Valorization of Bambusa tulda and Bambusa nutans Through Microwave Modification; Effect on Preservative Retention and Anatomical Analysis

Abstract Rising demand for sustainable building materials and numerous restrictions on sourcing and availability of timber have created an urgent need for exploring alternative lignocellulosic resources. Bamboo is abundant and fast-growing but underutilized; primarily because of poor treatability and subsequent rapid biological degradation. Enhancing treatability potentially transforms low-value culms into durable construction-grade material, promoting their sustainable utilization and reducing wastage. This study investigates microwave (MW) modification of Bambusa tulda and Bambusa nutans as a valorization strategy that could likely increase bamboo’s service and reduce waste by enabling more effective use of fast-growing bamboo in engineered products. MW energy was applied at 600, 900, and 1200 MJ/m 3 and its effects on weight percentage loss (WPL), anatomical matrix, and retention of a water-based BBA (Borax and Boric acid) preservative were measured. Increasing MW energy produced moisture-driven weight loss, peaking at 7.92% for B. tulda and 8.04% for B. nutans at 1200 MJ/m 3 , and induced microstructural changes, including cracks and delamination within vascular and fibre bundles. These anatomical modifications substantially enhanced radial preservative uptake, with maximum BBA retention of 22.10 ± 0.59 kg/m 3 in B. tulda and 21.42 ± 0.65 kg/m 3 in B. nutans observed at the highest applied energy level of 1200 MJ/m 3 . Quantified crack counts per mm 2 rose approximately 200% between the lowest and highest applied energy levels, reflecting increased permeability that facilitated retention. While higher MW doses improved treatability and have the potential to convert low-grade culms into durable, construction-ready material, they may also possibly compromise mechanical integrity through increased fibre separation, which could be a potential drawback of this method. Future work should therefore focus on optimization of MW parameters, assessing mechanical trade-offs, and developing hybrid reinforcement or composite strategies to balance enhanced preservative uptake with required structural performance. Graphical Abstract