Dynamic life cycle assessment of climate change impacts of hydrogen production from energy crops

Life Cycle Assessments (LCAs) are predominantly conducted using a static approach, which aggregates emissions over time without considering emissions timing. Additionally, LCAs often assume biogenic carbon neutrality, neglecting site-specific forest carbon fluxes and temporal trade-offs. This study applies both static and dynamic LCA and incorporates biogenic carbon to evaluate the climate change impact of hydrogen production. It focuses on gasification of eucalyptus woodchips cultivated on former marginal grasslands (BIO system), which avoids competition with land used for food production. A case study is presented in western Andalusia (Spain) with the aim to replace hydrogen produced via the conventional steam methane reforming (SMR) pathway (BAU system) at La Rábida refinery. The CO2FIX model was used to simulate biogenic carbon fluxes, providing insights into carbon sequestration dynamics, and it was found that the inclusion of biogenic carbon flows from eucalyptus plantations dramatically reduced CO₂ equivalent emissions (176 % in the static approach and 369 % in the dynamic approach) primarily due to soil and belowground biomass carbon sequestration. The dynamic LCA showed significantly lower CO₂ emissions than the static LCA (106 % reduction), shifting emissions from -1.79 kg CO₂/kg H₂ in the static approach to -3.69 kg CO₂/kg H₂ in the dynamic approach. These findings highlight the need to integrate emission dynamics and biogenic carbon flows into LCA methodologies to support informed decision-making and the development of more effective environmental policies.