- Utilisation of biomass for the supply of energy carriers
Because biomass is a widely available, renewable resource, its utilisation for the production of energy has great potential for reducing CO2 emissions and thereby preventing global warming. In this mini-review the `state of the art' of several fermentation processes is discussed, starting with the most advanced process of ethanol production. This is followed by methane production, an established process for waste water purification which is gaining more attention because of the inherent energy production. Subsequently ABE fermentation is discussed and finally the biological production of hydrogen. The last section proposes a new way to assess and compare the different processes by relating their merit to `work content' values and `lost work' instead of the combustion values of their products. It is argued that, especially when dealing with energy from biomass, the application of this methodology will provide a uniform valuation for different processes and products. The described fermentation processes enable the supply of pure energy carriers, either gaseous or liquid, from biomass, yet the introduction of these processes is hampered by two major problems. The first is related to technological shortcomings in the mobilisation of fermentable components from the biomass. The second, having a much greater impact, is linked with socio-economics: until full externality costs are attributed to fossil fuels, accounting for their role in pollution and global warming, the competitiveness of the processes described here will hardly stand a chance.
- Hazardous Air Pollution from Mobile Sources: A Comparison of Alternative Fuel and Reformulated Gasoline Vehicles
Winebrake, JJ; Deaton, ML
Journal of the Air & Waste Management Association [J. Air Waste Manage. Assoc.], vol. 49, no. 5, pp. 576-581, May 1999
Although there have been several studies examining emissions of criteria pollutants from in-use alternative fuel vehicles (AFVs), little is known about emissions of hazardous air pollutants (HAPs) from these vehicles. This paper explores HAP tailpipe emissions from a variety of AFVs operating in the federal government fleet and compares these emissions to emissions from identical vehicles operating on reformulated gasoline. Emissions estimates are presented for a variety of fuel/model combinations and on four HAPs (acetaldehyde, 1,3-butadiene, benzene, and formaldehyde). The results indicate that all AFVs tested offer reduced emissions of HAPs, with the following exceptions: ethanol fueled vehicles emit more acetaldehyde than RFG vehicles, and ethanol- and methanol-fueled vehicles emit more formaldehyde than RFG vehicles. The results from this paper can lead to more accurate emissions factors for HAPs, thus improving HAP inventory and associated risk estimates for both AFVs and conventional vehicles.
- Ozone-Forming Potential of Reformulated Gasoline
NATIONAL ACADEMY PRESS, 1999, 200 pp.
This study by a committee of the National Research Council was undertaken to examine the differences between the oxygen additives ethanol and methyl tertiary-butyl ether (MBTE) used in reformulated gasoline in the U.S. with the goal of reducing ozone pollution. The report finds that neither oxygen additive has a significant role in reducing ozone, a major component of smog. The Clean Air Act amendments of 1990 require the use of reformulated gasoline with oxygen additives in areas of the U.S. that have substantial ozone pollution; however, the oxygen additives in these gasolines have raised environmental concerns. The report notes that ozone-forming motor vehicle emissions have decreased in recent years, mainly because of improved equipment and more stringent air quality regulations.
- Alternative Fuel Motor vehicle tailpipe and evaporative emissions composition and ozone potential
Journal of the Air & Waste Management Association [J AIR WASTE MANAGE ASSOC], vol. 48, no. 7, pp. 578-591, Jul 1998
The 1988 Alternative Motor Fuels Act and the 1990 Clean Air Act Amendments require examination of the potential to favorably influence air quality by changing the composition of motor vehicle fuels. Motor vehicle tailpipe and evaporative emissions were characterized using laboratory simulations of roadway driving conditions and a variety of vehicle-fuel technologies (reformulated gasoline (RFG), methanol (M85), ethanol (E85), and natural gas (CNG)). Speciated organic compound (with Carter MIR ozone potential), CO, and NO sub(x) emission rates and fuel economy were characterized. The Carter MIR ozone potential of combined Federal Test Procedure (FTP) tailpipe and evaporative emissions was reduced more than 90% with CNG relative to RFG, M85, and E85 fuels. FTP toxic compound emissions (benzene, formaldehyde, acetaldehyde, and 1,3-butadiene) were greater with M85 and E85 fuels than with RFG fuel, and less with CNG fuel than RFG fuel. The most abundant toxic compound was benzene with RFG fuel, formaldehyde with M85 fuel, and acetaldehyde with E85 fuel. FTP MPG fuel economies were reduced with M85 and E85 fuels relative to RFG fuel, consistent with their lower BTU/gal. Energy efficiencies (BTU/mi) were improved with all the alternative fuels relative to RFG. Carter MIR ozone potential was generally reduced with the alternative fuels relative to RFG fuel under REP05 (high speeds and acceleration rates) driving conditions (most significantly with CNG). Toxic aldehyde emissions were reduced under REP05 conditions relative to FTP conditions with all the tested fuels, and toxic benzene emissions were elevated under high acceleration conditions.
Hartley, WR; Englande, AJJr; Harrington, DJ
Water Science & Technology [Water Sci Technol], vol. 39, no. 10, pp. 305-310, 1999
Methyl tertiary butyl ether (MTBE), a volatile oxygenate commonly used in fuels, is a frequent contaminant of some shallow groundwater. Based on limited reporting, concentrations of MTBE in drinking water were generally less than 10 mu g/L but excursions up to 770 mu g/L have been reported. Based on current MTBE toxicological data with emphasis on carcinogenic potential, and reproductive and developmental effects, a maximum drinking water level of 100 mu g MTBE/L is suggested. This recommended advisory level takes into consideration the equivocal evidence of the carcinogenicity of MTBE in humans and low potency in an oral exposure animal study. Definitive conclusions regarding health risks to the general population from MTBE contamination of drinking water are not possible due to a paucity of monitoring data. There is increased evidence of contamination of storm water and shallow groundwater from primarily, nonpoint sources. Considering MTBE mobility and stability in water, movement to deep groundwater and drinking water supplies seems probable. In light of projected increased MTBE use, there is a need for a more rigorous monitoring program to define the frequency of MTBE contamination of drinking water supplies and to develop risk management policies.
- Drinking water advisory: Consumer acceptability advice and health effects analysis on methyl/tertiary-butyl ether (MtBE)
US EPA, WASHINGTON, D.C. (USA), Dec 1997, 48 pp.
MtBE is a volatile, organic chemical. Since the late 1970's, MtBE has been used as an octane enhancer in gasoline. MtBE promotes more complete burning of gasoline, thereby reducing carbon monoxide and ozone levels. Hence, MtBE is commonly used as a gasoline additive in localities that participate in the Winter Oxygenated Fuels program and/or the Reformulated Gasoline program to achieve or maintain compliance with the National Ambient Air Quality Standards. A limited number of instances of significant contamination of drinking water with MtBE have occurred due to leaks from underground and above ground petroleum storage tank systems and pipelines. MtBE, due to its small molecular size and solubility in water, moves rapidly into groundwater, faster than other constituents of gasoline. Public and private wells have been contaminated in this manner. Nonpoint sources, such as recreational watercraft, are most likely to be the cause of small amounts of contamination of surface waters. Air deposition through precipitation of industrial or vehicular emissions may also contribute to surface and ground water contamination. The extent of any potential for build-up in the environment from such deposition is uncertain.
To assess the health benefits gained from the use of cleaner burning gasoline, an analysis was conducted of changes in the atmospheric concentration of eight VOCs: acetaldehyde, benzene, 1,3-butadiene, ethylbenzene, formaldehyde, POM, toluene, and xylenes resulting from the use of reformulated gasoline and oxyfuel containing the additive MTBE. Modeled ambient air concentrations of VOCs were used to assess three seasonally-based scenarios: baseline gasoline compared to (a) summer MTBE:RFG, (b) winter MTBE:RFG, and (c) MTBE oxyfuel. The model predicts that the addition of MTBE to RFG or oxyfuel will decrease acetaldehyde, benzene, 1,3-butadiene and POM, but increase formaldehyde tailpipe emissions. The increased formaldehyde emissions, however, will be offset by the reduction of formaldehyde formation in the atmosphere from other VOCs. Using a range of plausible risk estimates, the analysis predicts a positive health benefit, i.e., a decline in cancer incidence associated with use of MTBE:RFG and MTBE oxyfuel. Using EPA cancer risk estimates, reduction in 1,3-butadiene exposure accounts for the greatest health benefit while reduction of benzene exposure accounts for the greatest health benefits based on alternative risk estimates. An analysis of microenvironment monitoring data indicates that most exposures to VOCs are significantly below levels of concern based on established margin-of-safety standards. The analysis does suggest, however, that health effects associated with short-term exposures to acetaldehyde and benzene may warrant further investigation.
Stern, BR; Kneiss, JJ*
Journal of Applied Toxicology [J. APPL. TOXICOL.], vol. 17, no. 1 Suppl., pp. S1-S2, May 1997
Oxygenates are liquid fuel compounds that add oxygen to gasoline and help reduce harmful gasoline emissions, while expanding the total available supply of motor fuels in the USA. The widespread use of fuels reformulated with oxygenates is a major step toward developing a sustainable, clean transportation fuel for the 21st century. Despite improvements in motor vehicle technology over the past 25 years, cars and trucks remain a major source of air pollution in the USA. The development of reformulated fuels is part of a comprehensive national strategy for reducing motor vehicle pollution, as described in the 1990 Clean Air Act Amendments. Oxygenates are currently used in more than 30% of the US gasoline pool. By the end of the century, this figure is expected to reach as much as 70%. For nearly a century, the composition of gasoline in the USA has remained essentially unchanged. From the early 1900s until the introduction of unleaded gasoline in the early 1980s, the composition of gasoline was basic hydrocarbon gasoline plus a lead additive to increase octane rating, with seasonal vapor pressure adjustments for both winter and summer temperatures. However, during the past decade, gasoline producers in cooperation with federal and state agencies have been developing reformulated gasolines which are intended to reduce harmful pollution, and sustain engine performance, good driveability and consumer acceptance. (DBO)
- Alveolar breath sampling and analysis to assess exposures to methyl tertiary butyl ether (MTBE) during motor vehicle refueling
Lindstrom, AB; Pleil, JD
Journal of the Air & Waste Management Association [J. AIR WASTE MANAGE. ASSOC.], vol. 46, no. 7, pp. 676-682, 1996
Methyl tertiary butyl ether (MTBE) is added to gasoline (15% by volume) in many areas of the U.S. to help control carbon monoxide emissions from motor vehicles. In this study we present a sampling and analytical methodology that can be used to assess consumer's exposures to MTBE that may result from routine vehicle refueling operations. The method is based on the collection of alveolar breath samples using evacuated one-liter stainless steel canisters and analysis using a gas chromatograph-mass spectrometer equipped with a patented "valveless" cryogenic preconcentrator. To demonstrate the utility of this approach, a series of breath samples was collected from two individuals (the person pumping the fuel and a nearby observer) immediately before and for 64 min after a vehicle was refueled with premium grade gasoline. Results demonstrate low levels of MTBE in both subjects' breaths before refueling, and levels that increased by a factor of 35 to 100 after the exposure. Breath elimination models fitted to the post exposure measurements indicate that the half-life of MTBE in the first physiological compartment was between 1.3 and 2.9 min. Analysis of the resulting models suggests that breath elimination of MTBE during the 64 min monitoring period was approximately 115 mu g for the refueling subject while it was only 30 mu g for the nearby observer. This analysis also shows that the post exposure breath elimination of other gasoline constituents was consistent with previously published observations.
- Comparing the health benefits and risks of methyl-tertiary-butyl ether (MTBE) in reformulated gasoline (RFG) and winter oxyfuels in the U.S.
In the U.S., air pollution from automobile emissions has been responsible for numerous adverse consequences on health, including increased incidences of cardiovascular incidents, upper-respiratory distress, and an increase in the risk of cancer. Other industrialized nations have realized the same consequences to varying degrees. Because questions have arisen regarding the safety of MTBE and the effectiveness of MTBE in moving communities closer to compliance with standards, extensive scientific analyses were undertaken in order to provide the scientific community, legislators, authorities, and the public with the most recently available information regarding: (1) human health benefits from the reduction of air pollutants associated with MTBE use; (2) human exposure to MTBE and related compounds; (3) MTBE's potential for causing adverse health effects; and (4) a comparison of MTBE health effects and exposure concentrations causing them, for baseline fuel, MTBE alone, and MTBE in fuel.(DBO)
- Health effects of oxygenated fuels
ENVIRON. HEALTH PERSPECT. SUPPL., vol. 101, no. 6, pp. 151-160, 1993
The use of oxygenated fuels is anticipated to increase over the next decades. This paper reviews the toxicological and exposure information for methyl tertiary-butyl ether (MTBE), a fuel additive, and methanol, a replacement fuel, and discusses the possible health consequences of exposure of the general public to these compounds. For MTBE, the health effects information available is derived almost exclusively from rodent studies, and the exposure data are limited to a few measurements at some service stations. Based on these data, it appears unlikely that the normal population is at high risk of exposure to MTBE vapor. However, in the absence of health and pharmacokinetic data in humans or in nonhuman primates, this conclusion is not strongly supported. Similarly, there are a number of uncertainties to take into consideration in estimating human risk from the use of methanol as a fuel.
- Effect of reformulated diesel fuel on unregulated emissions of light duty vehicles
Rantanen, Leena; Juva, Ari; Niemi, Aapo; Mikkonen, Seppo; Aakko, Paivi; Lappi, Maija
SAE SPEC PUBL, SAE, WARRENDALE, PA, (USA), 1996, vol. 1206, pp. 1-14,
The implementation of strict emission control regulations led to a series of experiments aimed at evaluating the effects of diesel fuel reformulation on the emission behavior of both direct injection and indirect injection light duty vehicles. Three reformulated grade diesel fuels and two EN590 specification fuels were tested for Finnish-made vehicles fabricated between 1982 and 1992 using the US Federal light duty exhaust emission test procedures and the European exhaust emission test procedures. Results show that NO sub(x) emission is not affected by fuel reformulation. However, the data show that reformulation reduces particulate emissions in catalyst-based vehicles and non-catalyst vehicles by as much as 40% and 60%, respectively.
- Projection of health benefits from ambient ozone reduction related to the use of methyl tertiary butyl ether (MTBE) in the reformulated gasoline program
Erdal, S; Gong, H Jr; Linn, WS; Rykowski, R
Risk Analysis [Risk Anal.], vol. 17, no. 6, pp. 693-704, Dec 1997
To estimate potential public health benefits from ozone (O sub(3)) pollution reduction attributable to the use of methyl tertiary-butyl ether (MTBE) in gasoline, O sub(3) dose-response estimates from the biomedical literature were combined with model estimates of O sub(3) reduction. Modeling employed EPA MOBILE5a and Complex models to predict emission changes, industry AQIRP techniques to predict ambient O sub(3) changes, and the National Exposure Model to predict human exposures. Human health effects considered were lung function decrements and respiratory irritant symptoms (using dose-response functions measured in laboratory and field studies), and increased death rates (using concentration-response functions inferred statistically from public-health data). Other reported health effects, such as lung inflammation, increases in asthma attacks, and hospitalizations, were not addressed because of inadequate dose-response information. Even for the health responses considered, quantitation of improvements due to MTBE use is problematical, because MTBE affects only a small percentage of existing O sub(3) pollution, and because exposure-response relationships are not well understood for population subgroups most likely to be affected. Nevertheless, it is reasonable to conclude that even small MTBE-associated reductions in peak ambient O sub(3) levels (1-5 ppb, according to model estimates) should yield considerable public health benefits. Tens of millions of Americans are potentially exposed to O sub(3) in the concentration range associated with health effects. Even if only a small percentage of them are susceptible, any incremental reduction in O sub(3) (as with MTBE use) must mitigate or prevent effects for a meaningful number of people. Better quantitative estimates of benefit must await a more detailed understanding of each link in the chain of causation.
Barker, James F
IAHS Publication (International Association of Hydrological Sciences) [IAHS PUBL], no. 250, pp. 197-203, 1998
Natural attenuation by dispersion, sorption and biodegradation can provide adequate remediation of some organic contaminants in some groundwater environments. A significant problem with this approach for gasoline-impacted groundwater is the chemical methyl-tert-butyl-ether (MTBE). Uncertainty about the biodegradation of MTBE makes natural attenuation difficult to apply. A field experiment with coal tar creosote organics was able to clearly document the extent of biodegradation because the source mass was known and monitoring was extensive. Applying remediation by natural attenuation at a field site where naphthalene was the major contaminant was far less certain. Natural, in situ biodegradation processes can be enhanced with semi-passive methods. Field experiments dealing with denitrification of naphthalene and with a mixed plume of chlorinated solvents and toluene illustrate the promise of these technologies. It appears that remediation of organic contaminants in groundwater is moving away from aggressive, engineered remediation to semi-passive or natural attenuation approaches where risk reduction goals can still be met.
- Carcinogenicity studies on MTBE: Critical review and interpretation
Risk Analysis [Risk Anal.], vol. 17, no. 6, pp. 673-682, Dec 1997
Chronic inhalation of toxic concentrations of MTBE caused renal tubular cell neoplasms in male Fischer 344 rats and hepatocellular adenomas in female CD-1 mice. In Sprague-Dawley rats the oral administration of MTBE was associated with increased incidences of Leydig cell tumors and of lymphomas and leukemias (combined) in males and females, respectively. Neither lymphomas nor leukemias were individually increased in treated females. Leydig cell tumors are common in rats and do not predict human responses to drugs and chemicals. Neither MTBE nor its metabolite, t-butyl alcohol, possess mutagenic potential and a second metabolite, formaldehyde, is mutagenic in vitro but in vivo results are equivocal. MTBE-induced neoplasms are most likely produced through a nongenetic mechanism which requires chronic exposure to toxic doses. Because of the intense odor (and taste) of MTBE, humans will not tolerate either air or water concentrations sufficient to produce the cytotoxic precursors required to promote cellular proliferation.
- Risk characterization of methyl tertiary butyl ether (MTBE) in tap water
Stern, BR; Tardiff, RG
Risk Analysis [Risk Anal.], vol. 17, no. 6, pp. 727-744, Dec 1997
Methyl tertiary butyl ether (MTBE) can enter surface water and groundwater through wet atmospheric deposition or as a result of fuel leaks and spills. About 30% of the U.S. population lives in areas where MTBE is in regular use. Ninety-five percent of this population is unlikely to be exposed to MTBE in tap water at concentrations exceeding 2 ppb, and most will be exposed to concentrations that are much lower and may be zero. About 5% of this population may be exposed to higher levels of MTBE in tap water, resulting from fuel tank leaks and spills into surface or groundwater used for potable water supplies. This paper describes the concentration ranges found and anticipated in surface and groundwater, and estimates the distribution of doses experienced by humans using water containing MTBE to drink, prepare food, and shower/bathe. The toxic properties (including potency) of MTBE when ingested, inhaled, and in contact with the skin are summarized. Using a range of human toxic potency values derived from animal studies, margins of exposure (MOE) associated with alternative chronic exposure scenarios are estimated to range from 1700 to 140,000. Maximum concentrations of MTBE in tap water anticipated not to cause adverse health effects are determined to range from 700 to 14,000 ppb. The results of this analysis demonstrate that no health risks are likely to be associated with chronic and subchronic human exposures to MTBE in tap water. Although some individuals may be exposed to very high concentrations of MTBE in tap water immediately following a localized spill, these exposures are likely to be brief in duration due to large-scale dilution and rapid volatilization of MTBE, the institution of emergency response and remediation measures to minimize human exposures, and the low taste and odor thresholds of MTBE which ensure that its presence in tap water is readily detected at concentrations well below the threshold for human injury.
- A physiologically-based pharmacokinetic model assessment of methyl t-butyl ether in groundwater for a bathing and showering determination
Risk Analysis [RISK ANAL.], vol. 17, no. 5, pp. 583-598, Oct 1997
Methyl t-butyl ether (MTBE) is a gasoline additive that has appeared in private wells as a result of leaking underground storage tanks. Neurological symptoms (headache, dizziness) have been reported from household use of MTBE-affected water, consistent with animal studies showing acute CNS depression from MTBE exposure. The current research evaluates acute CNS effects during bathing /showering by application of physiologically-based pharmacokinetic (PBPK) techniques to compare internal doses in animal toxicity studies to human exposure scenarios. An additional reference point was the delivered dose associated with the acute Minimum Risk Level (MRL) for MTBE established by the Agency for Toxic Substances and Disease Registry. A PBPK model for MTBE and its principal metabolite, t-butyl alcohol (TBA) was developed and validated against published data in rats and humans. PBPK analysis of animal studies showed that acute CNS toxicity after MTBE exposure can be attributed principally to the parent compound since the metabolite (TBA) internal dose was below that needed for CNS effects. The PBPK model was combined with an exposure model for bathing and showering which integrates inhalation and dermal exposures. This modeling indicated that bathing or showering in water containing MTBE at 1 mg/L would produce brain concentrations similar to 1000-fold below the animal effects level and twofold below brain concentrations associated with the acute MRL. These findings indicate that MTBE water concentrations of 1 mg/L or below are unlikely to trigger acute CNS effects during bathing and showering. However, MTBE's strong odor may be a secondary but deciding factor regarding the suitability of such water for domestic uses.
This paper presents information on the ways in which people can be exposed to methyl tert-butyl ether (MTBE) via air and water and on the distribution of doses that can result from those exposures. Data on concentrations of MTBE in air were compiled for 15 different occupational, commuting, or residential exposure categories, and concentrations in potable water were compiled from five states in the MTBE-using areas of the United States. Based on these concentrations and characteristics of the exposed populations, average daily and lifetime average doses were estimated. Both the concentration data and several of the population characteristics were estimated as distributions rather than as point values so that the numbers of people exposed at various levels could be estimated. Arithmetic mean occupational doses via air were in the range of 0.1 to 1.0 mg/kg-day, while doses from residential exposures, commuting, and refueling were in the range of 0.0004 to 0.006 mg/kg-day. Lifetime doses for workers were in the range 0.01 to 0.1 mg/kg-day. The cumulative dose distribution for the entire population of the MTBE-using regions of the United States was estimated by combining the distributions of doses and the numbers of people in each exposure category. In the MTBE-using areas, arithmetic mean doses via air were estimated to be 0.0053 and 0.00185 mg/kg-day for the chronic and lifetime cases, respectively. Approximately 98.5% of the population living in MTBE-using regions uses water with concentrations affected only by atmospheric deposition, if at all, and too low to be detected with current methods (<2 mu g/liter). The remaining population uses water with an estimated geometric mean concentration of 0.36 mu g/liter, an arithmetic mean concentration of 49 mu g/l, and a 95th percentile concentration of 64 mu g/liter. Doses via ingestion, inhalation, and dermal absorption were included. The estimated arithmetic mean dose for the population exposed via water was 1.4 X 10 super(-3) mg/kg-day.
- Changes in disease rates in Philadelphia following the introduction of oxygenated gasoline
Southeastern Pennsylvania and southern New Jersey participated in the oxygenated fuel program in the winters of 1992-93 and 1993-94. Since January 1995 we have had reformulated gasoline (RFG) continuously. With one exception, all of the oil companies used exclusively MTBE as the oxygenate. Motivated by unusual symptoms that I experienced in synchrony with this program, I have been investigating changes in certain disease rates. Data from Public Health Clinics indicate substantial increases from 1993 through 1995 in six diseases responsive to irritant chemicals in the air. Normalized data on visits show asthma up 34%, winter rhinitis up 38%, conjunctivitis up 57%, otitis up 30%, chronic sinusitis up 60%, and dyspnea up 121%, all with a high level of statistical significance. Data from one school 40 miles west of Philadelphia, in the OG-RFG region, showed a doubling in asthma prevalence between October 1992 and October 1993. Data on feline asthma also show doubling from 1992 through 1995. Recent data from two asthma specialists suggest asthma prevalence is greater than 25% among minority children in the Philadelphia schools. It is suggested that an unidentified combustion product of MTBE in gasoline may be causing this problem, since existing automobile exhaust speciation studies are incomplete, with roughly 5% 'unidentified hydrocarbons'. One possible product, tert-butyl formate (TBF), is apparently an extremely powerful respiratory irritant. To date, no measurements of ambient TBF are available. Ozone data show no evidence for any large increase sufficient to explain these results. Ozone exceedences in southeastern Pennsylvania in 1995 and 96 were only slightly greater than during 1993 and 94. Average summer ozone concentrations, when plotted versus average summer temperature for summers of 1993 through 1996 show no evidence for reduction of ozone during the latter two years. Directions for further research are suggested.
Studies of the toxicology of methyl tertiary butyl ether (MTBE) were reviewed as a possible information base for evaluating the health effects of evaporative emissions from reformulated gasoline (RFG). The major metabolites of the oxidative demethylation of MTBE in vivo were methanol and tertiary butyl alcohol (TBA), whereas formaldehyde and TBA were the principal products of hepatic microsomal oxidation by cytochrome P-450. Pharmacokinetic studies in rats treated with intragastric MTBE in corn oil gave an initial disposition T sub(1/2) for MTBE of 0.32 h. The decline in the serum drug versus time curve for MTBE in rats was accompanied by a progressive increase in serum methanol concentrations to levels more than 50-200 times those of the parent compound. Repeated exposure of MTBE vapor by inhalation in rats resulted in dose-dependent increases in MTBE in the blood, brain, and adipose tissue compartments. Blood concentrations of TBA were also dose dependent and provided an estimate of the total amount of MTBE distributed to peripheral drug metabolizing compartments. Perirenal fat/blood MTBE concentration ratios ranged from 9.7 to 11.6 after 15 wk of intermittent exposure. During an oxyfuels program in Fairbanks, AK, blood levels of occupationally exposed workers were 0.2-31.5 mu g/L MTBE and 1.6 to 72.2 mu g/L TBA with a mean TBA : MTBE blood concentration ratio of 4.2. In patients who received MTBE by percutaneous, transhepatic puncture for the dissolution of cholesterol gallstones, concentrations of MTBE in fat tissue reached 60 and 300 mu g/g at a treatment time when mean blood MTBE was less than 20 mu g/ml. The results of laboratory and clinical studies indicate that metabolites of MTBE may contribute to the nephropathy, neoplasms, and other pathological changes associated with repeated exposure to MTBE in experimental animals. It is concluded that such studies can provide a well-defined database for quantitatitive safety comparisons and health risk-benefit analyses of MTBE and other oxygenates in RFG.
Long, G; Meek, ME; Savard, S
J. ENVIRON. SCI. HEALTH, PART C: ENVIRON. CARCINOG. ECOTOXICOL. REV., vol. C12, no. 2, pp. 389-395, 1994
"Methyl tertiary-butyl ether" (MTBE) is included on the List of Priority Substances to be assessed under the Canadian Environmental Protection Act (CEPA). Based on the lack of identified relevant data, MTBE is considered "unclassifiable with respect to carcinogenicity in humans". Although few data on concentrations in environmental media were identified, based upon levels of MTBE in ambient air and water predicted by fugacity modelling and limited information on concentrations in shellfish, the estimated average intake of MTBE for the most exposed age group in the general population in Canada is much less (by approximately 45 000 times) than the tolerable daily intake derived on the basis of data from bioassays in animal species.
- The effect of ethanol fuel on the emissions of vehicles over a wide range of temperatures
Knapp, KT; Stump, FD; Tejada, SB
Journal of the Air & Waste Management Association [J. Air Waste Manage. Assoc.], vol. 48, no. 7, pp. 646-653, Jul 1998
The emissions from a fleet of 11 vehicles, including three from the State of Alaska, were tested at 75, 0, and -20 degree F with base gasolines and E10 gasolines, that is, gasolines with 10% by volume ethanol added. The data for the changes in emissions for the test run at 75 degree F are included, since most other studies on the effects of E10 gasoline on emissions were run at that temperature. The three Alaskan vehicles were also tested at 20 degree F. The testing followed the Federal Test Procedure, and regulated emissions - CO, total hydrocarbons (THC), and nitrogen oxides (NO sub(x)) - CO sub(2), speciated organics, and fuel economy were measured. A total of 490 FTP tests were run. The data obtained indicated that with most vehicles, at the temperatures tested, improvements in both CO and THC emissions were obtained with the use of E10 fuel. At the lowest temperature used, -20 degree F, most vehicles had an increase in NO sub(x) emissions with the use of E10 fuel. At the other temperatures, however, more vehicles showed a decrease in NO sub(x) emissions with the use of E10. With all vehicles at all temperatures tested, the emissions of acetaldehyde increased significantly when E10 fuel was used. The highest increase was about 8 to 1. Benzene, formaldehyde, and 1,3 butadiene showed both increases and decreases in the emissions when using E10 fuel. Unexpected results were obtained with the fuel economy, with about half of the tests showing an increase in fuel economy with the use of E10 fuel.
AIR & WASTE MANAGEMENT ASSOCIATION, PITTSBURGH, PA 15222 (USA), 1997, [np]
Although there have been several studies examining emissions from in-use alternative fuel vehicles (AFVs), little is known about the deterioration of these emissions over vehicle lifetimes and how this deterioration compares with deterioration from conventional vehicles (CVs). This paper analyzes emissions data from 70 AFVs and 70 CVs operating in the federal government fleet to determine whether AFV emissions deterioration differs significantly from CV emissions deterioration. We conduct our analysis on three alternative fuel types (natural gas, methanol, and ethanol) and on five pollutants (carbon monoxide, carbon dioxide, total hydrocarbons, non-methane hydrocarbons, and nitrogen oxides). We find that for most cases we studied, deterioration differences are not statistically significant; however, several exceptions suggest that air quality planners and regulators must further analyze AFV emissions deterioration in order to properly include these technologies into broader air quality management schemes.
Concern over the increasing concentration of CO sub(2) in the Earth's atmosphere is causing us to re-evaluate how we use energy. In particular, we need to inquire if there are alternative energy systems which discharge less net CO sub(2) per unit of energy service. This paper deals with the CO sub(2) fluxes associated with the use of one biomass fuel, ethanol derived from corn. In a sustainable agricultural system, there is no net CO sub(2) flux to the atmosphere from the corn itself but there is a net CO sub(2) flux due to the fossil-fuel supplements currently used to produce and process corn. A comparison between ethanol from corn and gasoline from crude oil becomes very complex because of the variability of corn yield, the lack of available data on corn processing, and the complexity of treating the multiple products from corn processing. When the comparison is made on an energy content basis only, with no consideration of how the products are to be used, and at the margin of the current U.S. energy system, it appears that there is a net CO sub(2) saving associated with ethanol from corn.
- Determining emissions characteristics of in-use alternative fuel vehicles: a comparison of natural gas and reformulated gasoline vehicles
Deaton, Michael L; Winebrake, James J
PROC A WASTE MANAGE ASSOC ANNU MEET EXHIB, AIR & WASTE MANAGEMENT ASSOC, PITTSBURGH, PA, (USA), 1998, 10ppp,
New regulations and incentives are encouraging the use of clean, alternative fuel vehicles (AFVs) in urban areas. These vehicles are seen as one option for reducing air pollution from mobile sources. However, due to the limited number of AFVs on the road, little is known about actual emissions characteristics of in-use AFVs. This paper evaluates the emissions characteristics of in-use natural gas vehicles (NGVs) operating in the United States federal government fleet. Carbon monoxide (CO), nitrogen oxide (NOx), non-methane hydrocarbon (NMHC), and carbon dioxide (CO sub(2)) emissions from these NGVs are compared to control vehicles operating on reformulated gasoline. This study applies an analysis of covariance model that takes into account emissions deterioration and individual vehicle variability. Our results suggest that NGVs are generally cleaner than conventional vehicles; however, in the case of NOx and NMHC, emissions benefits are reduced over the lifetime of the vehicle due to higher NGV emissions deterioration rates.
- A comparative analysis of emissions deterioration for in-use alternative fuel vehicles
Winebrake, JJ; Deaton, ML
Journal of the Air & Waste Management Association [J. Air Waste Manage. Assoc.], vol. 47, no. 12, pp. 1291-1296, Dec 1997
Although there have been several studies examining emissions from in-use alternative fuel vehicles (AFVs), little is known about the deterioration of these emissions over vehicle lifetimes and how this deterioration compares with deterioration from conventional vehicles (CVs). This paper analyzes emissions data from 70 AFVs and 70 CVs operating in the federal government fleet to determine whether AFV emissions deterioration differs significantly from CV emissions deterioration. An analysis is conducted on three alternative fuel types (natural gas, methanol, and ethanol) and on four pollutants (carbon monoxide, total hydrocarbons, non-methane hydrocarbons, and nitrogen oxides). The results indicate that for most cases studied, deterioration differences are not statistically significant; however, several exceptions (most notably with natural gas vehicles) suggest that air quality planners and regulators must further analyze AFV emissions deterioration to properly include these technologies in broader air quality management schemes.
- Evaluating the environmental impact of alternative-fuel vehicles
Using a dynamic microsimulation model, I investigate total emissions in the Los Angeles area as electric, compressed natural gas (CNG), and methanol vehicles are introduced under various pricing conditions. Price reductions for alternative-fuel vehicles lead to reductions in total emissions despite the usage tradeoffs that households make between limited-range vehicles and older gasoline vehicles. Price reductions for CNG vehicles are as effective at reducing emissions as price reductions for electric vehicles. Overall, the introduction of CNG and methanol vehicles lead to health benefits of between $20 and $120 million (depending upon the year) while the introduction of electric vehicles brings additional benefits of between $3.5 and $70 million per year.
Journal of the Air & Waste Management Association [J. AIR WASTE MANAGE. ASSOC.], vol. 45, no. 10, pp. 770-777, 1995
This study examines exhaust emissions from 11 vehicles tested on compressed natural gas, liquefied petroleum gas, methanol, ethanol, and reformulated gasoline fuels (22 vehicle/fuel combinations). The paper highlights ozone precursor and toxic emissions. Emission rates from some of the presumably well-maintained, low-mileage test vehicles were higher than expected, but fuel effects were consistent with findings of similar studies. Aggregate toxic and non-methane organic emission rates from the variable/flexible fuel vehicles were higher with alcohol fuels than with reformulated gasoline. Lower specific reactivities for emissions with the alcohol fuels offset this negative trait. Specific reactivities of the organic emissions with the alternative fuels were consistently lower than those with the gasoline blends. Compressed natural gas and liquefied petroleum gas fuels had the lowest values. Although specific reactivities were expected to vary from fuel-to-fuel, they also varied considerably from vehicle-to-vehicle.
- Potential air quality effects of using ethanol-gasoline fuel blends: A field study in Albuquerque, New Mexico
Gaffney, JS; Marley, NA; Martin, RS; Dixon, RW; Reyes, LG; Popp, CJ
Environmental Science and Technology [ENVIRON. SCI. TECHNOL.], vol. 31, no. 11, pp. 3053-3061, Nov 1997
The use of alternate fuels has been proposed as a method of improving urban air quality by reducing combustion-related pollution. One such program mandates the use of oxygenates in the wintertime to reduce CO emissions in cities such as Albuquerque, NM. A field study was conducted in Albuquerque to determine the atmospheric impacts of the use of ethanol fuels. Atmospheric concentrations of ozone, oxides of nitrogen, CO, peroxyacetyl nitrate (PAN), aldehydes, and organic acids were measured in the summer of 1993, before the use of ethanol fuels, and in the winters of 1994 and 1995, during the use of 10% ethanol fuel (>99%). Data showed increased levels of peroxyacetyl nitrate (PAN) and aldehydes in winter. The formaldehyde/acetaldehyde ratio was 1.4, indicating an anthropogenic source, and PAN and acetaldehyde levels were anti-correlated over short time periods, indicating primary acetaldehyde emissions. A comparison of data taken at rural sites south of the city indicates that although there is a significant anthropogenic component to the aldehyde concentrations during the winter, there are also contributions from the photochemical oxidation of natural hydrocarbons.
- Greenhouse gas emission impacts of alternative-fueled vehicles: Near-term vs. long- term technology options
20 May 1997
Alternative-fueled vehicle technologies have been promoted and used for reducing petroleum use, urban air pollution, and greenhouse gas emissions. In this paper, greenhouse gas emission impacts of near-term and long-term light-duty alternative- fueled vehicle technologies are evaluated. Near- term technologies, available now, include vehicles fueled with M85 (85% methanol and 15% gasoline by volume), E85 (85% ethanol that is produced from corn and 15% gasoline by volume), compressed natural gas, and liquefied petroleum gas. Long- term technologies, assumed to be available around the year 2010, include battery-powered electric vehicles, hybrid electric vehicles, vehicles fueled with E85 (ethanol produced from biomass), and fuel-cell vehicles fueled with hydrogen or methanol. The near-term technologies are found to have small to moderate effects on vehicle greenhouse gas emissions. On the other hand, the long-term technologies, especially those using renewable energy (such as biomass and solar energy), have great potential for reducing vehicle greenhouse gas emissions. In order to realize this greenhouse gas emission reduction potential, R and D efforts must continue on the long-term technology options so that they can compete successfully with conventional vehicle technology.
- Can alternative car fuels reduce greenhouse gas emissions?
There has been controversy in the published literature regarding the scope for alternative fuels to reduce greenhouse gas emissions in passenger transport. This paper aims to resolve this question in an Australian context, and, where possible, to calculate the costs of emission reductions. Fossil-fuel-based alternatives give either marginal or uncertain reductions. Ethanol from sugar cane, the most promising biomass fuel, has high costs per tonne of CO sub(2) reduction, and, when other trace gases are considered, shows no definite improvement over petrol. Electric vehicles, if deployed today in Australia, would exacerbate greenhouse warming. Only if an alternative new energy source such as wind power generated 15% or more of total electricity would emission reductions occur compared to equivalent petrol-fuelled cars.
Goodman, Barbara J; Wyman, Charles E
PREPR DIV PET CHEM AM CHEM SOC., ACS, BOOKS & JOURNALS DIVISION, WASHINGTON, DC (USA), 1993, vol. 38, no. 2, pp. 300-303,
Domestic transportation fuels are almost exclusively (about 97%) derived from petroleum and account for about 64% of the total petroleum used in the United States. With OPEC controlling 75% of the world's oil reserves and approximately 50% of all petroleum used in the United States being imported, our nation is extremely vulnerable to supply disruptions. In addition, petroleum imports can account for about 40% of the U.S. balance-of-payment deficit, making us economically dependent. Air quality problems such as smog formation and carbon dioxide pollution result from use of gasoline in automobiles in many cities. Also, some experts predict that global climate change will result from carbon dioxide accumulation caused by burning petroleum and other fossil fuels. More and more agricultural land is being idled as crop productivity increases, resulting in a loss of agricultural income and employment. Few substitutes are currently available for petroleum-based transportation fuels. In recent years, however, interest in ethanol as a fuel extender, octane enhancer, oxygenate, and neat fuel has increased dramatically because of concerns associated with conventional transportation fuels. Ethanol derived from lignocellulosic biomass offers improved urban air quality, contributes no net carbon dioxide to the atmosphere, creates new markets for farm products, and substantially reduces petroleum imports from unreliable sources.