Advancing bioenergy sustainability through hydrogen nanobubble- enhanced anaerobic digestion of tobacco stalks for biogas production

Abstract

The rising demand for renewable energy, alongside environmental pressures from agricultural residue disposal, requires innovative bioconversion methods. This study evaluates how hydrogen nanobubble water (H₂-NBW) benefits the anaerobic digestion (AD) process of tobacco stalks, a widespread lignocellulosic residue type in northern Thailand. Testing of tobacco stalk AD was performed under mesophilic temperatures with AD dosages ranging from zero to 100 percent H₂-NBW. The experiment measured methane production, digestion kinetics, redox environment, and fiber degradation rates. The combination of H₂-NBW at a 60% concentration delivered the best performance by producing 262.1 ± 6.4 mL/g VS of methane with 88.2% methane content during the AD process. Laboratory measurements using kinetic models demonstrated higher methane production speeds and shorter time-to-initial-production stages when the H₂-NBW levels were between moderate and high values. The digestion performance benefits from increased hemicellulose and cellulose degradation along with a reduced crystallinity structure, combined with better pH and Oxidation-reduction potential (ORP) stability, as laboratory results show. This study shows that maintaining appropriate concentrations of H₂-NBW as a supplement will produce both excellent fuel gas properties and low-cost waste management potential. The research outcomes demonstrate favorable conditions for wider nanobubble-assisted AD applications, which can serve as a sustainable waste management approach for agriculture while contributing to global renewable energy targets.