ne of the activities of the Environmentally Compatible Energy Strategies research project at the Innational Institute for iplied Systems Analysis [IIASn, Lawenburg, Auseia] is to assess options and measures for mitigating dobal carbon dioxide emissions.The basis of this assessment is a comparative inventory of technological and economic measures, including efficiency improvement: conservation; enhanced use of low-carbon fuels: carbon-free sources of energy: and measures for removing carbon from fuels, flue gases, and the atmosphere and for enhancing carbon sinks and mating new ones. To include all potential options, the comparison is based on energy end-use accounting for the fully interlinked energy conversion chains up to energy resources. The analysis is supported by a fully interactive computer data bank system, named COZDB, that is capable of evaluating full energy chains with respect to their economic, technical, and environmental parameters. There are about 600 technologies in the database, and it has been distributed to more than 70 research organizations and individuals worldwide.
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Global energy and CO, emissions The technological and economic measures that minimize energy-related greenhouse gas emissions encompass the whole energy system . from primary energy to actual energy use, including various conversion, transport, distribution, and end-use systems. This is important for assessing the overall mitigation potential and possibilities. For example, energy end use is the least efficient part of current energy systems: therefore it is crucial to include in
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forming economies the overall efficiency is lower. This illustrates that there are large possibilities for more the mitigation assessment end-use efficient energy use and, in particutechnologies that provide transport, lar, for improvement of end-use industrial, or residential energy technologies. In order to assess the needs. A detailed assessment shows overall mitigation potential, includthat the global conversion effi- ing efficiency improvements, an inP ;entory of mitigation asures with the data,e C02DB was specifically designed at IIASA to integrate current and possible future conversion, transport, disbibution, and end-use systems into energy chains giving the whole clusters of technologies that define a particular reduction strategy (2).The first results indicated that overall energy efficiency would nearly double if the most efficient technologies available today I were amlied (31.The databas; -enables the assessment of such potential with greater consistency worldwide.
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ciencl -..--I primary energy to final energy forms is about 74% (1). The efficiency with which final energy forms are applied to provide useful energy is about 46%. This results in the overall primary-energy-touseful-energy conversion efficiency of 34%, shown in Figure 1. In developing countries and re-
1688 Environ. Sei. Technol.. VoI. 27, No. 10. 1993
Efficiency improvements The rates at which such efficiency improvements can be achieved depend to a large extent on the vintage structure of the capital stock of our economies, rates of diffusion of new technologies, and technology transfer. Energy intensity measures energy consumption per unit value added and thus gives an indication of overall energy efficiency for the whole economy. Figure 2 shows that the long-term improvement in energy intensity was about 1% per year in the industrialized countries. Improvement has been fask certain areas and periods than in others. For example, over the past 20 years, aircraft manufacturers have managed to improve energy efficiency of commercial jet transports by 3 4 % annually. In electricity generation, this improvement has been 2.53% per year between 1930 and the early 1970s. ~~~
0013-936W93/0927-1986$04.00/0 0 1993 American Chemical Society
These are about the upper boundary values observed over more recent history; the long-term improvement rate of energy intensity is about 1% per year. Because the world economic output is increasing at about 3% per year, historical rates of energy intensity improvement are not sufficient to stabilize carbon dioxide emissions. Decarbonization of energy Figure 3 illustrates the “decarbonization” in the world in terms of the rates of average CO, emissions per unit of energy consumed. The decarbonization occurred because of the continuous replacement of fuels with high carbon content, such as coal, by those with lower carbon content (such as oil and natural gas) and by carbon-free nuclear energy. The average rate is about 0.3% per year and, together with reduction of energy intensity, indicates that CO, emissions per unit of economic activity have been decreasing an average of 1.3% per year worldwide (Figures 2 and 3). In the long run, there is a clear need to shift to energy sources with low carbon content such as natural gas and, ultimately, to those w‘thout carbon-uch as hydro, solar, and nuclear energy-and to the sustain-
able use of biomass. Thus, technological and economic structural change will be of fundamental importance for improving efficiency and lowering carbon emissions (31. Inventory of mitigation measures The inventory of mitigation measures and the associated technology database are specifically designed to provide a uniform framework for
assessing ultimate reduction potential resulting from the introduction of new technologies over different time frames and in different regions. The database includes detailed descriptions of the technical, economic, and environmental performance of technologies as well as data pertinent to their innovation, commercialization, and diffusion characteristics and prospects.
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sions attributable to each step in the chain: in these examples costs to deliver the same service differ by about 30%, whereas CO, emissions to provide that service differ by more than 90%. Third, it allows analysis of trade-offs such as the potential to reduce CO, emissions by concentrating on energy end use-in this case, the type of bulb versus energy supply and the approximate costs of changing any part of the chain. This example illustrates that substantial CO, reduction potentials exist with currently available technologies. The specific carbon emissions include the direct releases from the end-use technologies themselves and all the emissions that result from the rest of the energy supply system, including energy production, import, conversion into fuels and electricity, and distribution to end-use.
Additional data files contain literature sources and assessments of data validity and concurrent uncertainty ranges. It is an interactive sofiware package designed to enter, update, and retrieve information on CO, reduction and removal technologies (4). The database can facilitate the assessment of CO, reduction strategies by combining many individual technologies; measures throughout the energychaincanbe analyzed, from primary energy exh'action to improvements in energy enduse efficiencies. This process is often called full-fuel-cycle analysis. COZDB cufiently has information on more than 600 technologies, most of them generic systems that are used or could be used anywhere. There are also many technologies that are more specific to a particular cowtry or region with emphasis on developing countries. C02DB was used at M S A in a study of global CO, reduction potentials and their costs (3).Figure 4 was generated us-
ing the inventory. It illustrates an analysis of the cost, CO, emissions, and energy requirements of different energy chains that provide the same service lighting (5). Each of the seven bars depicts a different combination of technologies that can now or could in the future provide lighting-for example, conventional incandescent bulbs versus energy-efficient compact fluorescent bdbs, and a conventional power plant burning hard coal versus a more modern combinedcycle natural-gas turbine with or without CO, scrubbing. The bottom bar in each graph compares one of the six US. energy chains with an identical chain in Austria. COZDB is mainly used to determine to what extent identical technological systems can have different costs and consequences in different situations. Figure 4 illustrates several other features of the COZDB inventory. First, it depicts all parts of an energy chain. Second, it gives a breakdown of the costs and emis-
THERE ARE ABOUT 600 TECHNOLOGIESIN TEE DATABASE, AND IT HAS BEEN DISTRIBUTED WORLDWIDE.
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Conclusion The objective of a comparative assessment of options and measures for reducing and removing emissions is to identify future technological systems and development paths with low specific energy requirements and low adverse environmental impacts. Efficiency has been improved and economies have decarbonized. The overall objective of this research at IJASA is to assess the conditions that would direct development toward M e r decarbonization and energy disintensification worldwide. The inventory of mitigation technologies and the COZDB database are tools for assessing the potential and relative contribution of NebojJa Nokidenovid leads the Environmentally Comp a t i b l e Energy Stmkgies Pmject at the International Institute for A p plied Systems Analysis in Laxenburg, Austria. He was f o r dear Research Center merly with the Nuclear Karlsruhe, Germanv, where he worked on nuclear materiais accountability.His research focuses on energy-reloted saumes of global change ond on development and response stmtegks for mitigating adverse environmental impacts. He is author and coauthor of manypopers and books an the dynamics of technological change, energy, and tmnsport systems. Nakidenovid holds bachelor's and master's degrees in economics and computer science from Princeton University and the University af Vienna, where he also received his PhD.
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Incandescent light bulb Hard coal power plant Compact fluorescent bulb Hard coal power plant
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Incandescent light bulb u.s. Combined cycle natural gas Compact fluorescent light bulb Combined cycle natural gas
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Incandescent light bulb Combined cycle natural gas U.S. with cabon scrubbing Compact fluorescent bulb Combined cycle natural gas with carbon scrubbing
different energy chains toward reducing CO, emissions. The identification of best energy and cost options is made easier: it also facilitates systems comparison with more comprehensive energy models.
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References I11 NakiCenoviC, N. et al. Technological Progress, Structural Change and EMcient Energy Use: Trends Worldwide and in Austria; study supported by
the Osterreicbische Elsktrizitatswirt-
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(3)
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schaft AG International Institute for Applied Systems Analysis: Laxenburg, Austria, 1990. Messner, S.: NakiCenoviC, N. Energy Conversion and Management 1992, 33(5-8),763-71. NakiCenoviC, N. et al. The InternationalJournal 1993, 18(5),401-609. Messner, S.; Strubegger. M., User's Guide to COZDB: The IIASA CO, Technology Data Bank [Version ?.oh International Institute for Applied Systems Analysis: Laxenburg, Austria, 1991; WP-91-31a. Schafer.A.; Schrattenholzer,L.; Messner, S. Inventory of Greenhouse-Gas Mitigation Measures: Examples from the IIASA Technology Data Bonk: International Institute for Applied Systems Analysis: Laxenburg, Austria, 1992; WP-92-85. NakiCenoviC, N. Options: Decarbonizing Global Energi? International Institute for Applied Systems Analysis: Laxenburg, Austria, 1992.
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