Fossil Fuels Will Be Around for a Long, Long Time
August / September 2004
Volume 2 Number 4
The good news is that the world has enough fossil fuel reserves (oil and especially coal) to supply its energy needs for hundreds of years. The bad news is that if we burn those reserves using current technology, we will likely release enough CO2 into the atmosphere to alter the climate significantly.
Fossil fuels are anticipated to continue to drive the U.S. economy for at least the next couple of decades. And even if we stopped burning them, developing countries such as China and India will still use their large coal reserves to fuel economic growth. While greener energy sources like wind, solar, and hydrogen may eventually be the ultimate solution, they currently provide only a small percentage of the nation's energy, and a full-scale transition to them may take decades. But we don't have decades to begin addressing the problem.
Currently, the world's CO2 levels are around 380 parts per million (ppm).
Predictions indicate that when the level of CO2 in the atmosphere reaches 450-750 ppm, the climate may become unstable. At our current rate of fossil fuel combustion, the world is likely to reach an intolerable level of atmospheric CO2 within 15-20 years. We may hit a "carbon wall" by 2020. Slowing, and eventually halting, this trend will rely on our ability to control CO2 emissions with a combination of approaches, including fuel switching, energy efficiency, and CO2 capture combined with long-term storage, or "sequestration." Los Alamos National Laboratory, in collaboration with university, government, and industrial partners, is working toward the development and implementation of land-based carbon sequestration approaches.
One of these approaches is terrestrial sequestration, which involves removing CO2 from the atmosphere and storing it in plants and soil. It's a way of enhancing what nature is already doing through photosynthesis by accelerating plant growth, restoring degraded lands, and preventing the release of stored carbon. To achieve this, the laboratory is working to develop methods to optimize vegetation growth, nutrient utilization, and water use to maximize carbon storage and prevent carbon loss; assess and improve land management practices to increase net carbon storage and land productivity; model ecosystem dynamics, and develop instruments and methods for rapid, accurate, and economical measurement of surface and subsurface carbon. The ability to accurately measure soil carbon could enable an economic incentive by converting sequestration capacity into tradable credits. The key to market-based trading in terrestrial carbon sequestration is the ability to measure the quantity of carbon stored in soils, plants and trees across diverse areas. Current methods to measure carbon in terrestrial systems are both time-consuming and costly, but Los Alamos's innovative Laser-Induced Breakdown Spectroscopy (LIBS) technology is poised to change that. Terrestrial sequestration not only decreases atmospheric CO2 but provides the additional benefits of improving soil fertility, increasing crop yields, and reducing erosion.
Another sequestration option currently under development at the laboratory involves long-term carbon storage in geologic reservoirs, or "geologic sequestration." Geologic reservoirs that may be able to contain CO2 include depleted oil and gas wells, deep unmineable coal seams and saline aquifers.
Containing carbon dioxide in a geologic storage reservoir is challenging because CO2 is mobile and buoyant, and the quantities that we need to store would be in the range of gigatons (i.e., billions of tons). Before CO2 can be safely stored in geologic reservoirs, we must be able to predict the long-term fate and impact of subsurface CO2. The key scientific challenges that must be addressed are: defining the fundamental physical and chemical mechanisms; characterizing, in detail, the subsurface, and modeling complex coupled processes over long periods of time. These challenges are particularly significant given the performance measure the Department of Energy has established to ensure safe and effective containment, which would allow a release of less than 0.01 percent of CO2 per year.
Because of the nuclear weapons underground testing program, Los Alamos has developed extensive expertise in engineering geologic systems for containment. This experience has resulted in unique capabilities for characterizing the subsurface and for predicting the behavior of engineered geologic systems over time. Science-based prediction capabilities are leveraged from the laboratory's experience with weapons and waste containment for earth systems. These tools bring new approaches and insight into characterization of geomaterials and geologic systems, fundamental physics and chemistry and predictive models of fluid flow and reactive transport. By applying these capabilities to the challenges of carbon management, Los Alamos may be able to develop affordable and environmentally safe methods for storing CO2 that could stabilize the atmosphere without immediate, large-scale, and costly changes to the energy infrastructure.
While terrestrial sequestration relies on the natural and direct absorption of CO2 from the atmosphere, geological storage is only possible when used in conjunction with effective separation and capture technologies. One approach is to capture CO2 right at the source from large emitters such as coal-fired power plants. Because power plant emissions are a mixture of gases, the first step in CO2 capture is to separate carbon dioxide from the mixed-gas stream. Los Alamos has developed new separation membranes and a patented acoustical phase separator that, unlike conventional technologies, are energy-efficient and can operate effectively in high temperatures. Once the CO2 is isolated, it can be transported via pipeline to a geological reservoir. But what about CO2 already in the atmosphere and the collective emissions of millions of small emitters, like automobiles? Los Alamos researchers have demonstrated, at gram-scale, the possibility of rapid and proportionately large removal of CO2 directly from the air using alkaline solutions. They are now examining the technological and economic feasibility of scaling up the process for future implementation.
Los Alamos has also been working on a power plant of the future that integrates clean power generation and CO2 separation and capture with the most novel and advanced approach to sequestration—€”mineralization. This power plant uses a process known as ZEC (Zero Emission Coal) to convert coal into hydrogen, which is in turn converted to electricity via a high-temperature solid-oxide fuel cell. Hydrogen gas is produced from water and coal using a calcium oxide (CaO) to calcium carbonate (CaCO3) intermediary reaction. No combustion is necessary.
Through a subsequent reaction, the calcium carbonate generated by hydrogen production is converted back into calcium oxide and a pressurized stream of pure CO2. The calcium oxide is recycled to drive further hydrogen production, and the pure CO2 stream is ready for storage. The proposed method of storage is the safest and most permanent of sequestration options. It involves turning CO2 into calcium carbonate rocks, something nature does over long periods of time. The CO2 is combined with magnesium silicates and the accelerated process converts the greenhouse gas into a stable mineral. All mineral end products are completely benign like their naturally occurring counterparts. Rather than temporary storage, mineral carbonation offers permanent fixation of CO2 thereby eliminating legacy issues for future generations. The mineral sequestration process is economically viable because the CO2 stream is non-mechanically pressurized in the hydrogen production process and the carbonation reaction is exothermic (i.e., it creates energy instead of consuming it). In addition, the types of mineral deposits needed to carry out the reaction are abundant enough to handle all the carbon locked in the world's coal reserves.
Eighty-five percent of the world's energy is derived from fossil fuels, and more than half of the electricity generated in the United States comes from coal. It is unlikely that any one approach or energy alternative alone will be effective enough to usurp fossil energy's enormous share of the market and infrastructure before we hit the carbon wall. The solution must come from many different directions, incorporating renewable and alternative energy sources, developing products and behaviors that are more energy-efficient, upgrading our aging infrastructure, implementing cleaner advanced fossil fuel technologies and better managing atmospheric carbon and CO2 emissions.
Anthony Mancino is with the LANL Office of Energy and Environmental Initiatives.
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