Direct Measurement of Fugitive Emissions of Hydrocarbons from a Refinery

Abstract

Refineries are a source of emissions of volatile hydrocarbons that contribute to the formation of smog and ozone. Fugitive emissions of hydrocarbons are difficult to measure and quantify. Currently these emissions are estimated based on standard emission factors for the type and use of equipment installed. Differential absorption light detection and ranging (DIAL) can remotely measure concentration profiles of hydrocarbons in the atmosphere up to several hundred meters from the instrument. When combined with wind speed and direction, downwind vertical DIAL scans can be used to calculate mass fluxes of the measured gas leaving the site. Using a mobile DIAL unit, a survey was completed at a Canadian refinery to quantify fugitive emissions of methane, C₂₊ hydrocarbons, and benzene and to apportion the hydrocarbon emissions to the various areas of the refinery. Refinery fugitive emissions as measured with DIAL during this demonstration study were 1240 kg/hr of C₂₊ hydrocarbons, 300 kg/hr of methane, and 5 kg/hr of benzene. Storage tanks accounted for over 50% of the total emissions of C₂₊ hydrocarbons and benzene. The coker area and cooling towers were also significant sources. The C₂₊ hydrocarbons emissions measured during the demonstration amounted to 0.17% of the mass of the refinery hydrocarbon throughput for that period. If the same loss were repeated throughout the year, the lost product would represent a value of US$3.1 million/yr (assuming US$40/bbl). The DIAL-measured hourly emissions of C₂₊ hydrocarbons were 15 times higher than the emission factor estimates and gave a different perspective on which areas of the refinery were the main source of emissions. Methods, such as DIAL, that can directly measure fugitive emissions would improve the effectiveness of efforts to reduce emissions, quantify the reduction in emissions, and improve the accuracy of emissions data that are reported to regulators and the public.     

Characteristics and diurnal variations of NMHCs at urban,suburban, and rural sites in the Pearl River Delta and a remote site in South China

The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. With rapid growth of the economy, it is suffering from deteriorating air quality. Non-methane hydrocarbons (NMHCs) were investigated at urban and suburban sites in Guangzhou (GZ), a rural site in PRD and a clean remote site in South China, in April 2005. Additional roadside samples in GZ and Qingxi (QX, a small industrial town in PRD), ambient air samples at the rooftop of a printing factory in QX and exhaust samples from liquefied petroleum gas (LPG)—fueled taxis in GZ were collected to help identify the source signatures of NMHCs. A large fraction of propane (47%) was found in exhaust samples from LPG-fueled taxis in GZ and extremely high levels of toluene (2.0–3.1 ppmv) were found at the rooftop of the printing factory in QX. Vehicular and industrial emissions were the main sources of NMHCs. The effect of vehicular emission on the ambient air varied among the three PRD sites. The impact of industrial emissions was widespread and they contributed greatly to the high levels of aromatic hydrocarbons, especially toluene, at the three PRD sites investigated. Leakage from vehicles fueled by LPG contributed mainly to the high levels of propane and n-butane at the urban GZ site. Ethane and ethyne from long-range transport and isoprene from local biogenic emission were the main contributors to the total hydrocarbons at the remote site. Diurnal variations of NMHCs showed that the contribution from vehicular emissions varied with traffic conditions and were more influenced by fresh emissions at the urban site and by aged air at the suburban and rural sites. Isoprene from biogenic emission contributed largely to the ozone formation potential (OFP) at the remote site. Ethene, toluene and m/p-xylene were the main contributors to the OFP at the three PRD sites.     

Source Fingerprints for Volatile Non-Methane Hydrocarbons

Non-methane hydrocarbon (NMHC) source profiles consisting of 35 hydrocarbon species were measured for vehicle and petroleum refinery emissions. Refueling emissions were found to be sensitive to the grade and volatility class of fuel and to be composed mainly of saturated hydrocarbons such as n-butane and 2-methy I butane. Unsaturated and aromatic hydrocarbons, which are released from the tailpipe of vehicles as products of combustion and unburned fuel, were more prevalent in roadway emissions comprising approximately 34 percent of the total NMHCs. Cold-start emissions were nearly indistinguishable from the roadway emission profile. The only significant differences were in toluene, ethylene and acetylene, which may be related to the efficiency of combustion when the vehicle is initially started. Saturated hydrocarbon distributions of the hot-soak profiles were found to be similar to refueling emissions. The only significant difference in the profiles was in the aromatic content, which may be related to the grade of the gasoline and the effectiveness of evaporative emission control devices. The temporal variation in refinery emissions was significant and may be related to variations in refinery activities such as the production and blending of feed stocks to produce different fuels.     

Ambient Air Measurements of Petroleum Refinery Emissions

An ambient air monitoring program to characterize airborne emissions from the Exxon petroleum refinery at Benicia, California was conducted during September 8–22, 1975. Ground level sampling facilities and an instrumented aircraft provided an integrated, three-dimensional monitoring network. Measurements made during the study included ozone, oxides of nitrogen, methane, carbon monoxide, individual C₂-C₆ hydrocarbons, halocarbons, condensation nuclei, visual distance and various meteorological parameters. The study focused on three major areas: (1) the characterization of gaseous components within the refinery effluent, especially non-methane hydrocarbons and ozone, (2) natural sunlight bag irradiation experiments to determine the ozone forming potential of refinery emissions, and (3) an investigation of changes in plume chemistry as refinery emissions were transported downwind.     

NMOC,ozone, and organic aerosol in the southeastern United States, 1999–2007: 1. Spatial and temporal variations of NMOC concentrations and composition in Atlanta,Georgia

Volatile organic compounds (VOCs) are emitted from anthropogenic and natural (biogenic) sources into the atmosphere. Characterizing their ambient mixing ratios or concentrations is a challenge because VOCs comprise hundreds of species, and accurate measurements are difficult. Long-term hourly and daily-resolution data have been collected in the metropolitan area of Atlanta, Georgia, a major city dominated by motor vehicle emissions. A series of observations of daily, speciated C₂–C₁₀ non-methane organic compounds (NMOC) and oxygenated hydrocarbons (OVOC) in mid-town Atlanta (Jefferson Street, JST) are compared with data from three urban-suburban sites and a nearby non-urban site. Annual-average mixing ratios of NMOC and OVOC at JST declined from 1999 through 2007. Downward trends in NMOC, CO, and NO_y corroborate expected emission changes as reflected in emission inventories for Atlanta’s Fulton County. Comparison of the JST NMOC composition with data from roadside and tunnel sampling reveals similarities to motor vehicle dominated samples. The JST annual average VOC-OH reactivities from 1999 to 2007 were relatively constant compared with the decline in annual-average NMOC mixing ratios. Mean reactivity at JST, in terms of concentration*k_OH, was approximately 40% alkenes, 22% aromatics, 16% isoprene and 6% other biogenics, 13% C₇–C₁₀ alkanes and 3% C₂-C₆ alkanes, indicating that biogenic NMOCs are important but not dominant contributors to the urban reactive NMOC mix. In contrast, isoprene constituted ～50% of the VOC-OH reactivities at two non-urban sites. Ratios of 24-hour average CO/benzene, CO/isopentane, and CO/acetylene concentrations indicate that such species are relatively conserved, consistent with their low reactivity. Ratios of more-reactive to less-reactive species show diurnal variability largely consistent with expected emission patterns, transport and mixing of air, and chemical processing.     

Emissions of liquefied petroleum gas (LPG) from motor vehicles

Continuous on-site measurements of 50 speciated volatile organic compounds (VOCs) were conducted in downtown Guangzhou to characterize the sources and concentration profiles of ambient VOCs. The synchronicity in diurnal variation between the VOCs and NO suggests that traffic emissions were responsible for the observed VOCs in downtown Guangzhou.It was found that the three major constituent species of liquefied petroleum gas (LPG), i.e., propane, iso-butane, and n-butane, together termed LPG alkanes, contributed, on average, 24% of the total VOCs (TVOCs). Their high correlation and synchronized diurnal variations between NO and the LPG alkanes suggest that their origin lies in LPG fueled car exhaust in Guangzhou. LPG buses and taxis were likely to be responsible for the bulk of ambient LPG species. Using propane and 3-methyl pentane (3MC5A) as the indicators for the LPG and gasoline emissions, respectively, the emissions of the LPG fleet were found to increase more than those of the gasoline fleet during the morning and evening rush hours, as well the noontime break in downtown Guangzhou.Although LPG alkanes account for 24% of the TVOC, their contribution to the total ozone forming potential (OFP) is only about 7%. Ethylene and propylene contribute about 26% to the total OFP despite their lower contribution of 16% to the TVOC.     

Determination of Motor Vehicle Profiles for Non-Methane Organic Compounds in the Mexico City Metropolitan Area

ABSTRACT

Non-methane organic compound (NMOC) profiles for on-road motor vehicle emissions were measured in a downtown tunnel and parking garages in Mexico City during 1996. Hydrocarbon samples from the tunnel and ambient air samples (C2-C12) were collected using stainless steel canisters, and carbonyl compounds were collected using 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridges. Canister samples were analyzed by gas chromatog-raphy/flame ionization detection (GC/FID) to ascertain detailed hydrocarbon composition. DNPH samples were analyzed by high performance liquid chromatography (HPLC). NMOC source profiles were quantified for evaporative emissions from refueling, cold start, and hot soak, and on-road operating conditions. The ultimate purpose will be to determine the apportionment of ambient NMOC concentrations using the Chemical Mass Balance (CMB) model. The tunnel profile contained 42.3 ppbC% of alkanes, 20.6 ppbC% of unsaturated compounds, and 22.4 ppbC% of aromatics. The most abundant species were acetylene with 7.22 ppbC%, followed by ipentane with 5.69 ppbC%, and toluene with 5.42 ppbC%. These results were compared with those from studies in the United States. The cold start profile was found to be similar to the tunnel profile, although there were differences in the content of acetylene, isopentane, and oxygenates. The abundance of saturated NMOC in the hot soak profile was similar to gasoline head space profiles; it was also much larger than saturated NMOC in the roadway profile.     

Contribution of LPG-Derived Emissions to Air Pollution in the Metropolitan Area of Guadalajara City

ABSTRACT

Measurements of hydrocarbon (HC) emissions generated by the use of liquefied petroleum gas (LPG) in the metropolitan area of Guadalajara City (MAG) are presented in this work. Based on measurements in the course of distribution, handling, and consumption, an estimated 4407 tons/yr are released into the atmosphere. The three most important contributors to LPG emissions were refilling of LPG-fueled vehicles and commercial and domestic consumption. The MAG shows a different contribution pattern of LPG emission sources compared with that of the metropolitan area of Mexico City (MAMC). These results show that each megacity has different sources of emissions, which provides more accurate strategies in the handling procedures for LPG to decrease the impact in O₃ levels. This work represents the first evaluation performed in Guadalajara City, based on current measurements, of the LPG contribution to polluting emissions.     

Nonmethane Organic Compound to Nitrogen Oxide Ratios and Organic Composition in Cities and Rural Areas

The observed ranges in nonmethane organic compound (NMOC) concentrations, NMOC composition and nitrogen oxides (NO_X) concentrations have been evaluated for urban and nonurban areas at ground level and aloft of the contiguous United States. The ranges in NMOC to NO_X ratios also are considered. The NMOC composition consistently shifts towards less reactive compounds, especially the alkanes, in air parcels over nonurban areas compared to the NMOC composition near ground level within urban areas. The values for the NMOC to NO_X ratios, 1.2 to 4.2, in air aloft over nonurban areas are lower than in air at ground level urban sites, ≥8, and much lower than in air at ground level nonurban sites, ≥20.

The layers of air aloft over a number of nonurban areas of the United States tend to accumulate NO_X emissions from the tall stacks of large fossil fuel power plants located at nonurban sites. During the night into the morning hours, the air aloft is isolated from any fresh NMOC emissions predominately coming from near surface sources. Conversely, during this extended period of restricted vertical mixing, air near the surface accumulates NMOC emissions while this air is isolated from the major NO_X sources emitting aloft. These differences in the distribution of NMOC and NO_X sources appear to account for the much larger NMOC to NO_X ratios reported near ground level compared to aloft over nonurban areas.

Two types of experimental results are consistent with these conclusions: (1) observed increases in surface rural NO_X concentrations during the morning hours during which the mixing depth increases to reach the altitude at which NO_X from the stacks of fossil fuel power plants is being transported downwind; (2) high correlations of total nitrate at rural locations with Se, which is a tracer for coal-fired power plant NO_X emissions.

The implications of these conclusions from the standpoint of air quality strategies are suggested by use of appropriate scenarios applied to both urban and regional scale photochemical air quality models. The predictions from urban model scenarios with NMOC to NO_X ratios up to 20 are that NO_X control will result in the need for the control of more NMOC emissions than necessary in the absence of NO_X control, in order to meet the O₃ standard. On a regional scale, control of NO_X emissions from fossil fuel power plants has little overall effect regionally but does result on a more local scale in both small decreases and increases in O₃ concentrations compared to the baseline scenario without NO_X control. The regional modeling results obtained to date suggest that NO_X control may be effective in reducing O₃ concentrations only for a very limited set of conditions in rural areas.     

Product Guide/1970

Abstract

In Mexico City, the use and composition of fuels determine that carbon monoxide (CO) comes mostly from mobile sources, and sulfur dioxide (SO₂) from fixed and mobile sources. By simultaneously measuring hydrocarbons (HC), CO, and SO₂ in the atmosphere of Mexico City, the relative amounts coming from different sources can be estimated. Assuming that some HC are emitted proportionally to CO emissions, we can establish that [HC]₁= m1? [CO], where the proportionality constant ml corresponds to the ratio of emissions factor for HC and CO in mobile sources. Similarly for fuels containing sulfur, it can be assumed that [HC]₂ = m2 ? [SO₂]. In this way, the total HC are [HC]_total=[HC]₀+ ml ? [CO]+ m2 ? [SO₂], where [HC]₀ corresponds mainly to other sources like solvent evaporation, gas consumption, and natural emissions. In this way, it can be estimated that in Mexico City 75% of average HC comes from mobile sources, 5% from sulfur-related sources, and 19% from natural sources and solvent evaporation. Compared with the HC/CO ratio measured in the exhaust pipe of vehicles, we estimated that 70% of HC emitted from mobile sources are evaporative losses, and only 30% come through the exhaust system.     

Contamination of the Lake Tahoe Air Basin by High Molecular Weight Petroleum Residues

The atmosphere of the Lake Tahoe air basin is contaminated with high molecular weight (> C₁₂) petroleum hydrocarbons. Aerosol samples were collected by high-volume filtration and the solvent-soluble organic matter was analyzed. The relative concentrations of petroleum residues found were as follows: winter > summer and day > night. This contamination is primarily due to the poorer combustion of diesel and home heating fuels at that altitude and during periods of colder climate.     

Comparison of receptor models for source apportionment of volatile organic compounds in Beijing, China

Identifying the sources of volatile organic compounds (VOCs) is key to reducing ground-level ozone and secondary organic aerosols (SOAs). Several receptor models have been developed to apportion sources, but an intercomparison of these models had not been performed for VOCs in China. In the present study, we compared VOC sources based on chemical mass balance (CMB), UNMIX, and positive matrix factorization (PMF) models. Gasoline-related sources, petrochemical production, and liquefied petroleum gas (LPG) were identified by all three models as the major contributors, with UNMIX and PMF producing quite similar results. The contributions of gasoline-related sources and LPG estimated by the CMB model were higher, and petrochemical emissions were lower than in the UNMIX and PMF results, possibly because the VOC profiles used in the CMB model were for fresh emissions and the profiles extracted from ambient measurements by the two-factor analysis models were "aged".     

Influence of fuel composition on polycyclic aromatic hydrocarbon emissions from a fleet of in-service passenger cars

The composition of exhaust emissions from eight in-service passenger cars powered by liquefied petroleum gas (LPG) and unleaded petrol (ULP) were measured on a chassis dynamometer at two driving speeds (60 and 80 km h⁻¹) with the aims of evaluating their polycyclic aromatic hydrocarbon (PAH) contents and investigating the effects of the type of fuel on vehicle performance, ambient air quality and associated health risks. Naphthalene, fluorene, phenanthrene, anthracene, pyrene, chrysene, benzo(a)anthracene and benzo(b)fluoranthene were the most prominent PAHs emitted by both ULP and LPG powered cars. The total emission factors of PAHs from LPG cars were generally lower than (but statistically comparable with) those of ULP cars. Similarly, the total BAP_eq of the PAHs emitted by LPG cars were lower than those from ULP cars. Multi-criteria decision making (MCDM) methods showed that cars powered by LPG fuel performed better than those powered by ULP fuel in term of PAH levels. The implications of these observations on the advantages and disadvantages of using ULP and LPG fuels are discussed.     

Speciated non-methane organic compounds emissions from food cooking in Mexico

Non-methane organic compound (NMOC) emissions from different sorts of food preparation sites, were quantified for the first time in Mexico, in order to develop emission profiles for further application in the chemical mass balance receptor model (CMB). Restaurants using charcoal grills and LP gas stoves, “tortillerı́as”, food frying places and rotisseries were sampled using SUMMA^® stainless-steel canisters to analyse NMOC by high-resolution gas chromatography. The results obtained show that profiles determined from food cooking processes have similarities to those found in LP gas combustion, which is the most common fuel in Mexico used for this purpose, although there were differences in the relative composition of propane and butane in both cases. This suggests that, the rates of combustion of propane and butane are different. It has also been detected that propene, a reactive olefin is produced during the combustion process. The obtained profiles of restaurants, rotisseries and fried food show an important contribution of two carbon compounds (ethane, ethylene and acetylene) that can be attributed to the complex process of grease and meat cooking. The presence of these compounds cannot be attributed to vehicular sources since the concentrations are higher than in ambient air. These were also determined from aromatic compounds such as benzene, toluene and xylene in the combustion of vegetal charcoal. The measured concentrations indicate that NMOC emissions from cooking may become an important indoor source of NMOC under crowded conditions in closed places.     

Development of Instrumentation for Continuous On-line Monitoring of Non-Methane Organic Carbon in Air Emissions

ABSTRACT

Non-methane organic carbon (NMOC) is a measure of total organic carbon in an air emission, excluding that from methane. Thus, it measures the total amount of carbon, irrespective of the structure and functional groups in the molecule. The U.S. Environmental Protection Agency (EPA) Method 25 is used for quantification of NMOC in emission sources and in ambient air. This method involves laboratory analysis of collected air samples and cannot be used for real-time measurements. It is prone to interferences from CO₂, CH₄, and CO, as well as moisture. In this paper, a novel method for continuous, on-line monitoring of NMOC in air emissions and ambient air is presented. Detection limits are at ppb levels, and interference of permanent gases have been eliminated.     

Effect of SME biodiesel blends on PM2.5 emission from a heavy-duty engine

To explore the effect of biodiesel and sulfur content on PM_2.5 emissions, engine dynamometer tests were performed on a Euro II engine to compare the PM_2.5 emissions from four fuels: two petroleum diesel fuels with sulfur contents of 50 and 100 ppm respectively, and two B20 fuels in which soy methyl ester (SME) biodiesel was added to each of the above mentioned petroleum diesel fuels (v/v: 80%/20% for petroleum diesel and SME respectively). Gaseous pollutants and PM_2.5 emissions were sampled with an AVL AMA4000 and Model 130 High-Flow Impactor (MSP Corp). Measurements were made of the PM_2.5 mass, organic carbon (OC), elemental carbon (EC) and the water-soluble ion distribution. The results showed that PM_2.5 emissions decreased with lower sulfur content or blending with SME biodiesel, and the decrease would be more by applying both two methods together. Particles of approximately 0.13 μm contributed 48–83% of PM_2.5 emissions. The impact of sulfur content on this percentage was different for low and high engine speed. The majority of PM_2.5 was comprised of OC and EC, and the carbon emission rate had the same trend as PM_2.5. Since the EC abatement of B20 was larger than OC, the OC/EC ratio of B20 was always larger than that of petroleum diesel. For petroleum diesel, the OC/EC increased with sulfur content, which was not the case for B20. The SO₄^2? had highest emission rate in the water-soluble ions of PM.     

Receptor Model Evaluation of the Southeast Michigan Ozone Study Ambient NMOC Measurements

Abstract

Large-scale studies like the Southeast Michigan Ozone Study (SEMOS) have focused attention on quantifying and spedating inventories for volatile organic compounds (VOCs). One approach for evaluating the accuracy of a VOC emission inventory is the development of a chemical mass balance (CMB) receptor model for ambient non-methane organic compound (NMOC) measurements. CMB evaluations of ambient hydrocarbon data provide a sample-specific allocation of emissions to individual source categories. This study summarizes the results of an application of the CMB model to the NMOC data from the SEMOS study. Comparison of CMB results with emission inventory values for the Detroit area show that vehicle emissions are well represented by the inventory, as are architectural coatings and coke ovens. Estimated emissions from petroleum refineries and graphic arts industries are much lower in the inventory than determined from the receptor allocation. Under-reporting of fugitive VOC emissions from petroleum refineries is an ongoing problem. Emissions from graphic arts industries are underestimated in the inventory partly because of the broad characterization of the emission factor (i.e., mass emitted/capita), which may be less useful when specific locations and days are under consideration. This study also demonstrates the effectiveness of the CMB approach when used prospectively to track the implementation of emission control strategies. While vehicle emission concentrations were unchanged from 1988 to 1993, measurement-based CMB results suggest a decrease in evaporative emissions during this time period resulting from Reid vapor pressure (RVP) reductions (from 11.0 psi in 1988 to 8.6 psi in 1993) and fleet turnover. Changes in emissions from coke plants and petroleum refineries were also seen in the CMB allocations for these sources.     

Source apportionment of sediment-associated aliphatic hydrocarbon in a eutrophicated shallow lake, China

Chaohu Lake, one of the most eutrophicated lakes in China, has been suffering from long-term outside pollution, urban sewage, river outflows, and agricultural runoff which expectedly have been the main contributors of hydrocarbons. However, the contributions from these various sources have not been specified. The present study is aimed at identifying the potential sources of hydrocarbons in surface sediment around the whole lake and assessing the relative contributions using principal components analysis?Cmultiple linear regression (PCA-MLR). Sixty-one surface sediments covering the whole Chaohu Lake and three main estuaries of inflowing rivers were collected, dried, extracted, and analyzed for 27 normal alkanes (n-alkanes, from C₁₂ to C₃₈, defined ??₂₇AH) and unresolved complex mixture (UCM) by GC/MS. Diagnostic ratios and PCA-MLR were utilized to apportion their sources. The concentrations of ??₂₇AH and UCM ranged from 434 to 3,870?ng/g and 11.9 to 325???g/g dry weight, respectively, for all samples. The concentrations of ??₂₇AH in western region and estuary of Nanfei River were slightly higher but without statistical significance than those from eastern region and estuaries of Yuxi River and Hangbu River. The concentration of UCM from western region was significantly higher than that obtained from eastern region. These results reflect the importance of input of urban runoff by Nanfei River and serious eutrophication in western region. Aliphatic hydrocarbons in Chaohu Lake were mainly derived from high plant wax with mixed sources of phytoplankton and petroleum. Weak microbial decomposition of n-alkanes would be expected to occur from the low ratios of isoprenoid hydrocarbons pristine (pri) and phytane (phy) to n-C₁₇ and n-C₁₈, respectively. Higher plant, fossil combustion, petroleum residue, and phytoplankton were proposed as the main origines of aliphatic hydrocarbons by PCA while the contributions of individual n-alkane homologues, pri and phy from the identified sources (31?% from higher plant, 30?% from fossil combustion, 26?% from petroleum, and 19?% from phytoplankton) were well predicted using MLR. The distribution profile and corresponding diagnostic ratios of normal alkanes show the promising potential as a useful proxy for estimating the source and loading of pollutants in Chaohu Lake.     

Comprehensive primary particulate organic characterization of vehicular exhaust emissions in France

A study to characterize primary particulate matter (PM_2.5 and PM₁₀) from the French vehicular fleet was conducted during winter 2008, in a tunnel in Marseille, France. The carbonaceous fraction represents 70% of the aerosol mass and elemental carbon fraction (EC) represent 60% of the carbonaceous fraction. The organic carbon OC was characterized in term of its water soluble fraction, functionalization rate and HULIS content. Seventy trace organic compounds including alkanes, polycyclic aromatic hydrocarbons (PAH), petroleum biomarkers and carboxylic acids were also quantified, in order to determine an organic emission profile for chemical mass balance modeling studies. Such source profiles were still missing in Europe and particularly in France. The profile obtained in this study is consistent with profiles determined in tunnel or dynamometer studies performed in other countries during the last ten years. These results suggest that organic compounds profiles from vehicular exhaust emissions are not significantly influenced by the geographic area and are thus suitable for use in aerosol source apportionment modeling applied across extensive regions. The chemical profile determined here is very similar to those obtained for diesel emissions with high concentrations of EC relative to OC (EC/OC = 1.8) and low concentrations of the higher molecular weight PAH. These results are consistent with the high proportion of diesel vehicles in the French fleet (49%).     

A Life-Cycle Comparison of Alternative Automobile Fuels

ABSTRACT

We examine the life cycles of gasoline, diesel, compressed natural gas (CNG), and ethanol (C₂H₅OH)-fueled internal combustion engine (ICE) automobiles. Port and direct injection and spark and compression ignition engines are examined. We investigate diesel fuel from both petroleum and biosources as well as C₂H₅OH from corn, herbaceous bio-mass, and woody biomass. The baseline vehicle is a gasoline-fueled 1998 Ford Taurus. We optimize the other fuel/powertrain combinations for each specific fuel as a part of making the vehicles comparable to the baseline in terms of range, emissions level, and vehicle lifetime. Life-cycle calculations are done using the economic input-output life-cycle analysis (EIO-LCA) software; fuel cycles and vehicle end-of-life stages are based on published model results.

We find that recent advances in gasoline vehicles, the low petroleum price, and the extensive gasoline infrastructure make it difficult for any alternative fuel to become commercially viable. The most attractive alternative fuel is compressed natural gas because it is less expensive than gasoline, has lower regulated pollutant and toxics emissions, produces less greenhouse gas (GHG) emissions, and is available in North America in large quantities. However, the bulk and weight of gas storage cylinders required for the vehicle to attain a range comparable to that of gasoline vehicles necessitates a redesign of the engine and chassis. Additional natural gas transportation and distribution infrastructure is required for large-scale use of natural gas for transportation. Diesel engines are extremely attractive in terms of energy efficiency, but expert judgment is divided on whether these engines will be able to meet strict emissions standards, even with reformulated fuel. The attractiveness of direct injection engines depends on their being able to meet strict emissions standards without losing their greater efficiency. Biofuels offer lower GHG emissions, are sustainable, and reduce the demand for imported fuels. Fuels from food sources, such as biodiesel from soybeans and C₂H₅OH from corn, can be attractive only if the co-products are in high demand and if the fuel production does not diminish the food supply. C₂H₅OH from herbaceous or woody biomass could replace the gasoline burned in the light-duty fleet while supplying electricity as a co-product. While it costs more than gasoline, bioethanol would be attractive if the price of gasoline doubled, if significant reductions in GHG emissions were required, or if fuel economy regulations for gasoline vehicles were tightened.