Microbially degradable phenolic foams based on depolymerized Kraft lignin for hydrophilic applications

Hydrophilic phenol-formaldehyde (PF) foams, widely used in floral and hydroponic applications, are produced using phenol typically derived from non-renewable petroleum-based resources. This study examines the potential of depolymerized Kraft lignin (DKL) as a sustainable substitute for phenol in the synthesis of hydrophilic biobased foams. At 50 % DKL substitution, the foams demonstrated excellent water absorption capacities (up to 2557 %), relatively low densities (∼62 kg/m³), and nearly 100 % open-cell content. Its compressive strength (20.64 kPa at 10 % deformation) is comparable to commercially available floral and hydroponic foams. Additionally, foams with 10 % phenol substitution by DKL exhibited better thermal stability compared to neat phenolic foams. After 15 days of incubation with Laccase-producing bacterium Bacillus sp., 30 % and 50 % DKL foams exhibited the highest weight loss of 39.03 % and 38.9 %, respectively. Qualitative degree of biodegradation was further assessed using scanning electron microscopy and FT-IR analysis of the degraded samples.