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HTC biocoal and phosphorus recovery from sewage sludge

AVA-CO2 has announced it will receive support from the German Federal Environmental Foundation (DBU) to set up a phosphorus extraction pilot plant in Karlsruhe. The project aims to demonstrate that with phosphorus recovery technology, recycling fertiliser with a high, plant-available nutrient content can be produced efficiently and cost-effectively from sewage sludge.

The German hydrothermal carbonisation (HTC) developer, AVA-CO2 has announced it will receive support from the German Federal Environmental Foundation (DBU) to set up a phosphorus extraction pilot plant in Karlsruhe. The company is developing hydrothermal processes to produce materials and energy from biomass and its “AVA cleanphos” process has already been successfully tested in AVA-CO2’s laboratories. It will now be tested at pilot scale for the next 12 months, in cooperation with the project partners – the University of Hohenheim and the project group for material cycles and resource strategy at the Fraunhofer Institute for Silicate Research. The project aims to demonstrate that with phosphorus recovery technology, recycling fertiliser with a high, plant-available nutrient content can be produced efficiently and cost-effectively from sewage sludge.

Samples of AVA-CO2 hydrothermally carbonised sewage sludge pellets (photo courtesy AVA-CO2).

Samples of AVA-CO2 hydrothermally carbonised sewage sludge pellets (photo courtesy AVA-CO2).

According to the company, its recovery technology could prove a breakthrough for the wastewater treatment industry for compliance with the amended German Sewage Sludge Ordinance. The process has the potential to be more efficient and cost-effective than existing methods, as municipal sewage sludge is converted first into HTC-coal before the phosphate is isolated, creating two products of commercial interest – a valuable fertiliser, and phosphorus-free HTC-coal that could be used as a substitute for brown or black coal.

– The HTC process, in combination with the AVA cleanphos solution, paves the way for a useful, long-term application for sewage sludge, commented Thomas Kläusli, Chief Marketing Officer at AVA-CO2.

For the agricultural sector, the method also offers new possibilities.

– Although sewage sludge contains a lot of valuable phosphate, there is a lot to be said against its use in agriculture. It can carry pathogenic substances and contains many heavy metals. Many existing phosphorus recovery technologies incinerate sewage sludge to extract the phosphorous from the ash. However, these methods are more expensive and complicated than the HTC route, said Prof. Dr. Andrea Kruse, agricultural technologist at the University of Hohenheim.

5070/AS

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