Pollutant threshold values for mineral recycling fertilisers: the Swiss concept

Phosphorus is an essential nutrient for plant growth. Switzerland is reliant upon the import of phosphorus fertilisers, which come from deposit reserves and are increasingly burdened with pollutants. On the other hand, there are hitherto unused phosphorus stocks in sewage sludge and slaughterhouse waste that could completely replace fertiliser imports. Therefore, Switzerland has introduced the mandatory recycling of phosphorus from both sewage sludge and meat and bone meal. This creates new ’mineral recycling fertilisers’, which have the potential to substantially reduce pollutant inputs in Swiss soils. A concept of threshold values for inorganic and organic pollutants has therefore been developed for mineral recycling fertilisers that will ensure a hazard-free application of the fertilisers in agriculture. This paper documents how the pollutant threshold values, which are implemented in Swiss legislation, were derived for mineral phosphorus recycling fertilisers.