Biomass is one of the most abundant and renewable organic resources available globally, offering significant potential as a sustainable alternative to fossil-based materials in energy production, construction, and environmental remediation. However, the inherently hydrophilic nature of raw biomass limits its practical performance in many applications, as high moisture affinity reduces energy density, promotes biological degradation, and weakens material stability. Dry torrefaction, a mild thermal pretreatment process conducted at temperatures between 200 and 300 ^oC under low or controlled oxygen conditions, has been widely recognized as an effective method to enhance biomass hydrophobicity by modifying its surface chemistry and structural composition. This study investigates the effects of dry torrefaction on the surface hydrophobicity of three feedstocks: bamboo, coffee grounds, and microalgae. A total of 33 experimental runs were designed using a combination of the Taguchi L9 (3⁴) orthogonal array and response surface methodology with Box-Behnken Design (RSM-BBD), covering four factors: feedstock type (A), torrefaction temperature (B) at 240, 270, and 300 ^oC, residence time (C) at 20, 40, and 60 minutes, and oxygen content (D) at 0, 21, and 30 %. Hydrophobicity was evaluated through water contact angle (WCA), equilibrium moisture content (EMC), and water activity measurements. Structural and chemical changes were characterized using FTIR, BET, XPS, and SEM/EDX analyses to identify molecular-level mechanisms driving surface hydrophobicity. Machine learning models were applied to predict hydrophobicity properties from process parameters, and a sensitivity analysis was performed to identify the relative influence of feedstock type, temperature, time, and oxygen content on hydrophobicity. Life cycle assessment (LCA) and Techno-economic analysis (TEA) were also conducted to evaluate the sustainability and economic feasibility of the process. The findings aim to provide new insights for optimizing torrefaction conditions to enhance biomass applications beyond energy, including construction and water filtration materials.