• Energy Research

Steam methane reforming (SMR) using natural gas is the most commonly used technology for hydrogen production. Industrial hydrogen production contributes to pollutant emissions, which may differ from the theoretical estimates due to process conditions, type and state of installed pollution control equipment. The aim of this study was to estimate the impacts of hydrogen production using facility-level real emissions data collected from multiple US EPA databases. The study applied the ReCiPe2016 impact assessment method and considered 12 midpoint and 14 endpoint impacts for 33 US SMR hydrogen production facilities. Global warming impacts were mostly driven by CO2 emissions and contributed to 94.6% of the endpoint impacts on human health, while global warming impact on terrestrial ecosystems contributed to 98.3% of the total endpoint impacts on ecosystems. The impacts estimated by direct emissions from the 33 facilities were 9.35 kg CO2e/kg H2which increased to 11.2 kg CO2e/kg H2when the full life cycle of hydrogen production including upstream emissions was included. The average global warming impact could be reduced by 5.9% and 11.1% with increases in hydrogen production efficiency by 5% and 10%, respectively. Potential impact reductions are also found when natural gas hydrogen production feedstock is replaced by renewable sources, with the greatest reduction of 78.1% found in hydrogen production via biomass gasification, followed by 68.2% reduction in landfill gas and 53.7% reduction in biomethane-derived hydrogen production.

Abstract Increasing global energy demand and concerns of carbon emissions have driven the utilisation of renewable sources such as biomass. Biomass pyrolysis in the presence of catalyst, i.e., biomass catalytic pyrolysis (CP), is one of the most efficient routes for generating renewable hydrocarbon fuels or commodity chemicals. Most previous review papers on biomass CP focused on the summary of catalyst classification, properties and performance based on product yields and oil quality. Information on biomass CP process especially effects of different reaction atmospheres has not been reviewed or discussed in sufficient detail. This paper aims to provide a review and insights of the essential process factors and system structure of the lignocellulosic biomass CP with emphasis on process performance indexes such as bio-oil’s effective hydrogen to carbon ratio, deoxygenation degree, carbon efficiency and energy efficiency. The paper sections are organised in order of biomass CP catalysts, biomasss CP assessment, modification of essential process factors (e.g., biomass pre-treatment, co-feeding with other materials, atmosphere and temperature) and variations in the system structure (e.g., heat source alternatives, staged catalysis and process integration). Variations in process factors and system structure can possibly tailor the products and improve the economic attraction. A number of questions about biomass CP are still unclear. The current status, challenges and future research directions of biomass CP are also discussed in the paper. The comprehensive review and insights of the biomass CP process in this work will provide reference for the research and industrialisation of biomass CP for renewable fuel production.