Recent Advances in Cellulose Fiber Foams: From Processing and Structure to Functionalization and Sustainability

The transition from fossil-based polymeric foams to renewable and more sustainable alternatives has increased interest in cellulose fiber foams. Cellulose provides a biodegradable, renewable, and, in many cases, recyclable material platform for developing lightweight structures for packaging, insulation, cushioning, and other applications. However, achieving an appropriate balance between structural and mechanical performance, moisture resistance, and environmental sustainability remains challenging. This review provides a comprehensive overview of recent advances in cellulose fiber foams. It covers the manufacture of cellulose-based porous materials, including fiber selection and treatment, foam formation, functionalization, and end-of-life strategies. Special attention is given to the effects of fiber characteristics, pretreatment methods, and processing conditions on foam structure and properties. Different manufacturing approaches are examined, along with the role of functional additives in improving foam stability, hydrophobicity, and mechanical performance. The environmental implications of cellulose fiber foams are also discussed, with an emphasis on recyclability, biodegradability, compostability, and the potential limitations introduced by functionalization. Overall, cellulose fiber foams constitute a promising renewable material platform with the potential to replace synthetic foams in selected applications. Future research should focus on establishing robust structure–property relationships, improving functional performance, assessing environmental impacts across the entire life cycle, and developing circular end-of-life strategies to facilitate industrial implementation.