Abstract
Wine lees have a great potential to obtain clean energy in the form of biogas through anaerobic digestion due to their high organic load. However, wine lees are a complex substrate and may likely give rise to instabilities leading to failure of the biological process. This work analysed the digestion of wine lees using two different approaches. First, electro-oxidation was applied as pre-treatment using boron-doped diamond-based electrodes. The voltage was 25 V and different treatment times were tested (ranging from 0.08 to 1.5 h) at 25 °C. Anaerobic digestion of wine lees was evaluated in batch tests to investigate the effect of electro-oxidation on biogas yield. Electro-oxidation exhibited a significant positive effect on biogas production increasing its value up to 330 L kg−1 of volatile solids after 1.5 h of treatment, compared to 180 L kg−1 of volatile solids measured from raw wine lees. As a second approach, the addition of biochar to the anaerobic digestion of wine lees was investigated; in the experimental conditions considered in the present study, the addition of biochar did not show any positive effect on anaerobic digestion performance.
Highlights
Nowadays, Italy, France and Spain are the three top wine producers worldwide, with 14.8 million m3 of wine produced in 2018 [1]
The main objective of this study was to investigate the improvement of Anaerobic digestion (AD) of wine lees (WL) by two different approaches: one was the application of EO as pre-treatment and the other was the use of BC as an additive
The present study aimed to address the following research questions (RQ): (RQ1) Is AD appropriate for the valorisation of WL from a technical perspective, considering potential inhibitors? (RQ2) Could EO through BDD anodes act as an effective pre-treatment to improve the performance of AD of WL? (RQ3) Can BC be a valuable additive to improve the performance of AD of WL? (RQ4) Is the effect of BC associated with its physical properties rather than with the electro-chemical ones?
Summary
France and Spain are the three top wine producers worldwide, with 14.8 million m3 of wine produced in 2018 [1]. The winemaking industry generates large quantities of solid waste and wastewater. Solid residues derived from this industry include stalks from destemming, grape marcs (or pomace) from pressing, and lees from the settling of leftover products from the fermentation and dead yeast cells on the bottom of the vessel. The transformation of 1000 kg of processed grape produces 0.75 m3 of wine and 130 kg of marc, 60 kg of lees, 30 kg of stalks, and 1.65 m3 of wastewater [2]. Winery wastes may be used to extract valuable chemicals (e.g., phenols, antioxidants, tartaric acid, lignocellulose), as feedstock for the production of bioenergy by means of thermo-chemical and biological processes, and for agricultural and environmental applications (composting, animal feed, biosorbents) [3,4,5]. European Council Regulations 479/2008/EC and 555/2008/EC have permitted many of the aforementioned applications
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