CO2 Reduction (co2 + reduction)

Distribution by Scientific Domains


Selected Abstracts


A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emission

ECOLOGY LETTERS, Issue 10 2009
Lingli Liu
Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source]


Detecting active methanogenic populations on rice roots using stable isotope probing

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2005
Yahai Lu
Summary Methane is formed on rice roots mainly by CO2 reduction. The present study aimed to identify the active methanogenic populations responsible for this process. Soil-free rice roots were incubated anaerobically under an atmosphere of H2/13CO2 or N2/13CO2 with phosphate or carbonate (marble) as buffer medium. Nucleic acids were extracted and fractionated by caesium trifluoroacetate equilibrium density gradient centrifugation after 16-day incubation. Community analyses were performed for gradient fractions using terminal restriction fragment polymorphism analysis (T-RFLP) and sequencing of the 16S rRNA genes. In addition, rRNA was extracted and analysed at different time points to trace the community change during the 16-day incubation. The Methanosarcinaceae and the yet-uncultured archaeal lineage Rice Cluster-I (RC-I) were predominant in the root incubations when carbonate buffer and N2 headspace were used. The analysis of [13C]DNA showed that the relative 16S rRNA gene abundance of RC-I increased whereas that of the Methanosarcinaceae decreased with increasing DNA buoyant density, indicating that members of RC-I were more active than the Methanosarcinaceae. However, an unexpected finding was that RC-I was suppressed in the presence of high H2 concentrations (80%, v/v), which during the early incubation period caused a lower CH4 production compared with that with N2 in the headspace. Eventually, however, CH4 production increased, probably because of the activity of Methanosarcinaceae, which became prevalent. Phosphate buffer appeared to inhibit the activity of the Methanosarcinaceae, resulting in lower CH4 production as compared with carbonate buffer. Under these conditions, Methanobacteriaceae were the prevalent methanogens. Our study suggests that the active methanogenic populations on rice roots change in correspondence to the presence of H2 (80%, v/v) and the type of buffer used in the system. [source]


FLOX® Steam Reforming for PEM Fuel Cell Systems,

FUEL CELLS, Issue 4 2004
H.-P. Schmid
Abstract Primary energy savings and CO2 reduction is one of the key motivations for the use of fuel cell systems in the energy sector. A benchmark of domestic cogeneration by PEMFC with existing large scale power production systems such as combined steam-gas turbine cycle, clearly reveals that only fuel cell systems optimising overall energy efficiency (>,85%) and electrical efficiencies (>,35%) show significant primary energy savings, about 10%, compared with the best competing technology. In this context, fuel processing technology plays a dominant role. A comparison of autothermal and steam reforming concepts in a PEMFC system shows inherent advantages in terms of efficiency at low complexity for the latter. The main reason for this is that steam reforming allows for the straightforward and effective use of the anode-off gas energy in the reformer burner. Consequently, practical electrical system efficiencies over 40% seem to be achievable, most likely by steam reformers. FLOX®-steam reforming technology has reached a high state of maturity, offering diverse advantages including: compact design, stable anode off-gas usage, high efficiency, as well as simple control behaviour. Scaling of the concept is straightforward and offers an opportunity for efficient adaptation to smaller (1,kW) and larger (50,kW) units. [source]


Implications of system expansion for the assessment of well-to-wheel CO2 emissions from biomass-based transportation

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2010
Elisabeth Wetterlund
Abstract In this paper we show the effects of expanding the system when evaluating well-to-wheel (WTW) CO2 emissions for biomass-based transportation, to include the systems surrounding the biomass conversion system. Four different cases are considered: DME via black liquor gasification (BLG), methanol via gasification of solid biomass, lignocellulosic ethanol and electricity from a biomass integrated gasification combined cycle (BIGCC) used in a battery-powered electric vehicle (BPEV). All four cases are considered with as well as without carbon capture and storage (CCS). System expansion is used consistently for all flows. The results are compared with results from a conventional WTW study that only uses system expansion for certain co-product flows. It is shown that when expanding the system, biomass-based transportation does not necessarily contribute to decreased CO2 emissions and the results from this study in general indicate considerably lower CO2 mitigation potential than do the results from the conventional study used for comparison. It is shown that of particular importance are assumptions regarding future biomass use, as by expanding the system, future competition for biomass feedstock can be taken into account by assuming an alternative biomass usage. Assumptions regarding other surrounding systems, such as the transportation and the electricity systems are also shown to be of significance. Of the four studied cases without CCS, BIGCC with the electricity used in a BPEV is the only case that consistently shows a potential for CO2 reduction when alternative use of biomass is considered. Inclusion of CCS is not a guarantee for achieving CO2 reduction, and in general the system effects are equivalent or larger than the effects of CCS. DME from BLG generally shows the highest CO2 emission reduction potential for the biofuel cases. However, neither of these options for biomass-based transportation can alone meet the needs of the transport sector. Therefore, a broader palette of solutions, including different production routes, different fuels and possibly also CCS, will be needed. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Optimization of energy usage for fleet-wide power generating system under carbon mitigation options

AICHE JOURNAL, Issue 12 2009
A. Elkamel
Abstract This article presents a fleet-wide model for energy planning that can be used to determine the optimal structure necessary to meet a given CO2 reduction target while maintaining or enhancing power to the grid. The model incorporates power generation as well as CO2 emissions from a fleet of generating stations (hydroelectric, fossil fuel, nuclear, and wind). The model is formulated as a mixed integer program and is used to optimize an existing fleet as well as recommend new additional generating stations, carbon capture and storage, and retrofit actions to meet a CO2 reduction target and electricity demand at a minimum overall cost. The model was applied to the energy supply system operated by Ontario power generation (OPG) for the province of Ontario, Canada. In 2002, OPG operated 79 electricity generating stations; 5 are fueled with coal (with a total of 23 boilers), 1 by natural gas (4 boilers), 3 nuclear, 69 hydroelectric and 1 wind turbine generating a total of 115.8 TWh. No CO2 capture process existed at any OPG power plant; about 36.7 million tonnes of CO2 was emitted in 2002, mainly from fossil fuel power plants. Four electricity demand scenarios were considered over a span of 10 years and for each case the size of new power generation capacity with and without capture was obtained. Six supplemental electricity generating technologies have been allowed for: subcritical pulverized coal-fired (PC), PC with carbon capture (PC+CCS), integrated gasification combined cycle (IGCC), IGCC with carbon capture (IGCC+CCS), natural gas combined cycle (NGCC), and NGCC with carbon capture (NGCC+CCS). The optimization results showed that fuel balancing alone can contribute to the reduction of CO2 emissions by only 3% and a slight, 1.6%, reduction in the cost of electricity compared to a calculated base case. It was found that a 20% CO2 reduction at current electricity demand could be achieved by implementing fuel balancing and switching 8 out of 23 coal-fired boilers to natural gas. However, as demand increases, more coal-fired boilers needed to be switched to natural gas as well as the building of new NGCC and NGCC+CCS for replacing the aging coal-fired power plants. To achieve a 40% CO2 reduction at 1.0% demand growth rate, four new plants (2 NGCC, 2 NGCC+CCS) as well as carbon capture processes needed to be built. If greater than 60% CO2 reductions are required, NGCC, NGCC+CCS, and IGCC+CCS power plants needed to be put online in addition to carbon capture processes on coal-fired power plants. The volatility of natural gas prices was found to have a significant impact on the optimal CO2 mitigation strategy and on the cost of electricity generation. Increasing the natural gas prices resulted in early aggressive CO2 mitigation strategies especially at higher growth rate demands. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Monitoring of end-tidal carbon dioxide partial pressure changes during infrarenal aortic cross-clamping: a non-invasive method to predict unclamping hypotension

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 2 2001
G. Boccara
Background: To assess the variations in end-tidal CO2 in response to aortic cross-clamping and the relationship with systolic arterial pressure (SAP) changes induced by unclamping. Methods: Thirty-three patients undergoing infrarenal aortic abdominal aneurysm repair by aorto-aortic prothetic bypass were prospectively studied. All patients were anesthetized with iv midazolam (0.05 mg · kg,1), thiopentone (3,5 mg · kg,1), fentanyl (5 ,g · kg,1), pancuronium (0.1 mg · kg,1) and the maintainance of anesthesia used was 1,1.5% end-tidal isoflurane and iv fentanyl. The perioperative management was standardized. End-tidal CO2 and SAP were measured 5 min before (Pre-XAA), 15 min after infrarenal aortic cross-clamping (XAA), 5 min before (Pre-UXAA) and immediately after unclamping (UXAA). Results: A total of 16 (48.5%) from 33 patients presented decrease in SAP following aortic unclamping, and 13 out of these patients had arterial hypotension defined as SAP <90 mmHg. End-tidal CO2 variation (PreXAA,PreUXAA) induced by aortic clamping was correlated with SAP variation (PreUXAA,UXAA) induced by unclamping (r=0.763; P=0.0001). An end-tidal CO2 reduction above 15% after aortic cross-clamping was found to have a 100% sensitivity to detect a SAP decrease greater than 20% after unclamping, with a 100% specificity and a negative predictive value of 1.0. Complete aortic occlusion duration was not correlated to SAP unclamping variation (,SAP). Intraoperative characteristics (fluid loading, hematocrits, urinary output) were comparable, although blood loss was higher in patients experiencing ,SAP>20%. Conclusions: End-tidal CO2 variation monitoring during aortic cross-clamping may provide a reliable and non-invasive method to predict unclamping hypotension. When the aortic clamp was released, systolic hypotension (>20%) occurred in those subjects who had a decrease in end-tidal CO2 greater than 15% during aortic cross-clamping. [source]


Optimization of energy usage for fleet-wide power generating system under carbon mitigation options

AICHE JOURNAL, Issue 12 2009
A. Elkamel
Abstract This article presents a fleet-wide model for energy planning that can be used to determine the optimal structure necessary to meet a given CO2 reduction target while maintaining or enhancing power to the grid. The model incorporates power generation as well as CO2 emissions from a fleet of generating stations (hydroelectric, fossil fuel, nuclear, and wind). The model is formulated as a mixed integer program and is used to optimize an existing fleet as well as recommend new additional generating stations, carbon capture and storage, and retrofit actions to meet a CO2 reduction target and electricity demand at a minimum overall cost. The model was applied to the energy supply system operated by Ontario power generation (OPG) for the province of Ontario, Canada. In 2002, OPG operated 79 electricity generating stations; 5 are fueled with coal (with a total of 23 boilers), 1 by natural gas (4 boilers), 3 nuclear, 69 hydroelectric and 1 wind turbine generating a total of 115.8 TWh. No CO2 capture process existed at any OPG power plant; about 36.7 million tonnes of CO2 was emitted in 2002, mainly from fossil fuel power plants. Four electricity demand scenarios were considered over a span of 10 years and for each case the size of new power generation capacity with and without capture was obtained. Six supplemental electricity generating technologies have been allowed for: subcritical pulverized coal-fired (PC), PC with carbon capture (PC+CCS), integrated gasification combined cycle (IGCC), IGCC with carbon capture (IGCC+CCS), natural gas combined cycle (NGCC), and NGCC with carbon capture (NGCC+CCS). The optimization results showed that fuel balancing alone can contribute to the reduction of CO2 emissions by only 3% and a slight, 1.6%, reduction in the cost of electricity compared to a calculated base case. It was found that a 20% CO2 reduction at current electricity demand could be achieved by implementing fuel balancing and switching 8 out of 23 coal-fired boilers to natural gas. However, as demand increases, more coal-fired boilers needed to be switched to natural gas as well as the building of new NGCC and NGCC+CCS for replacing the aging coal-fired power plants. To achieve a 40% CO2 reduction at 1.0% demand growth rate, four new plants (2 NGCC, 2 NGCC+CCS) as well as carbon capture processes needed to be built. If greater than 60% CO2 reductions are required, NGCC, NGCC+CCS, and IGCC+CCS power plants needed to be put online in addition to carbon capture processes on coal-fired power plants. The volatility of natural gas prices was found to have a significant impact on the optimal CO2 mitigation strategy and on the cost of electricity generation. Increasing the natural gas prices resulted in early aggressive CO2 mitigation strategies especially at higher growth rate demands. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Designing for Low-Carbon Lifestyles

ARCHITECTURAL DESIGN, Issue 1 2010
Mukti Mitchell
Abstract Carpenter, shipbuilder and pioneer of sustainable living Mukti Mitchell collaborates with Ken Yeang on an article espousing the widespread adoption of low-carbon lifestyles. As well as discussing the adoption of CO2 reductions at the individual and global levels, they look at the extent to which architectural design can facilitate lifestyle carbon reductions. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Europäische Ansätze für Energieeffizienz-Monitoring auf der Basis von Energieausweis-Daten

BAUPHYSIK, Issue 3 2009
Tobias Loga Dipl.-Phys.
Energieeinsparung; Gebäudebestand Abstract Das DATAMINE-Projekt wurde angesichts des Bedarfs nach konkreten Daten über den tatsächlichen energetischen Zustand des europäischen Gebäudebestands und die bestehenden Potentiale zur Energieeinsparung und CO2-Emissionsminderung ins Leben gerufen. Diese Daten sollen längerfristig helfen, das politische Instrumentenbündel (ordnungsrechtliche, steuerliche, Förder-Maßnahmen, Informationsvermittlung) so zu gestalten, dass es wirkungsvoll und kosteneffizient ist. Entsprechend dem DATAMINE-Konzept basieren die Informationen auf Energieausweisen, die gemäß EU-Gebäuderichtlinie ausgestellt werden, sobald ein Gebäude gebaut, verkauft oder vermietet wird. Im Rahmen des DATAMINE-Projekts wurden in zwölf Ländern Feldversuche mit größeren Gebäudedaten-Sammlungen durchgeführt, jeder mit unterschiedlichen Analysezielen. Dabei nutzte jedes Land die gleiche Datenstruktur für die Sammlung seiner Energieausweis-Daten, die im Vorfeld gemeinsam entwickelt worden war. Diese lässt sich auf die verschiedenen Zertifizierungssysteme anwenden, die die europäischen Länder auf Grund der Unterschiede in Informationsbedürfnissen, Gebäudearten und Klima entwickelt haben. Rund 19.000 Datensätze wurden im gemeinsamen DATAMINE-Format gesammelt. In einem Ländervergleich konnten verschiedene Energieeffizienz-Indikatoren gegenübergestellt werden. Das Ergebnis der Analysen ergibt einen genaueren Einblick in den aktuellen Stand der energetischen Modernisierung spezifischer Gebäudegruppen in den beteiligten Ländern. Schließlich wurden Schlussfolgerungen in Bezug auf die Entwicklung von Monitoringsystemen in jedem Land und auf EU-Ebene gezogen. European attempt at energy performance monitoring based on data collections and certification schemes. The launch of the DATAMINE project has been driven by the need for concrete data on the actual energy performance of the European building stock as well as the potential energy savings and CO2 reductions. In the longer term data can help develop tailored, cost-efficient complementary measures to energy performance legislation, such as soft loans and tax incentives. DATAMINE aims to construct a knowledge base using the information on the energy performance certificates issued when buildings are constructed, sold or rented. In the framework of DATAMINE test projects were carried out on large samples of buildings in 12 countries, each with individual monitoring targets. In each country the same data structure was used for data collection which had been developed at the forefront. Full allowance is made for the Europe-wide differences in certification schemes, since each country has a scheme tailored to its specific needs, building stock and climate. Around 19,000 datasets have been collected in the common DATAMINE format. Cross-country analysis of the collected data was performed comparing different energy performance indicators. The result of the evaluation activities gives a clearer insight into the current state of refurbishment of specific building subsets in each country. Finally conclusions were drawn regarding the development of monitoring systems in each country and on EU level. [source]