Biomass ash-based soil improvers: from laboratory developments to long-term field testing

Séminaire de Sónia Rodrigues, maître de conférence à l’université d’Aveiro (Portugal).

Elle travaille sur les thématiques de transfert de polluants en écosystèmes terrestre et de mise au point de systèmes de remédiations des territoires. Elle discutera certains de ses travaux dans le cadre d’un projet H2020 dont elle était porteuse, qui visait la  restauration de sols sur sites miniers portugais de la ceinture pyriteuse ibérique.

Résumé

It has long been recognized that biomass ash-based products, if processed properly, are suitable to be used as liming agent or fertilizer (Silva et al., 2019; Cruz et al., 2019). Thus, in 2021, thermal oxidation materials including biomass ash-based products were added as a component material category in the EU Fertilizing Products Regulation (EU 2019/1009; EU 2021/2087). However, these materials cannot be directly applied to soils. Some form of processing is required to ensure efficient soil pH correction, fertilization, guarantee soil protection, and reduce potential sanitary and environmental risks. Also, long-term field studies are needed to validate and quantify potential benefits resulting from the application of ash-based products to soils. 

We tested different ash formulations (with or without addition of organic wastes) and stabilization conditions (indoors vs. outdoors) to optimize physico-chemical properties of ash-based granules to be used as soil improvers (Mendes et al., 2021; Cruz et al, under review). We observed that limitations for biomass ash application to soil can be reduced by processing of ash or ash mixtures via granulation followed by stabilization by mineral carbonation (Cruz et al., 2023). We also conducted a long-term monitoring field experiment on the efficacy and safety of different formulations of biomass ash materials to ameliorate chemically, physically, and biologically highly acidic and polluted mining soils in Portugal. This study was initiated in 2018 in the scope of LIFE No_Waste  project (LIFE14 ENV/PT/000369). 

Here, we will present results obtained in the formulation and stabilization of ash-based soils improvers as well as results obtained after 3 years of soil monitoring (2018-2021) upon application of these materials to soil. The relevance of data and process knowledge obtained by these studies to further improve criteria for the use of thermal oxidation materials as components in fertilizers under the EU Regulation 2019/1009 will also be discussed.