Fuel Life Cycle Research Articles

Life cycle greenhouse emissions of compressed natural gas–hydrogen mixtures for transportation in Argentina

We have developed a model to assess the life cycle greenhouse emissions of compressed natural gas–hydrogen (CNG–H 2) mixtures used for transportation in Argentina. The overall fuel life cycle is assessed through a well-to-wheel (WTW) analysis for different hydrogen generation and distribution options. The combustion stage in road vehicles is modeled using the COPERT IV model. Hydrogen generation options include classical steam methane reforming (SMR) and water electrolysis (WE) in central plants and distributed facilities at the refueling stations. Centralized hydrogen generation by electrolysis in nuclear plants as well as the use of solar photovoltaic and wind electricity is also considered. Hydrogen distribution options include gas pipeline and refrigerated truck transportation for liquefied hydrogen. A total number of fifteen fuel pathways are studied; in all the cases the natural gas–hydrogen mixture is made at the refueling station. The use of WE using nuclear or wind electricity appears to be less contaminant that the use of pure CNG.

Mitigation of Aviation Emissions of Carbon Dioxide

This paper investigates the interaction between economic, technological, and operational measures intended to reduce air transport-related emissions of carbon dioxide (CO2). In particular, the introduction of aviation to the European Union Emissions Trading Scheme (ETS) in 2012 may prompt increased uptake of presently available options for emission reduction (e.g., retrofitting winglets, expanding maintenance programs) by airlines operating in Europe. Carbon prices may also determine the use of options currently under development [e.g., open-rotor engines, second-generation biofuels, and improved air traffic management (ATM)]. The results of a several studies analyzing airline costs and emission reductions that are possible from different mitigation options are applied to a systems model of European aviation. With a set of nine scenarios (three internally consistent projections for future population, gross domestic product, oil and carbon prices, each run with three policy cases), technology uptake and the resulting effect on fuel life cycle CO2 emissions with and without an ETS are analyzed. Some options are rapidly taken up under all scenarios (e.g., improved ATM), others are taken up more slowly by specific aircraft classes depending on the scenario (e.g., biofuels), and others have negligible impact in the cases studied. High uptake of one mitigation option may also reduce the uptake of other options. European aviation fuel life cycle emissions could be reduced below 2005 levels before 2050 if cellulosic biomass fuels are made available by 2020. However, the land use requirements in this scenario may limit its practicality at currently projected cellulosic biomass yields.

Expansion of Renewable Energy Industries and Implications for Occupational Health

RECENT PASSAGE OF THE AMERICAN RECOVERY AND Reinvestment Act of 2009 provides significantly increased funding for renewable energy industries that are expected to increasingly supplant the traditional fossil fuel energy industries of coal, oil, and natural gas. Although fossil fuel energy has historically been priced lower than renewable energy, hidden costs to energy production have not been fully included or internalized in the market price of fuel, thereby distorting true costs. These additional costs are known as externalities of energy. One such externality of energy is adverse effects on human health. Human health problems associated with high carbon dioxide emissions from energy production have largely been described as resulting from air pollution; spread of vector and waterborne infectious diseases; flood, drought, and malnutrition; and deaths due to terrorist attacks and military intervention. A reduction in these problems has been touted as an important benefit of a transition to renewable energy. However, benefits to US energy workers in the form of reduced workplace injury and fatality have been an underemphasized advantage of change in energy policy. Study of fuel externalities has led to methodological approaches that consider the entire fuel life cycle: fuel extraction, other raw material extraction, structure construction, equipment manufacturing, material transport, energy generation, power distribution, and by-product disposal. The major segments of the fuel cycle are a useful framework for considering available occupational health evidence comparing fossil fuel energy with 3 renewable energies with significant potential for growth: wind, solar, and biomass.

Comparison of Flexible Fuel Vehicle and Life-Cycle Fuel Consumption and Emissions of Selected Pollutants and Greenhouse Gases for Ethanol 85 Versus Gasoline

The objective of this research is to evaluate differences in fuel consumption and tailpipe emissions of flexible fuel vehicles (FFVs) operated on ethanol 85 (E85) versus gasoline. Theoretical ratios of fuel consumption and carbon dioxide (CO2) emissions for both fuels are estimated based on the same amount of energy released. Second-by-second fuel consumption and emissions from one FFV Ford Focus fueled with E85 and gasoline were measured under real-world traffic conditions in Lisbon, Portugal, using a portable emissions measurement system (PEMS). Cycle average dynamometer fuel consumption and emission test results for FFVs are available from the U.S. Department of Energy, and emissions certification test results for ethanol-fueled vehicles are available from the U.S. Environmental Protection Agency. On the basis of the PEMS data, vehicle-specific power (VSP)-based modal average fuel and emission rates for both fuels are estimated. For E85 versus gasoline, empirical ratios of fuel consumption and CO2 emissions agree within a margin of error to the theoretical expectations. Carbon monoxide (CO) emissions were found to be typically lower. From the PEMS data, nitric oxide (NO) emissions associated with some higher VSP modes are higher for E85. From the dynamometer and certification data, average hydrocarbon (HC) and nitrogen oxides (NOx) emission differences vary depending on the vehicle. The differences of average E85 versus gasoline emission rates for all vehicle models are −22% for CO, 12% for HC, and −8% for NOx emissions, which imply that replacing gasoline with E85 reduces CO emissions, may moderately decrease NOx tailpipe emissions, and may increase HC tailpipe emissions. On a fuel life cycle basis for corn-based ethanol versus gasoline, CO emissions are estimated to decrease by 18%. Life-cycle total and fossil CO2 emissions are estimated to decrease by 25 and 50%, respectively; however, life-cycle HC and NOx emissions are estimated to increase by 18 and 82%, respectively.

Allocation issues in LCA methodology: a case study of corn stover-based fuel ethanol

Allocation issues in LCA methodology: a case study of corn stover-based fuel ethanol

BIODIESEL FROM MICROALGAE: THE EFFECT OF FUEL PROPERTIES ON POLLUTANT EMISSIONS

Recently, biofuels have been presented as a viable alternative for the main challenges of the energy industry: the depleting supplies of petroleum and the global warming due to greenhouse effect. Biofuels may be produced from several different feedstocks, such as sugarcane, animal fat, oil crops or even microalgae. Replacing conventional petroleum sourced fuels with biofuels may significantly reduce global greenhouse effect gases emission when considering the life cycle of such fuels. Even with this advantage, biofuels present new challenges concerning the engine adaptation and the pollutant emissions. In this context, this paper aims to clarify the relation between fuel properties of microalgae biodiesel and pollutant emissions, studying which properties are desirable in these new fuels to guarantee engine operation without degradation of performance in comparison to conventional diesel.

Energy Use and Emissions from Marine Vessels: A Total Fuel Life Cycle Approach

Regional and global air pollution from marine transportation is a growing concern. In discerning the sources of such pollution, researchers have become interested in tracking where along the total fuel life cycle these emissions occur. In addition, new efforts to introduce alternative fuels in marine vessels have raised questions about the energy use and environmental impacts of such fuels. To address these issues, this paper presents the Total Energy & Emissions Analysis for Marine Systems (TEAMS) model. TEAMS can be used to analyze total fuel life cycle emissions and energy use from marine vessels. TEAMS captures “well-to-hull” emissions, that is, emissions along the entire fuel pathway, including extraction, processing, distribution, and use in vessels. TEAMS conducts analyses for six fuel pathways: (1) petroleum to residual oil, (2) petroleum to conventional diesel, (3) petroleum to low-sulfur diesel, (4) natural gas to compressed natural gas, (5) natural gas to Fischer-Tropsch diesel, and (6) soybeans to biodiesel. TEAMS calculates total fuel-cycle emissions of three greenhouse gases (carbon dioxide, nitrous oxide, and methane) and five criteria pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter with aerodynamic diameters of 10 μm or less, and sulfur oxides). TEAMS also calculates total energy consumption, fossil fuel consumption, and petroleum consumption associated with each of its six fuel cycles. TEAMS can be used to study emissions from a variety of user-defined vessels. This paper presents TEAMS and provides example modeling results for three case studies using alternative fuels: a passenger ferry, a tanker vessel, and a container ship.

Energy and Emission Benefits of Alternative Transportation Liquid Fuels Derived from Switchgrass: A Fuel Life Cycle Assessment

We conducted a mobility chains, or well-to-wheels (WTW), analysis to assess the energy and emission benefits of cellulosic biomass for the U.S. transportation sector in the years 2015-2030. We estimated the life-cycle energy consumption and emissions associated with biofuel production and use in light-duty vehicle (LDV) technologies by using the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model. Analysis of biofuel production was based on ASPEN Plus model simulation of an advanced fermentation process to produce fuel ethanol/protein, a thermochemical process to produce Fischer-Tropsch diesel (FTD) and dimethyl ether (DME), and a combined heat and power plant to co-produce steam and electricity. Our study revealed that cellulosic biofuels as E85 (mixture of 85% ethanol and 15% gasoline by volume), FTD, and DME offer substantial savings in petroleum (66-93%) and fossil energy (65-88%) consumption on a per-mile basis. Decreased fossil fuel use translates to 82-87% reductions in greenhouse gas emissions across all unblended cellulosic biofuels. In urban areas, our study shows net reductions for almost all criteria pollutants, with the exception of carbon monoxide (unchanged), for each of the biofuel production option examined. Conventional and hybrid electric vehicles, when fueled with E85, could reduce total sulfur oxide (SO(x)) emissions to 39-43% of those generated by vehicles fueled with gasoline. By using bio-FTD and bio-DME in place of diesel, SO(x) emissions are reduced to 46-58% of those generated by diesel-fueled vehicles. Six different fuel production options were compared. This study strongly suggests that integrated heat and power co-generation by means of gas turbine combined cycle is a crucial factor in the energy savings and emission reductions.

Life cycle analysis of vehicles powered by a fuel cell and by internal combustion engine for Canada

The transportation sector is responsible for a great percentage of the greenhouse gas emissions as well as the energy consumption in the world. Canada is the second major emitter of carbon dioxide in the world. The need for alternative fuels, other than petroleum, and the need to reduce energy consumption and greenhouse gases emissions are the main reasons behind this study. In this study, a full life cycle analysis of an internal combustion engine vehicle (ICEV) and a fuel cell vehicle (FCV) has been carried out. The impact of the material and fuel used in the vehicle on energy consumption and carbon dioxide emissions is analyzed for Canada. The data collected from the literature shows that the energy consumption for the production of 1 kg of aluminum is five times higher than that of 1 kg of steel, although higher aluminum content makes vehicles lightweight and more energy efficient during the vehicle use stage. Greenhouse gas regulated emissions and energy use in transportation (GREET) software has been used to analyze the fuel life cycle. The life cycle of the fuel consists of obtaining the raw material, extracting the fuel from the raw material, transporting, and storing the fuel as well as using the fuel in the vehicle. Four different methods of obtaining hydrogen were analyzed; using coal and nuclear power to produce electricity and extraction of hydrogen through electrolysis and via steam reforming of natural gas in a natural gas plant and in a hydrogen refueling station. It is found that the use of coal to obtain hydrogen generates the highest emissions and consumes the highest energy. Comparing the overall life cycle of an ICEV and a FCV, the total emissions of an FCV are 49% lower than an ICEV and the energy consumption of FCV is 87% lower than that of ICEV. Further, CO 2 emissions during the hydrogen fuel production in a central plant can be easily captured and sequestrated. The comparison carried out in this study between FCV and ICEV is extended to the use of recycled material. It is found that using 100% recycled material can reduce energy consumption by 45% and carbon dioxide emissions by 42%, mainly due to the reduced use of electricity during the manufacturing of the material.

Reduction of energy consumption in biodiesel fuel life cycle

Essential requirements for biofuel are that (a) it should be produced from renewable raw material, and (b) it should have a lower negative environmental impact than that of fossil fuels. Apart from direct assessment of the engine emissions, environmental impact is also determined by performing life cycle analysis. Life cycle energy balance depends on specific climatic conditions and the agro- and processing technologies used. Rapeseed oil methyl ester life cycle energy ratios in Lithuanian conditions have been calculated as a function of rapeseed productivity, oil pressing and transesterification technologies used. Opportunities to improve biodiesel fuel life cycle energy efficiency, by implementing new technologies in agriculture as well as in industrial processing, were reviewed. The effectiveness of new technologies was evaluated on the basis of energy balance comparison.

Incremental life cycle analysis: using uncertainty analysis to frame greenhouse gas balances from bioenergy systems for emission trading

There are many scales that can be employed to calculate net greenhouse gas emissions from bioenergy systems, ranging from single point source (stack gas) measurement, to full, multi-layered life cycle analyses considering all of the inputs and outputs throughout the economy. At an appropriate scale within these extremes, a method can be selected to support verification activities related to project-based trading of greenhouse gas emissions. The boundaries of the analysis must be carefully selected in order to meet the twin goals of the verification activity: (1) to meet scientific standards for emission balance quantification, and (2) to meet cost-effectiveness criteria of the emission trading community. A methodology is proposed for verifying greenhouse gas reductions arising from substitution of bioenergy fuel for fossil fuel in electric generation. The method utilizes an incremental progression through the fuel life cycle, pausing at each level to evaluate the potential benefits and uncertainties of a next-level expansion. A case study is analyzed for greenhouse gas benefits of switchgrass substitution for coal combustion in an existing electric generation facility. Using the incremental technique to set boundaries on the analysis, replacement of coal with switchgrass is found to provide a reduction of net greenhouse gas emissions at a rate of 102 g CO 2-equivalent per million Joules (g/MJ) of switchgrass input. At full production, co-firing 5 percent switchgrass, the emission reduction would total more than 305,500 metric tons CO 2-eq annually.

Exergetic environmental assessment of life cycle emissions for various automobiles and fuels

This paper examines material emissions produced during thirteen fuel life cycles for automobiles, on mass and exergy bases. The masses of fuel life cycle emissions are compared with the chemical exergies of these emissions. For the emissions data used, the chemical exergy results suggest that compressed natural gas use in motor vehicles produces emissions that are the most out of equilibrium with the natural environment, relative to all other fuel life cycle paths considered. It is also shown that diesel use in grid-independent hybrid electric vehicles has the lowest chemical exergies of emissions of all thirteen fuel-vehicle combinations under consideration, suggesting a lower degree of potential environmental impact. The exergy methodology presented for assessing the potential for environmental impact may help in the development and design of transportation technologies that are more environmentally benign than those presently used.

Extension of Load Follow Capability of a PWR Reactor by Optimal Control

The problem of extending that part of the fuel life cycle during which a reactor is capable of sustaining load-follow operation is formulated as an optimal control problem. A two-node model representation of pressurized water reactor dynamics is used, leading to a set of non-linear ordinary differential equations. Differential Dynamic Programming is used to solve directly the resulting nonlinear optimization problem and obtain the trajectories of soluble boron concentration and control rod insertion. Results of computations performed for a reference reactor are presented, showing how the optimal control policy stretches the capability of the reactor to follow an average daily load curve towards the end of the fuel life cycle.

Optimal Control of a PWR Reactor to Extend Load Follow Capability

The problem of extending that part of the fuel life cycle during which a reactor is capable of sustaining load-follow operation is formulated as an optimal control problem. A two-node model representation of pressurized water reactor dynamics is used, leading to a set of non-linear ordinary differential equations. Differential Dynamic Programming is used to solve directly the resulting non-linear optimization problem and obtain the trajectories of soluble boron concentration and control rod insertion. Results of computations performed for a reference reactor are presented, showing how the optimal control polijy stretches the capability of the reactor to follow an average daily load curve towards che end of the fuel life cycle.