Emissions from the Production, Storage, and Transport of Crude Oil and Gasoline

Transcription

1 Air & Waste ISSN: X (Print) (Online) Journal homepage: Emissions from the Production, Storage, and Transport of Crude Oil and Gasoline Mark A. DeLuchi To cite this article: Mark A. DeLuchi (1993) Emissions from the Production, Storage, and Transport of Crude Oil and Gasoline, Air & Waste, 43:11, , DOI: / X To link to this article: Published online: 06 Mar Submit your article to this journal Article views: 1426 View related articles Citing articles: 7 View citing articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 23 November 2017, At: 07:58

2 TECHNICAL PAPER ISSN / Air Waste Manage. Assoc. 43: Emissions from the Production, Storage, and Transport of Crude Oil and Gasoline Mark A. DeLuchi Institute of Transportation Studies University of California Davis, California The production, storage, and transport of crude oil and gasoline produces emissions of volatile organic compounds (VOCs), nitrogen oxides (NO), sulfur oxides (SO X ), particulate matter (PM), carbon monoxide (CO) and toxic air pollutants. This paper estimates upstream VOC and petroleum refinery emissions from the use of gasoline in the United States in the year The analysis encompasses the entire gasoline production and marketing cycle, from drilling for oil to refuelling vehicles, and accounts for all emissions regulations likely to be in place by the year The results are that upstream VOC emissions are likely to be between 6 and 10 grams per gallon of gasoline consumed in the year 2000, and between 3 and 10 grams/gallon in the long run, and that SO X and NO X emissions from refineries will be about 3 grams each per gallon of gasoline consumed. If these estimates are accurate, then upstream VOC emissions and refinery SO X emissions, expressed in grams/mile, likely will exceed tailpipe gram/mile emissions from new cars in the year 2000, and refinery NO X emissions will be a significant fraction of tailpipe NO X emissions. The production, storage, and transport of crude oil and gasoline produces emissions of volatile organic compounds (VOCs), nitrogen oxides (NO x ), sulfur oxides (SO x ), particulate matter (PM), carbon monoxide (CO) and toxic air pollutants. For example, at every stage in the production and marketing of gasoline, from drilling for crude oil to refuelling vehicles, volatile organic compounds (VOCs) are emitted. 1 These VOCs evaporate from large storage tanks, spill from trucks and hoses and vehicle refuelling lines, leak from equipment throughout petroleum refineries, evaporate from refinery wastewater treatment systems, and are displaced from the cargo compartments of trucks and marine vessels. In addition, petroleum refineries produce substantial amounts of nitrogen oxides (NO x ), sulfur oxides (SO x ), and particulate matter (PM). 1 Implications Policies designed to reduce gasoline consumption for example, policies that promote the use of nonpetroleum fuels, or improve fleet-average fuel economy, or reduce the use of the private automobile can have the important side benefit of of gasoline. These "upstream" emissions, from drilling for crude oil to refuelling vehicles, are significant, and will remain so even the 1990 Amendments to the Clean Air Act, in fact, this analysis indicates that upstream VOC and refinery SO X emissions, expressed in grams/mile, likely will exceed tailpipe gram/mile emissions from new cars in the year 2000, and that refinery NO X emissions will be a significant fraction of tailpipe NCr emissions. Generally, the less gasoline and crude oil processed, stored, and transported, the less the total VOC emissions throughout the system, and the less the total emissions from refineries. This reduction in "upstream" emissions could be an important side benefit of policies designed to reduce consumption of gasoline. (Such policies include improving the fuel economy of gasoline vehicles, using alternative transportation fuels, and reducing the use of motor vehicles.) However, the 1990 Amendments to the Clean Air Act call for extensive and stringent regulations that will significantly reduce upstream emissions of VOCs. 2 To project upstream emissions in the future, after the new regulations have taken effect, one must perform a detailed analysis of emission sources, emission factors, emission control regulations, fuel throughput, and fuel characteristics. This paper quantifies upstream VOC and petroleum refinery emissions from the use of gasoline in the United States in the year The resulting estimates of upstream gram/gallon emissions can be used to determine the emission reduction side-benefit of policies that directly or indirectly reduce gasoline consumption. The General Method The primary objective of this analysis is to determine total upstream VOC emissions, and NO x, PM, SO x, and CO emissions from refineries, per gallon of gasoline consumed by motorists in the United States in the year The method is as follows. First, uncontrolled emissions from each emissions source (e.g., crude oil tankers) are estimated in grams per gallon of fuel that passes through the source. Then, controlled emissions are estimated, by accounting for the extent and in-use effectiveness of emission controls on the source in the year (This step fully accounts for emission regulations planned or already promulgated as a result of the 1990 Amendments to the U.S. Clean Air Act.) 2 Finally, the intermediate result of "grams emitted per gallon of fuel through the source" is converted to "grams emitted per gallon consumed by motorists," by multiplying by the ratio of throughput at the emission source to total national gasoline supply. Grand total upstream grams-per-gallon emissions for the whole gasoline fuel cycle are simply the sum of grams/gallon emissions from each source. The calculations and data are fully documented in the report from which this paper is derived. 3 (That report also estimates refinery emissions from the production of diesel fuel.) The Method in More Detail Sources of Emissions As regards VOC emissions, the analysis encompasses the entire gasoline production and use system: production, treatment, and storage of crude oil in the field; shipment of crude oil by Copyright Air & Waste Management Association 1486 November 1993 Vol. 43 AIR & WASTE

3 tankers; storage of crude oil at refineries; refining crude oil into gasoline; storage of gasoline at bulk terminals and bulk plants; transfer of gasoline from terminals and plants to trucks and ships; truck and marine shipment of gasoline; gasoline transfer from trucks to service stations; and refuelling vehicles. These stages will be described in more detail. This paper also presents estimates of emissions of NO x, SO x, PM, and CO emissions from process areas throughout petroleum refineries (including boilers), and from the generation of electricity bought by refineries. Emission Control Regulations Because emission controls have the potential in many cases to eliminate over 90 percent of the uncontrolled emissions, assumptions about how extensively controls will be used, and exactly how effective they will be in use (as opposed to in the laboratory, or in theory), strongly determine the final emission results. The emission control scenarios in this paper are based on regulations that I expect will be in force by the year 2000, and include all regulations that are expected to result from the 1990 Amendments to the Clean Air Act. 2 Of course, there is uncertainty about the regulatory future; this is reflected in the two base cases shown in Table I. (Uncertainty regarding such things as the effectiveness of emission controls or the magnitude of uncontrolled emissions, due perhaps to controls being less effective "in use" than as tested in laboratories, or uncontrolled emissions simply being larger than previously estimated or measured, is considered in scenario analyses.) The difference between the two base cases concerns controls on bulk plants, service stations, and vehicles (for refuelling): in one scenario, bulk plants and service stations are controlled as emitters of hazardous air pollutants (HAPs; see next section), and vehicles have onboard refuelling controls, whereas in the other scenario there are no HAP controls on bulk plants and service stations, and no onboard refuelling controls. This paper refers to three kinds of U.S. Environmental Protection Agency (EPA) regulations or actions, different in scope and stringency. National Emission Standards for Hazardous Air Pollutants (NESHAP). NESHAP, which are authorized under Title III of the Clean Air Act [the Hazardous Air Pollutant Program (HAP)], generally are the most stringent and extensive kind of EPA Table I. Two base-case VOC emission control scenarios, year Drilling wells Crude oil production Refineries Bulk terminals 0 Bulk plants 9 Stage I refuelling no Federal regulations NESHAP adopted Title I adopted, but small terminals not covered NESHAP adopted NESHAP adopted no new standards 4 no new standards" pumpside controls only National Emissions Standards for Hazardous Air Pollutants (NESHAP). 6 Including truck loading. d Current Title I nonattainment area regulations still apply. * I n both scenarios percent of total national gasoline consumption passes through pumpside Stage II refuelling controls. regulation. NESHAP can apply to existing as well as new sources, to "area" as well as "major" sources, and in air quality attainment as well as nonattainment areas. Generally, new sources are subject to more stringent standards than existing sources, and must comply immediately with the standards, whereas existing sources must comply within three years. Similarly, major sources must achieve the maximum degree of emissions reduction, whereas area sources may be allowed to use generally available control technologies and management practices. 2 Many VOCs are HAPs, and hence potentially subject to NESHAP. Most of the major VOC emission sources in the crude oil and gasoline production and use cycles emit a mix of both hazardous and non-hazardous VOCs. However, since the hazardous VOCs typically cannot be controlled separately from the nonhazardous VOCS, the NESHAP applying to HAPs from a given source effectively apply to all VOCs from the source. The 1990 Clean Air Act Amendments direct the EPA to assess, and if necessary, regulate HAP emissions from every major VOC emission source in the crude oil and gasoline production and use system. 2 Presently, it appears that every stage of the cycle, with the possible exception of bulk gasoline storage plants and service station gasoline storage tanks, will be subject to NESHAP (Table I). New Source Performance Standards (NSPS). NSPS apply only to newly built or modified emissions sources. They require the best available control technology, as opposed to the maximum achievable control technology that is required under NESHAP. The effect of NSPS on total emissions depends on the rate of turnover and modification of the regulated sources. Thus NSPS are less strict, and less broad, than NESHAP, although they also are national in scope. Nonattainment. The EPA also may regulate emission sources under Title I of the Clean Air Act, "Nonattainment." Nonattainment regulations apply to emissions of the so-called "criteria" pollutants, which are those that cause a region to violate any one of the National Ambient Air Quality Standards. Title I regulations apply to existing sources, and can require either best available or reasonably available control technology. Under Title I, VOC emissions can be regulated as precursors to ozone. The regulatory assumptions used in this analysis are explained in detail in DeLuchi et al. 3 NESHAP adopted NESHAP adopted pumpside + onboard Fuel Characteristics Most of the VOC emissions from the upstream emission sources are evaporative emissions. Evaporative emissions are determined by the tendency of a fuel to evaporate, a tendency which is represented by the true vapor pressure (TVP) of the fuel. For many emission sources, evaporative emissions are directly proportional to the TVP. 4 The TVP of gasoline is a function of temperature and of a quantity known as the Reid Vapor Pressure (RVP). Because the TVP of a high RVP gasoline in hot weather can be three times the TVP of a low RVP gasoline in cool summertime weather, 4 calculated VOC emissions can vary by a factor of three, due to differences in TVP alone. It therefore is important to estimate TVP in this case, national average summertime TVP in the year 2000 as accurately as possible. In this analysis, the estimation of TVP proceeds in three steps: first, a consumption weighted national average summer- AIR & WASTE Vol. 43 November

4 TECHNICAL PAPER Table II. VOC emissions from petroleum storage tanks. Source: DeLuchi et al. 3 Bulk plants crude oil Field Uncontrolled filling and emptying emissions, mg/liter Included below included below 1279 included included below Uncontrolled breathing, standing, and other evaporative emissions, mg/liter Control effectiveness Controlled flow, fraction of all flow through the stage 0.55/0.90" Fuel through stage, fraction of net fuel consumed Grams-VOCs/gal-fuel-consumed' ; /0.27* Classified by the type of roof present in I). The general form of the equation used here and in Tables III, V, and VI: Q * (Ul (1-Ce) Cf + Ul (1-Cf) + S) F 3,7854/1000 where: G -- grams of VOCs emitted per gallon of end-use gasoline consumption Ut»uncontrolled rate of emissions from sources subject to control, scaled to the TVP used here (mg/liter) Ce «effectiveness of emission controls (fraction) Cf = controlled throughput divided by total throughput for the stage F»throughput for the stage divided by total national consumption S - Emission rate from sources not subject to controls (mg/liter) time RVP is estimated, using EPA's recent state-by-state and month-by-month RVP regulations, 5 and data on gasoline throughput by state and month. 6 The resulting national average RVP standard is 8.76, and the resulting RVP of gasoline in the vehicle tank is [Sensitivity analyses presented later will examine several gasoline RVP scenarios: attainment area gasoline (meeting a 9.0 RVP limit), nonattainment area conventional gasoline (meeting a 7.8 RVP limit), and reformulated gasoline (7.0 RVP limit)]. Second, the average temperature is estimated for five different storage points in the gasoline marketing system (bulk tanks or large vessel compartments, tanker trucks, vehicle tanks, refuelling lines, and underground tanks). Third, TVP is estimated as a nonlinear function of RVP and temperature, using a graph provided for this purpose in the EPA's AP Because the ozone problem in the United States is most severe in the summertime, this paper presents emission estimates for the summertime months only (May through September). Also, the base-case analysis here assumes conventional gasoline, rather than reformulated gasoline, in the year (The upstream emissions differences between conventional and reformulated gasoline turn out to be relatively minor, though.) The Scope of the Analysis The two base cases of Table I cover emissions for the nation as a whole, including Alaska and Hawaii. Some of the scenario analyses estimate emissions separately for ozone attainment areas and ozone nonattainment areas. In all cases, only those emissions that occur in or near the continental U.S. are counted; emissions associated with the production of imported oil and imported gasoline, and VOC emissions from ships on the high seas, are excluded because these emissions are of no concern in the U.S. However, the analysis does account for second-order VOC emissions in the U.S., e.g., emissions from the production and use of the petroleum fuels used by marine vessels that transport petroleum, by multiplying most results by an "own-use" factor of As mentioned, the analysis is targeted for the year Not only does it account for regulations likely to be in place by the year 2000, it uses Energy Information Administration (EIA) projections 8 of Alaskan oil production, lower-48 oil production, imports of crude oil, imports of petroleum products, total supply of gasoline and diesel fuel, and refinery production of petroleum products in the year The Relationship Between Gasoline Consumption, Gasoline Throughput, and VOC Emissions It is clear that upstream gasoline throughput is directly related to end-use gasoline demand (with some short lag, and ignoring changes in gasoline stocks). However, it is not immediately clear if VOC emissions from every upstream source necessarily are a function of gasoline throughput at the source. DeLuchi et al. 3 examine the relationship between throughput and emissions with respect to four basic kinds of VOC emissions from the gasoline production and marketing system: displacement of vapor (e.g., from refuelling vehicle tanks, or filling bulk plants); spills of liquid (e.g., from vehicle refuelling, or truck loading); emissions from refineries (unburnt hydrocarbons from fuel burned for 1488 November 1993 Vol. 43 AIR & WASTE

5 Table III. VOC emissions from loading crude oil and gasoline onto vessels. Source: DeLuchi et al. 3 In-transit tosses, ing/liter Uncontrolled loading joss, mg/iiter Uncontrolled ballasting losses, mg/iitor Control effectiveness, loading Controlled flow, fraction of alf flow through the stage Petroleum through the stage, fraction of total gasoline consumed Grams-VQCs/galfon-M consumed u 1 Alaska tanker ,027 Crude oil Lower 48 tanker barges , ,007 0, o ,024 Gasoline All U.S. tanker barge n transfer of crude oil to trains and trucks (according tofciadata, 9 refineries receive less than 2 percent of their crude by rail or truck), and assume that crude oil has an RVP of 5, In reality, the RVP of crude varies. Emission factors expressed in AP-42 as total hydrocarbon emissions have been converted here to nonmethane HGs, or VOCs, by multiplying by 0.85, as recommended in AP See note b to Table II for the general form of the equation used here. process heat, and fugitive HC emissions); and evaporation of liquid from storage (e.g., from bulk terminals). In each case, they ask: are these VOC emissions directly a function of gasoline throughput? They arrive at the following conclusions regarding the four kinds of emissions: 1) Displacement Emissions. No matter what the response of the gasoline production and marketing system to a decline in gasoline consumption, the less gasoline transferred, the less vapor displaced, and the lower the VOC emissions attributable to vapor displacement. 2) Spillage Emissions. Spills of liquids from all activities except refuelling vehicles probably are a direct function of throughput and gasoline end-use consumption. However, total spillage emission from gasoline refuelling is not directly related to gasoline throughput; rather, it is a function of the number of times motorists refuel, which in turn is a function of the range of gasoline vehicles and the total vehicle miles traveled in gasoline vehicles. Thus, whether or not spillage emissions will be reduced if gasoline consumption is reduced depends on how gasoline consumption is reduced. If gasoline consumption is reduced by reducing the total number of trips made in motor vehicles, or by substituting alternative fuels for gasoline, then the number of times people refuel with gasoline, and hence the number of gasoline spills, will be reduced. However, if gasoline consumption is reduced by improving fleet average fuel economy, the number of times people refuel probably will not change, because most cars have roughly the same range, regardless of fuel economy. 3 Hence, if one is analyzing upstream VOC emissions as a function of fleet average fuel economy, one should not count emissions from spills associated with gasoline refuelling. Otherwise, one should. 3) Refinery Emissions. It is clear that all else being equal, the less gasoline a refinery makes, the less VOC it will emit. If the refinery makes less gasoline, it will process less crude oil, and so use less total energy to distill, separate, crack, rearrange, and recombine crude oil into gasoline. The less energy the refinery uses, the lower the emissions from fuel combustion to raise process heat. Similarly, the less crude oil, gasoline, gasoline components, and gasoline by-products pumped and processed throughout the refinery, the less the fugitive vapor emissions from valves, pumps, and so on. The difficulty, though, is that in the case of refineries all else will not be equal, because a drop in demand for gasoline will affect refinery output of other products, such as diesel fuel and residual fuel oil. Nevertheless, DeLuchi et al. 3 believe that while the analysis of refinery VOC emissions as a function of gasoline demand is complicated, it probably is reasonable to assume that overall, VOC emissions from refineries will decline with gasoline demand. 4) Evaporative Emissions from Storage Vessels. Some types of evaporative emissions from storage vessels (such as bulk gasoline terminals) are a function of the physical characteristics of the vessels (e.g., vessel diameter), but not of the amount of gasoline put through the vessel or the number of storage turnovers. 4 These kinds of evaporative emissions will decline as a result of a drop in gasoline consumption only if the industry responds to the decline by reducing the number or size of storage vessels, as opposed to reducing throughput or turnovers on the existing vessels. However, in the short run, the industry is likely to respond to a change in gasoline demand by changing the capacity utilization of the existing infrastructure, and not by changing the physical infrastructure itself, because of sunk costs and uncertainty about future demand. In the longer run, industry may change the physical infrastructure. Therefore, there may be a lag of years between a reduction in gasoline consumption and the consequent reduction in some kinds of upstream emissions. The upstream emissions (from bulk plants, bulk terminals, and crude oil storage vessels) which might greatly lag the changes in gasoline consumption amount to 0.4 to 0.5 grams/gallon. Description and Characterization of Sources VOC Emissions Drilling for Oil Oil drilling operations release hydrocarbons when the drilling muds are degassed. Emissions from drilling per se as distinguished from emissions from the flow testing of wells, from the separation of gas and oil and water, and from the temporary storage of crude oil in gathering tanks in the field (all of which are considered in the next paragraph) are not controlled at present, and probably will remain uncontrolled, because they are relatively minor. Production and Treatment of Crude Oil, and Storage In the Field Freshly lifted crude oil is treated to remove water and dissolved gases. This treatment, especially when done at high temperature, can force the emission of some of the lighter hydrocarbon gases. The separated crude oil then is gathered and stored temporarily in small tanks, awaiting delivery to pipelines and then to ships or much larger storage terminals at refineries. Because these small gathering tanks are filled and emptied frequently, and AIR & WASTE Vol. 43 November

6 TECHNICAL PAPER Table IV. Emissions from petroleum refineries, including emissions from bought electricity, per gallon of gasoline or diesel fuel consumed, year 2000." Source: DeLuchi et al. 3 voc 00 Low-sulfur diesel fuel (1.07) 107 (1.05) 1.05 (0.76) 0.76 (1.86) 1.89 (!$6) 1.69 (1,50)1.51 (2.37)2,73 (199)2.28 (119)133 (2,46)2,38 (2.33)2.67 (199)2.16 (0.28)0 JO (0,24)0.26 (0.15)0.16 are emissions from refinery boilers and refinery process areas (refinery process area emissions are emissions from all areas of a refinery other than boilers: catalytic crackers, blowdown systems, vacuum distillation columns, wastewater systems, valves and flanges, etc.). The numbers not in parentheses are total emissions, equal to the emissions from refinery boilers and process areas Reformulated gasoline is assumed here to be a low-aromatics, low-sulfur, low-rvp gasoline, with MTBE added. typically do not have emission controls, they can emit considerable amounts of VOCs, especially when the oil is still hot from the separation treatment. Recently, the EPA has begun to re-examine emissions from oil production, and the preliminary data suggest that oil production may release more VOCs than previously believed. 10 It now seems likely that the EPA will regulate oil and gas production as sources of HAPs. 11 VOC emissions from this stage are estimated in Table II. Loading Crude Oil and Petroleum Products onto Marine Vessels Crude oil is shipped from oil production fields to refineries, and petroleum products are shipped from refineries to storage terminals, via pipelines and ships. When crude oil or a petroleum product is loaded into the cargo compartment of a ship, it expels VOC vapors from the compartment. At present, marine vessel loading operations are uncontrolled in all but a few states. However, the 1990 Amendments to the Clean Air Act direct the EPA to promulgate a rule by 1993 that will cover VOC emissions from vessel loading operations. 2 The EPA is now developing the rule, 12 which will apply in both attainment and nonattainment areas, but only to large facilities. Several states also have proposed or promulgated rules affecting loading at marine terminals. If ships place ballast water in compartments previously filled with crude oil or petroleum products, the water will displace a substantial amount of VOC vapor. However, most ballast water today is held in compartments that hold only ballast water, and hence cannot emit VOCs. Emissions from marine vessels are estimated in Table III. Loading and Storage of Crude Oil at Refineries Crude oil typically is stored at refineries before being processed into petroleum products. Some of the volatile components of crude oil evaporate or are displaced from storage tanks, both when the crude oil is standing in the tank, and when the tank is being loaded and unloaded. These emissions are a function of the type of tank (tanks with a fixed roof emit a good deal more VOCs than do tanks with an internal or external floating roof), the geometry and capacity of the tank, the TVP of the liquid, the ambient wind and temperature, the petroleum throughput of the tank, and other factors. 4 There are little or no emissions from the loading of floating-roof tanks, because there is no vapor space and hence no vapor to be displaced when the crude oil is loaded. However, all tanks produce some standing evaporative emissions. Newly built or modified crude oil storage tanks at refineries already are subject to NSPS. By the year 2000, most existing refinery storage tanks will be subject to NESHAP. 13 Emissions from storage vessels are estimated in Table II. Table V. VOC emissions from gasoline truck loading and transfer operations. Source: EPA 17 and DeLuchi et al. 3 splash fill Spills and leaks, mg/liter In-transit losses, mg/liter Uncontrolled loading loss, mg/liter Control effectiveness, loading Controlled flow, fraction of all , O.SS/ /0.5Q* Fuel through stage, fraction of total fuel consumed Grams-VOCs/ga!~consumed" /0.06* 0,28/0.21* left of the slash mark applies to base-case A; the estimate on the right refers applies to base-case S. b See note b to Table II for the general form of the equation I. The estimate on the 1490 November 1993 Vol. 43 AIR & WASTE

7 Table VI. VOC emissions from refilling service station and vehicle tanks. Source: EPA 17 and DcLuchi et al. 3 splash fill submerge Ml Spills and leaks, mg/liter Emptying fosses, mg/liter Uncontrolled refilling loss, my/liter Control effectiveness, refilling Controlled flow, fraction of all Fuel through stage, fraction of total fuel consumed , /0.90 b «1.00 0,00/0.28 b Gmm$»VQGs/gall0n consume 1.43/ /0.15* r, of the date of the test) from refuelling hoses not equipped with vapor recovery. Recent tests in California indicate that there is 31 percent less spillage from hoses equipped with vapor recovery (Stage II pumpside controls). 19 Therefore, I estimate mg/liter spillage as 84 ((i -C) C), where C is the fraction of total gasoline put through vapor-recovery hoses. Note that as discussed in the text, one should not count spills from vehicle refuelling in an analysis of upstream VOC emissions as a function of fuel economy. c See note b to Table II for the general form of the equation used here. Petroleum Refinery Boilers Refineries burn a large amount of refinery gas, natural gas, oil, and other fuels to raise steam for process heat. The combustion of these fuels produces minor amounts of VOC and CO emissions, and substantial amounts of NO x, SO x, and PM. The model used here calculates gram/gallon emissions from refinery boilers using EIA data on the amount and kind of fuels consumed by refineries, EIA projections of product output by refineries, EPA emission factors for uncontrolled industrial boilers, NSPS and AP-42 emission factors for controlled industrial boilers, recent EPA regulations pertaining to industrial boilers, and other data. 3 These emissions from refinery boilers, along with emissions from the generation of bought electricity, are included in the totals in Table IV. Fugitive and Process Area Emissions from Petroleum Refineries Hydrocarbons leak, evaporate or are otherwise emitted from many parts of a refinery, from valves to catalytic crackers to wastewater treatment systems. Most of these emissions from new sources already are regulated under NSPS, and by the year 2000, most fugitive emissions from most existing sources will be subject to NESHAP. 13 To estimate emissions from each process area, the model presented here uses AP-42 emission factors and crude oil throughput for each area, and apportions refinery emissions to individual products. 3 These emissions are included in the gram/gallon totals of Table IV. Storage of Gasoline at Bulk Terminals and Bulk Plants Gasoline is delivered by pipeline, tanker, barge, or tank car from refineries to large storage tanks at marketing facilities called "bulk terminals." Gasoline evaporates from these storage tanks, and gasoline vapors are displaced or exposed to the air when tanks are drawn down. New bulk terminal tanks already are subject to recent NSPS. The EPA now is formulating NESHAP regulations, which will subject essentially all terminals to relatively stringent controls. Some gasoline is further distributed to smaller storage facilities called "bulk plants." The amount of gasoline throughput at bulk plants has been declining, and is likely to continue to decline, as distributors increasingly use trucks to go directly from terminals to retail outlets, by-passing the bulk plants. 14 Most of the bulk plants in nonattainment areas already are regulated under state air quality improvement plans. Bulk plants are exempt from the NSPS that apply to gasoline storage terminals, and may or may not be subject to NESHAP. 15 Because of this uncertainty, this analysis has one base case in which only bulk plants in nonattainment areas are controlled, and one which nearly all bulk plants are regulated as emitters of HAPs. Gram/gallon emissions from bulk plants and bulk terminals are estimated in Table II. Truck Loading at Gasoline Bulk Terminals and Bulk Plants Gasoline is transferred from storage facilities to tanker trucks that distribute the gasoline to refuelling stations. When the gasoline is loaded into the tanker truck, vapors are displaced from the truck storage tank. Usually some gasoline is spilled during the transfer as well. Gasoline also evaporates from the trucks while they are in transit. Truck loading at terminals, which already is subject to NSPS, will be subject to forthcoming NESHAP, which means that nearly all terminal-to-truck throughput will be controlled by the year Most of the bulk plant-to-truck transfers in nonattainment areas already are regulated under state air quality improvement plans. However, as noted, bulk plants, and bulk plant-to-truck transfers, may or may not be subject to NESHAP. 15 Because of this uncertainty, this analysis considers one base case in which only bulk plant transfers in nonattainment areas are controlled, and one in which nearly all bulk plant transfers are regulated as sources of HAPs. These emissions are estimated in Table V. Emissions from Underground Service Station Tanks The transfer of gasoline from tanker trucks to underground tanks at refuelling stations displaces vapors in the station tanks, and can result in leaks and spills of gasoline. There also are breathing and emptying losses from the drawing down of the underground tanks. To estimate these emissions, the model first AIR & WASTE Vol. 43 November

8 TECHNICAL PAPER Table VII. The author's 50-state VOC-emissions estimates compared with EPA's NEDS estimates, grams VOC per gallon gasoline consumed. Source: DeLuchi et al. 3 EPA NEDS J8 Gasoline processes 12, J ,05 Total grams/gallon^ * Estimate based on EPA's National Emissions Data System (NEDS). 1 See DeLuchi et al. 3 for details. same methods and sources of data as in the year 2000 See DeLuchi et al. 3 for details. Year 2000 crude oil cycle emissions are the sum of gram/gal emissions from: drilling for oil, crude-oil transfer (Table III), and crude oil treatment of bought electricity (Table IV), Product cycle emissions are il, Hi, V, and VI), and HC emissions from fuel-distribution trucks and ship engines (not shown here). The two cases (2000-A and 2000-B) refer to the two base-case control I. sions sources which the NEDs estimates do not: emissions from the generation of electricity bought by refineries; from the tailpipes of gasoline delivery trucks; and from ship engines, in Ihe NEDS accounting systems, these emissions are assigned elsewhere for example, emissions from the electricity generation, not petroleum processes. These are minor items, however. calculates uncontrolled loading losses, which are a function of TVP, temperature, and the method of loading, and then applies assumptions about emission controls. As with bulk plants, there are two base cases, because of uncertainty regarding future regulations: one base case in which only those stations in nonattainment areas are regulated, and one in which virtually all stations are regulated as emitters of HAPs. These emissions are estimated in Table VI. Emissions from Refuelling Vehicles Virtually all gasoline consumed in the U.S. passes through a refuelling station. When motor vehicles are refueled, gasoline vapors are displaced from the vehicle tanks, and gasoline is spilled from the refuelling nozzle. The estimation of refuelling emissions begins here with a calculation of uncontrolled emissions as a function of the RVP and temperature of gasoline. Next, it accounts for emission controls on refuelling. The extent of use and effectiveness of controls in the year 2000 is somewhat complicated, given the Clean Air Act' s conditional requirement of both on-board and offboard (pumpside) controls, and uncertainty regarding promulgation of onboard controls. (Although the EPA has decided not to require onboard controls, they have been sued for this decision, and the outcome is not certain.) Therefore this paper presents two base cases, one in which onboard controls are not adopted (basecase A) and one in which they are (base-case B). I calculate that if onboard controls are adopted, and first appear on the 1997 model year, then in the year percent of gasoline consumption will pass through onboard controls. 3 Emissions from vehicle refuelling are estimated in Table VI. Discussion of Results Summary of VOC Results Total estimated gram/gallon VOC emissions in the year 2000 are shown in Tables VII and VIII. To facilitate comparison with the EPA's NEDS 1 estimates, the emissions estimates in Tables VII and VIII are lumped into the three general categories reported in the EPA's NEDS (crude oil processes, refineries, and gasoline processes). According to this analysis, in the summertime in the U.S. in the year 2000, between 6.2 and 8.7 grams of VOCs will be emitted upstream per gallon of gasoline used by motor vehicles. The high end of the range (base-case A) assumes that bulk plants and refuelling stations will not be subject to NESHAP, and that vehicles will not have onboard refuelling controls. The low end of the range (base-case B) assumes that bulk plants and refuelling stations will be regulated under NESHAP, and that (in the year 2000) some vehicles will have onboard refuelling controls. This range counts emission of spills from vehicle refuelling. (These spillage emissions of motor vehicles amount to 0.26 grams/gallon in this analysis, which should not be counted in an analysis of the emission reduction side benefit of improving the fuel economy.) Both base cases assume conventional gasoline, which requires less input energy and processing than does reformulated gasoline, and hence results in slightly lower upstream VOC emissions. However, the VOC emissions difference between conventional and reformulated gasoline is trivial only 0.02 grams/gallon. 3 Most of the total upstream gram/gallon VOC emissions come from gasoline processes (storage, transfer, and refuelling), with smaller amounts coming from refineries, and a very small amount coming from the production, treatment, storage, and transfer of crude oil. Most of the emissions from gasoline processes occur at the refuelling station, as a result of refuelling vehicles and transferring gasoline from tanker trucks to station tanks (Table VI). These emissions are large in both base cases, but are significantly less in base-case B than in base-case A, because of NESHAP regulations and onboard refuelling controls in base-case B. A nontrivial amount of emissions come from trucks at terminals in both cases (Table V). Virtually all of the VOC emissions from refineries are from fugitive sources (including emissions from wastewater treatment systems) or process areas, as opposed to boilers or electricity plants (Table IV). Most of the emissions from the crude oil cycle are from the storage of crude oil in the field and at refineries (Table II). Although these are estimated to be the largest emission sources in the crude oil part of the system, they are minor relative to most sources in the gasoline marketing part of the system, because crude oil typically has a much lower TVP than gasoline, and because of the assumption in this analysis that all the major emission sources in the crude oil cycle will be controlled under the nonattainment or HAP provisions of the Clean Air Act. However, these emissions could turn out to be significantly higher than estimated here, primarily because the emission factors for crude oil production, treatment, and storage are not well known, but also because emissions regulations have not been finalized. It is important to recognize that the base cases estimate a national average emission rate in the summertime in the U.S. in the year The emission rate might be different in individual 1492 November 1993 Vol. 43 AIR & WASTE

9 Table Villa. Grams VOC emitted per gallon of gasoline consumed, scenario analyses" A B C D E F G bast-cast A base-ease B lax control 28 percent 100 percent no onboard 100 percent onboard onboard onboard ooma NESHAP some NESHAP tuli NESHAP full NESHAP 1, g S J ,03 assume conventional gasoline. All scenarios except H assume that A. This is the yt)a< 2000 base-case A from Table VII. (No NESHAP controls.) Note that because there are no onboard refuelling controls, and all expected regulations are assumed to be fully in force by the year 2000, the upstream gram/gallon emission results of this case pertain to any individual vehicle as well as additional regulations) B. This is base-case 8 from Table Vii. (NESHAP for bulk plants or refuelling stations, and onboard refuelling controls covering 28 percent of throughput.) Note that because onboard controls are year 2000, not to Individual cars in the year 2000 or to years beyond Those cases are considered in the following. C. This is the lax control" case, in which both the extent and sions from the treatment of crude oil are 5 times higher than In states, or in ozone nonattainment or attainment regions, where regulations and other factors are likely to be different from the national average. (See the discussion of the scenario analyses which follows.) The rate will be lower outside of the summer months, because the average temperature of gasoline, and hence its TVP, will be lower. And between now and the year 2000 the emission rate will gradually decline to the estimated year 2000 level; after the year 2000, it may continue to decline. Finally, as noted, there may be a lag of many years between any reduction in gasoline consumption and the consequent reduction in emissions, because of the time required for the gasoline marketing infrastructure to respond. Refinery Emissions of NO,,, S0 x, and PM Refineries emit large amounts of NO x, SO x, and PM, as well as VOCs, and hence reducing gasoline consumption will substantially reduce these emissions. SO x emissions from refineries are large because a considerable amount of sulfur must be removed from crude oil to make gasoline. (This effect will be more pronounced with low-sulfur reformulated gasoline.) As shown in Table IV, refineries and the power plants that supply them with cases A and B. This estimate represents the plausible upper bound on upstream gram/gallon VOC emissions for individual run. 0. cover 28 percent of gasoline throughput in the year E. Same as case D, except that 100 percent of vehicles have onboard controls (in the iong run), instead of 28 percent in the year This can be viewed either as upstream emissions attributable to any vehicle that has onboard controls (under Case 0), or as average upstream emissions for the fleet in the iong mn, after onboard controls have been completely phased in (under Case 0). f, 6. onboard controls. This can be viewed either as upstream (under Case B), or as average upstream emissions for the fleet in the iong run, after onboard controls have been completely phased in (under Case B). H. Assumes that 100 percent of throughput is controlled at every major upstream stage, to a high degree of effectiveness. As- II pumpside refuelling controls and onboard refuelling controls. This represents the likely lower bound on upstream VOC emissions in the long run. electricity could emit 2.7 grams of SO x per gallon of conventional gasoline consumed by motorists (2.9 grams of SO x per gallon of low-sulfur reformulated gasoline) in the year 2000, even with relatively tight controls on sulfur emissions. They also could emit about 2.3 grams NO x and 0.3 grams PM per gallon of conventional gasoline (2.7 grams NO x per gallon of reformulated gasoline) in the year 2000 (Table IV). The manufacture of reformulated gasoline will result in greater emissions because reformulated gasoline will have more sulfur removed than will conventional gasoline, and will require more energy to manufacture. Validation of the Model As a check on the methods and data, I have run my emissions model for the year 1988, to compare the VOC emission results with the EPA's NEDS-based VOC estimates for the year The changes made to the model year 1988 are summarized in Reference 3. As shown in Table VII, the modelling results agree with the NEDS-based results for 1988 to within 5 to 10 percent. The model's estimates of emissions from refineries and from the gasoline cycle are very close to the NEDS-based estimates. The model's estimate of emissions from the crude oil cycle is not quite as close, probably AIR & WASTE Vol. 43 November

10 TECHNICAL PAPER Table Vlllb: Grams VOCs emitted per gallon of gasoline consumed, RVP and regulatory scenarios. Nonattainment Reformulated 7.0RW sold in ozone attainment areas cannot exceed $.0 RVP, Also, the produced at 7,41 RVP, and after weathering (2.5 percent x 2) ends onboard refuelling controls). (Under the new EPA regulations, gasoline sold in somsozone nonattainmsntareascannotexceed7.8 RVP. Also, fl» national average 8VP could be as low as 7.8 ti many The 7.0 RVP case is the same as the 7.8 case, applicable standard is 7.0 RVP, reformulated Some kinds of reformulated gasoline probably will meet a 7.0 RVP because the data for crude oil cycle emissions are relatively poor. The good agreement between the model and the NEDS-based results is not surprising, however, because in many cases the model uses the same basic data and methods as are used in NEDS. Nevertheless, the agreement does make the model more credible. The projected national upstream VOC emission rate in the year 2000 is considerably lower than the estimated actual rate for 1988 at all three major stages (Table VII). In the crude oil cycle, the projected decline in national VOC gram/gallon emissions from 1988 to 2000 is mainly due to control of crude oil treatment and storage, under Title I Nonattainment regulations and Title III NESHAP. The projected decline in national VOC emissions from refineries is due mainly to control of fugitive emissions (including emissions from wastewater systems), under NSPS and NESHAP. The projected decline in national gasoline cycle emissions is due mainly to NESHAP and NSPS regulations on bulk terminals, Title I controls on vehicle refuelling, and, in base-case B, onboard refuelling controls and NESHAP controls on bulk plants and refuelling stations. VOC Emission Scenario Analyses The single biggest uncertainty in this analysis is the ultimate extent and effectiveness of regulations now being considered. In particular, the final result depends heavily on whether or not one assumes new, nationwide emission standards on bulk plants Stage I refuelling, and vehicle refuelling. Table VIII shows several scenarios that consider these and other uncertainties. The first two cases of Table Villa repeat base cases A and B from Table VII for the year Case G, in which bulk plants and refuelling stations are assumed to be subject to NESHAP and 100 percent of vehicles are assumed to have onboard refuelling controls, can be viewed as case B in the long run, or as case B applying to individual controlled vehicles in the year 2000, rather than to the national fleet. Hence, according to this analysis, the entire gasoline vehicle fleet in the long run, or a single (controlled) vehicle in the year 2000, will generate upstream VOC emissions between 4.9 (case B in the long run) and 8.8 (case A) grams/gallon. In between case A (no NESHAP, no onboard) and case G (NESHAP, 100 percent onboard) are two variations: NESHAP but no onboard (case F) or no NESHAP but 100 percent onboard (case E). Both of these variations result in emissions of about 6.8 grams/gallon. Also presented are plausible upper (case C) and lower (case H) long-run (or single-vehicle) emission rates. Case C relaxes both the extent and effectiveness of emission controls on most sources by about 5 absolute percentage points, compared to case A. This represents a situation in which the EPA exempts more emission sources than in case A, and in which emission controls are not as effective in use as expected. At the other end of the spectrum, case H assumes stringent control of 100 percent of throughput at every major upstream VOC emissions source. This represents very aggressive regulation, monitoring, and enforcement. If one accepts these as bounds, then the long-run national average upstream VOC emission rate will be between 3 and 10 grams/gallon. Table Vlllb shows gram/gallon VOC emissions for different combinations of RVP and regulatory regimes. In areas with a 9.0 RVP limit, and no controls on bulk plants, service stations, or vehicle refuelling, upstream emissions attributable to gasoline use may be quite high nearly 14 grams/gallon. On the other hand, in areas that use 7.8-RVP conventional gasoline or 7.0-RVP reformulated gasoline, and control 100 percent of throughput at bulk plants and service stations, emissions attributable to gasoline use will be down to around 4 grams/gallon. Most of the difference between these two scenarios is due to the more extensive use of emission controls, rather than to the lower RVP limit. For example, reducing the RVP standard from the base-case national average of 8.76 (as in Table Villa) to 7.8 (as in Table Vlllb), and holding everything else constant, would reduce upstream emissions by 0.36 grams/gallon. Going from a 7.8-R VP standard for conventional gasoline to a 7.0 standard for reformulated gasoline a drop of the same percentage, and almost the same magnitude, as in going from 8.76 to 7.8 would provide less of an absolute reduction [0.25 grams/gallon if one includes the effect of reformulation on refinery emissions; 0.27 if one does not (Table Vlllb)] and less of a percentage reduction. This is because the relationship between RVP and TVP is nonlinear, and there are diminishing returns to reducing RVP. Tasks for Future Researchers The following emission sources appear to be insignificant, and probably can be ignored in any future analysis of this sort: VOC emissions from drillingforoil per se; from ship engines; from the tailpipes of trucks distributing gasoline; and from vessel cleaning; 16 and VOC and CO emissions from refinery boilers and power plants. Future efforts should concentrate instead on the following areas: measuring and modeling VOC emissions from crude oil production, treatment, and storage; measuring and modeling the in-use TVP of gasoline at all stages of gasoline marketing each month of the year; characterizing the extensiveness and in-use effectiveness of controls on gasoline storage and transfer; predicting how the petroleum production, refining, and marketing industries actually will respond to a drop in gasoline consumption; integrating engineering emission factor models with economic models to account for the effect of changes in gasoline demand on the amount and quality of crude oil demanded, refinery operations, and the production of other products; and using detailed refinery production and emissions models to allocate refinery emissions to individual products November 1993 Vol. 43 AIR & WASTE

11 Conclusion: How Important are Upstream Emissions? The gram/gallon emission results presented in Tables VII and VIII can be expressed as grams/mile, for comparison with tailpipe emissions, simply by dividing by the appropriate in-use fuel economy. For example, upstream VOC emissions of 8.70 grams/ gallon (base-case A) are equivalent to 0.42 grams/mile from a car and track fleet that gets 20.6 mpg in actual (in-use) city and highway driving (20.6 mpg is the in-use city and highway mpg for a fleet of new cars with a test mpg of 28 and new trucks with a test mpg of 21, and a test to in-use adjustment factor of 0.8 approximately the current situation). Even if new car test fuel economy was as high as 40 mpg (for light tracks, 32 mpg), and in-use fleet average fuel economy was 29.2 mpg, upstream VOC emissions would still be 0.30 grams/ mile under base-case A, and 0.21 grams/mile under base-case B. Thus, upstream VOC emissions in the year 2000 likely will be between 0.22 and 0.43 grams/mile. By comparison, the Tier I emission standards of the Clean Air Act Amendments of 1990 limit tailpipe VOC emissions to 0.25 grams/mile, and the Tier II standards limit emissions to grams/mile. 2 Upstream VOC emissions therefore are likely to be equal to or greater than tailpipe emissions from new vehicles in the year 2000, and perhaps beyond (unless tailpipe emissions greatly exceed the standards). Only if upstream emissions are very low (3 grams/gallon in the long ran, as in case H of Table Villa), and fuel economy is very high (29.2 mpg, fleet average, in use), will upstream gram/mile emissions be relatively low about 0.10 grams/mile. But even in this best case, upstream emissions will approach the Tier-II tailpipe-voc standard, and exceed standards promulgated in California for "ultra-low emission vehicles." Similarly, SO x emissions attributable to manufacturing gasoline almost certainly will exceed SO x emissions from the combustion of gasoline by vehicles. Current gasoline, which contains about 0.03 percent sulfur by weight, produces about 1.7 grams SO 2 per gallon burned (assuming complete oxidation to SO 2 ). Low-sulfur reformulated gasoline, if it contained about percent sulfur by weight, 18 would produce about 0.27 grams SO 2 per gallon burned. As discussed, petroleum refining probably will produce around 3 grams/ gallon in the year However, one should keep in mind that the transportation sector is not a major source of SO x emissions to begin with. Also, SO x emissions from refineries will continue to decline beyond the year 2000, as more new coke fired boilers and fluid catalytic cracking units meet NSPS. At 25 mpg (fleet average, in-use) refinery NO x emissions will amount to 0.11 grams/mile (assuming reformulated gasoline), which is about one-quarter of the 0.40 gram/mile Tier-I NO x standard, and about half of the 0.20 gram/mile Tier-II standard. In summary, this analysis indicates that the production, storage, and transport of gasoline is and will be a large emissions source in some cases, larger than the tailpipes of new vehicles. Consequently, policies intended to reduce gasoline consumption can have the important side benefit of reducing these substantial upstream emissions. This benefit should be considered in policy evaluations. Acknowledgments Charles Amman of General Motors, John DeCicco of the American Council for an Energy-Efficient Economy, Jerry Hader of the American Petroleum Institute, Larry Jones of the U.S. Environmental Protection Agency, David Markwordt of the U.S. Environmental Protection Agency, Dan Santini of Argonne National Laboratory, and Chris Saricks of Argonne National Laboratory all provided useful comments on the longer report from which this article is derived. The Environmental Protection Agency's Office of Office of Mobile Sources in Ann Arbor, Michigan and Office of Air Quality Planning and Standards in Research Triangle Park, North Carolina, provided very useful information. However, I am fully responsible for the content. Partial funding was provided by Oak Ridge National Laboratory. References 1. 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Jordan, "Comparison of spill frequencies and amounts at vapor recovery and conventional service stations in California," J. Air Waste Manage. Assoc. 42:284 (1992). About the Author The author is with the Institute of Transportation Studies, University of California, Davis, CA This manuscript was submitted for peer review on April 23,1992. The revised manuscript was received on February 19,1993. AIR & WASTE Vol. 43 November