Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Chapter l INTRODUCTION Emissions regulations for heavy-duty vehicles set limits on releases of hydrocarbons, carbon monoxide, oxides of nitrogen (NOX), and visible smoke. (The U.S. Environmental Protection Agency (EPA) has proposed changes in heavyâduty regulations that would replace visible smoke limits by limits on particulate emissions.) A heavyâduty vehicle is defined by EPA as one with a gross vehicle weight rating (GVWR) of 8,500 pounds or above. Both diesel-powered and gasoline-powered engines are used as heavyâduty engines, though the heaviest vehicles are almost all equipped with diesel engines. The heavy-duty vehicle market consists of a wide variety of vehicles, including trucks, buses, large vans, and recreational vehicles. The manufacturers of many of these vehicles do not manufacture their own engines, but instead purchase engines from others. A given engine may thus have a variety of applications in many different vehicles. To account for the variety of the heavy-duty vehicle fleet, the applicable emissions regulations are based on the output of the engine itself rather than on the performance of the vehicle. That is, standards are set in terras of the permissible amounts of emittants per unit of energy output (i.e., grams per brake horsepower-hour). This is in contrast to the light-duty vehicle regulations, which limit the various emissions to specified amounts per unit distance of vehicle travel (i.e., grams per mile). The Clean Air Act as amended l977 (42 USC 740l et seq.) set emission reduction targets for gaseous emissions from heavy-duty engines. For NOX the target is a 75-percent reduction from a baseline representing uncon- trolled gasoline engine emissions. For hydrocarbons and carbon monoxide, the limit is a 90-percent reduction from the uncontrolled gasoline engine baselines. The specification of the uncontrolled gasoline engine's emissions as the baseline for all engines makes the requirements for hydrocarbons and carbon monoxide stricter for gasoline engines than for diesels, because uncontrolled diesels have lower emissions of these species than gasoline engines. On the other hand, the NOX reduction is a more difficult requirement for diesels, because uncontrolled diesel engines emit more NOX than uncontrolled gasoline engines.
EPA has published an advance notice of proposed rulemaking (U.S. Environmental Protection Agency, l98la), interpreting the 75-percent emissions reduction target for NOX as requiring an NOX emission level of l.7 g/bph-h, as measured on the new heavy-duty "transient" test procedure (described later in this chapter and more fully in Appendix C). Associated with this emissions level are new definitions of useful life and new enforcement audit requirements, described in a later section of this chapter, "Regulatory Options Under the Clean Air Act." This committee has investigated the available technology for reducing the NOX emissions of heavy-duty vehicles, has evaluated the technological feasibility of meeting various possible NOX standards, and has assessed the corresponding impacts on fuel economy, costs, and emissions of other species. In carrying out this study, the committee has reviewed recent technical literature and conducted a number of interviews and site visits, as outlined in Appendix A. The time available has limited the amount of information the committee was able to review in detail. Also, in many important areas data are simply unavailable. Many of our conclusions are therefore tentative, indicating the need for additional studies. Other conclusions have been expressed with large ranges of uncertainty. THE HEAVY-DUTY FLEET AND ITS USE PATTERNS The heavyâduty vehicle industry typically uses gross vehicle weight ratings (GVWR) as a basis for reporting production and sales data. The traditional industry categories are as shown in Table l. EPA's heavy- TABLE l Vehicle Weight Classes Used By The U.S. Vehicle Industry Class GVWR (Ib) l 0-6,000 2 6,00l-l0,000 3 l0,00l-l4,000 4 l4,00l-l6,000 5 l6,00l-l9,500 6 l9,50l-26,000 7 26,00l-33,000 8 33,00l and over
duty vehicle classification, including all vehicles with GVWRs over 8,500 pounds, thus encompasses some vehicles in industry's class 2 and all of classes 3 through 8. Emission control for heavy-duty vehicles is complicated by the hetero- geneity of the heavy-duty vehicle population, the diversity of engines and engine-transmission combinations, and the wide range of operating conditions and patterns of use. The buyer typically specifies the type of vehicle and the type and manufacturer of the engine, transmission, and other vehicle equipment. The choice of a gasoline or diesel engine is determined primarily by economics. Diesels have better fuel economy in terms of miles per gallon but higher initial costs. If the higher cost of the diesel engine can be recovered from fuel savings in something like three years, the buyer will choose a diesel unless there are compelling reasons not to do so. Table 2, taken from the EPA draft regulatory analysis, (U.S. Environmental Protection Agency, l980a), shows heavy-duty vehicle sales by weight class and by year. The growth in the 8,50l-l0,000 pound class, and the decrease in classes 3, 4, and 5 (and perhaps 6) is evident. Table 3, adapted from the same source, shows the economic judgment already being made in favor of the diesel engine in classes 7 and 8, and probably in class 6. Most current projections of diesel use in heavy-duty vehicles (e.g., Jambekar and Johnson, l98l) forecast increasing use of diesel engines in the lighter heavy-duty weight classes. The emissions projections in this chapter and the cost projections in Chapter 5 use these projections. This shift to diesels would result in an increase in emissions without additional controls. Heavy-duty trucks operate in both rural and urban areas. The proportion of use in each is important, because rural areas have better air quality than urban areas, and correspondingly less need to control emission. Table 4 shows that the heaviest trucks (in classes 7 and 8), almost all of which are diesel-powered (Table 3), drive most of their miles in rural areas. With the information in Tables 3 and 4, one can calculate roughly the relative amounts of pollutants emitted in rural and urban areas by heavy-duty trucks if one knows the amounts of pollutants emitted by the various classes of such vehicles. This latter can be deduced roughly from the amounts of fuel used by the different classes; in l973, class 3 trucks consumed 2.6 percent of total highway fuels; class 4, 0.l9 percent; class 5, l.5 percent; class 6, 3.l percent; class 7, l.2 percent; and class 8, 9.9 percent. One can conclude from all of this that about half of the pollution produced by gasoline-powered heavy-duty vehicles was emitted in urban areas, while only about one-sixth of the heavy-duty diesel emissions were produced in urban areas. HEAVY-DUTY EMISSIONS REGULATIONS Test Procedures In the current steady-state test procedures for certifying the compliance of heavy-duty engines with emissions standards, the emissions are measured
O 01 jO 4J tf 3 3 CO woe â¢H Â«, ^.2 01 > 4J ON rH <J- ON NO h^ in O rH CO CO in ,â t r^. O CO 00 o |HÂ« O 01 rH rH oo Â«o tv ON rH _rj f. 00 CM en CM ^j-" m O CM vO 1 01 O 01 CO ON in m ON en vO !^ yf pd in * en m NO m 01 a 4J Â« CM oo NO NO rH en â¢Â§ rH CO rH in 5 CO o CO m â¢* ~* rH rH NO O k i 1 â¢a -a ON in 0 vO CA CM vO o 01 CO rH o CO in o ON 0 td 4-* o OO in o NO o 0 4J CO >* H CO en en en CM CM en CM vo" (j 8 o "i o ^ 41 5 00 01 f. j2 ^, 0 > in NO 00 00 NO m ^-J- 00 4-1 ,iQ CO o O CM ON ON NO i-H CM h 01 CO O vO 00 r- o co â¢# co CO rH r-T rH Co" *B CO cn co en .3. o m o o o *O o co ot i*^ NO o f^ vO co VH â¢ 01 J3 CO ^/ rH rH rH rH rH rH rH CO tJ 41 01 nj Â« rH H u r~- | ^^ id -H rl CO rH O ON vÂ£> ON 00 00 â¢* *e 0 CO 4-1 O 8 co CO O O CO rH *-H ON NO rH in 01 4J o td CO O O CM m CM ON vO oo rH CO 01 O ^j.' CLJ 9C "4H O t-H vD CO f-~ ^ CM CM CM o 0 si co g CO r*l O CM CO â¢* â¢* CM CM en CO - â¢H < 4J -0 *~4 D- (_j JQ U UH O. CO rH 0 CM oo NO en O rH rH CO 3 O. 01 *^ 8 01 CO O O NO ON ON rÂ» CM 00 CM 4-1 O M rH on m o m i-H en CM O CM fll (1) co CO iH rH ON vO 9> r-J O ON CM m ON r^ V V fi CO ON rH y Â£. O t-H CM CO in NO m 1-H ON !** 4-1 01 cd ki i~H QJ â¢^ ix > i-i c x Ol O CO >, in I *~^ 4J IH| a 01 4-1 CO 3 01 O O rH O |J CM 00 ON O CM NO NO en CM ON JO 01 01 00 5 I 00 rH e^ â¢< co o m cd â¢ Â« rH ON ON ON ON en SJ rH en A CO *- <r p/ id e rH vO O CO -3- en ft^ r>. â¢O > O rH rH rH CM en CO 3: 4-1 o c cd W g 4. iH cd a) 3C Â£2 u CO -3* 1 â¢*"** CO 4J 01 jS** rH O rH ON rH r^ 00 O ^f co â¢w 0 01 O O vO in CO Â«O O CM <J- in B C5 O C CO o O CO ON CM m rH f^ CO 3 iH M id - - H A 9t A A H O C H â¢-H <f vO CM in en >o 00 co o a. 4-1 O rH rH rH â¢H râj IM ^^ O rH cd o o c x 4J m co e co co 1 ^^ rH â¢ g 01 rH 0 vO _}- ^ ^ NO oo CO ao 0 â¢a CO O O CO O O vO CO rH rH 5 rH ON m m 0 00 4-> H CA cfl Â« â¢ H O c^ A A H CO o Â«Jti f: rl .-H 0 â¢* p^ ~rr o en ON oo CM r--. ^ O rH rH rH CO en <t rH in in CO â¢ > I- l \^s 01 Co a O rH Ol td 4J id CO 0 01 01 â¢ ^^ id ON vO r*> CM rH m ON rH cd CO nt &. I o CM en rH o O CO CM â¢ 4J rH 0 oo en O o CM in ON CO â¢rl O 3 CO o O O M f. A A A M rH 0 â¢a â¢H m â¢ 00 f^* en fs. ,^- rH rÂ» CM D.T3 0 B 4-> -0 -3- 00 r- â¢* O CM en rH co e ^â¢i O 4H -H CO 00 rH 4-1 O g o a. 4J 0 c T3 Cd Q CO CM CM m m O 00 CO o 01 iH m (Xi m m m o O 00 CO O 4-1 0 â¢ rH |^ r-. r-~ en CM CM 00 01 O c x o CO & rJ1 oo" O M o â¢ cd co CO CM m o oN â¢0 0 T3 CO â¢^â¢t o m rH r^-. CM ON 00 r^ CM <1 | rH *Â£ -Â£ m m CM ON m r^. O en ON S rH > 0 O 00 M en CM CM rH CM CM CM CM rH % 0 e g 3 h eo co Â£ NO m - en CM QJ **D A H ON r~- ON ON u o 01 ON ON ON ON OV H rH rH H iH H rH rH t-H CO CA
CO 41 CO 01 OJ > CD PB 01 rH ^ co 3o k i ^^ O |j U 01 o 00 rH > Cd 0 0 to CO O CO Â«-O 01 cd rO fi rH CO H CO 0) O 01 CJ ^-* j3 Cd 01 cn 1 X"N Â£> l~^ rH O H 0 0 rN (O CO O O 4J 4 J CO Â« Â« ^ o CO vO CO Â£J H rH CM CO E 14H CJ s^ cd O 1 '-v 01 CO vO rH O B 01 0 0 M co in o *â I CO B * â¢ rH (J Cd ON vO ^ c rH rH CM 01 CJ *-s IH O 0 01 1 ^"^ 01 PM m rH O bO 0 0 CO co co o m 4J 0t eo â¢> Â« C Cd vO O^ 01 * rH rH rH o co CJ N-/ M CO * cd CJ st I ^-x CO rH O Ir*^ MOO co XI CO O O Cd a Â« . CO ^H *^ NO rH CJ i-t rH Cd CO OT co O O o o >-, MOO k i M â¢ â¢> O Cd CO ^f CJ CJ v^ ^ c0 to H CM I ^v 01 rH O CO CO O O i M u~> O â¢H cd â¢ â¢ O rH 00 O rn CJ N_^ r-( M (^ Cd â¢ 01 < SH CO O 00 ON I ! I I I ! ! cn CM C7N ov CO Â§ 01 4-J 0. cd â¢a o CO
rH 01 T3 CO to in to vO No ^o ^5 r>* f*^ s cu *^ *^ ^tf* ^J* *^* ^^ *^ rH rH 1 Q ooooooooo 3 0 1 & I rH 00 Â« cu C f> iH *â¢t *J â¢H rH O c" H rH O CO CO 55i5SSStC55 o o O O o "o o ooooooooo â¢t o oo rH o C \^ 1 O â¢H 4-1 CO o o o m â¢a O 01 Cd rH (C 00 * H o CO CO cd co 3 s 1 CO ^ 4J 4J â¢S cd cd CO M Ij rH P *j X! Â§ a o 6O s-4 cm 1 01 O SI H 1 "S rH C 01 n) co XI CJ 01 i-4 O 4J a cd n Q CO â¢H 2 5 f) CO y 01 cd iâ¢H W o co SOURCE : 8 8 1 CO Xt M (4 < Â« 5
while the engine is running on a dynamometer and operating at a defined series of steady loads and speeds. Engines must meet the standard after operation for l,000 or l,500 hours (for gasoline and diesel engines, respect- ively). EPA enforces emission standards for light-duty vehicles by production- line tests called selective enforcement audits (SEAs). In these audits, 40 percent of the engines tested are allowed to have emissions greater than the standard. This is called the acceptable quality level (AQL) requirement. Standards for heavy-duty engines are not currently enforced by such audits. The certification test procedures for l984 and beyond call for emission measurements while the engine is run through a "transient cycle," with second-by-second changes in speed and load (U.S. Environmental Protection Agency, l980b). This cycle requires the installation of new dynamometers, capable of driving the engine to simulate conditions, such as downhill driving, which are not encountered in the steady-state tests. (Appendix C describes and compares the steady-state and transient test cycles.) In addition, the new test procedures require engines to meet the standards until the ends of their "useful lives" (the engine manufacturer's suggested mileage before rebuilding for diesels.) Emission regulations for heavy-duty engines of model years l984 and later contain a new l0-percent AQL requirement, so that 90 percent of the engines tested in a production line audit must meet the applicable standard. (EPA recently announced (U.S. Environmental Protection Agency, l98lb) plans to defer enforcement audits two years and to relax the AQL requirement to 40 percent.) The AQL requirement and the point in the engine's lifetime when the standards apply are important factors in assessing control technology. Much of the data received by the committee are from new engines. Such data cannot be directly interpreted in terms of legal emissions standards. Emissions of new production engines must be lower than the standards with which they are intended to comply by a deterioration factor that accounts for any increase in emissions as the engines age and a safety factor to account for production line variability during enforcement audits. The deterioration factor is defined as the ratio of the emissions of the engine at the end of its useful life to those of the new engine. This factor is determined as part of the engine certification procedure for new engines. Once it is determined, subsequent emissions tests are made on new engines and the results are multiplied by the deterioration factor to yield a value for useful-life emissions. This value is the one that must meet the standard. Another safety factor is used by manufacturers to ensure passing production line enforcement audits, based on the regulatory specification of the AQL and the manufacturer's estimate of production line variability. This factor decreases if production line variability decreases or if regu- lations are changed to allow the AQL (the percentage of engines that can fail the standard in a production line audit) to increase. The effects of these various requirements can be summarized by a numerical example. Manufacturers are now required to meet a standard of
8 l0 g/bhp-h for the sum of hydrocarbons and NOX. With a. deterioration factor of l.25, a new engine must meet a standard of l0 divided by l.25, or 8 g/bhp-h. If the manufacturer decides to set a l0-percent margin of safety to satisfy the proposed production-line audit requirement, engines would have to be designed to meet an emissions standard of 8 (0.l x 8), or 7.2 g/bhp-h. Thus an evaluation of the technological feasibility of meeting this l0-g/bhp-h standard must look for a new engine capable of achieving an emission level of 7.2 g/bhp-h. Table 5 summarizes manufacturer and EPA estimates of new-engine emissions levels required to meet various NOX standards. Because of the relatively recent institution of the transient test cycle, the available data on engine emissions are derived largely from the old steady-state procedures. There is no general correlation between emissions measured on the two cycles; correlations are different for different emission species, for different engine types, and even for different manufacturers. The best correlations between the two cycles are those for NOX emissions, but these correlations permit only estimates of transient-cycle emissions from measurements on the steady-state cycle. The effect of the new test cycle on manufacturers' abilities to develop systems for meeting new emission standards within a given time is also important. For example, installing new dynamometer installations will require some time. It will also take time for manufacturers to develop data bases on the performances of their current and prototype engines, measured on the new transient cycle, and to evaluate the impact of a new definition of useful engine life. Proposed Emissions Standards The Clean Air Act as amended l977 (42 USC 740l et seq.) prescribed specific reduction targets for gaseous emissions and the "greatest degree of emissions reduction achievable" for particulate emissions. In carrying out these mandates, EPA has promulgated emissions standards for hydrocarbons and carbon monoxide to become effective in the l984 model year. In addition, the agency has pro- posed standards for NOX and particulate matter that would be effective in the l986 model year. These are (in grams per brake horsepower-hour) l.3 for hydrocarbons, l5.5 for carbon monoxide, l.7 for NOX, and 0.25 for particulates. These emissions are to be measured on the new heavy-duty transient test procedure and must be met by engines until the ends of their useful lives. At the time of this report, EPA is revising all these standards, and changing the l0-percent AQL requirement back to 40 percent (U.S. Environmental Protection Agency, l98lb). UNCONTROLLED ENGINE EMISSIONS AND CURRENT STANDARDS Current emission standards for heavy-duty engines regulate hydrocarbons, carbon monoxide, and oxides of nitrogen (NOx). There are also opacity standards for
CO ~ CO ,0 O 01 CO h *O C 3 01 a> â¢a M 3 CO o 4J â¢a o â¢H O -* co m 01 M 4J cd â¢ â¢ â¢ c Â£ CO IH iH CO CÂ»J â¢H W 3 1 1 1 2^ 4-1 C P-4 iH ON in CO V CO cd i iH CM iH 01 H 14-1 X-N o t^ JS Â« 00 I 1 X 4J O si 01 -H a o ^^ 4-1 CO k i M a â¢H ^J ffc, 0 ^ CO H 41 a. 4-1 (X â¢O Ed 01 (X â¢H M â¢^ cd â¢a M M rH O I i 01 nt PM I 1 0 o â¢a H W rH rH 4J c Â£= a CO 01 M T3 Â£> ca â¢H ft fl â¢a CO CO â¢ 01 M i CO CO a O c o ot â¢o CO 00 c 4J O. CO a 1â 1 â¢ 4J O -.y CO â¢ A â¢ 4J T3 -J tek c M o- o 4-1 Â« O a 1 1 4-1 01 â¢H 4-1 c <Â£} H 4-1 01 E~* 01 01 01 (O i C C r-f .H rH -H 01 iH 01 rH o 0 01 o S. c 01 â¢H 0 o â¢H CO O CO O a 4J Pt u 0Â° 4> co 41 co A O 9 4J â¢H Â« -H cd 01 O OD W Q O O U rH 4-1 M 0 4J O O O1 â¢ A |Li o M 01 dj 01 Â«t k i rH 0Â° o 4-J *H o 4J 2 â¢5 rj 4J CO 0 c d g â¢H 01 â¢ 2 CO M CO i Ol *o 4-1 Ol O iÂ«H Q M ^*s a ,c â¢a i c a â¢H â¢8 CO C .H 01 01 m 4J 4-1 A A â¢H rH &5 fl} s â¢U U3 CO ^ s^ o a U cO 01 l-l CO Â« â¢H Â°J â¢a 4-1 r^ t^ o O n H O H 3 P H H S3 rH r-\ ~3 ~3 cO O
l0 diesel smoke. As required by the Clean Air Act, EPA is proposing standards for diesel participates, to become effective in the l986 model year. Table 6 gives estimates of emissions from uncontrolled heavy-duty engines. The significant points of this table are the differences between gasoline and diesel engines. Without emission controls, gasoline engines have much higher emissions of hydrocarbons and carbon monoxide than diesel engines, while diesel engines have higher emissions of NOX. The committee estimates the uncontrolled NOX emissions of diesel engines as one and one-half to three times as great as those of gasoline engines without NOX controls. Particulate emissions from gasoline engines are usually associated with lead salts from the lead additives used to improve octane numbers. Recent regulations limiting the lead content of fuel, have reduced emissions of lead particulates from gasoline-fueled vehicles. Diesel particulates are organic in nature, resulting from the diesel combustion process. Gasoline engines are generally considered insignificant sources of organic particu- lates. EPA has assumed that they can comply easily with any particulate standard and is not proposing that gasoline engine manufacturers run certi- fication tests on particulate emissions. Current and proposed emission regulations for heavy-duty engines are tabulated in Tables 7 (federal standards) and 8 (California standards). The levels shown for l986 are only proposed levels, not actual regulations. The l984 hydrocarbon and carbon monoxide standards are currently undergoing revision (U.S. Environmental Protection Agency, l98lb). In some cases standards for heavy-duty engines have been expressed as a limit on the sum of hydrocarbons plus oxides of nitrogen (HC + NOX). This combined standard allows the manufacturers flexibility in designing engines to achieve reductions in these two species. More recently the standards have included limitations on both hydrocarbons and HC + NOX. The ability to use this trade-off is limited by the hydrocarbon standard. If an engine with no hydrocarbon emissions were produced, it could have NOX emissions of l0 g/bhp-h, according to the l98l federal standards. If a l98l federal engine just met the l.5-g/bhp-h hydrocarbons standard, it would have an NOX emissions limit of 8.5 g/bhp-h. In evaluating the status of emissions control in heavy-duty engines, it is apparent that for gasoline engines, the main control problems are hydrocarbons and carbon monoxide, while for diesels, NOX emissions will be most difficult to control. Quantitative comparisons are difficult because emissions as measured on the transient and steady-state cycles are not directly comparable and because data on uncontrolled diesel engines cover a wide range. For purposes of rough estimation, however, one may take the NOX emissions of current federal diesel engines as 8 g/bhp-h on the transient cycle. The reduction from the initial, uncontrolled levels of l0-20 g/bhp-h shown in Table 6 thus corresponds to a 20â to 60-percent reduction. The California engines in current production have NOX emissions of about 6 g/bhp-h on the transient cycle, corresponding to reductions of 40-70 percent.
ll cu O G 01 h cu 4H X^v /â s râ V s-N V cd cd -O TJ Pi ^^ N-' ^^ â¢ CU 8 s o Â£ o â¢g k M-l Cd x : 3 o â¢ C 0 X cO **^^ k i O 00 bO â¢o z 00 vÂ£> rH oN OÂ» â¢O ^H rMj ^^ "*! fa A o 2 O O o m CN 00 4J W CO S~*i s^ rH â¢ 00 l O*\ cu jC O o O râ 1 vÂ£i >^ C â¢H I Z â¢ N0 Â«^ ,B bO m 1-1 rH ^ O 0 J>^ G f* o 0 W ^^^ a 0 4-1 M 01 4J 4J C 2 <u < Â« | CO co Q rH O X a 0 Q 1 01 Â£> O o a O p^ fe W CJ CM vO m vO â¢H â¢H 5 01 cO O CO rH m 8P .8 o x m O 01 0 0 4J EC CO * U a vO O o o TJ o t*** ]Lj 00 4-1 8 â¢H cy^ ^ ON tH CO o rH iH C iH CO Â£ rH 1 0 O â¢H h M Â«d 00 M Â£3 Crt *O JUl |N* â¢H U [V] O M a ON 00 G O cd rH O h a. o 0 C O â¢o <*> T PQ g o 0 <n o â¢H & H rH iH rH CO i-j (j 4J 3 01 T-- 4H â¢ cd o J> 01 g u C H SrH O h 4-1 â 3 o 4-4 a C 01 O CO O >â¢> â¢H O â¢B 01 0 01 8 01 TJ â¢o â¢H â¢H M CO CO 4J â¢H 4J rH CO O o 1 3 O 1 D â¢H G a o â¢H 01 X cd IH e o> CO H O aN <n JÂ«4 H â¢H G 01 iH CO iH rH H H M 01 G v 0 cd 4-j cd CO H â¢H cd k i c d C k i ? rH 4J â¢Â° cu 0 9 vO C C O O O 01 ca cu â¢H r^ â¢H iH 4-1 }wj â¢H x: 0 9 C bo D. iH O CO V i-i O CO 01 CO 01 â¢H â¢H â¢s 4-1 W 8> Â§ co rH cd a 01 cd u C ^Â» cd â¢H cd H Cu O H W H o o o O cd ja o â¢o
12 TABLE 7 Federal Exhaust Emission Standards for Heavy-Duty Vehicles Years Gaseous Emission Limits g/bhp-h unless otherwise noted8 Smoke(Z opacity)1* Carbon Hydrocarbons Hydrocarbons Monoxide NOX plus NOX Pre-1969 _ __ _ _ 1970-1973 275ppm 1.5Z â â 40/20/â 1974-1978 â 40 â 16 20/15/50 1979-1983Â° d 1.5 25 â 10 20/15/50 1984-19856 f 1.3 15.5 10.7 â 20/15/50 1986 & Laterf 1.3 15.5 Â« â h aPrior to 1984 the steady-state procedure is used; for 1984 and later the transient test is specified. Units are grams per brake horsepowerâ hour unless otherwise noted. ^Smoke limits are on special cycle for measuring diesel smoke. The numbers are percent opacity limits for three conditions: acceleration, lug, and peak. COptional standard of 25 g/bhp-h carbon monoxide and 5 g/bhp-h hydrocarbons plus available for 1977-1983 in California and 1979-1983 federally. ^Changes in details of the test procedure made in 1979. Change in hydrocarbon analyzer gives higher measured hydrocarbons value by 0.5 g/bhpâ h for same engine. eOptional steady-state standards for 1984 diesels only are 0.5, 15.5 and 9 g/bhp-h for hydrocarbons, carbon monoxide, and NO^ respectively. U.S. Environmental Protection Agency (1981b) has announced that they will revise the 1984 hydrocarbons and carbon monoxide standards to a level that will not require catalysts on gasoline heavy-duty engines. 8The statutory Clean Air Act standard is 1.7 g/bhp-h; the U.S. Environmental Protection Agency (1981 a) has announced its intention to propose a standard of approximately 4 g/bhp-h. hThe U.S. Environmental Protection Agency (1981c) has proposed a particulate standard of 0.25 g/bhp-h for 1986.
l3 TABLE 8 California Exhaust Emission Standards for Heavy-Duty Vehicles Gaseous Emission Limits (g/bhp-h unless otherwise noted) Years Carbon Hydrocarbons Hydrocarbons Monoxide NOx plus NOX Pre-1968 __ 1969-1971 275 ppm 1.5% 1972 180 ppm l.0 1973-1974 40 â 16 1975-l976 30 â 10 1977-1978b 1.0 25 7.5 l979C 1.5 25 7.5 1980-1983C 1.0 25 â 6 l984 and later3 0.5 25 â 4.5 aCalifornia has used the same test cycle as EPA. All numbers in this table are from the steady-state cycles. For 1984, manufacturers can choose the option of complying with the federal standards, using the transient cycle, except that the applicable NOX standard is 5.1 g/bhp-h rather than 10.7 g/bhp-h. Units are g/bhp-h unless otherwise noted. ''Optional standard of 25 g/bhp-h for carbon monoxide and 5 g/bhp-h for the sum of hydrocarbons and NOx are available for 1977-1983 in California and 1979-1983 federally. cChanges in details of the test procedures were made in 1979. The change in the hydrocarbon analyzer raises the measured value of hydrocarbons by 0.5 g/bhp-h in a given engine.
l4 The l977 Clean Air Act amendments' requirement that all engines meet a common NOX emissions standard, determined by taking a 75-percent reduction from the emissions levels of the average uncontrolled gasoline engine, means that the diesel engine must reduce NOX emissions more than the gasoline engine. For the range of uncontrolled diesel emissions (one and one-half to three times the emissions of the average uncontrolled gasoline engine) the percentage reduction requirements for the diesel engine range from 83 to 92 percent. CONTRIBUTION OF HEAVY-DUTY ENGINES TO TOTAL EMISSIONS In l977 the total national emissions of oxides of nitrogen (NO + NO2) from man-made sources were about 2.2 million tons. Of this, about l0 percent came from heavy-duty vehicles. EPA estimates that, without further regu- lation of heavy-duty vehicles, this percentage will grow to l5 percent by l990. The relative contribution of heavy-duty engines to total NOX emissions depends on the location. In rural areas, without other significant sources of NOX emissions, the relative contribution of the heavy-duty engine will be larger, but these will be areas of relatively low ambient pollutant concentrations. Estimates of the total emissions of NC^ and of the relative contri- butions of heavy-duty engines of each type are displayed in Tables 9-ll. Table 9 shows the nationwide inventory in l977 as prepared by EPA using a modified emissions factor forecast, and an alternative inventory prepared by the Ford Motor Company. The inventories are in good agreement on total emissions and the contributions of different sources, though the EPA inventory assigns a greater contribution to heavy-duty engines than the Ford inventory. Table l0 tabulates EPA forecasts of an increase in both total emissions and heavy-duty emissions, but with the emissions from heavy-duty vehicles, assuming no further NOX controls, increasing at a faster pace. The emissions forecasts in Tables 9 and l0 are based on estimates of growth in population and industrial activity, the types of fuels to be used, and the emission control technology to be applied. Table ll shows the current emissions and forecasts for the Los Angeles (South Coast Air Basin) and San Francisco (Bay Area) air quality regions. Here the percentage contributions from heavy-duty vehicles are greater than the nationwide average. This is because controls on emissions from light-duty vehicles and stationary sources are more stringent in these regions than in the nation as a whole. Without further NOx emissions standards for heavy-duty vehicles, heavy-duty vehicles are predicted to contribute 24 percent of the total NOX inventory in the South Coast Air Basin by l987. This is 44 percent of the total mobile source emissions inventory forecast for that year. The ultimate impacts of emissions depend not only on the kinds of emissions that leave a mobile source, and their amounts, but also on their transport and the extent to which they are transformed chemically in the
15 CO 01 u â¢H >> 4-1 fa t Â§ o â¢H co a M X O a I cu "8 CO <u 4J CD H M cu cdQ 4-j cd C 4J 01 O O 4J ^ k i co rÂ» CM o o 01 >4-l CX. 0 -* s u w o 4-1 X*N ^ o CO lJ h JS a cd o o cu 4J *T3 4-1 Â£N ^ C*J -^ vO C |_i O cn iH CM co 01 O *-H ^ vO *^ ^^ r** I to 3 8, i-l O* H M s--* CM IH o CO 01 0 spg 4-1 4-1 Cd C 4J â¢H 01 O 4-> O 4J CO I-l â¢^ r** co o M 01 <4H -Â» o CO CX O H 0-. M CO 'h o cu 00 ^D *^f ^O 4-1 >\ CM o "^ r~ o oo m sj- r- ^â J w ^^ ^* â¢H Â« CO CM co co a C 0) k i CO o i-H 301 â¢H O O O CO â¢H 01 CO k i ^! C3 d tfj 01 -H r-4 01 O II > rH 01 rH CO w >-, CO 01 ^O i-H O CO i-l U-l grH cd 0 T i o ^> C0 cO I > 4-1 4J CO O O 0 01 H H CO â¢8 g. 01 01 CO td o 00 9* co CO
16 CO 01 o CO "â¢W *H 01 O 42 rH 01 O C > â¢H O 42 â¢H >> 01 4 J 4J s-\ B* S34J 43 0 C 1 1 â¢H 1 01 k i S O ^ f U > M H C cO a1 o cu a â¢ cj SB ^ rH iH 01 PS Ml 1 o o o â¢ â¢H cO 4J o 3 oo 43 ON â¢H H -. C M J^ o O CJ x-s C M cu ) 01 cd bfi If s ^ cu <f 4J CO O C c O t-i O 01 vH dj CO O. CO CO â¢H 4J ) k i o CD i/^ iH M #i O 01 â¢H CO C>J CO cu PH B G 4J 1 01 ta o O CM t^ O M i-j O r^ co M it NO CO P-i +rf 4-1 *H co co i-J â¢o O W CM CM c H ^ 4-1 3 G Â§ 1 0 o â¢H â¢H CO 1 M 0* CO 55 â¢ Â» P B (_) f" ^ ^^ prf â¢ O^ O*^ B cu ^^ o^ o >H i-t (H co
l7 TABLE ll California Air Resources Board NOX Emissions Inventory (Current and Forecast) for South Coast Air Basin and Bay Area Air Quality Management District Estimated and Forecast Emissions by Year l979 l987a Source of Emissions (tons per (percentage (tons per (percentage day) of total) day) of total) South Coast Air Basin Heavy-duty vehicles: 245 l8 274 24 Gasoline (6l) (56) Diesel (l84) (2l8) Total motor vehicles 830 60 622 54 Total all sources l,380 l00 l,l58 l00 Bay Area Air Quality Management District Heavy-duty vehicles: l26 l6 l39 l9 Gasoline (32) (30) Diesel (94) (l09) Total motor vehicles 4l7 55 3l7 44 Total all sources 765 l00 720 l00 Assumptions: New heavy-duty engines controlled to hydrocarbon emission levels of 0.5 g/bhp-h and hydrocarbon-plus-NOjj emission levels of 4.5 g/bhp-h (measured on the steady-state cycles) in l984 and later years. Light-duty engines controlled to NOX emission levels of 0.4 g/bhp-h in l983 and later years. SOURCE: Informal communication, R. Bradley, California Air Resources Board, January 1981.
18 atmosphere. The impact of mobile source emission controls thus depends not only on the control technology used, but also on how the vehicles are operated. A 75-percent reduction in the NOX emissions of heavy-duty vehicles cannot be translated directly into a change in atmospheric concentrations of any chemical species that results from NOX emissions. Such a trans- lation requires a knowledge of the emission source patterns for the region in question, the total atmospheric loading of emissions from all sources in the region, and the detailed transformation processes. Such knowledge is not available now. Although complete knowledge of all these processes is not available, it is possible to make good estimates of the effects of emissions control on air quality. For example, in regions where heavy-duty engines make a significant contribution to overall NOX emissions, a significant reduction in the atmospheric burden of species formed from these emissions would be associated with reductions of heavy- duty NOX emissions. In evaluating the significance of these numbers it is important to consider the reduction in urban NOX emissions required to attain and main- tain air quality standards. It is further necessary to consider the cost of reducing a given amount of NOX emissions from heavy-duty vehicles compared to the cost of the same reduction of NOX emissions from other sources. The relationships between NOX emission levels and those of other emissions should also be considered. This type of evaluation is beyond the scope of our report, but it should be an important ingredient in an overall regulatory program. REGULATORY OPTIONS UNDER THE CLEAN AIR ACT The Clean Air Act as amended l977 (42 USC 740l et seq.) is routinely referred to as "technology forcing" legislation, under which standards should be set in anticipation of technology's becoming available. The meaning of this term is less than clear. Nevertheless, the concept is legally sanctioned, and in specific instances the courts have upheld agency regulatory action based on the belief that technology "on the horizon" would be further developed to achieve compliance (Federal Court of Appeals, l975). The mobile source provisions in the original Act of l970 differed sig- nificantly from most other pieces of regulatory legislation in assigning much less discretion to the regulatory agency, Congress chose, essentially, to write the emissions standards itself, specifying the required reductions in emissions in the legislation. Although subsequent events have modified the l970 standards and legisla- tion somewhat, their basic purpose and structure have not been abandoned. Still, new concernsâenergy conservation, international trade, cost and technological feasibilityâpervade the regulatory process. These issues were brought to the fore in the l977 amendments, which added the sections of the Act under which NOX emissions of heavy-duty vehicles are to be controlled. In an important sense, the structure of the l970 Act is preserved; Congress
l9 has itself specified a goal (a 75-percent reduction of NOX emissions from their uncontrolled levels). However, the new concerns mentioned above are reflected in a new kind of authority, which allows EPA under certain circum- stances to promulgate regulations that will not achieve a 75-percent reduction, at least for some time. EPA has two options by which it may modify the statutorily prescribed standard. These are contained in Sections 202(a)(3)(B) and (C) and Section 202(a)(3)(E) of the Clean Air Act as amended l977 (42 USC 740l et seq.). Briefly, under the former option EPA may depart from the 75-percent reduction only if two tests are met: (l) that the standard cannot be achieved by tech- nology "reasonably expected to be available for such model year without increasing cost or decreasing fuel economy to an excessive and unreasonable degree" and (2) if the National Academy of Sciences has not issued a report with findings "substantially contrary" to those of EPA. Under the authority of Section 202(a)(3)(B) once these facts are determined EPA may revise the 75-percent standard to a level that is "the maximum degree of emission re- duction which can be achieved by means reasonably expected to be available for production of such period." This standard will be temporary (for three model years only). Under the second option, EPA may revise the statutory standard after a "pollutant-specific study" of the health effects of the pollutant in question has been conducted. Then, EPA may promulgate a standard, under Section 202(a)(l), (2), and (3), that reflects the greatest degree of emission reduction achievable through the application of technology that the Administration determines will be available... giving appropriate consideration to the cost of applying such technology within the period of time available to manufacturers and to noise, energy and safety factors associated with the application of such technology. It should be noted in this context that in adding these various "escape clauses," Congress specifically said that it was ignorant of the technological feasibility of its 75-percent reduction goal. (U.S. Congress, l977). EPA has asserted that this second option comes into play only for "health effects reasons." The first option, in EPA's view, comes into play when there is "a feasibility problem." (U.S. Environmental Protection Agency, l98la). Since EPA believes that "there is a feasibility problem for [heavy- duty diesels]" it proposes to promulgate a temporary standard under Section 202(a)(3)(B).* Thus, the ultimate standard must reflect "the maximum degree of emission reduction which can be achieved by means reasonably expected to be available. * The Clean Air Act contemplated that the regulatory standard for the 75-percent reduction in NOX emissions would be in place shortly after the passage of the l977 amendments. Accordingly, section 202(a)(3)(B) of the Act provided for periodic revisions to be promulgated between June l, l980, and December 3l, (footnote continued on next page)
20 REFERENCES California Air Resources Board. l976. "Public Hearing on Proposed Changes to Regulations Regarding Exhaust Emissions Standards and Test Procedures for l979 and Subsequent Model Year Heavy-Duty Engines." Sacramento, Calif.: California Air Resources Board. (Staff report 76-20-2) October 5. Federal Court of Appeals for the 2d Circuit. l975. Society of the Plastics Industry v. OSHA, 509 F.2d l303 (2d Cir. l975). Jambekar, A. B., and J. H. Johnson. l98l. "Effect of Truck Dieselization on Fuel Usage." Warrendale, Pa.: Society of Automotive Engineers. (SAE Paper No. 8l0022.) U.S. Congress. l977. Legislative History to Public Law 95-95, U.S. Code Cong, and Admin. News, 95th Cong. lst sess., p. l544. U.S. Environmental Protection Agency. l980a. "Draft Regulatory Analysis, Environmental Impact Statement and NOX Pollutant Specific Study for Proposed Gaseous Emission Regulations for l985 and Later Model Year Light-Duty Trucks and l986 and Later Model Year Heavy-Duty Engines." Office of Mobile Source Air Pollution Control. Washington, D.C.: U.S. Environmental Protection Agency, November 5. . l980b. "Control of Air Pollution From New Motor Vehicles and Motor Vehicle Engines: Gaseous Emission Regulations for l984 and Later Model Year Heavy-Duty Engines." (Final rule.) Federal Register 45(l4):4l36. January 2l. ._ l98la. "Control of Air Pollution from New Motor Vehicle Engines: Gaseous Emission Regulations for l985 and Later Model Year Light-Duty Trucks and l986 and Later Model Year Heavy-Duty Engines." (Advance notice of proposed rulemaking.) Federal Register 46(l2):5838. January l9. . l98lb. "Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines: Certification and Test Procedures." (Notice of intent.) Federal Register 46(70):2l628. April l3. . l98lc. "Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines: Particulate Regulation for Heavy-Duty Diesel Engines." (Proposed rule.) Federal Register 46(4):l9l0. January 7. l980, or between June l and December 3l of each third year thereafter. EPA has never promulgated regulations to implement the 75-percent reduction. Although the December 3l, l980, date has already passed, EPA believes that the authority of 202(a)(3)(B) can still be used to promulgate a standard with a reduction of less than 75 percent. Were this incorrect, EPA's options (before l983) would be to revise the standard under 202(a)(3)(E), i.e., for "health effect reasons," or promulgate a 75-percent reduction standard. This issue has some importance, because the factors to be taken into account are different in each circumstance, and the NAS role is nonexistent under 202(a)(3)(E).