Improving the Anaerobic Digestion of Wine-Industry Liquid Wastes - Treatment by Electro-Oxidation and Use of Biochar as an Additive
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-16 |
| Journal | Energies |
| Authors | CristiĂĄn B. Arenas, Marco Chiappero, Xiomar GĂłmez, Silvia Fiore, Elia Judith MartĂnez Torres |
| Institutions | Polytechnic University of Turin, Universidad de LeĂłn |
| Citations | 26 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Problem Addressed: Anaerobic Digestion (AD) of Wine Lees (WL) is severely limited by high acidity, high organic load (COD > 270 g L-1), and the presence of inhibitory compounds like polyphenols and melanoidins.
- Core Solution (EO): Electro-Oxidation (EO) using Boron-Doped Diamond (BDD) electrodes was successfully applied as a pre-treatment to detoxify and simplify the WL substrate.
- Performance Gain: EO pre-treatment significantly improved AD performance, increasing the specific biogas potential by 83% (from 180 L kg-1 VS for raw WL up to 330 L kg-1 VS after 1.5 h of EO).
- Mechanism: EO achieved 25% to 60% removal of inhibitory polyphenols and converted complex organic molecules into simpler, readily digestible Volatile Fatty Acids (VFAs), primarily acetic acid.
- Process Conditions: The EO treatment utilized mild, potentially cost-effective conditions: low voltage (25 V) and low current density (11 to 18 mA cm-2).
- Additive Evaluation: The addition of biochar (BC) or inert pumice stone (PS) at 10 g L-1 concentration did not show any positive effect on AD performance under the experimental conditions tested.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Raw WL pH | 3.60 ± 0.02 | - | Highly acidic substrate |
| Raw WL Chemical Oxygen Demand (COD) | 271 ± 14 | g L-1 | High organic load |
| Raw WL Total Polyphenols | 58.02 ± 2.90 | mg GAE L-1 | Primary AD inhibitor |
| EO Electrode Material | Boron-Doped Diamond (BDD) | - | Anode and Cathode |
| EO Applied Voltage | 25 | V | Constant operational parameter |
| EO Treatment Time Range | 0.08 to 1.5 | h | Tested range for pre-treatment |
| EO Current Density Range | 11 to 18 | mA cm-2 | Low current density conditions |
| Maximum Polyphenol Removal | 60 | % | Achieved after 1.5 h EO treatment |
| Maximum Current Efficiency (CE) | ~30 | % | Calculated based on TOC reduction |
| Raw WL Specific Biogas Potential (P) | 180 (approx. 0.18) | L kg-1 VS | Baseline AD performance |
| EO-Treated WL Specific Biogas Potential (P) | 330 (approx. 0.33) | L kg-1 VS | Achieved after 1.5 h EO treatment |
| Average Methane Content | 58 | % | Across all AD digesters |
| Biochar/Pumice Concentration | 10 | g L-1 | Additive dosage in AD tests |
| AD Operating Temperature | 37 ± 1 | °C | Mesophilic batch digestion |
| Substrate/Inoculum Ratio (S/I) | 1:1 | VS basis | Batch test setup |
| Biochar Total Surface Area | 26.40 | m2 g-1 | SWP550 Biochar |
Key Methodologies
Section titled âKey Methodologiesâ- Substrate Preparation: Wine Lees (WL) were collected from a Barbaresco wine production facility. Inoculum was sourced from mesophilic wastewater treatment plant (WWTP) digesters.
- Electro-Oxidation (EO) Setup: EO was performed in a 70 mL batch cell using two Boron-Doped Diamond (BDD) electrodes (42 cm2 effective surface area, 5 mm gap).
- EO Operating Conditions: A constant voltage of 25 V was applied at 25 °C. Treatment times ranged from 0.08 h (5 min) to 1.5 h (90 min), resulting in current densities between 11 and 18 mA cm-2.
- EO Performance Metrics: EO effectiveness was assessed by measuring the removal of Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), ethanol, and total polyphenols, alongside the increase in Volatile Fatty Acids (VFAs). Current efficiency (CE) was calculated based on TOC reduction.
- Anaerobic Digestion (AD) Setup: Batch AD tests were conducted in 250 mL reactors at 37 °C (mesophilic). The substrate (WL or EO-treated WL) and inoculum were mixed at a 1:1 ratio based on volatile solids (VS).
- pH Control: Sodium bicarbonate (NaHCO3) was added initially to adjust the pH to 7.5, mitigating potential inhibition caused by high VFA concentrations.
- Additive Testing: Biochar (BC, softwood pyrolysis at 550 °C) and granular pumice stone (PS, inert control) were tested as additives, both powdered and added at a concentration of 10 g L-1.
- AD Performance Metrics: Biogas and methane production were monitored over time, corrected to STP, and kinetic parameters (Biogas Potential P, Maximum Rate Rmax, and Lag Phase λ) were determined using the modified Gompertz model.
Commercial Applications
Section titled âCommercial Applicationsâ- Industrial Wastewater Pre-treatment: Utilizing BDD-based EO systems (e.g., Pro Aqua Diamond Electrodes) for the detoxification and conditioning of high-strength, inhibitory industrial effluents (wineries, distilleries, food processing) prior to conventional biological treatment.
- Biogas Yield Optimization: Integration of EO as a front-end technology to maximize the specific methane production from complex organic wastes, improving the economic viability of AD plants.
- Advanced Oxidation Technology (AOT): Deployment of BDD electrodes for the efficient, chemical-free oxidation of recalcitrant organic pollutants (melanoidins, complex acids) in water streams.
- Electrochemical Reactor Design: Development of low-energy electrochemical cells optimized for high-volume, low current density applications, focusing on maximizing hydroxyl radical generation for organic matter breakdown.
- Carbon Material Research: Continued investigation into the use of conductive carbon materials (like biochar) as AD additives, focusing on optimizing dosage and surface properties to promote direct interspecies electron transfer (DIET) in specific waste streams.
View Original 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 kgâ1 of volatile solids after 1.5 h of treatment, compared to 180 L kgâ1 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.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2016 - Integrated approach to winery waste: Waste generation and data consolidation [Crossref]
- 2016 - Grape Winery Waste as Feedstock for Bioconversions: Applying the Biorefinery Concept [Crossref]
- 2015 - Challenges and strategies for solid-state anaerobic digestion of lignocellulosic biomass [Crossref]
- 2015 - Treatment of winery wastewater by physicochemical, biological and advanced processes: A review [Crossref]
- 2012 - Biogas production of winemaking waste in anaerobic fermentation process
- 2016 - Renewable energy from thermophilic anaerobic digestion of winery residue: Preliminary evidence from batch and continuous lab-scale trials [Crossref]