Boosting sustainable hydrogen production through the gasification of biorefinery sludges

Abstract

Decarbonisation of energy production is vital to prevent further climatological disasters; sustainable hydrogen production from unique underutilised feedstocks will presents a viable pathway to overcome further energy crises and transition away from fossil reserves. By tapping into severely underutilised lignin-rich biorefinery waste streams such as sludges, produced post hydrolysis (sugar extraction, pre-fermentation), a wealth of hydrogen was unlocked via gasification at 950 °C in 1 % O₂/N₂, producing a gas-rich product mixture (>70 wt%) in a batch downdraft reactor. Subject to an optimised pre/post-treatment regime, low nitrogen and ash (<2 wt%) containing 1–2 mm sludges derived from barley and wheat straws were found to create a producer gas with hydrogen concentrations of 27.95 vol.% and 22.12 vol.%, respectively, as a result this work has pioneered a waste-to-hydrogen pathway for biorefinery sludges, achieving competitive H₂ yields without energy-intensive steam/catalysts. The formed sludges were found to be superior to both raw and leached parent feedstocks without NaOH hydrolysis, in terms of hydrogen production and solid fuel calorific values.