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A trinity of sense: Using biomass in the transport sector for climate change mitigation
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis analyses two strategies for decreasing anthropogenic carbon dioxide (CO2) emissions: to capture and store CO2, and to increase the use of biomass. First, two concepts for CO2 capture with low capture penalties are evaluated. The concepts are an integrated gasification combined cycle where the oxygen is supplied by a membrane reactor, and a hybrid cycle where the CO2 is captured at elevated pressure. Although the cycles have comparatively high efficiencies and low penalties, they illustrate the inevitable fact that capturing CO2 will always induce significant efficiency penalties. Other strategies are also needed if CO2 emissions are to be forcefully decreased. An alternative is increased use of biomass, which partially could be used for production of motor fuels (biofuels). This work examines arguments for directing biomass to the transport sector, analyses how biofuels (and also some other means) may be used to reduce CO2 emissions and increase security of motor fuel supply. The thesis also explores the possibility of reducing CO2 emissions by comparatively easy and cost-efficient CO2 capture from concentrated CO2 streams available in some types of biofuel plants. Many conclusions of the thesis could be associated with either of three meanings of the word sense: First, there is reason in biofuel production – since it e.g. reduces oil dependence. From a climate change mitigation perspective, however, motor fuel production is often a CO2-inefficient use of biomass, but the thesis explores how biofuels’ climate change mitigation effects may be increased by introducing low-cost CO2 capture. Second, the Swedish promotion of biofuels appears to have been governed more by a feeling for attaining other goals than striving for curbing climate change. Third, it seems to have been the prevalent opinion among politicians that the advantages of biofuels – among them their climate change mitigation benefits – are far greater than the disadvantages and that they should be promoted. Another conclusion of the thesis is that biofuels alone are not enough to drastically decrease transport CO2 emissions; a variety of measures are needed such as fuels from renewable electricity and improvements of vehicle fuel economy.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 68 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:62
Keyword [en]
Biofuel, biomass, carbon dioxide capture and storage, energy systems, ethanol, hybrid cycle, mixed conducting membrane reactor, pressurized fluidized bed combustion, Sweden, transport
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9292ISBN: 978-91-7415-107-7 (print)OAI: oai:DiVA.org:kth-9292DiVA: diva2:54448
Public defence
2008-11-07, F3, KTKH, Lindstedtsvägen 26, Stockholm, 13:30 (English)
Opponent
Supervisors
Note
QC 20100823Available from: 2008-10-22 Created: 2008-10-16 Last updated: 2010-08-23Bibliographically approved
List of papers
1. An integrated gasification zero emission plant using oxygen produced in a mixed conducting membrane reactor
Open this publication in new window or tab >>An integrated gasification zero emission plant using oxygen produced in a mixed conducting membrane reactor
2006 (English)In: Proceedings of the ASME Turbo Expo 2006, vol 4, 2006, 33-40 p.Conference paper, Published paper (Refereed)
Abstract [en]

Integrated gasification combined cycles (IGCCs) exhibit conditions favourable to CO, sequestration. In this article, simulations of the Integrated Gasification Zero Emission Plant (IGZEP) concept are presented. The idea behind this concept is to use oxygen produced in a Mixed Conducting Membrane (MCM) reactor in an IGCC. Previous studies have shown that it is beneficial to integrate an MCM reactor in a natural gas fired cycle, and the objective of this article is to quantify the advantages of integrating the same type of reactor with an IGCC the way it is suggested in the IGZEP concept. The core of the membrane reactor is a ceramic membrane, which separates oxygen from air exiting the gas turbine compressor. The reactor operates at temperatures around 900 degrees C and is driven by a difference in oxygen partial pressure. The oxygen permeating the membrane is used in a Texaco gasifier, whereas the oxygen-depleted air is sent to a high temperature combustor. The rest of the cycle is essentially similar to a "standard" IGCC. The simulations performed resulted in a CO(2) capture penalty of 6.4% points (Lower Heating Value, LHV) and a net cycle efficiency of 32.5% (LHV). Despite this quite low efficiency, the IGZEP concept is interesting since one of the main reasons for the low net efficiencies is the low efficiency of the Texaco gasifier model used. Other models for Texaco gasifiers with higher efficiency have been found in literature. Nevertheless, it is judged more interesting to compare IGZEP's penalty for oxygen generation with that of existing competitors. It is shown that the total oxygen production penalty can be decreased from 4.9% points in the reference case to 4.3% points in IGZEP. That is, about 0.6% points in net efficiency may be gained by replacing a standard (non-integrated) cryogenic air distillation unit with an MCM reactor. Other studies have also shown that this strategy may entail lower investment and electricity production costs.

Keyword
Integrated gasification combined cycle, Mixed conducting membrane, Oxygen production penalty
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9350 (URN)000243378600004 ()2-s2.0-33750852524 (Scopus ID)0-7918-4239-8 (ISBN)
Conference
51st ASME Turbo Expo 2006 Location: Barcelona, SPAIN Date: MAY 06-11, 2006
Note
QC 20100820Available from: 2008-10-22 Created: 2008-10-22 Last updated: 2011-09-30Bibliographically approved
2. The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture
Open this publication in new window or tab >>The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture
2009 (English)In: International journal of greenhouse gas control, ISSN 1750-5836, Vol. 3, no 3, 255-262 p.Article in journal (Refereed) Published
Abstract [en]

This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.

Keyword
Carbon dioxide capture; Hybrid power cycles; PFBC
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-10978 (URN)10.1016/j.ijggc.2008.09.002 (DOI)000266179200002 ()2-s2.0-64449085290 (Scopus ID)
Note
QC 20100727Available from: 2009-09-01 Created: 2009-09-01 Last updated: 2010-08-20Bibliographically approved
3. The Swedish policy instruments’ inconsistent valuation of avoided CO2 emissions
Open this publication in new window or tab >>The Swedish policy instruments’ inconsistent valuation of avoided CO2 emissions
2006 (English)In: World Renewable Energy Congress IX and Exhibition, 2006, 2006Conference paper, Published paper (Refereed)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9362 (URN)
Note
QC 20100820Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2010-08-23Bibliographically approved
4. Arguments in Swedish Policy Documents for Using Biomass for Production of Bio-based Motor Fuels: Why an Energy Engineer Could Feel Like Being in a Novel Written by Kafka
Open this publication in new window or tab >>Arguments in Swedish Policy Documents for Using Biomass for Production of Bio-based Motor Fuels: Why an Energy Engineer Could Feel Like Being in a Novel Written by Kafka
2008 (English)In: World Renewable Energy Congress X and Exhibition, 2008, 2636-2641 p.Conference paper, Published paper (Refereed)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9363 (URN)
Note
QC 20100823Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2010-08-23Bibliographically approved
5. System study of carbon dioxide (CO2) capture in bio-based motor fuel production
Open this publication in new window or tab >>System study of carbon dioxide (CO2) capture in bio-based motor fuel production
2008 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 33, no 2, 352-361 p.Article in journal (Refereed) Published
Abstract [en]

A number of different technologies for producing renewable motor fuels have been studied; some effects of applying carbon dioxide (CO2) capture to the production of renewable motor fuels are described in this paper. Some of the technologies studied are well suited for CO2 capture. However, it is shown that the advantages with CO2 capture for these technologies are not enough to offset their shortcomings described in previous studies, which show that the largest CO2 reduction from biomass in Sweden may be achieved by producing fuel pellets for coal substitution or using the biomass in combined heat and power plants. A conclusion of the present paper is that even with v capture added to the respective technology, it is inefficient to use renewable resources for motor fuel production if the aim is to achieve as high CO2 emission reduction as possible per input of biomass. Therefore, the large Swedish subsidies of the production of motor fuels appear sub-optimal, also when the possibility of CO2 capture is considered. Nevertheless, incorporating CO2 capture in the production of renewable motor fuels from biomass might be a cost-effective way of reducing CO2 emissions.

Keyword
biomass; CO2 reduction; fermentation; anaerobic digestion
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9364 (URN)10.1016/j.energy.2007.09.005 (DOI)000253574700029 ()2-s2.0-38149135080 (Scopus ID)
Note
QC 20100823Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2017-12-14Bibliographically approved
6. Biofuel production with CCS as a strategy for creating a CO2-neutral road transport sector
Open this publication in new window or tab >>Biofuel production with CCS as a strategy for creating a CO2-neutral road transport sector
2009 (English)In: 9th International Conference on Greenhouse Gas Control Technologies, GHGT-9: Washington DC; 16 November 2008 through 20 November 2008 / [ed] Gale J.; Herzog H.; Braitsch J., 2009, 4111-4118 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, three biofuel-producing processes with carbon dioxide capture and storage (CCS) are studied: two (fermentation) ethanol processes and one process producing methanol (via gasification). In these processes CO2 is captured from streams which are relatively pure, i.e. the main impurity is water vapour which may be easily removed. Owing to this, the costs for CO2 capture, both in terms of economic cost and energy penalty, are very low and these processes could thus constitute some of the first instances where CCS is implemented. The paper highlights under which conditions biofuel production with CCS may create a CO2-neutral transport sector.

Series
Energy Procedia, ISSN 1876-6102 ; Vol. 1 : issue 1
Keyword
Biofuel; biomass potential; carbon dioxide capture and storage; CO2-neutral; ethanol; methanol; security of supply; Sweden; transport
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9366 (URN)10.1016/j.egypro.2009.02.219 (DOI)000276074404017 ()2-s2.0-67650109062 (Scopus ID)
Note
QC 20100823Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2010-08-23Bibliographically approved
7. Strategies for a road transport system based on renewable resources: The case of an import-independent Sweden in 2025
Open this publication in new window or tab >>Strategies for a road transport system based on renewable resources: The case of an import-independent Sweden in 2025
2010 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 87, no 6, 1836-1845 p.Article in journal (Refereed) Published
Abstract [en]

When discussing how society can decrease greenhouse gas emissions, the transport sector is often seen as posing one of the most difficult problems. In addition, the transport sector faces problems related to security of supply. The aim of this paper is to present possible strategies for a road transport system based on renewable energy sources and to illustrate how such a system could be designed to avoid dependency on imports, using Sweden as an example. The demand-side strategies considered include measures for decreasing the demand for transport, as well as various technical and non-technical means of improving vehicle fuel economy. On the supply side, biofuels and synthetic fuels produced from renewable electricity are discussed. Calculations are performed to ascertain the possible impact of these measures on the future Swedish road transport sector. The results underline the importance of powerful demand-side measures and show that although biofuels can certainly contribute significantly to an import-independent road transport sector, they are far from enough even in a biomass-rich country like Sweden. Instead, according to this study, fuels based on renewable electricity will have to cover more than half of the road transport sector's energy demand.

Keyword
Road transport; Import-independent; Biofuel; Synthetic fuel; Demand-side strategies
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9252 (URN)10.1016/j.apenergy.2010.02.011 (DOI)000278306300005 ()2-s2.0-77951091042 (Scopus ID)
Note
QC 20100823. Uppdaterad från submitted till published (20100823). Tidigare titel: Strategies for a road transport system based on renewable resources: the case of a self-sufficient Sweden in 2025Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved

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Citation style
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  • ieee
  • modern-language-association-8th-edition
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  • Other locale
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Output format
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