EPA420-F-00-049 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY ANN ARBOR, Ml 481 05 November 10, 2000 OFFICE OF AIR AND RADIATION MEMORANDUM SUBJECT: Updated Emission Modeling for Large SI Engines FROM: Alan Stout, Mechanical Engineer Assessment and Modeling Division THRU: Glenn Passavant, Senior Program Manager Assessment and Modeling Division TO: Docket A-98-01 The Environmental Protection Agency (EPA) has developed the NONROAD Emissions Model to compute nationwide emission levels for a wide variety of nonroad engines. The purpose of this memorandum is to describe the inputs to the NONROAD model and present estimated emission contributions from nonroad spark-ignition engines rated above 19 kW (25 hp). These engines are referred to in this document as Large SI engines. These modeling results support the Agency's final finding that these engines contribute to air pollution in the United States. The NONROAD model incorporates information on emission rates, operating data, and engine population to determine annual emission levels of various pollutants. Operating data and population are determined separately for dozens of different applications. The model uses the following equation to calculate total emissions for each group of engines; individual parameters are described further below: Emissions = EF x DF x p x LF x TF x Hours x Units Where, EF = emission factor in g/hp-hr DF = deterioration factor (dimensionless) P = rated engine power in horsepower LF = load factor (dimensionless) TF = transient adjustment factor (dimensionless) Hours = operating hours per year for each unit Units = population of engines operating in a given year ------- Emission and Deterioration Factors Engine emissions are measured on an engine dynamometer, with results reported as a mass of emissions per unit of work (g/kW-hr or g/hp-hr). Southwest Research Institute recently compiled a listing of test data from past and current testing projects.1 These tests were all conducted on new or nearly new engines. Table 1 summarizes this test data. All engines were operated on the steady- state ISO C2 duty cycle, except for two engines that were tested on the steady-state D2 cycle. The results from the different duty cycles were comparable. Lacking adequate test data for engines fueled by natural gas, we model those engines to have the same emission levels as those fueled by liquefied petroleum gas (LPG), based on the similarity between engines using the two fuels (in the case of hydrocarbon emissions, this is based on nonmethane measurements). The listed emission levels for gasoline engines represent a composite of emissions from air-cooled and water-cooled engines. Table 1 New-Engine Emission Factors for Large SI Engines (g/hp-hr) Fuel LPG Gasoline NOx 11.99 7.13 THC 1.68 6.22 CO 28.23 203.4 PM 0.06 0.06 Emission levels often change as an engine ages. In most cases, emission levels increase with time, especially for engines equipped with technologies for controlling emissions. We developed deterioration factors for uncontrolled Large SI engines based on measurements with comparable highway engines.2 Table 2 shows the deterioration factors that apply at the median lifetime estimated for each type of equipment. For example, a deterioration factor of 1.26 for hydrocarbons multiplied by the emission factor of 6.22 g/hp-hr for new gasoline engines indicates that modeled emission levels increase to 7.84 g/hp-hr when the engine reaches its median lifetime. The deterioration factors are linear multipliers, so the modeled deterioration at different points can be calculated by simple interpolation. Table 2 Deterioration Factors Pollutant THC CO NOx Median Life Deterioration Factor 1.26 1.35 1.03 Operating Parameters The NONROAD model relies on the OE Link database from Power Systems Research to 2 ------- provide market information for individual engine models, each with an established power rating." Engines typically operate at a variety of speeds and loads, such that operation at rated power is rare. To take into account the effect of operation at idle and partial load conditions, a load factor indicates the degree to which average engine operation is scaled back from full load. For example, at a 0.3 (or 30 percent) load factor, an engine rated at 100 hp would be producing an average of 30 hp over the course of normal operation. For highly mobile equipment, this can vary widely (and quickly) between 0 and 100 percent of full power. Table 3 shows the load factors that apply to the various applications of nonroad equipment. Emissions during transient operation can be significantly higher than during steady-state operation. Based on emission measurements from highway engines comparable to uncontrolled Large SI engines, we have measured transient emission levels that are 30 percent higher for HC and 45 percent higher for CO relative to steady-state measurements.3 The NONROAD model therefore multiplies steady-state emission factors by 1.3 for HC and 1.45 for CO to estimate emission levels during normal, transient operation. Test data do not support adjusting NOx emission levels for transient operation. Also, the model applies no transient adjustment factor for generators, pumps, or compressors, since engines in these applications are less likely to experience transient operation. Power Systems Research also specifies a value for annual operating hours that apply to various applications, as shown in Table 3. These figures represent an average annual usage that applies over the course of an engine's lifetime. Population The NONROAD model generally uses population data based on information from Power Systems Research, which is based on historical sales information adjusted according to survival and scrappage rates. We are, however, using different population estimates for forklifts based on a recent market study.4 That study identified a 1996 population of 491,321 for Class 4 through 6 forklifts, which includes all forklifts powered by internal combustion engines. Approximately 80 percent of those were estimated to be fueled by propane, with the rest running on either gasoline or diesel fuel. Assuming an even split between gasoline and diesel for these remaining forklifts leads to a total population of spark-ignition forklifts of 442,000. The NONROAD model therefore uses this estimate for the forklift population, which is significantly higher than that estimated by Power Systems Research. Table 3 shows the estimated population figures used in the NONROAD model for each application, adjusted for the year 2000. The split between LPG and gasoline in various applications warrants further attention. Engines are typically sold without fuel systems, which makes it difficult to assess the distribution of engines sales by fuel type. Also, engines are often retrofitted for a different fuel after a period of operation, making it still more difficult to estimate the prevalence of the different fuels. The high percentage of propane systems for forklifts, compared with about 60 percent estimated by Power aPower Systems Research is a firm that provides marketing data on engines and equipment. The OE Link database is a compilation of historical annual sales for individual engine models sold in the U.S. The database is available from Power Systems Research (612- 454-0144). ------- Systems Research, can be largely attributed to expenses related to maintaining fuel supplies. LPG cylinders can be readily exchanged with minimal infrastructure cost as compared to gasoline storage. Natural gas systems typically offer the advantage of pipeline service, but the cost of installing high-pressure refueling equipment is an obstacle to increased use of natural gas systems. Some applications of nonroad SI equipment face much different refueling situations. Lawn and garden equipment is usually not centrally fueled and therefore operates almost exclusively on gasoline, which is more readily available. Agriculture equipment is predominantly powered by diesel engines. Most of these operators likely have storage tanks for diesel fuel. For those who use spark-ignition engines in addition to, or instead of, the diesel models, we would expect them in many cases to be ready to invest in gasoline storage tanks as well, resulting in little or no use of LPG or natural gas for those applications. For construction, general industrial, and other equipment, there may be a mix of central and noncentral fueling, and motive and portable equipment. We therefore believe that estimating an even mix of LPG and gasoline for these engines is most appropriate. The estimated distribution of fuel types for the individual applications used in the NONROAD model are listed in Table 3. An additional issue related to population figures is the level of growth factored into emission estimates for the future. The NONROAD model incorporates application-specific growth figures based on projections from Power Systems Research. The projected growth is reflected in the population estimates included in Table 3. The model also projects growth rates separately for the different fuels for each application. MODELING RESULTS Total mobile-source emission estimates for the years 2000 and 2007 are summarized in Tables 4 and 5. These tables show relative contributions of the different mobile source categories to the overall mobile source emissions inventory. The emission figures are projected to change somewhat between 2000 and 2007. Population growth and the effects of other regulatory control programs are factored into the later emissions estimates. Of the total mobile-source emissions in 2007, Large SI engines are estimated to contribute about 3 percent of HC, NOx, and CO emissions, and about 0.3 percent of PM emissions. The appendix shows how the different Large SI applications contribute to the total emissions for the category. ------- Table 3 Operating Parameters and Population Estimates for Various Applications of Large SI Engines Application Forklift Generator Welder Commercial turf Pump Air compressor Baler Irrigation set Aerial lift Scrubber/sweeper Chipper/grinder Leaf blower/vacuum Oil field equipment Trencher Specialty vehicle/cart Skid/steer loader Rubber-tired loader Gas compressor Paving equipment Terminal tractor Bore/drill rig Ag. tractor Concrete/industrial saw Roller Crane Other material handling Paver Other agriculture equipment Other construction Avg. Rated HP 69 59 67 28 45 65 44 97 52 49 66 79 44 54 66 47 71 110 39 93 78 82 46 55 75 67 48 162 126 Load Factor 0.30 0.68 0.58 0.60 0.69 0.56 0.62 0.60 0.46 0.71 0.78 0.94 0.90 0.66 0.58 0.58 0.71 0.60 0.59 0.78 0.79 0.62 0.78 0.62 0.47 0.53 0.66 0.55 0.48 Hours per Year 1800 115 408 682 221 484 68 716 361 516 488 282 1104 402 65 310 512 6000 175 827 107 550 610 621 415 386 392 124 371 2000 Population 504,696 146,246 19,246 55,433 35,981 17,472 18,659 5,367 38,901 13,363 13,015 11,797 7,855 3,627 9,145 7,436 3,177 788 1,109 2,716 2,607 1,599 2,266 1,362 1,240 1,605 1,367 5,501 1,276 2007 Population 603,099 217,525 27,008 64,265 50,340 24,404 20,977 3,917 38,565 13,252 15,102 13,621 7,845 3,950 9,635 8,099 3,460 1,005 1,207 2,687 2,839 1,798 2,468 1,483 1,351 1,591 1,488 6,102 1,390 Percent LPG/CNG 95 100 50 0 50 50 0 50 50 50 50 0 100 50 50 50 50 100 50 50 50 0 50 50 50 50 50 0 50 ------- Application Pressure washer Aircraft support Crushing/processing equip Surfacing equipment Tractor/loader/backhoe Hydraulic power unit Other lawn & garden Refrigeration/AC Total Population Avg. Rated HP 39 99 63 40 58 50 61 55 Load Factor 0.85 0.56 0.85 0.49 0.48 0.56 0.58 0.46 Hours per Year 115 681 241 488 870 450 61 605 2000 Population 1,227 910 235 314 360 330 402 169 915,678 2007 Population 1,722 1,131 256 342 392 351 466 201 1,127,323 Percent LPG/CNG 50 50 50 50 50 50 0 100 ------- Table 4 Modeled Annual Emission Levels for Mobile Source Categories in 2000 (thousand short tons) Category Large SI Recreational SI NonroadSK19kW Marine SI Nonroad CI Marine CI Locomotive Aircraft Total Nonroad Total Highway Total Mobile Source NOx tons 306 21.3 106 32 2,625 1,001 1,192 178 5,461 7,988 13,449 percent 2% 0.16% 0.8% 0.2% 20% 7% 9% 1% 41% 59% 100% HC tons 125 587 1,460 928 316 31 47 183 3,677 3,772 7,449 percent 2% 8% 20% 12% 4% 0% 1% 2% 49% 51% 100% CO tons 2,294 4,231 18,359 2,144 1,217 133 119 1,017 29,514 49,701 79,215 percent 3% 5% 23% 3% 2% 0.2% 0.2% 1% 37% 63% 100% PM tons 1.6 5.6 50 38 253 42 30 39 459 240 699 percent 0.2% 0.8% 7% 5% 36% 6% 4% 6% 66% 34% 100% Table 5 Modeled Annual Emission Levels for Mobile Source Categories in 2007 (thousand short tons) Category Large SI Recreational SI Nonroad SKI 9 kW Marine SI Nonroad CI Marine CI Locomotive Aircraft Total Nonroad Total Highway Total Mobile Source NOx tons 369 22.4 96 42 2,253 1,018 773 200 4,773 5,529 10,302 percent 4% 0.22% 0.9% 0.4% 22% 10% 8% 2% 46% 54% 100% HC tons 141 616 933 733 214 33 43 205 2,918 2,317 5,235 percent 3% 12% 18% 14% 4% 1% 1% 4% 56% 44% 100% CO tons 2,517 4,445 21,406 2,056 1,128 142 119 1,200 33,013 44,276 77,289 percent 3% 6% 28% 3% 1% 0.2% 0.2% 2% 43% 57% 100% PM tons 1.9 5.9 58 33 226 44 27 41 437 186 623 percent 0.3% 0.9% 9% 5% 36% 7% 4% 7% 70% 30% 100% ------- REFERENCES 1. "Three-Way Catalyst Technology for Off-Road Equipment Powered by Gasoline and LPG Engines—Interim Report Volume 2: Cost-Effectiveness Analysis" Jeff J. White, et al, May 1998, p. 15 (Docket A-98-01, document U-D-4). 2 . "Revisions to the June 2000 Release of NONROAD to Reflect New Information and Analysis on Marine and Industrial Engines," EPA memorandum from Mike Samulski to Docket A-98-01 (Document IV-B-1). 3 . "Regulatory Analysis and Environmental Impact of Final emission Regulations for 1984 and Later Model Year Heavy Duty Engines," U.S. EPA, December 1979, p. 189 (Docket A-98-01, document IV-B-2). 4 . "The Role of Propane in the Fork Lift/Industrial Truck Market: A Study of its Status, Threats, and Opportunities," Robert E. Myers for the National Propane Gas Association, December 1996 (Docket A-98-01, document U-D-2). ------- APPENDIX Emission Modeling Outputs by Application ------- 2000 Emission Levels by Application 2007 Emission Levels by Application APPLICATION FORKLIFTS GENERATORS GAS COMPRESSORS COMMERCIAL TURF OIL FIELD EQUIP. WELDERS AERIAL LIFTS CHIPPER/GRINDER AIR COMPRESSORS PUMPS SCRUB/SWEEPER IRRIGATION SETS LEAFBLOWER/VACUUM TERMINAL TRACTORS RUBBER-TIRED LOADER OTH LAWN&GARDEN SKID/STEER LOADER TRENCHERS CONCRETE/IND. SAWS OTH AG.EQUIP. SWATHERS AIRPORT GSE AG. TRACTOR HYD POWER UNIT ROLLERS OTHER CONSTR. BALERS SPECIALTY VEH/CARTS OTH MAT'L HANDLING CRANES BORE/DRILL RIGS PAVERS TRACT/LDR/BACKHOE PRESSURE WASHERS PAVING EQUIP. HYDR. POWER UNITS REFRIGERATION/AC CRUSH/PROC EQUIP. SURFACING EQUIP. RAILWAY MAINT. FRONT MOWERS OTHER LAWN&GARDEN PLATE COMPACTORS COMBINES TOTALS NOx 247,543 9,020 5,979 4,986 4,659 3,912 3,632 3,512 3,329 2,683 2,627 2,498 2,166 1,768 883 818 669 558 531 497 452 376 359 356 308 307 276 241 225 196 184 182 93 50 48 45 35 32 32 11 9 7 3 o 6 HC* 56,558 1,402 1,000 6,348 961 2,227 2,045 2,111 1,928 1,473 1,472 1,308 2,742 1,014 523 460 421 331 314 603 573 214 456 211 182 182 350 228 150 116 109 108 55 29 29 27 7 19 19 7 12 9 4 4 CO 1,242,159 24,476 17,877 241,464 18,846 74,983 68,709 71,922 65,182 36,621 49,412 43,082 104,089 34,212 17,791 15,437 14,487 11,243 10,667 22,809 21,745 7,198 17,328 7,163 6,203 6,203 13,307 5,164 5,212 3,943 3,706 3,669 1,884 980 969 926 138 652 648 232 457 336 165 136 PM 1,178 42 30 47 22 25 23 23 21 27 16 15 20 11 6 5 4 4 o J 5 4 2 3 2 2 2 3 4 2 1.3 1.2 1.2 0.6 0.3 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0.03 0.03 NOx 297,973 13,199 7,632 5,781 4,653 5,633 3,842 4,077 4,741 3,827 2,784 1,623 2,501 1,859 978 866 737 618 587 546 506 482 404 393 341 339 310 254 226 217 204 202 103 72 53 47 41 36 35 13 11 8 3 o 3 HC* 64,892 2,018 1,277 7,367 960 2,940 1,689 2,450 2,531 1,912 1,222 1,228 3,173 836 549 381 439 347 329 670 638 246 513 221 191 191 391 239 118 121 114 113 58 38 30 30 8 20 20 8 14 10 4 4 CO 1,357,677 35,025 22,820 280,270 18,827 96,845 53,038 83,456 83,883 46,876 38,288 43,716 120,514 26,386 18,417 11,954 14,944 11,630 11,044 25,338 24,178 8,042 19,495 7,408 6,421 6,407 14,807 5,407 3,908 4,074 3,825 3,795 1,950 1,253 1,001 1,024 163 674 671 254 523 385 167 152 PM 1,408 60 38 55 22 34 22 26 29 36 16 12 24 11 6 5 5 4 4 5 5 3 4 2 2 2 3 4 1.4 1.4 1.3 1.3 0.6 0.4 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0.03 0.03 306,100 88,343 2,293,833 1,557 368,760 100,549 2,516,932 1,854 *The hydrocarbon figures include exhaust emissions, but exclude evaporative emissions. 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