Investigating the degradation of tannin furanic foams in soil environments

In the search for bio-based alternatives to petroleum-based materials, extensive research has been carried out on tannin- based foams over the last decades, demonstrating their potential use as insulation materials for buildings. These foams have been studied in depth for their chemical and physical properties and were already considered for upscaling. However, concerns remain about the end of their life cycle. While tannin foams can be partially recycled in new tannin foams, reused as ammonia scavenger, or thermally valorised, their impact on soil upon disposal or when potentially used as ammonia mitigators in agriculture remains unclear. This study investigated the degradation dynamics and potential effects of tan- nin furanic polymer on soil health. A decrease in the mass of the tannin foam particles by about 10% within 24 weeks indicated microbial degradation, which was further enhanced by the occurrence of leachable fractions throughout the experiment. Chemically, this degradation was associated with a reduction in carbohydrates and/or furanics, leading to a relative increase in aromatic components, paralleled by increased β-glucosidase activity. Phenol oxidase and arylesterase activities fluctuated depending on time and soil type, suggesting their roles in different stages of phenolic degradation, while catechol oxidase activity either decreased or remained unchanged. Enzymatic activities for FDA and β-glucosidase, indicators of soil health and microbial activity, tendentially increased in the presence of tannin foam, showing that the tested foam had no negative effect on general soil microbial activity.