Biomanufacturing of hydrogen from waste molasses: A full-scale application

Abstract

Biomanufacturing of hydrogen by acidogenic fermentation presents a promising avenue for sustainable hydrogen production; however, data on its full-scale application remain limited. Here we evaluate the performance of a 100 m³ continuous-flow stirred-tank reactor (CSTR) utilizing waste molasses and inoculated with aerobic excess sludge for hydrogen production. The reactor operated at 35 °C with a constant hydraulic retention time of 5.8 h, while the organic loading rate (OLR) was incrementally increased from 9.3 to 57.3 kg COD m⁻³ d⁻¹. By day 19, stable ethanol-type fermentation was established, yielding an average of 265 m³ of hydrogen per day. Over the subsequent 72 days, the reactor maintained continuous operation, achieving an average hydrogen production rate of 282 m³ d⁻¹ at an average OLR of 28.5 kg COD m⁻³ d⁻¹. Bioaugmentation with Ethanoligenens harbinense YUAN-3 at a 0.5 % volume fraction relative to the mixed liquor volatile suspended solids further enhanced hydrogen production to an average of 348 m³ d⁻¹. Despite fluctuations in the OLR between 17.1 and 55.2 kg COD m⁻³ d⁻¹, ethanol-type fermentation persisted throughout the bioaugmentation period. These findings demonstrate the viability of full-scale acidogenic fermentation for efficient hydrogen biomanufacturing from high-strength organic wastewater.