Improving the Anaerobic Digestion of Wine-Industry Liquid Wastes - Treatment by Electro-Oxidation and Use of Biochar as an Additive

At a Glance

Metadata	Details
Publication Date	2020-11-16
Journal	Energies
Authors	Cristián B. Arenas, Marco Chiappero, Xiomar Gómez, Silvia Fiore, Elia Judith Martínez Torres
Institutions	Universidad de León, Polytechnic University of Turin
Citations	26
Analysis	Full AI Review Included

Technical Documentation & Analysis: BDD Electro-Oxidation for Bioenergy

Reference Paper: Improving the Anaerobic Digestion of Wine-Industry Liquid Wastes: Treatment by Electro-Oxidation and Use of Biochar as an Additive (Energies 2020, 13, 5971)

Executive Summary

This research validates the critical role of Boron-Doped Diamond (BDD) electrodes in enhancing bioenergy production from complex organic waste streams, specifically wine lees (WL). The key findings and material requirements are summarized below:

Core Application: BDD electrodes were successfully utilized for electro-oxidation (EO) pre-treatment of wine lees to improve subsequent anaerobic digestion (AD) performance.
Performance Achievement: EO pre-treatment significantly increased the specific biogas potential of WL from 180 L kg^-1 VS (raw) up to 330 L kg^-1 VS after only 1.5 hours of treatment, an improvement of approximately 83%.
Enabling Mechanism: The BDD anode’s capability to generate highly reactive hydroxyl radicals (OH•) efficiently oxidized recalcitrant organic inhibitors (polyphenols, melanoidins), converting them into simpler, more biodegradable volatile fatty acids (VFAs).
Operational Conditions: The process demonstrated effectiveness under mild conditions (25 V, 25 °C, low current density 11-18 mA cm^-2), highlighting the energy efficiency potential of BDD technology.
Material Requirement: The success hinges on the chemical stability and wide potential window of high-quality MPCVD BDD electrodes, which 6CCVD is uniquely positioned to supply for scale-up and optimization.

Technical Specifications

The following hard data points were extracted, demonstrating the operational parameters and performance metrics achieved using BDD electro-oxidation:

Parameter	Value	Unit	Context
Electrode Material	Boron-Doped Diamond (BDD)	N/A	Anode and Cathode
Effective Surface Area	42	cm²	BDD Electrode Size used in batch cell
Electrode Distance	5	mm	Gap between BDD electrodes
Applied Voltage	25	V	Constant input for EO pre-treatment
Operating Temperature	25 ± 1	°C	Ambient/Mesophilic conditions
Current Density Range	11 to 18	mA cm^-2	Low current density applied
Maximum Treatment Time	1.5	h	Duration yielding peak biogas production
Raw Biogas Potential (WL)	180 (0.18)	L kg^-1 VS	Untreated substrate baseline
Treated Biogas Potential (WL_1.5 h)	330 (0.330)	L kg^-1 VS	Maximum yield after EO pre-treatment
Polyphenol Removal	25 to 60	%	Reduction of key AD inhibitors
Maximum Current Efficiency (CE)	~30	%	Calculated based on TOC removal

Key Methodologies

The electro-oxidation (EO) pre-treatment utilized high-performance BDD electrodes under controlled batch conditions:

Electrode Configuration: Two BDD electrodes (anode and cathode) were configured with an effective surface area of 42 cm² and maintained at a 5 mm separation distance within a 70 mL batch cell.
Substrate Preparation: Wine Lees (WL) were used as the substrate, characterized by a highly acidic pH (3.60 ± 0.02) and high organic load (68.11 g L^-1 Total Organic Carbon).
EO Operation: A constant voltage of 25 V was applied, resulting in current densities ranging from 11 to 18 mA cm^-2. The temperature was maintained at 25 ± 1 °C.
Treatment Variation: Treatment times were varied from 0.08 h (5 min) up to 1.5 h (90 min) to assess the kinetic effects on organic compound degradation.
Analytical Assessment: EO performance was measured by tracking the decrease in Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), decolourisation (475 nm), and the increase in Volatile Fatty Acids (VFAs), particularly acetic acid.
Anaerobic Digestion (AD): EO-treated WL samples were subjected to batch AD tests at 37 °C, with performance evaluated by cumulative specific biogas potential (L kg^-1 VS) and kinetic modeling (Modified Gompertz).

6CCVD Solutions & Capabilities

This research confirms the commercial viability of BDD electrodes for advanced electrochemical processes in waste valorization and bioenergy. 6CCVD is an expert supplier of MPCVD diamond materials necessary to replicate, optimize, and scale this technology.

Applicable Materials

To achieve the high chemical stability and efficient radical generation demonstrated in this study, the following 6CCVD materials are required:

Application Requirement	6CCVD Material Recommendation	Key Specification
High-Efficiency Electro-Oxidation	Heavy Boron-Doped Diamond (BDD)	High doping concentration for maximum conductivity and hydroxyl radical (OH•) generation efficiency.
Electrode Substrate	BDD on Silicon or Niobium	Provides robust mechanical support and excellent electrical contact for industrial cell designs.
Chemical Resistance	BDD Films (0.1 µm to 500 µm)	Superior resistance to acidic (pH 3.6) and high-COD environments typical of winery waste.

Customization Potential

The success of electrochemical wastewater treatment relies heavily on precise electrode geometry and integration. 6CCVD offers full customization capabilities that directly address the needs of researchers and engineers scaling this technology:

Custom Dimensions: While the paper used 42 cm² electrodes, 6CCVD supplies BDD plates and wafers up to 125 mm in diameter (PCD) or custom rectangular plates, enabling seamless transition from lab-scale (70 mL cell) to pilot-scale reactors.
Thickness Control: We provide precise control over BDD film thickness (SCD/PCD: 0.1 µm - 500 µm) and substrate thickness (up to 10 mm), allowing optimization of material usage and electrical resistance for specific current density requirements (11-18 mA cm^-2).
Advanced Metalization: For robust electrical connections required in high-voltage/high-current EO systems, 6CCVD offers in-house metalization services, including Ti/Pt/Au, W, Cu, and Pd layers, ensuring low-resistance contact points and long electrode lifespan.
Surface Finish: We provide high-quality polishing services (Ra < 5nm for inch-size PCD) to ensure consistent surface morphology, which is critical for reproducible electrochemical performance and minimizing fouling in complex organic matrices like wine lees.

Engineering Support

The research highlights the need for optimizing BDD properties (doping, surface area) to maximize Current Efficiency (CE) and TOC removal.

Process Optimization: 6CCVD’s in-house PhD team specializes in diamond material science and can assist engineers in selecting the optimal BDD doping level and film structure required to maximize hydroxyl radical production for similar Electrochemical Wastewater Treatment projects.
Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of high-specification BDD materials, minimizing lead times for critical research and development cycles.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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 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.

Tech Support

Original Source

DOI: https://doi.org/10.3390/en13225971

References

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]