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1.
Consumption accounting of urban greenhouse gas emissions is preferable to production accounting, because cities are open systems which depend on the import of large quantities of externally produced goods. In this paper we use environmental input–output analysis to construct CO2 production and consumption accounting inventories for Xiamen, a rapidly developing coastal city in southeast China. We found that, in 2007, total emissions embodied in production were 21.8 Mt CO2, of which 17.1 Mt CO2 were embodied in exports and 4.7 Mt CO2 resulted from local demand on local production. If the large amounts of emissions embodied in the Xiamen reprocessing trade are excluded from the analysis, total imported emissions were 12.2 Mt CO2, consumption emissions were 16.9 Mt CO2, and Xiamen was a net exporter of 4.9 Mt CO2. Although Xiamen's rapid economic growth is dependent on large-scale flows of embodied emissions, most of these emissions are not produced or consumed within the city system.  相似文献   

2.
This study was designed to consider all nitrogen fertilizer-related effects on crop production and emission of greenhouse gases on loamy sandy soils in Germany over a period of nine years (1999–2007). In order to set up a CO2 balance for the production of energy crops, different nitrogen pathways were investigated, such as direct N2O emissions from the soil and indirect emissions related to NO3 leaching and fertilizer production. Fluxes of N2O were measured in an experimental field using closed chambers. Poplar (Populus maximowiczii × P. nigra) and rye (Secale cereale L.) as one perennial and one annual crop were fertilized at rates of 0 kg N ha?1 yr?1, 75 kg N ha?1 yr?1 and 150 kg N ha?1 yr?1. The mean N2O emissions from the soil ranged between 0.5 kg N ha?1 yr?1 and 2.5 kg N ha?1 yr?1 depending on fertilization rate, crop variety and year. The CO2 fixed in the biomass of energy crops is reduced by up to 16% if direct N2O emissions from soil and indirect N2O emissions from NO3 leaching and fertilizer production are included. Taking into account the main greenhouse gas emissions, which derive from the production and the use of N fertilizer, the growth of poplar and rye may replace the global warming potential of fossil fuels by up to 17.7 t CO2 ha?1 yr?1 and 12.1 t CO2 ha?1 yr?1, respectively.  相似文献   

3.
《Biomass & bioenergy》2005,28(5):475-489
Nonrenewable energy consumption and greenhouse gas (GHG) emissions associated with ethanol (a liquid fuel) derived from corn grain produced in selected counties in Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, and Wisconsin are presented. Corn is cultivated under no-tillage practice (without plowing). The system boundaries include corn production, ethanol production, and the end use of ethanol as a fuel in a midsize passenger car. The environmental burdens in multi-output biorefinery processes (e.g., corn dry milling and wet milling) are allocated to the ethanol product and its various coproducts by the system expansion allocation approach.The nonrenewable energy requirement for producing 1 kg of ethanol is approximately 13.4–21.5 MJ (based on lower heating value), depending on corn milling technologies employed. Thus, the net energy value of ethanol is positive; the energy consumed in ethanol production is less than the energy content of the ethanol (26.8 MJ kg−1).In the GHG emissions analysis, nitrous oxide (N2O) emissions from soil and soil organic carbon levels under corn cultivation in each county are estimated by the DAYCENT model. Carbon sequestration rates range from 377 to 681 kg C ha−1 year−1 and N2O emissions from soil are 0.5–2.8 kg N ha−1 year−1 under no-till conditions. The GHG emissions assigned to 1 kg of ethanol are 260–922 g CO2 eq. under no-tillage. Using ethanol (E85) fuel in a midsize passenger vehicle can reduce GHG emissions by 41–61% km−1 driven, compared to gasoline-fueled vehicles. Using ethanol as a vehicle fuel, therefore, has the potential to reduce nonrenewable energy consumption and GHG emissions.  相似文献   

4.
The impact of anaerobic digestion (AD) technology on mitigating greenhouse gas (GHG) emissions from manure management on typical dairy, sow and pig farms in Finland was compared. Firstly, the total annual GHG emissions from the farms were calculated using IPCC guidelines for a similar slurry type manure management system. Secondly, laboratory-scale experiments were conducted to estimate methane (CH4) potentials and process parameters for semi-continuous digestion of manures. Finally, the obtained experimental data were used to evaluate the potential renewable energy production and subsequently, the possible GHG emissions that could be avoided through adoption of AD technology on the studied farms. Results showed that enteric fermentation (CH4) and manure management (CH4 and N2O) accounted for 231.3, 32.3 and 18.3 Mg of CO2 eq. yr?1 on dairy, sow and pig farms, respectively. With the existing farm data and experimental methane yields, an estimated renewable energy of 115.2, 36.3 and 79.5 MWh of heat yr?1 and 62.8, 21.8 and 47.7 MWh of electricity yr?1 could be generated in a CHP plant on these farms respectively. The total GHG emissions that could be offset on the studied dairy cow, sow and pig farms were 177, 87.7 and 125.6 Mg of CO2 eq. yr?1, respectively. The impact of AD technology on mitigating GHG emissions was mainly through replaced fossil fuel consumption followed by reduced emissions due to reduced fertilizer use and production, and from manure management.  相似文献   

5.
Previous estimates of environmental impacts associated with the front end of the nuclear fuel cycle (FEFC) have focused primarily on energy consumption and CO2 emissions. Results have varied widely. This work builds upon reports from operating facilities and other primary data sources to build a database of front end environmental impacts. This work also addresses land transformation and water withdrawals associated with the processes of the FEFC. These processes include uranium extraction, conversion, enrichment, fuel fabrication, depleted uranium disposition, and transportation.To allow summing the impacts across processes, all impacts were normalized per tonne of natural uranium mined as well as per MWh(e) of electricity produced, a more conventional unit for measuring environmental impacts that facilitates comparison with other studies. This conversion was based on mass balances and process efficiencies associated with the current once-through LWR fuel cycle.Total energy input is calculated at 8.7 × 10 3 GJ(e)/MWh(e) of electricity and 5.9 × 10 3 GJ(t)/MWh(e) of thermal energy. It is dominated by the energy required for uranium extraction, conversion to fluoride compound for subsequent enrichment, and enrichment. An estimate of the carbon footprint is made from the direct energy consumption at 1.7 kg CO2/MWh(e). Water use is likewise dominated by requirements of uranium extraction, totaling 154 L/MWh(e). Land use is calculated at 8 × 10 3 m2/MWh(e), over 90% of which is due to uranium extraction. Quantified impacts are limited to those resulting from activities performed within the FEFC process facilities (i.e. within the plant gates). Energy embodied in material inputs such as process chemicals and fuel cladding is identified but not explicitly quantified in this study. Inclusion of indirect energy associated with embodied energy as well as construction and decommissioning of facilities could increase the FEFC energy intensity estimate by a factor of up to 2.  相似文献   

6.
《Biomass & bioenergy》2006,30(4):296-303
Mitigating global climate change via CO2 emission control and taxation is likely to enhance the economic potential of bioenergy production and utilization. This study investigated the cost competitiveness of woody biomass for electricity production in the US under alternative CO2 emission reductions and taxes. We first simulated changes in the price of coal for electricity production due to CO2 emission reductions and taxation using a computable general equilibrium model. Then, the costs of electricity generation fueled by energy crops (hybrid poplar), logging residues, and coal were estimated using the capital budgeting method. Our results indicate that logging residues would be competitive with coal if emissions were taxed at about US$25 Mg−1 CO2, while an emission tax US$100 Mg−1 CO2 or higher would be needed for hybrid poplar plantations at a yield of 11.21 dry Mg ha−1 yr−1 (5 dry tons ac−1 yr−1) to compete with coal in electricity production. Reaching the CO2 emission targets committed under the Kyoto Protocol would only slightly increase the price of fossil fuels, generating little impact on the competitiveness of woody biomass. However, the price of coal used for electricity production would significantly increase if global CO2 emissions were curtailed by 20% or more. Logging residues would become a competitive fuel source for electricity production if current global CO2 emissions were cut by 20–30%. Hybrid poplar plantations would not be able to compete with coal until emissions were reduced by 40% or more.  相似文献   

7.
《Biomass & bioenergy》2006,30(7):605-617
In this study, micro-level data from wood energy producers in Hedmark County were gathered and analysed. The aim was to find how much greenhouse gas (GHG) emissions various kinds of wood energy cause (not only CO2, but also CH4 and N2O), which energy they substitute, their potential to reduce GHG emissions, and the major sources of uncertainty. The method was life cycle assessment. Six types of wood energy were studied: fuel wood, sawdust, pellets, briquettes, demolition wood, and bark.GHG emissions over the life cycle of the wood energy types in this study are 2–19% of the emissions from a comparable source of energy. The lowest figure is for demolition wood substituting oil in large combustion facilities, the highest for fuel wood used in dwellings to substitute electricity produced by coal-based power plants.Avoided GHG emissions per m3 wood used for energy were from 0.210 to 0.640 tonne CO2-equivalents. Related to GWh energy produced, avoided GHG emissions were from 250 to 360 tonne CO2-equivalents. Avoided GHG emissions per tonne CO2 in the wood are 0.28–0.70 tonne CO2-equivalents. The most important factors were technology used for combustion, which energy that is substituted, densities, and heating values. Inputs concerning harvest, transport, and production of the wood energy are not important.Overall, taking the uncertainties into account there is not much difference in avoided GHG emissions for the different kinds of wood energy.  相似文献   

8.
《Biomass & bioenergy》2007,31(8):543-555
The energetic and environmental performance of production and distribution of the Brassica carinata biomass crop in Soria (Spain) is analysed using life cycle assessment (LCA) methodology in order to demonstrate the major potential that the crop has in southern Europe as a lignocellulosic fuel for use as a renewable energy source.The Life Cycle Impact Assessment (LCIA) including midpoint impact analysis that was performed shows that the use of fertilizers is the action with the highest impact in six of the 10 environmental categories considered, representing between 51% and 68% of the impact in these categories.The second most important impact is produced when the diesel is used in tractors and transport vehicles which represents between 48% and 77%. The contribution of the B. carinata cropping system to the global warming category is 12.7 g CO2 eq. MJ−1 biomass produced. Assuming a preliminary estimation of the B. carinata capacity of translocated CO2 (631 kg CO2 ha−1) from below-ground biomass into the soil, the emissions are reduced by up to 5.2 g CO2 eq. MJ−1.The production and transport are as far as a thermoelectric plant of the B. carinata biomass used as a solid fuel consumes 0.12 MJ of primary energy per 1 MJ of biomass energy stored. In comparison with other fossil fuels such as natural gas, it reduces primary energy consumption by 33.2% and greenhouse gas emission from 33.1% to 71.2% depending on whether the capacity of translocated CO2 is considered or not.The results of the analysis support the assertion that B. carinata crops are viable from an energy balance and environmental perspective for producing lignocellulosic solid fuel destined for the production of energy in southern Europe. Furthermore, the performance of the crop could be improved, thus increasing the energy and environmental benefits.  相似文献   

9.
《Biomass & bioenergy》2006,30(3):273-277
Upflow anaerobic sludge blanket (UASB) reactor was installed to replace the conventional anaerobic lagoon treating bagasse wash wastewater from agro-based pulp and paper mill, to generate bio-energy and to reduce greenhouse gas emissions. The plant was designed to treat 12 ML d−1 of wastewater having two 5 ML capacity reactors, 5.75 kg COD m−3 d−1 organic loading rate and 20 h hydraulic retention time. In the plant 80–85% COD reduction was achieved with biogas production factor of 520 L kg−1 COD reduced. In 11 months 4.4 million m3 of biogas was generated from bagasse wash wastewater utilizing UASB process. Utilization of the biogas in the Lime Kiln saved 2.14 ML of furnace oil in 9 months. Besides significant economic benefits, furnace oil saving reduced 6.4 Gg CO2 emission from fossil fuel and conversion of the anaerobic lagoon into anaerobic reactor reduced 2.1 Gg methane emission which is equal to 43.8 Gg of CO2.  相似文献   

10.
The paper evaluates the role of the bio-fuels production in the transportation sector in the world, for programs of greenhouse gases emissions reductions and sustainable environmental performance. Depending on the methodology used to account for the local pollutant emissions and the global greenhouse gases emissions during the production and consumption of both the fossil and bio-fuels, the results can show huge differences. If it is taken into account a life cycle inventory approach to compare the different fuel sources, these results can present controversies. A comparison study involving the American oil diesel and soybean diesel developed by the National Renewable Energy Laboratory presents CO2 emissions for the bio-diesel which are almost 20% of the emissions for the oil diesel: 136 g CO2/bhp-h for the bio-diesel from soybean and 633 g CO2/bhp-h for the oil diesel [National Renewable Energy Laboratory—NREL/SR-580-24089]. Besides that, important local environmental impacts can also make a big difference. The water consumption in the soybean production is much larger in comparison with the water consumption for the diesel production [National Renewable Energy Laboratory—NREL/SR-580-24089]. Brazil has an important role to play in this scenario because of its large experience in bio-fuels production since the seventies, and the country has conditions to produce bio-fuels for attending great part of the world demand in a sustainable pathway.  相似文献   

11.
《Biomass & bioenergy》2006,30(7):638-647
The use of firewood for domestic heating has the potential to reduce fossil-fuel use and associated CO2 emissions. The level of possible reductions depends upon the extent to which firewood off-sets the use of fossil fuels, the efficiency with which wood is burnt, and use of fossil fuels for collection and transport of firewood. Plantations grown for firewood also have a cost of emissions associated with their establishment. Applying the FullCAM model and additional calculations, these factors were examined for various management scenarios under three contrasting firewood production systems (native woodland, sustainably managed native forest, and newly established plantations) in low-medium rainfall (600–800 mm) regions of south-eastern Australia. Estimates of carbon dioxide emissions per unit of heat energy produced for all scenarios were lower than for non-renewable energy sources (which generally emit about 0.3–1.0 kg CO2 kWh−1). Amongst the scenarios, emissions were greatest when wood was periodically collected from dead wood in woodlands (0.11 kg CO2 kWh−1), and was much lower when obtained from harvest residues and dead wood in native forests (<0.03 kg CO2 kWh−1). When wood was obtained from plantations established on previously cleared agricultural land, use of firewood led to carbon sequestration equivalent to −0.06 kg CO2 kWh−1 for firewood obtained from a coppiced plantation, and −0.17 kg CO2 kWh−1 for firewood collected from thinnings, slash and other residue in a plantation grown for sawlog production. An uncertainty analysis, where inputs and assumptions were varied in relation to a plausible range of management practices, identified the most important influencing factors and an expected range in predicted net amount of CO2 emitted per unit of heat energy produced from burning firewood.  相似文献   

12.
Municipal residue biomass (MRB) in the municipal solid waste (MSW) stream is a potential year-round bioenergy feedstock. A method is developed to estimate the amount of residue biomass generated by the end-user at the scale of a country using a throughput approach. Given the trade balance of food and forestry products, the amount of MRB generated is calculated by estimating product lifetimes, discard rates, rates of access to MSW collection services, and biomass recovery rates. A wet tonne of MRB could be converted into about 8 GJ of energy and 640 kg of carbon dioxide (CO2) emissions, or buried in a landfill where it would decompose into 1800 kg of CO2 equivalent (in terms of global warming potential) methane (CH4) and CO2 emissions. It is estimated that approximately 1.5 Gt y?1 of MRB are currently collected worldwide. The energy content of this biomass is approximately 12 EJ, but only a fraction is currently utilized. An integrated assessment model is used to project future MRB generation and its utilization for energy, with and without a hypothetical climate policy to stabilize atmospheric CO2 concentrations. Given an anticipated price for biomass energy (and carbon under a policy scenario), by the end of the century, it is projected that nearly 60% of global MRB would be converted to about 8 EJ y?1 of energy in a reference scenario, and nearly all of global MRB would be converted into 16 EJ y?1 of energy by the end of the century under a climate policy scenario.  相似文献   

13.
This paper examines policy and technology scenarios in California, emphasizing greenhouse gas (GHG) emissions in 2020 and 2030. Using CALGAPS, a new, validated model simulating GHG and criteria pollutant emissions in California from 2010 to 2050, four scenarios were developed: Committed Policies (S1), Uncommitted Policies (S2), Potential Policy and Technology Futures (S3), and Counterfactual (S0), which omits all GHG policies. Forty-nine individual policies were represented. For S1–S3, GHG emissions fall below the AB 32 policy 2020 target [427 million metric tons CO2 equivalent (MtCO2e) yr−1], indicating that committed policies may be sufficient to meet mandated reductions. In 2030, emissions span 211–428 MtCO2e yr−1, suggesting that policy choices made today can strongly affect outcomes over the next two decades. Long-term (2050) emissions were all well above the target set by Executive Order S-3-05 (85 MtCO2e yr−1); additional policies or technology development (beyond the study scope) are likely needed to achieve this objective. Cumulative emissions suggest a different outcome, however: due to early emissions reductions, S3 achieves lower cumulative emissions in 2050 than a pathway that linearly reduces emissions between 2020 and 2050 policy targets. Sensitivity analysis provided quantification of individual policy GHG emissions reduction benefits.  相似文献   

14.
Emissions of greenhouse gases such as CO2, CO, CH4 and NOX from fossil fuel use are implicated in climate change. The use of bioethanol is one means to reduce fossil fuel use and emissions of greenhouse gases. This study investigated research to produce ethanol from sugar beet and use as fuel in Turkey. The calculated demand for bioethanol amounted to some 220,000 m3 where a 5% ethanol mix in petrol was used. Turkey has the potential to produce 30 million ton of sugar beet, which is sufficient to meet the bioethanol demand.  相似文献   

15.
《Energy Conversion and Management》2005,46(11-12):1790-1808
Based on the results of previous studies, the efficiency of a Brayton/Hirn combined cycle fuelled with a clean syngas produced by means of biomass gasification and equipped with CO2 removal by chemical absorption reached 33.94%, considering also the separate CO2 compression process. The specific CO2 emission of the power plant was 178 kg/MW h. In comparison with values previously found for an integrated coal gasification combined cycle (ICGCC) with upstream CO2 chemical absorption (38–39% efficiency, 130 kg/MW h specific CO2 emissions), this configuration seems to be attractive because of the possibility of operating with a simplified scheme and because of the possibility of using biomass in a more efficient way with respect to conventional systems. In this paper, a life cycle assessment (LCA) was conducted with presenting the results on the basis of the Eco-Indicator 95 impact assessment methodology. Further, a comparison with the results previously obtained for the LCA of the ICGCC was performed in order to highlight the environmental impact of biomass production with fossil fuels utilisation. The LCA shows the important environmental advantages of biomass utilisation in terms of reduction of both greenhouse gas emissions and natural resource depletion, although an improved impact assessment methodology may better highlight the advantages due to the biomass utilisation.  相似文献   

16.
The present paper analyzes the CO2 emissions from mobile communications and portable wireless electronic devices in the Korea environment. The quantitative and qualitative contributions to CO2 emission reduction of the substitution of renewable energy for traditional electricity as the power supply in these devices are also investigated.Firstly, the national CO2 emission coefficient is temporarily estimated as 0.504 tCO2/MWh, which can be regarded as the basis for calculating CO2 emissions in mobile devices. The total annual CO2 emissions from mobile devices is calculated as approximately 1.4 million tons, comprising 0.3 million tCO2 for portable wireless electronic devices and 1.1 million tCO2 for electric equipment required for mobile communication service.If renewable energy sources are substituted for traditional electricity sources in the supply for mobile devices, solar cell and wind turbine systems can reduce CO2 emissions by about 87% and 97%, respectively. However, the use of fuel cell systems will only slightly reduce the CO2 emissions. However, the use of the direct methanol fuel cell system can release 8% more CO2 emissions than that emitted by using traditional electricity sources.  相似文献   

17.
Using detailed electricity consumption and solar generation data from homes in an Austin TX neighborhood between 2013 and 2015, we calculate the environmental benefits of electric vehicles and rooftop solar panels. We estimate time-varying electric grid marginal emissions and water consumption rates in ERCOT through a regression based analysis, and find that emissions and water consumption rates are lowest at high demand times due to those hours' reliance on cleaner natural gas generators. We utilize these emissions and water consumption rates to estimate the avoided GHGs and water consumption from grid electricity that solar panels provide. For electric vehicles, we estimate the net effect of this technology, given the avoided gasoline consumption but increase in grid-related charging. We find that, on average, solar panels avoid approximately 75% of yearly grid-related emissions (0.7 tons CO2/year per kW of solar capacity) and yearly grid-related water consumption (400 gal/year per kW of solar capacity), where the benefits depend on the orientation of the panels. We also find that electric vehicle deployment results in avoiding up to 70% of fuel-related emissions (3.5 tons CO2/year) and 60% of fuel-related water consumption (1400 gal/year), though the benefits significantly decrease with the efficiency of the counterfactual vehicle.  相似文献   

18.
Policies formulated to reduce greenhouse gas (GHG) emissions, such as a low-carbon fuel standard, frequently rely on life-cycle assessment (LCA) to estimate emissions, but LCA results are often highly uncertain. This study develops life-cycle models that quantitatively and qualitatively describe the uncertainty and variability in GHG emissions for both fossil fuels and ethanol and examines mechanisms to reduce those uncertainties in the policy process. Uncertainty regarding emissions from gasoline is non-negligible, with an estimated 90% confidence interval ranging from 84 to 100 g CO2e/MJ. Emissions from biofuels have greater uncertainty. The widths of the 90% confidence intervals for corn and switchgrass ethanol are estimated to be on the order of 100 g CO2e/MJ, and removing emissions from indirect land use change still leaves significant remaining uncertainty. Though an opt-in policy mechanism can reduce some uncertainty by incentivizing producers to self-report fuel production parameters, some important parameters, such as land use change emissions and nitrogen volatilization, cannot be accurately measured and self-reported. Low-carbon fuel policies should explicitly acknowledge, quantify, and incorporate uncertainty in life cycle emissions in order to more effectively achieve emissions reductions. Two complementary ways to incorporate this uncertainty in low carbon fuel policy design are presented.  相似文献   

19.
In the European Union, light duty vehicles (LDVs) are subject to emission targets for carbon dioxide (CO2) and limits for pollutants such as nitrogen oxides (NOx). CO2 emissions are regulated for both passenger vehicles (PV) and light commercial vehicles (LCV), as individual manufacturers are required to reach fleet averages of 130 g/km by 2015 and 175 g/km by 2017, respectively. In the case of PVs, it has been found that there is a significant divergence between real-world and type-approval CO2 emissions, which has been increasing annually, reaching 40% in 2014. On-road exceedances of regulated NOx emission limits for diesel passenger cars have also been documented. The current study investigated the LCV characteristics and CO2 and NOx emissions in the European Union. A vehicle market analysis found that LCVs comprise 17% of the diesel LDV market and while there were some data for CO2 emissions, there were hardly any data publicly available for NOx emissions. Monitoring the divergence in CO2 emissions revealed that it increased from 14% in 2006 to 33% in 2014, posing an additional annual fuel cost from 120€ in 2006 to 305€ in 2014, while a significant percentage of Euro 5 vehicles exceeded NOx emission standards.  相似文献   

20.
Fast growing, short-rotation tree crops provide unique opportunities to sequester carbon on phosphate-mined lands in central Florida and, if used as a biofuel, can reduce CO2 emissions associated with electricity generation. Base case land expectation values (LEVs) of phosphate-mined land under Eucalyptus amplifolia (EA) forestry range from 762 to 6507 $ ha?1 assuming real discount rates of 10% and 4%, respectively. Assuming 5 $ Mg?1 C, these LEVs increase from 3% to 24% with incentives for in situ carbon sequestration benefits, or 21% to 73% given in situ carbon sequestration with additional incentives for reducing CO2 emissions through the use of EA as an energy feedstock. Potential benefits from below-ground C sequestration and mine land reclamation are estimated to be worth an additional 5642–11,056 $ ha?1.  相似文献   

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