Researchers from the University of São Paulo and Universidad de Jaén in Brazil have shown that hydrogen can be produced from vine shoots—the main waste generated during vine pruning in viticulture, with up to 2 tons generated per hectare annually. Their work evaluates, for the first time, the possibility of using vine shoots as a substrate for the fermentative H₂ production, evaluating one type of each physical, chemical and biological pre-treatments in order to increase biofuel production.

Unlike other treatments that employ chemical or physical reagents, their process is more environmentally friendly, as it does not require recycling of waste products and does not release toxic compounds. It also increases hydrogen production up to almost 250% compared to other pretreatment methods, according to Juan Miguel Romero-García, one of the authors of a paper describing the work in the journal Industrial Crops and Products.

Rabelo et al.

Vine shoots are composed of cellulose (28–40%), hemicellulose (17–28%) and lignin (25–32%) in addition to extractives (∼3%). This residue has low economic value and very limited use, and it is generally destined for burning and soil disposal, the researchers said.

In the study, the team used physical pre-treatments by steam explosion (SE), chemical by organosolv (OS) and biological by laccase (LAC) to disrupt the vine shoot cell fiber and increase the biomass hydrolysis and fermentation into hydrogen.

After steam explosion, there was a slight decrease in cellulose and hemicellulose contents in biomass fibers, while a decrease in lignin content occurred after the organosolv pre-treatment.

There were no quantifiable changes after laccase pre-treatment; however, the enzyme-substrate oxidative reactions were favorable for hydrolysis and fermentation since an increase in soluble sugars and H₂ production was observed with LAC vine shoots as substrate.

300.1 mL H₂/L were obtained from raw material vine shoots, while 649.4, 399.8 and 749.7 mL H₂/L were obtained from biomass pre-treated by SE, OS and LAC, respectively.

The researchers also evaluated the hydrolysis of pre-treated biomass by the addition of cellulase to improve H₂ production. Higher amounts of H₂ were obtained from hydrolyzed biomass in relation to non-hydrolyzed ones (154.2%, 602.0% and 167.1% more with SE, OS and LAC hydrolyzed, respectively).

In all cases, the mixed acid pathway was carried out by Clostridium butyricum, since acetic and butyric acids were produced.

Resources

• Camila A.B. Silva Rabelo, Alfonso M. Vidal, Rocío Casanova-González, Juan Miguel Romero-García, Maria Bernadete A. Varesche, Inmaculada Romero, Eulogio Castro (2023) “Vine shoots pre-treatment strategies for improved hydrogen production and metabolites redistribution in Clostridium butyricum,” Industrial Crops and Products, Volume 204, Part B, doi: 10.1016/j.indcrop.2023.117317.