Quality standards for urban waste composts: The need for biological effect data

Area of Science:

• Environmental Science
• Ecotoxicology
• Soil Science

Background:

• The EU Circular Economy Package promotes urban waste composts (UWC) but lacks ecotoxicological risk assessment.
• Current UWC quality frameworks rely on physical-chemical and agronomical data, neglecting bioavailability and synergistic effects.
• Assessing UWC impacts on non-target soil organisms is crucial for safe application and market acceptance.

Purpose of the Study:

• To evaluate the ecotoxicological effects of different UWC types on crop soils using standard tests.
• To compare the toxicity of source-separated vs. mixed urban waste composts under simulated overuse scenarios.
• To identify key factors (salinity, potentially toxic elements) influencing UWC phytotoxicity and invertebrate toxicity.

Main Methods:

• Five UWC types (two source-separated, three mixed) were tested using ISO guideline ecotoxicological assays.
• Standard tests included plants (e.g., *Lactuca sativa*) and soil invertebrates (e.g., *Eisenia andrei*, *Folsomia candida*).
• Doses simulated overuse and repeated application scenarios common in agricultural practices.

Main Results:

• Toxicity varied among UWC types, with source-separated composts showing higher toxicity at elevated doses.
• No Observed Effect Concentrations (NOEC) were generally above maximum annual doses, except for one source-separated UWC.
• UWC toxicity order: *T. aestivum* < *L. sativa* < *E. crypticus* < *F. candida* < *E. andrei*.
• Salinity was identified as a primary driver of negative effects, surpassing the impact of potentially toxic elements.

Conclusions:

• Existing UWC regulations need to incorporate ecotoxicological data for a realistic risk assessment.
• Salinity management is critical for mitigating UWC ecotoxicity in soil applications.
• Biological susceptibility data is essential for adapting UWC application practices and enhancing consumer confidence.