In the relentless pursuit of mitigating climate change, scientists and engineers are exploring every possible avenue to reduce atmospheric carbon dioxide (CO2) levels. Among the most promising strategies is carbon capture and sequestration (CCS), a process that involves capturing CO2 emissions from industrial sources, compressing the gas, transporting it, and injecting it into underground or underwater storage. A groundbreaking study published in the journal ‘Thermo’ (which translates to ‘Heat’ in English) delves into the energy requirements and practicalities of this technology, offering a comprehensive look at what it takes to make CCS a viable solution.
At the heart of this research is Efstathios E. Michaelides, a professor in the Department of Engineering at Texas Christian University. Michaelides and his team have meticulously analyzed the thermodynamic and transport properties of CO2, providing a detailed roadmap for its capture, compression, and storage. Their findings highlight the substantial energy demands of CCS, but also point to ways in which these demands can be met efficiently.
The study examines two key industrial sectors: cement production and coal-fired power plants. Both are major contributors to global CO2 emissions, making them prime candidates for CCS implementation. “The mechanical power needed for the sequestration of CO2 is substantial in both cases,” Michaelides explains. “However, the cement unit needs less power because of the availability of high-temperature waste heat.”
One of the most intriguing aspects of the research is the exploration of deep-ocean injection as a long-term storage solution. Unlike inland or aquifer sequestration, which face significant challenges due to the vast quantities of CO2 emitted and its properties, ocean sequestration leverages the fact that CO2 dissolution in seawater produces a heavier liquid mixture. This makes it a more feasible option for long-term storage.
The study also delves into the power requirements for CO2 compression and transportation. Compressing CO2 to supercritical pressures—higher than 7.4 MPa—is essential for efficient pipeline transportation. This process, however, requires significant power. “The compression of this gas to supercritical pressures is necessary for its transportation in pipelines, and this requires significant power,” Michaelides notes.
The research provides a holistic evaluation of the energy and power needed for CCS to become a realistic solution. For a cement plant in Texas, the total work required for CO2 capture and sequestration in the Gulf of Mexico is calculated to be 0.802 MJ per kilogram of CO2. For a coal power plant, this figure rises to 1.159 MJ per kilogram. If the work in the latter case is provided by the power plant itself, its thermal efficiency would drop by approximately 10 percentage points.
The implications of this research are far-reaching. For the energy sector, it underscores the need for innovative solutions to reduce the energy demands of CCS. It also highlights the potential of waste heat recovery in industrial processes, a strategy that could significantly enhance the efficiency of CO2 capture and sequestration.
As the world continues to grapple with the challenges of climate change, studies like this one are crucial. They provide the scientific foundation for developing practical, scalable solutions that can help us achieve our climate goals. By understanding the energy requirements and practicalities of CCS, we can pave the way for a more sustainable future.
Michaelides’ work, published in ‘Thermo’, offers a detailed and nuanced look at the energy demands of CCS. It serves as a call to action for the energy sector, urging stakeholders to invest in research and development to make CCS a viable and efficient solution. As we strive to reduce our carbon footprint, this research provides a roadmap for turning CCS from a theoretical concept into a practical reality.
