Rice straw to renewable hydrogen: comparative life cycle assessment of gasification and dark fermentation for hydrogen production in Thailand

Abstract

The global transition toward renewable hydrogen highlights the need for robust environmental assessments of biomass-based pathways. Rice straw, an abundant agricultural residue in Thailand, is a promising feedstock, yet direct comparative evaluations of its thermochemical and biological conversion routes in Southeast Asia remain limited. This study fills this gap by conducting a life cycle assessment of hydrogen production from rice straw via gasification and dark fermentation under Thailand's agricultural conditions. Using the ReCiPe 2016 (Hierarchist) method, both midpoint and endpoint indicators are analyzed. Results show that the global warming potentials of gasification (∼14.2 kg CO₂-eq per kg H₂) and dark fermentation (∼14.6 kg CO₂-eq per kg H₂) are comparable, representing a substantial reduction compared to fossil-based hydrogen production (∼30–35 kg CO₂-eq per kg H₂). However, dark fermentation has markedly higher impacts on fine particulate matter formation, terrestrial acidification, and fossil resource scarcity, largely driven by upstream straw production and chemicals used in the dark fermentation process, whereas gasification burdens stem from its energy-intensive conversion stage. These findings underscore the need for technology-specific strategies to advance the development of renewable hydrogen in Thailand. For dark fermentation, improvements in circular nutrient and chemical management are critical, while gasification pathways should prioritize energy efficiency and integration with renewable energy sources. Overall, these results indicate that biomass-based hydrogen is not inherently more environmentally friendly than fossil-based hydrogen, particularly when assessed from a cradle-to-gate perspective. Further investigation with uncertainty quantification may help strengthen the results and support policymakers in making informed decisions for hydrogen development within the country's Bio-Circular-Green economy strategy and 2050 net-zero target.