Work

Simultaneous Biogas Upgrading and Bicarbonate Product Delivery via Electrochemical pH Swing

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Biogas upgrading through the separation of carbon dioxide (CO 2 ) to produce high-quality biomethane can significantly enhance the usability of biogas product. This study demonstrates an energy-efficient approach to biogas upgrading by leveraging electrochemical pH swing principles and integrating ionically conductive materials into bipolar membrane electrodialysis (BMED). The developed BMED process effectively captures CO 2 from biogas, producing high-quality biomethane while generating a bicarbonate solution product. The bicarbonate solution product can be further utilized in various applications such as algae cultivation, fertilizers, and a direct carbon supplementation to the crop-soil ecosystem. In this study, both theoretical (thermodynamic) and practical (experimental) perspectives are employed to evaluate the effect of different voltages and gas flow rates on CO 2 capture efficiency, current density, operational capacity, and specific energy consumption. Experimental results indicate that gas flow rate is a critical factor influencing upgrading performance. The specific energy consumption of the BMED ranges from 1.11 to 3.58 kWh per kg of CO 2, with current densities between 60 and 130 A/m 2 . To validate the experimental data, thermodynamic models are developed based on gas–liquid equilibrium (NaOH-H 2 O–CO 2 ) and activity coefficients using the electrolyte nonrandom two-liquid model. This study also explores the interrelationships among current density, energy consumption, and CO 2 capture scale. Furthermore, response surface models are constructed to identify optimal trade-offs between specific energy consumption and bicarbonate product purity, with thermodynamic modeling supporting future scale-up design. One of the optimal operating conditions could achieve a product purity of 1.95 g HCO 3 – /L. Overall, this work offers engineering insights into the operation of BMED enhanced with ionically conductive materials, presenting a promising energy-efficient solution for biogas upgrading.

Source: ACS Engineering Au

DOI: 10.1021/acsengineeringau.5c00041

Authors: Shu-Yuan Pan, Po-Chih Tseng, Cheng-Hsiu Yu

Institutions: National Taiwan University, National Taiwan University of Science and Technology

Language: English

Topic: Membrane-based Ion Separation Techniques

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Climate action, Affordable and clean energy, Responsible consumption and production

Open Access status: gold

Estimated APC paid: $3,500