Comparative Evaluation of Green Solvent Efficiency in Biomass Extraction Processes

Thesis Abstract

The growing demand for sustainable and environmentally friendly extraction processes in biomass industries necessitates the evaluation of green solvents aimed at replacing conventional, often toxic, solvents. This study investigates and compares the efficiency of selected green solvents—ethanol, limonene, and supercritical carbon dioxide—in extracting bioactive compounds from lignocellulosic biomass, specifically agricultural waste corn stover and hardwood sawdust. The primary aim is to identify the most effective green solvent for maximizing yield, purity, and bioactivity of extracted compounds while minimizing environmental impact. To achieve this, the specific objectives include evaluating extraction yields, analyzing the chemical composition of extracts, assessing bioactivity via antioxidant assays, and comparing energy consumption and process sustainability across solvents. The research adopts a quantitative, experimental research design, employing a comparative approach to evaluate extraction efficiency under controlled laboratory conditions. The study population comprises biomass samples from agricultural and forestry sources, with a sample size of 60 experimental runs—20 per solvent—determined through power analysis to ensure statistical robustness. Biomass samples are prepared through standardized drying and milling. Data collection involves the use of Soxhlet extraction apparatus for ethanol and limonene, and a supercritical fluid extractor for carbon dioxide, all operated under optimized parameters derived from preliminary trials. The chemical composition of extracts is characterized through Fourier-transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC-MS), and high-performance liquid chromatography (HPLC). Bioactivity is assessed using DPPH and FRAP antioxidant assays, while process efficiency and sustainability metrics are evaluated via energy consumption monitoring and life cycle assessment (LCA). The validity and reliability of measurement instruments are ensured through calibration, repeatability tests, and validation against standard reference materials. Data analysis incorporates descriptive statistics, analysis of variance (ANOVA), and Tukey's post hoc tests to compare extraction yields, chemical profiles, and bioactivities across solvents. Regression analysis examines relationships between extraction parameters and bioactivity outcomes, while thematic analysis is used to interpret qualitative data on process sustainability. A modified process model, integrating insights from the Tragedy of the Commons theory and Green Chemistry principles, guides the evaluation of environmental and economic trade-offs associated with each solvent. Expected findings indicate that supercritical carbon dioxide provides the highest purity and bioactivity of bioactive compounds with the lowest residual solvent and environmental footprint, while ethanol offers an economically viable and scalable alternative with comparable efficiency. Limonene, though less effective than supercritical CO2 and ethanol in some criteria, demonstrates advantages in select bioactive compounds and sensory attributes. The study is anticipated to reveal significant differences among solvents concerning extraction efficiency, compound profiles, and sustainability metrics, contributing valuable empirical data to the body of green extraction technology literature. The comparison will also elucidate the trade-offs inherent in selecting solvents based on process efficiency, ecological impact, and economic feasibility. This research advances knowledge by providing a systematic, comparative framework for evaluating green solvents in biomass extraction, integrating chemical, bioactivity, and sustainability assessments within a single analytical model. It offers practical recommendations for industry stakeholders aiming to adopt environmentally sustainable extraction technologies. The study concludes that supercritical CO2 is the most effective solvent in terms of environmental and extraction efficiency, but ethanol remains relevant for cost-sensitive applications. Recommendations include further scale-up studies, lifecycle cost analyses, and exploration of hybrid extraction methods combining solvents for optimized outcomes. Finally, this research lays the groundwork for future investigations into innovative green solvents and integrated extraction processes, supporting the ongoing transition toward sustainable biomass valorization.