Recycling phosphorus – Are you familiar with the FOEN website and this report published online by the FOEN?

Online1 you will find the latest updated information and a very interesting report from EBP2.



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Phosphorus is essential to both human life and agriculture. It is a key component of DNA, cells and bones, as well as an essential nutrient for plant growth, which is why it is used extensively as a fertiliser in agriculture. Despite its importance, phosphorus is often lost in waste management, particularly through the disposal of sewage sludge and other phosphorus-rich residues from treatment and recycling plants. Given the depletion of the world’s phosphorus reserves and the resulting environmental and import problems, the need for sustainable phosphorus management is becoming increasingly apparent.

Phosphorus is mainly mined in the form of phosphates, which are found mainly in sedimentary marine deposits and, to a lesser extent, in magmatic rocks. The distribution of these phosphate deposits is geographically uneven, with a concentration in a few countries, leading to geopolitical dependence. For Switzerland in particular, which has strict limit values for heavy metals in fertilisers, dependence on phosphorus imports, especially from countries whose phosphate deposits contain little cadmium, is an important issue. The conflict in Ukraine has further reinforced the importance of phosphorus supply independence.

In Switzerland, the direct spreading of sewage sludge containing phosphorus on agricultural land has been banned since 2006, leading to an interruption in the phosphorus cycle. Phosphorus requirements, particularly for fertilisers, are currently covered by imports. The net annual quantity of imported phosphorus is 14,600 tonnes, illustrating the country’s dependence on foreign sources.

To preserve natural resources and reduce dependence on imports, Switzerland has taken steps to close the phosphorus cycle through recycling. From 2026, phosphorus from wastewater, sewage sludge or sludge ash will have to be recovered and recycled in material form. This will not only reduce dependence on problematic mineral fertilisers, but will also help to preserve primary phosphate reserves and complete an important cycle of materials. 

The legal framework for phosphorus recovery in Switzerland comprises the Federal Environmental Protection Act (D- USG), the Water Protection Act (D- GSchG) and the Ordinance on Waste Treatment (OTD), which together form the basis for an obligation to recover phosphorus from certain waste streams. Recovery must be based on the state of the art, and the aim is to recover at least as much phosphorus in the long term as is currently imported. 

Phosphorus recycling offers both ecological and economic advantages. By closing the materials cycle, it is possible to use raw materials efficiently and preserve natural resources. Implementing phosphorus recycling is a decisive step towards more sustainable use of this essential element and greater independence from uncertain and polluting sources of phosphorus. 

In April 2019 EBP submitted a report to the FOEN evaluating technologies for Switzerland (the report is now available with additions for 2021).

Source: BAFU Website

This study addresses the future-oriented issue of phosphorus (P) recovery from sewage sludge and animal and bone meal in Switzerland. The aim is to provide an assessment of various P recovery technologies, based on the latest developments and knowledge.

The study identifies and evaluates various P recovery technologies that appear suitable for use in Switzerland. The selection process is based on technological maturity, ecological performance and the implementation of pilot projects in Switzerland. Compared with a previous study, only nine technologies have been selected, compared with 20 in the previous selection. This reduction reflects a concentration on more efficient and feasible technologies. In particular, processes that crystallise directly from the aqueous phase have been excluded, due to their limited recovery rate and the need for biological elimination of P. Thermochemical processes using the ash from single-combustion have also been excluded.

Selected technologies and their characteristics

The study highlights different approaches to P recovery, including:

  • Acid digestion and crystallisation: technologies such as the ExtraPhos process, which treats sewage sludge by acid digestion, but which is limited in practice due to ecological and economic concerns.
  • Thermochemical digestion of sewage sludge: processes such as EuPhoRe and Pyrophos, which use monocombustion of sewage sludge to recover phosphorus, the technical complexity and heavy metal depletion requirements are challenges to be overcome.
  • Wet chemical extraction from ash: This approach includes technologies such as CleanMAP, EcoPhos, Phos4Life, REALphos and TetraPhos, which extract phosphorus from the ash of incinerated sewage sludge. They offer a number of advantages in terms of efficiency, product quality and environmental sustainability.

Conclusions and recommendations from EBP’ Report

It is clear that the choice of appropriate technology is highly dependent on local conditions, such as waste availability, infrastructural conditions and ecological priorities. The study underlines the importance of ongoing development and adaptation of technologies to Switzerland’s specific needs and conditions, in order to ensure that phosphorus recovery is efficient, sustainable and economically justifiable.

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