process is, therefore, not only extremely eco-friendly, efficient and cost effective, it also helps to conserve our planet’s natural resources. It closes material life cycles, protects our fields, rivers and lakes and helps to reduce Europe’s long-term dependency on phosphate imports.
Josef Lehmkuhl was the brains behind this novel process. Josef Lehmkuhl worked as Head of Research & Development at the REMONDIS Lippe Plant and continued to work in an advisory capacity after he retired from full-time work. During this time he made a name for himself among his peers, especially in the areas of aluminium chemistry and phosphorus recycling. It was primarily thanks to him and his fascination for research that this idea made it off the drawing board and has been turned into a cost-effective process with a promising future. Unfortunately, Josef Lehmkuhl passed away unexpectedly on 04 April 2015. The plant, which will show that phosphoric acid can be recovered cost effectively from sewage sludge ash on an industrial scale, is now being managed by his colleague and co-researcher, Dr Martin Lebek from REMONDIS Aqua.