Biohydrogen Production from the Organic Fraction of Municipal Solid Waste Via Thermophilic Lactate-Driven Dark Fermentation

Abstract

Lactate-driven dark fermentation (LD-DF) has gained increasing interest due to its potential to mitigate hydrogen inhibition issues associated with lactic acid bacteria. This work aims at investigating thermophilic LD-DF of the organic fraction of municipal solid waste (OFMSW). First, enrichment strategies involving an anaerobic sequencing batch reactor and a continuous reactor were compared to obtain a high-performance mixed culture capable of thermophilic LD-DF. The continuous cultivation strategy resulted in a more robust inoculum, better suited for thermophilic LD-DF. Secondly, a series of batch tests were performed, systematically evaluating pH within a range of 5.5 to 7.0 and initial total solids (TS) content between 5% and 10%. The optimal conditions for biohydrogen production were identified as pH 7.0 and a 7.5% TS content. Finally, the influence of the hydraulic retention time (HRT ranging from 18 to 9 h) was investigated to optimize thermophilic LD-DF of OFMSW under continuous operation. The best performance was achieved at an HRT of 9 h, with hydrogen productivities reaching up to 3.9 NL H2/L-d and hydrogen yields up to 61.7 NmL H2/g VSadded. The high hydrogen generation performance was associated with Clostridium sensu stricto 7 and Caproiciproducens, accompanied by lactic acid bacteria. This study provides valuable insights into the production and management of biocatalysts for thermophilic LD-DF and offers useful experience for the design and efficient operation of LD-DF processes utilizing OFMSW at thermophilic temperatures.

Keywords: bioenergy, dark fermentation, Inoculum production, Municipal Waste, Renewable hydrogen, Thermophilic conditions