Chemical modification of four North American wood species using waste-derived carbohydrate and biosourced acids

• Whey ultrafiltration permeate used as biosourced polyol source for wood modification • Polyesterification improved dimensional stability and reduced hygroscopicity of four different North American wood species • Wood anatomy strongly influenced the solution uptake and cell wall bulking, key points for modification effectiveness • Dairy coproduct valorization offers a sustainable wood modification pathway Wood chemical modification techniques have focused on European species, leaving a knowledge gap regarding North American wood species, which are often more refractory. Therefore, this study aimed to explore the polyesterification of four different North American species using whey ultrafiltration permeate, a carbohydrate-rich coproduct from the cheese industry, as a renewable reagent within a circular bioeconomy framework. Whey ultrafiltration permeate powder was combined with citric acid or malic acid to prepare two different aqueous treatment solutions. Four different North American wood species were modified with these two solutions. Modified samples had gained significant weight between 15 and 47%, depending on wood species, with a weight loss of <4% after leaching, indicating a good fixation of chemicals within the wood matrix. The anti-swelling efficiency and moisture exclusion efficiency were >40% for all species, whether the treatment solution. The initial pyrolysis temperature was significantly decreased and residual mass after 800°C was >26% for all species. Bending strength remained comparable to untreated samples, whereas surface hardness increased up to 127% for sugar maple. Citric acid yielded marginally superior results to malic acid, notably in resistance to water leaching, dimensional stability, and moisture exclusion efficiency, likely due to its higher potential for cross-link formation. These findings demonstrate that carbohydrate‑based polyesterification using whey permeate is an effective and sustainable method for improving North American wood species properties while valorizing dairy industry coproducts.