Microalgae Cultivation in Electrochemically Oxidized Anaerobic Digestate from Coffee Waste Biomass
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-09-20 |
| Journal | Journal of the Japan Institute of Energy |
| Authors | H. P. Chen, Gen Yoshida, Fetra J. Andriamanohiarisoamanana, Ikko Ihara |
| Institutions | Kobe University |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Boron-Doped Diamond for Advanced Oxidation Processes (AOPs)
Section titled âTechnical Documentation & Analysis: Boron-Doped Diamond for Advanced Oxidation Processes (AOPs)âThis document analyzes the research paper, âMicroalgae Cultivation in Electrochemically Oxidized Anaerobic Digestate from Coffee Waste Biomass,â focusing on the critical role of Boron-Doped Diamond (BDD) electrodes in achieving high-efficiency decolorization for sustainable biomass utilization.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the efficacy of using Boron-Doped Diamond (BDD) electrodes for the electrochemical oxidation (EO) of highly colored liquid digestate (LD) derived from coffee waste, enabling subsequent microalgae cultivation.
- Core Value Proposition: BDD anodes provide a highly efficient, non-sacrificial method for decolorizing complex organic wastewater, overcoming the light permeability barrier for phototrophic microalgae growth.
- Material Performance: The BDD electrodeâs wide electrochemical window and high overpotential for oxygen evolution facilitated the generation of highly reactive hydroxyl radicals (OH), achieving up to 85% color removal.
- Process Efficiency: The EO process significantly reduced Chemical Oxygen Demand (COD) by 82% while retaining the majority of essential nutrients (80% NH4-N and 99% PO4-P).
- Application Success: The electrochemically oxidized liquid digestate (ELD) proved superior to diluted LD, resulting in the highest specific growth rate (0.79 ± 0.11 d-1) for Chlorella sorokiniana.
- Optimal Conditions: The best microalgae growth was achieved using 10 times diluted, 2-hour treated ELD, yielding a final cell density of 1.28*107 cells/ml.
- 6CCVD Relevance: This work validates the necessity of high-quality, custom-dimension BDD material for scaling advanced electrochemical wastewater treatment and nutrient recovery systems.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, focusing on the BDD electrode parameters and performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Anode/Cathode Material | Boron-Doped Diamond (BDD) | - | Used for Electrochemical Oxidation (EO) |
| Electrode Area (Total) | 50 | cm2 | BDD plate dimension |
| Electrode Area (Immersed) | 35 | cm2 | Active area during EO |
| Inter-Electrode Gap | 0.5 | cm | Reactor configuration |
| Applied Current Intensity | 1.5 | A | Constant current condition |
| Maximum Color Removal | 85 | % | Achieved after 180 min (3 h) EO treatment |
| Initial Color Density (LD) | 9500 ± 750 | Pt-Co unit | Raw liquid digestate characteristic (Table 1) |
| Final Color Density (2h ELD) | 0.305 | - | Optimal medium for microalgae growth |
| COD Removal Rate (EO) | 82 | % | Reduction from 7200 ± 440 mg/L to 980 ± 75 mg/L |
| NH4-N Retention (3h EO) | 80 | % | Essential nutrient retained for cultivation |
| Optimal Specific Growth Rate | 0.79 ± 0.11 | d-1 | Achieved using 2h ELD (10x diluted) |
| Optimal Final Cell Density | 1.28*107 | cells/ml | Achieved after 21 d cultivation |
| EO Operating Temperature | 35 | °C | Maintained by water bath |
Key Methodologies
Section titled âKey MethodologiesâThe following steps outline the preparation of the electrochemically oxidized liquid digestate (ELD), highlighting the critical role of the BDD-based EO process.
- Digestate Pre-treatment: Liquid digestate (LD) was separated from solids using a mesh filter, followed by double centrifugation (6000 rpm, 15 min) to remove suspended solids.
- Microfiltration: The liquid fraction was further purified using a microfiltration membrane (0.2 ”m) to obtain the final liquid digestate (LD).
- EO Reactor Setup: Electrochemical oxidation was conducted in a 500 mL cylindrical reactor containing 200 mL of solution, equipped with a three-piece undivided cell.
- BDD Electrode Integration: Boron-Doped Diamond (BDD) plates (50 cm2) were used as both the anode and cathode, with an inter-electrode gap of 0.5 cm.
- Process Control: The solution was stirred at 800 rpm and maintained at 35 °C. A constant current of 1.5 A was applied for reaction times ranging from 1 to 5 hours to produce ELD.
- Cultivation: C. sorokiniana was cultivated in various dilutions of LD and ELD (0 to 20 times dilution) under continuous light (150 ”mol photons m-2 s-1) at 25 ± 1 °C.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful implementation of this advanced oxidation process hinges entirely on the quality and customization of the Boron-Doped Diamond (BDD) electrodes. 6CCVD is uniquely positioned to supply the necessary materials to replicate, scale, and optimize this research for industrial application.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research into larger-scale wastewater treatment systems, the following 6CCVD materials are required:
- Boron-Doped Diamond (BDD) Plates: The core material for the EO process. 6CCVD provides high-quality, MPCVD-grown BDD films optimized for electrochemical applications, featuring the wide potential window and high overpotential necessary for efficient hydroxyl radical generation (OH).
- Polycrystalline Diamond (PCD) Substrates: For large-area electrode manufacturing, 6CCVD offers robust PCD substrates up to 125mm in diameter, which can be coated with BDD films to create large, durable anodes suitable for industrial reactors.
- Thickness Control: We offer BDD film thicknesses from 0.1 ”m up to 500 ”m, allowing engineers to specify the optimal doping profile and film thickness for maximum electrochemical stability and lifespan under high current density (1.5 A in this study).
Customization Potential
Section titled âCustomization PotentialâThe research utilized specific electrode dimensions (50 cm2 plates, 35 cm2 immersed area). 6CCVD specializes in providing materials tailored precisely to reactor geometry and operational needs.
| Research Requirement | 6CCVD Customization Service | Benefit to Researcher/Engineer |
|---|---|---|
| Specific Plate Size (50 cm2) | Custom Dimensions & Laser Cutting | We provide BDD plates cut to exact specifications, ensuring optimal fit and active area for pilot or full-scale reactors, minimizing material waste. |
| Electrical Contact Integration | Custom Metalization Services | 6CCVD offers in-house metalization (Ti, Pt, Au, W, Cu) for creating robust, low-resistance electrical contacts on BDD electrodes, crucial for maintaining the constant current (1.5 A) required for efficient EO. |
| Large-Scale Deployment | Wafers up to 125mm | Our capability to produce inch-size PCD/BDD wafers up to 125mm allows for the design of high-throughput, modular electrochemical cells necessary for scaling biomass treatment. |
| Surface Finish | Polishing (Ra < 5nm for PCD/BDD) | While the BDD film is the active component, precise polishing ensures uniform flow dynamics and consistent performance across the electrode surface. |
Engineering Support
Section titled âEngineering SupportâThe successful application of BDD in this study relies on understanding the materialâs electrocatalytic properties relative to the specific wastewater matrix (coffee digestate). 6CCVDâs in-house PhD team provides expert consultation on:
- Material Selection: Assisting researchers in selecting the optimal BDD doping level and film thickness for maximizing OH radical generation and minimizing side reactions (like oxygen evolution).
- Process Optimization: Providing guidance on integrating BDD electrodes into flow-through or batch reactors for similar Electrochemical Wastewater Decolorization and Nutrient Recovery projects.
- Failure Analysis: Ensuring long-term electrode stability and performance under aggressive oxidation conditions.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Anaerobic digestate contains rich nutrients, such as nitrogen and phosphorus, which could be reused in microalgae cultivation. However, a clear growth medium is required for the cultivation to facilitate light permeable condition. The aim of this work was to investigate microalgae cultivation in electrochemically oxidized liquid digestate from coffee waste biomass. After removing the solid fraction of the digestate through microfiltration, the liquid digestate was treated by electrochemical oxidation using a boron-doped diamond anode. The liquid digestate (LD) and electrochemically oxidized liquid digestate (ELD) were used as media for microalgae cultivation.The effects of dilution from 5 to 20 times of the LD and reaction time from 1 to 5 h of the ELD on microalgae growth were also investigated. The results showed that the electrochemical oxidation had little influence on ammonium concentration in the digestate, whereas a color removal of up to 85% was observed. The ELD showed better microalgal growth performances than diluted LD, based on the data from optical density at 680 nm and cell density. The 10 times diluted, 2 h ELD achieved the best growth performance (additional optical density of 1.5 (-)) in all conditions. Our experiments proved that the ELD as a highly light permeable medium, better improved the growth performance of C. sorokiniana cultivation when compared with the LD medium.