Intensification of the Biohydrogen Production Process

Abstract

Background. In the last decades, humanity has faced the challenge of finding new ways to obtain renewable, environmentally friendly energy carriers. Hydrogen is one of such energy carriers; however, the current methods of its production require fossil fuels and are accompanied by significant CO2 emissions. Consequently, the energy costs needed to obtain hydrogen by electrolysis exceed the amount of energy produced by burning the hydrogen. Simultaneously, the hydrogen yields for alternative ways, such as fermentation, remain low. Objective. The aim of the work is the development of approaches to intensify the biohydrogen obtaining process from agricultural waste. Methods. An increase in hydrogen yield was achieved using specifically grown microorganisms of the Clostridium spp. A combination of the waste fermentation process with the production of hydrogen in a microbial fuel cell (MFC), which was fed with the liquid fraction after fermentation, was employed. Results. The yield of hydrogen depends on the component composition of the raw material. Higher lignin content in the raw material reduces the yield of hydrogen. The addition of Clostridium spp. to the natural consortium in the amount of 10% of the total inoculum led to an increase in hydrogen yield. The combination of two processes – fermentation and hydrogen production in a MFC – increased the yield of hydrogen by 1.7 times, along with a higher degree of organic raw materials utilization. Conclusions. The additional introduction of Clostridium spp. to the hydrogen-producing consortium leads to a 7–10% increase in the yield of hydrogen, depending on the composition of the raw material. The yield of hydrogen obtained in the fermentation process for the substrate containing corn silage is 12 ± 1% higher than for the wheat straw. In general, the combination of the fermentation and hydrogen production in the MFC in a two-stage process leads to an overall increase in the yield of hydrogen by 60 ± 5%.

Keywords

• biohydrogen
• renewable energy carriers
• agricultural wast
• microbial fuel cell
• microbial consortium