Nigerian coal seams offer dual solution for clean energy and carbon storage
Molecular simulations reveal subbituminous coals from Nigeria's Anambra Basin preferentially capture carbon dioxide while releasing methane, paving the way for advanced energy strategies
image: Investigating adsorption properties of CO₂ and CH₄ in subbituminous coals from Mamu and Nsukka formations: a molecular simulation approach
Credit: Victor Inumidun Fagorite, Uzochukwu Nelson Ikechukwu & Henry Olumayowa Oluwasola
A new investigation led by researchers at the African Centre of Excellence in Future Energies and Electrochemical Systems (ACE-FUELS) at the Federal University of Technology, Owerri, provides a detailed molecular-level blueprint for using Nigerian coal deposits to simultaneously capture carbon dioxide (CO₂) and enhance natural gas production. The work by Victor Inumidun Fagorite and his colleagues offers a scientific foundation for implementing CO₂-Enhanced Coalbed Methane (ECBM) technology, a process with significant economic and environmental potential for the nation.
A Molecular-Level Investigation
The team's objective was to characterize the gas adsorption capabilities of subbituminous coals from the Mamu and Nsukka geological formations. The inquiry began with extensive laboratory analyses, including proximate, ultimate, and FT-IR techniques, to confirm the coal's specific chemical and physical nature. Following this characterization, the scientists employed sophisticated computational tools, creating a unique amorphous subbituminous coal model using molecular dynamics (MD) simulations. This virtual model allowed them to meticulously observe the interactions between individual CO₂ and methane (CH₄) molecules and the coal structure under various conditions.
The Preferential Capture of Carbon Dioxide
Through Grand Canonical Monte Carlo (GCMC) simulations, the analysis consistently showed that the subbituminous coal model has a much stronger affinity for CO₂ compared to CH₄. A key indicator of this preference is the isosteric heat of adsorption, which was significantly higher for CO₂. This higher value signifies a stronger energetic interaction between CO₂ molecules and the coal's surface, particularly with its heteroatom functional groups. Essentially, the coal grabs onto CO₂ more tightly than it does CH₄, creating the ideal conditions for displacing trapped methane.
Pressure and Temperature as Critical Levers
When examining a mixture of both gases, the model confirmed CO₂'s superior adsorption selectivity. The researchers also identified how this selectivity responds to changing environmental conditions. At lower pressures, CO₂ selectivity was extremely high but decreased as temperatures rose. In contrast, at higher pressures (above 6 MPa), the influence of temperature became minimal. This detailed understanding of the pressure and temperature dynamics is essential for designing and optimizing real-world ECBM operations to achieve maximum efficiency in both methane extraction and CO₂ sequestration.
"Our work connects the fundamental atomic interactions within coal to a tangible, national-scale opportunity for Nigeria," states Victor Inumidun Fagorite, the corresponding author from ACE-FUELS and the Research Department, Clean Technology Hub. "By building a robust molecular model, we have established a predictive framework that can guide the development of CO₂-ECBM projects. This is about transforming a domestic resource into a tool for both economic growth through enhanced gas recovery and for climate action by permanently storing CO₂ underground."
From Simulation to National Strategy
The findings provide a critical theoretical and practical roadmap for harnessing Nigeria's subbituminous coal resources for carbon capture and storage. While the current simulation focused on the microporous structure of coal, the authors acknowledge that future work could incorporate the role of larger mesopores for an even more comprehensive model. Nevertheless, this research lays the groundwork for developing policies and pilot projects aimed at boosting the nation's energy supply while contributing to its net-zero emissions targets, demonstrating how geological assets can be repurposed for a sustainable future.
Corresponding Author: Victor Inumidun Fagorite
Original Source: https://doi.org/10.1007/s44246-024-00160-x
Contributions: Conceptualization of title, structuring of the paper, analysis of data was carried out by Victor Inumidun Fagorite. Materials sourcing and some data analysis was carried out by Uzochukwu Nelson Ikechukwu, Henry Olumayowa Oluwasola. The final paper draft and structuring, reviewing and modifications was performed by Samuel Okechukwu Onyekuru Conrad Kenechukwu Enenebeaku, Nnemeka Princewill Ohia, Okechukwu Ebuka Agbasi and Emeka Emmanuel Oguzie. All authors contributed to writing and proofreading the paper. Hence, the final manuscript was reviewed and approved by all authors.