Phosphorus recycling from sewage sludge ash: Demonstration plant is in operation

The large-scale demonstration plant for phosphorus recovery from the ash of sewage sludge officially went into operation this week. The plant was built as part of the AMPHORE project using the PARFORCE® process at the Emschergenossenschaft's Bottrop sewage treatment plant and is operated by PhosRec Posphor-Recycling GmbH. The NRW water management associations Ruhrverband, Wupperverband, Linksniederrheinische Entwässerungsgenossenschaft (LINEG), Emschergenossenschaft and Lippeverband (EGLV) founded PhosRec Phosphor-Recycling GmbH in March 2020 to prepare for the obligation to recover phosphorus from sewage sludge that will apply in Germany from 2029.

Phosphorus is an important raw material, but it is finite - the availability of deposits is very limited. It is used extensively as a fertiliser and passes into wastewater via the food cycle. In principle, this makes wastewater a sustainable source from which the essential nutrient phosphorus can be recovered and recycled as a material for fertilisers, for example.

However, this source is currently hardly utilised and the raw material phosphorus is largely lost as a result: "Until now, sewage sludge has mainly been incinerated and the ashes deposited in landfill sites. The phosphorus contained in the ashes was thus removed from the economic cycle," says Dr Yvonne Schneider, Managing Director of PhosRec Phosphor-Recycling GmbH.

Prof. Dr Torsten Frehmann, Managing Director of PhosRec Phosphor-Recycling GmbH, adds: "As the (waste) water industry, we want to make an active and positive contribution to covering part of the demand for mined and artificial fertilisers in the EU with recovered phosphorus." This not only fulfils a future obligation, but also closes a nutrient cycle and exploits an existing source of resources in the EU.

The demonstration plant in Bottrop is expected to recover the phosphorus it contains in the form of phosphoric acid from very different sewage sludge ashes in a large number of campaigns by mid-2026. Phosphoric acid is a high-quality basic chemical that is required in a large number of industrial processes and for the production of mineral fertilisers.

The plant in Bottrop is designed for a capacity of 1,000 tonnes of sewage sludge ash per year. It is automated and based on the patented PARFORCE® technology. Planning and construction were carried out by PTC-PARFORCE Technology Cooperation GmbH from Marl. Construction of the plant began in summer 2023 and was completed in December 2023. In the first half of 2024, functional tests were carried out on all individual components and the entire system, and the inauguration took place in May 2024. The necessary performance tests were completed in the second half of the year.

On the one hand, the plant is intended to demonstrate that marketable phosphorus can be obtained from very different sewage sludge ashes in accordance with the legally required quota of at least 80 per cent. On the other hand, practical experience is to be gained in large-scale operation with the process under different operating conditions.

Background:

The planning and construction of the large-scale demonstration plant as well as the trial operation are supported by the Federal Ministry of Education and Research (BMBF) as part of the joint project "Regional sewage sludge and ash management for phosphorus recycling for a metropolitan area" (AMPHORE) within the funding programme "Regional Phosphorus Recycling" (RePhoR). RePhoR is part of the BMBF's "Research for Sustainability" (FONA) strategy. AMPHORE is the largest of the seven funded RePhoR joint projects on phosphorus recovery and is being funded by the BMBF with around 8.7 million euros.