|ognizant Communication Corporation|
A Journal of Science Serving Legislative, Regulatory, and Judicial Systems
Human Advancement · Environmental Protection · Industrial Development
Volume 7, Supplement 1, 2000
Technology, Vol. 7S, pp. 3-12, 2000
1072-9240/00 $20.00 + .00
Copyright © 2000 Cognizant Comm. Corp.
Printed in the USA. All rights reserved.
Carbon Dioxide Recovery in a Power Plant with Chemical-Looping Combustion
Masaru Ishida, Masashi Yamamoto, and Takehiro Ohba
Tokyo Institute of Technology, Yokohama, Japan
Greenhouse gas abatement is crucial but a complicated and difficult problem. A breakthrough in this field requires the development of a new technology for CO2 capture with little or no energy penalty. To achieve the objective, a novel gas turbine power plant is proposed. The chemical-looping combustor in the proposed system consists of a fuel reactor where fuel reacts with metal oxide and an air reactor where the metal reacts with oxygen in air. Because CO2 is obtained by condensing water vapor in the outlet gas from the fuel reactor, this new system requires no additional energy consumption for CO2 separation (and thus no energy penalty) and no equipment for CO2 separation. This paper identifies the breakthrough points in the proposed system and summarizes some of the experimental results.
The Economics of Co2 Separation and Capture
Howard J. Herzog
MIT Energy Laboratory, Cambridge, MA
Carbon management and sequestration offers an opportunity for reducing greenhouse gas emissions that can complement the current strategies of improving energy efficiency and increasing the use of non-fossil energy resources. The focus of this paper is the capture of CO2 from large stationary sources-primarily power plants. This paper begins with an overview of CO2 separation and capture technology; followed by a detailed analysis of costs associated with today's technology for CO2 separation and capture; followed by a discussion of opportunities to lower costs in the future. Based on this cost analysis, a composite model for costs from several types of power plants was developed, followed by a sensitivity study. For coal, new technologies like gasification show the most long-term promise. By 2012, incremental costs for CO2 sequestration could be less than 1¢/kWh from advanced coal plants, and less than 1.5¢/kWh from gas plants.
Development of the Technologies for Carbon Dioxide Recovery from Power Plant Flue Gas
Zeng Xianzhong, Guo Bing, Chen Changhe, and Xu Xuchang
The State Key Laboratory of Clean Combustion of Coal, Tsinghua University, Beijing, P. R. China
The principal technologies for CO2 recovery from flue gas (including chemical absorption, physical absorption, physical adsorption, cryogenic distillation, and membrane separation) are reviewed and their advantages and disadvantages are compared. Current researches and applications of these technologies are described. Some research issues, such as operational problems, solvent stability, adsorbent capacity, membrane selectivity, and by-product generation are considered. These issues-together with the aim to increase recovery efficiencies and lower recovery costs-are used for suggestive directions of further research. Although these technologies are basically feasible from a technical perspective, their efficiency, reliability, and economics are still uncertain. Most technologies are expensive and energy intensive. Therefore, further researches are needed to develop more effective CO2 separation processes at much lower capital and operating costs.
Forecasting World Food Supplies: The Impact of the Rising Atmospheric Co2 Concentration
Craig D. Idso and Keith E. Idso
Center for the Study of Carbon Dioxide and Global Change, Tempe, AZ
Based on food production databases assembled and maintained by the United Nations, identification has been made for the specific crops that supply 95% of the food needs of the world, six large regions into which the world may be divided, and fourteen individual countries of particular interest. Trends have been projected in the productivities of these crops in each of these geographical areas to the year 2050, finding that expected advances in agricultural technology and expertise will significantly increase the food production potential of many countries and regions. However, these expected advances will not increase production fast enough to meet the demands of the even faster-growing human population of the planet. The scientific literature was reviewed to determine the implications of the ongoing rise in the air's CO2 concentration for world food production. Based on this information, calculations indicate that over the next half-century, the aerial fertilization effect of atmospheric CO2 enrichment will boost world agricultural output by about half as much as the expected advances in agricultural technology and expertise will increase it. Taken together, these two effects should provide just enough of an augmentation in food production to supply the dietary requirements of the projected human population of the globe in the year 2050. The implication of these results is that in order to avoid the unpalatable consequences of widespread hunger in the decades ahead, the atmospheric CO2 concentration will have to rise at an unrestricted rate. Otherwise, the rate of world population growth will have to drop even faster than it is anticipated to naturally decline.
Atmospheric Co2 Enrichment: Implications for Ecosystem Biodiversity
Keith E. Idso,1 Craig D. Idso,1 and Sherwood B. Idso2
1Center for the Study of Carbon Dioxide and Global Change,
2U.S. Water Conservation Laboratory, Phoenix, AZ
Several experiments suggest that atmospheric CO2 enrichment will likely have little impact on genotypic diversity within species and will probably not reduce the species richness of earth's many ecosystems. A number of studies suggest that these consequences are determined by a suite of complex and interacting phenomena that occur in the belowground environment, where plant roots intimately intermingle with various types of soil fungi in ways that sometimes tend to increase ecosystem biodiversity.
Atmospheric CO2 enrichment is also effective in countering what are often assumed to be biodiversity-degrading effects of global warming, as higher atmospheric CO2 concentrations tend to ameliorate heat stress in plants and increase the temperatures at which plants function at their optimum. These phenomena enable plants to maintain the high-temperature boundaries of their ranges in the face of regional or global warming at the same time that the warming allows them to push poleward at their low-temperature boundaries. The net effect is to increase the sizes of their ranges. Herbivores that selectively feed on specific plants thus have the opportunity to likewise expand their ranges, as do carnivores that feed on them. Thus, with a greater overlapping of the ranges of both plants and animals, the species richness of nearly all of earth's ecosystems tends to rise.
Co2, Global Warming and Coral Reefs: Prospects for the Future
Sherwood B. Idso,1 Craig D. Idso,2 and Keith E. Idso2
1U.S. Water Conservation Laboratory, Phoenix, AZ
2Center for the Study of Carbon Dioxide and Global Change, Tempe, AZ
Reconstructions of surface air temperature and atmospheric CO2 concentration derived from Antarctic ice cores have revealed that air temperature always rose or fell in advance of similar changes in the air's CO2 content throughout all major climate transitions between glacial and interglacial periods of the past half-million years. This demonstrates that changes in atmospheric CO2 concentration cannot be the principal cause of climate change. A review of the literature also reveals that there is no simple linkage between high temperatures and coral bleaching. Indeed, scientists are beginning to realize that bleaching may in fact be an adaptive mechanism for surviving high temperatures. Many reef specialists also suggest that reefs may not only tolerate rising sea levels but actually benefit from them. On the other hand, the rising CO2 content of the atmosphere may induce changes in ocean chemistry that could slightly reduce coral calcification rates. However, potential positive effects of hydrospheric CO2 enrichment may more than compensate for this modest negative phenomenon.
The geologic record reveals that earth's coral reefs are well equipped to deal with major environmental changes, the most immediately threatening of which could well be a rapid global cooling instead of the catastrophic warming that has been predicted for several years. Currently, however, a number of local or place-specific anthropogenic activities are rendering reefs more susceptible to the deleterious effects of all potential climatic and/or environmental fluctuations. It is imperative, therefore, that these local problems be immediately addressed in order to help coral reefs better withstand the vagaries of natural and inevitable global change.
A Zero-Co2 Emission Power Cycle Using Coal
John Ruether,1 Patrick Le,2 and Charles White3
1U. S. Department of Energy, Federal Energy Technology Center,
2U. S. Department of Energy, Federal Energy Technology Center, Morgantown, WV
3EG&G, Morgantown, WV
A novel power cycle named Matiant generates electricity with nominally zero gaseous CO2 emissions from a hydrocarbon gas feed. The Matiant cycle is basically a gas cycle consisting of a supercritical CO2 Rankine-like cycle topping a regenerative CO2 Brayton cycle. Carbon dioxide produced can be removed from the process as a liquid at high pressure, facilitating its disposition by direct sequestration, e.g., by injection underground or in the deep ocean. The present paper develops analysis based on oxygen-blown dry coal entrained gasification providing fuel to the Matiant cycle. Oxygen for both the gasifier and the Matiant cycle is prepared by use of an Ion Transport Membrane (ITM) instead of a conventional cryogenic air separation unit. ITM is a revolutionary approach for producing high purity oxygen from a high temperature pressurized air stream at high flux rate. ASPEN Plus is used as the simulation tool to compute energy balances and performance of the subsystems and of the overall system.
The power system simulated delivers 152.6 MWe net at an overall thermal efficiency of 43.6% (HHV). A key to achieving high system efficiency is use of heat from the gasifier to preheat the air feed to the ITM. Of the carbon contained in the syngas produced in the gasifier, 99.5% is captured and leaves the system as a compressed liquid. The high thermal efficiency and high fractional CO2 capture result in low specific carbon emission compared to other technical approaches for power generation from coal with CO2 capture. Specific carbon emission for the process is 3.2 g CO2/kWh.
Potential Economic Benefits of Developing Carbon Sequestration Technology for Use in Stabilizing the Concentration of Co2 in the Atmosphere
Dave Beecy,1 Chuck Schmidt,2 Phil DiPietro,3 and Jim Carey3
1U.S. Department of Energy, Office of Fossil Energy, Germantown,
2U.S. Department of Energy, Federal Energy Technology Center, Pittsburgh, PA
3Energetics, Inc., Washington, DC
Carbon sequestration could make continued and expanded use of fossil fuels possible in a future global economy where emissions of greenhouse gases are tightly constrained. However, if carbon capture and sequestration is to be viable for broad applications, new technologies must be developed to lower the cost of capturing CO2 from fossil-based energy systems, and the environmental acceptability of carbon sequestration either underground or in the deep ocean must be verified through controlled field tests. The objective of this analysis is to quantify the potential economic benefit that could be realized by the United States over the next 50 years if such research and development (R&D) efforts are undertaken and successful. The economic benefits are estimated under a scenario in which global anthropogenic carbon emissions are reduced to stabilize the concentration of carbon dioxide in the atmosphere at 550 ppm (mL/L). Under such a scenario it is estimated that reductions in U.S. carbon emissions begin in 2010 and increase gradually to 30% below business as usual by 2050. It is also estimated that improvements in energy efficiency and use of non-carbon energy sources provide 50% of the needed emissions reduction. Reductions beyond that using non-sequestration technology would be expensive, conservatively estimated at $300 per Mg of carbon. The cost goal for U.S. Department of Energy's Carbon Sequestration R&D Program is $10 per Mg of carbon, net of any revenues from value-added by-products (e.g., enhanced oil recovery, coal bed methane). Under these assumptions, successful development of sequestration technology would lower the cost of CO2 emissions reduction within the United States economy by a total of $2.7 trillion through 2050.
Carbon Dioxide Sequestration by Ex-Situ Mineral Carbonation
W. K. O'Connor, D. C. Dahlin, P. C. Turner and R. P. Walters
U.S. Department of Energy, Office of Fossil Energy, Albany Research Center, Albany, OR
The process developed for carbon dioxide sequestration utilizes a slurry of water mixed with olivine- forsterite end member (Mg2SiO4), which is reacted with supercritical CO2 to produce magnesite (MgCO3). Carbon dioxide is dissolved in water to form carbonic acid, which likely dissociates to H+ and HCO3-. The H+ hydrolyzes the silicate mineral, freeing the cation (Mg2+), which reacts with the HCO3- to form the solid carbonate. Results of the baseline tests, conducted on ground products of the natural mineral, have demonstrated that the kinetics of the reaction are slow at ambient temperature (22°C) and subcritical CO2 pressures (below 7.4 MPa). However, at elevated temperature and pressure, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant conversion to the carbonate occurs. Extent of reaction is roughly 90% within 24 h, at 185°C and partial pressure of CO2 (Pco2) of 11.6 MPa. Current studies suggest that reaction kinetics can be improved by pretreatment of the mineral, catalysis of the reaction, and/or solution modification. Subsequent tests are intended to examine these options, as well as other mineral groups.
Deep Ocean Sequestration of Captured Co2
Hamid Sarv1 and Joseph John2
1McDermott Technology, Inc., a McDermott Company, Alliance,
2Mentor Subsea Technology Services, a J. Ray McDermott Company, Houston, TX
Technical and economical feasibility of large-scale CO2 transportation and ocean sequestration at depths of 3000 m or greater was investigated. Two options were examined for transporting and storing captured CO2. Both cases involved transporting 200 x 106 Mg CO2/year or the equivalent emissions from forty 500 MWe (20 GWe total generating capacity) coal-burning power plants in the U.S. equipped with flue gas desulfurization and carbon dioxide scrubbing and compression systems. Suitable onshore collection centers for storing previously-scrubbed and captured CO2 from areas with high populations of fossil fuel burning power plants were selected. In one case, CO2 was pumped from a land-based collection center through six parallel-laid subsea pipelines. Another case considered oceanic tanker transport of liquid carbon dioxide to an offshore floating platform or a barge for vertical injection through a large-diameter pipe to the ocean floor. Since the cost of running a pipeline or tanker transport increases with increasing depth, strategical locations in the Gulf of Mexico and the Pacific and Atlantic Oceans were also identified to minimize the expense.
Based on the preliminary technical and economic analyses, tanker transportation and offshore injection through a large-diameter, 3000-m vertical pipeline from a floating structure appears to be the best method for delivering liquid CO2 to deep ocean floor depressions for distances greater than 400 km. Other benefits of offshore injection are high payload capability and ease of relocation. For shorter distances (less than 400 km), CO2 delivery by subsea pipelines is more cost-effective. Our analyses also indicate that large-scale sequestration of captured CO2 in oceans is technologically feasible and has many commonalties with other strategies for deep-sea natural gas and oil exploration installations.
Carbon Dioxide Utilization-Microalgae Biofixation
Yoshiaki Ikuta,1 Joseph C. Weissman,2 and John R. Benemann3
1SeaAg Japan, Inc., Tokyo, Japan
2SeaAg, Inc., Vero Beach, FL
3University of California, Berkeley, CA
This paper is a review of microalgae production. It describes various approaches used to produce microalgae. The paper describes production of microalgae-in particular Spirulina and Chlorella-for human food supplements. Another microalgae process for CO2 capture is for animal feed production. The paper describes a process for production of bivalves, such as clams and oysters, using microalgae cultured in open ponds with CO2 enrichment. It also describes demonstration facilities that are used to produce bivalves by feeding microalgae cultivated in about 4,500 m2 outdoor algae ponds that have been operated satisfactorily for over a year in Japan and for many years in the U.S.
Production of Extracellular Polymers by a Freshwater Microalga, Chlamydomonas Sp. strain YM-1
Koyu Hon-Nami and Atsushi Hirano
Energy and Environment R&D Center, Tokyo Electric Power Co., Yokohama, Japan
This paper reports on studies with the objective to convert atmospheric CO2 to biomass. Partially purified extracellular substances were prepared by ethanol precipitation from the culture medium of a freshwater microalga, Chlamydomonas sp. strain YM-1. The resulting material was subjected to elemental analysis indicating a molar ratio of C: H: O = 14: 29: 15 and negligible amounts of sulfur and nitrogen. The combined matrix-assisted laser desorption ionization and time of flight mass spectrometry (MALDI-TOF/MS) showed a wave-shape curve with a constant peak-to-peak distance of 380 Da, gradually decreasing in intensity with increasing mass range, and finally the peak reaching into noise above 14,000 Da. These findings, in addition to the observation of dependency on pH of the cultured medium with cell buoyancy, suggest that extracellular substances are mixtures of acidic polymers with molecular mass of 380 Da. The effectiveness of MALDI-TOF/MS for structural studies of extracellular products, and the possible utilizations of these products for CO2 mitigation are discussed.
Spatial and Temporal Distribution of 14C in Cellulose in Tree Rings in Central and Eastern Canada: Comparison with Long-Term Atmospheric and Environmental Data
T. G. Kotzer and W. L. Watson
Environmental Technologies Branch - AECL, Chalk River Laboratories, Chalk River, Ontario
Dendrochronologically-characterized tree rings from several different species across Central- and Eastern-Canada and spanning a time range of several decades have been analyzed for their 14C specific activities using oxygen combustion-direct liquid scintillation counting techniques. 14C specific activities varied between 218 and 439 Bq kg-1 C (± 10 to 15 %) and yielded a good correlation with the 14C measured in long-term records of 14C-in-air values, although 14C levels in Canada are slightly higher (10-20 per mil). An average pre-bomb 14C value of 225 Bq kg-1 C was obtained from tree rings between the years 1910 to 1945, which agrees with the value for NBS oxalic acid standard for "modern" 14C at 226 Bq kg-1 C. Present-day levels of 14C in the tree rings are on the order of 250 Bq kg-1 C, indicating that they, like 14CO2-in-air values, are indicating that the specific activities of 14C in the environment have yet to reach "pre-nuclear testing" levels. Specific activities of 14C in tree rings from several sites in Canada show no systematic changes with respect to their distance from CANDU heavy water nuclear power-generating stations, suggesting that these stations have had negligible effects on the atmospheric radiocarbon budget for mid-latitudinal North America. The radiocarbon data from the tree rings suggest that atmospheric 14C has an atmospheric half-time on the order of approximately 15 years, similar to that from other data sets
U.S. Trends in Crude Death Rates Due to Extreme Heat and Cold Ascribed to Weather, 1979-97
Indur M. Goklany1 and Sorin R. Straja2
2Institute for Regulatory Science, Columbia, MD
From 1979 to 1997, U.S. deaths coded in death certificates as resulting from extreme cold (hypothermia) caused by either "weather conditions" or an "unspecified origin" exceeded deaths due to extreme heat (hyperthermia) from similar underlying causes by 80% to 125%. During this period, the population aged substantially, and recent analysis indicate an upward trend in summertime "extreme heat stress events" for the U.S., which may or may not have been due to any global warming. Counterintuitively, trend analysis using the death certificate data from 1979 to 1997 shows no increases in crude death rates (CDRs) attributed to extreme heat for either the entire population or, more remarkably, the more susceptible older age groups (i.e., those aged 65-and-over, 75-and-over, and 85-and-over). Less surprisingly, over the same period, CDRs attributed to extreme cold for the population and the older subgroups also show no trends, upward or downward. The lack of trends suggests that adaptation and technological change may be just as important determinants of such trends as more obvious meteorological and demographic factors
Soft Energy Path Synthesis fromCarbon Dioxide to Biofuel Ethanol Through Cyanobacterial Biotechnology
Department of Chemical Engineering, Tokyo Institute of Technology, Tokyo, Japan
In an attempt to present the kinetics data of Synechococcus leopoliensis for the design of large-scale biological CO2 removal systems under a diluted solar flux, a series of experiments were performed. To reduce the contamination risk of a large-scale culture, a medium that contained only eight inorganic chemicals besides CO2 was developed. This medium supported the growth of S. leopoliensis with a specific growth rate of 0.0303 h-1 to a reasonably high population density of 0.761g/L. To investigate the effect of light/dark cycles of solar flux, S. leopoliensis cells were grown under different diurnally-intermittent illuminations. Diurnally-intermittent illumination always elevated the growth rate over continuous illumination. The diurnal interposition of a 15 h dark period caused an increase in the specific growth rate in the first 48 h of cultivation. The CO2 transfer rate, determined by mass balance of CO2 in the entry and exit gases in the bioreactor, was 5.5 to 8.9 times that determined from the amount of carbon incorporated into cell materials. The laboratory kinetic information was used to estimate the consumption of CO2 from power electric plants and production of 95% ethanol for a motor fuel.
Potential Consequences of Increasing Atmospheric Co2 Concentration Compared to Other Environmental Problems
Indur M. Goklany
This paper examines the validity of the assertion that anthropogenic
climate change is the overriding environmental concern facing the globe
today. Examination of recent trends for some climate-sensitive indicators
(e.g., global food security; U.S. deaths due to storms and floods; global
death rates due to infectious and parasitic diseases; and biomass in the
northern forests) shows that matters have improved notwithstanding any
climate change to date. For others (such as global deforestation and sea
level rise), recent trends have continued to worsen; but so far the contribution
of any anthropogenic climate change to these impacts seems to have been
relatively minor. Next, based largely upon the Intergovernmental Panel
on Climate Change's 1995 Impact Assessment, the paper determines that over
the next several decades the projected global impacts of climate change
upon food security, deforestation, biodiversity, and human health could
be an order of magnitude smaller than those due to other stressors such
as population growth, poverty, land conversion, or baseline (i.e., non-climate
change related) rates of infectious and parasitic diseases. Therefore,
eliminating anthropogenic climate change, even if feasible, would-for the
next several decades-do little to reduce the much larger baseline rates
of global deforestation, biodiversity loss, and infectious and parasitic
diseases. Hence, climate change, while a potentially serious long-term
problem, is not today-nor likely to be in the foreseeable future-as urgent
as other current environmental and public health problems. The paper then
proposes an integrated approach to deal with today's urgent environmental
problems while enhancing the ability to address the long term-problem of