Recent Advances in Bio-Based Adhesives and Formaldehyde-Free Technologies for Wood-Based Panel Manufacturing

Conventional formaldehyde-based adhesives for wood-based composite panels are subject to significant concerns due to their formaldehyde emissions. Over the past decade, the wood adhesive industry has undergone a considerable transformation that is characterized by a major push in bio-adhesive development. Various bio-based materials have been explored to create alternatives to conventional formaldehyde-based adhesives. Moreover, growing interest in circularity has led to increasingly exploiting industrial coproducts and by-products to find innovative solutions.

Industrial production generates many coproducts that can serve as renewable resources to produce eco-friendly materials. These coproducts offer alternative supply sources for material production without encroaching on food production. Many bio-based compounds or coproducts, such as saccharides, proteins, tannins, and lignocellulosic biomass, can also be used to develop bio-based adhesives. As part of ongoing efforts to reduce formaldehyde emissions, new hardeners and crosslinkers are being developed to replace formaldehyde and bio-scavengers. Other alternatives, such as binderless panels, are also emerging.

This review focuses on sources of bio-based material derived from by-products of various industries, which have many advantages and disadvantages when incorporated into adhesives. Modification methods to enhance their properties and performance in wood-based panels are also discussed. Additionally, alternatives for developing low-emission or formaldehyde-free adhesives are addressed, including hardeners, bio-scavengers, and binderless options. Finally, the environmental impact of bio-based adhesives compared to that of synthetic alternatives is detailed.