Structure-Property Relationships of Lignin-Based Structural Building Materials

Buildings enable long-term storage of carbon due to their long lifespans (> 50 years). Engineered wood, including wood biopolymer composites, is a potential replacement for concrete and steel in construction to limit CO₂ emissions. However, current formaldehyde-based binders used in engineered wood are toxic and have environmental concerns, so there is a need to explore bio-based, formaldehyde-free binders. Lignin is one of the most abundant biopolymers on earth and is a natural glue which holds up a plant’s structural framework. Currently, lignin (Kraft) is treated as a low-value waste product by the paper and pulp industry, with a significant amount burned for fuel. The use of lignin from waste streams and agricultural waste in building materials emerges as a cost-effective solution. However, the chemical composition of lignin is sensitive to lignocellulose source and method of extraction, leading to inhomogeneity. Extracting lignin through ionic liquids (IL) or deep eutectic solvents (DES), are environmentally friendly and energy efficient. However, the effects of lignin variability on adhesive performance have not been well explored. Specifically, ideal characteristics for the development of structural wood composites have not been systematically studied. To address this gap, this study aims to develop structure-property relationships of lignin-based adhesives from different sources and extraction methods. The study includes a comprehensive baseline characterization of the different lignin and repeated mechanical strength measurements of lignin-based adhesives.