Biofuels produced from lignocellulosic biomass are a promising alternative to fossil fuels. To produce hydrocarbon fuels via biomass pyrolysis, the pyrolysis product (i.e., bio-oil) needs to be upgraded through hydrogenation, which requires a large amount of hydrogen gas (H2) as a reagent. However, the current H2 supply is from reforming natural gas, which compromises the green nature of biofuels. The objective of the study is to produce H2 from biofuel-related byproducts using a microbial electrolysis cell (MEC). MEC is a bioelectrochemical technology using microbes as catalyst and organic substrates as feedstock to produce H2 with a small voltage input (0.3-1.0 V). The MEC substrates in this study were two furanic and three phenolic compounds representative of the problematic and challenging components in lignocellulosic pyrolysates and hydrolysates. The proposed MEC application can productively transform the unwanted biofuel byproducts to useful H2, which reduces the release of organic waste and offers a sustainable H2 supply for bio-oil upgrading. The H2 yield in this study (26 - 42%) is higher than that obtained by the dark fermentation of glucose. The five compounds were completely transformed in 7 days, indicating a great potential for eliminating these inhibitory components in pyrolysates and hydrolysates. The highest H2 production rate (0.14 L/L-d) was achieved at hydraulic retention time of 6 h and organic loading rate of 3.2 g/L-d. The biotransformation of the five compounds was carried out via fermentation followed by exoelectrogenesis, through syntrophic interactions between fermenters, acetogens and exoelectrogens detected in the anode biofilm. The fermentation metabolites included catechol, phenol, and acetate. Acetate was then utilized in exoelectrogenesis for H2 production, while catechol and phenol were not further transformed. This study provides fundamental understandings to promote the integration of MEC technology into biofuel production for a green and sustainable H2 supply.

Green, sustainable H2 supply for upgrading bio-oil to biofuel: Conversion of furanic and phenolic byproducts to H2 using bioelectrochemical technology

251st National Meeting (2016)

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