Compost from organic solid waste: Quality assessment and European regulations for its sustainable use

• OFMSW compost is increasingly used in agriculture as a soil conditioner or fertilizer.
• Regulations on compost quality show heterogeneity and blind spots in its characterization.
• The need for standardized procedures to assess compost quality is highlighted.
• The reliability of Italian regulation phytotoxicity parameter is evaluated.

Composting represents the most common option to recover material from the organic fraction of municipal solid waste, due to the possibility to use compost as a fertilizer. To this end the assessment of compost quality needs to be adequately enforced in national regulations. This work aims at reviewing European regulations regarding compost quality, in order to identify the most common parameters used to define compost characteristics as fertilizer. It was found that the majority of European States requires the fulfilment of specific criteria, but a lack of uniformity in regulations and guidelines can be observed. In particular the approach to the evaluation of stability and maturity, which account for compost safe use on soils, shows great heterogeneity throughout Europe. As stability and maturity go hand in hand, the proper characterization of compost toxicity should rely on the determination of both parameters. The results of an annual monitoring of compost under the Italian regulation highlighted, indeed, that the evaluation of the germination index can provide only partial information on the product maturity but not reliable operating indication on compost inhibitory properties.