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72 impacts of empty miles on fuel consumed in different rail emissions at a "like" port. The detailed methodology requires movements, with a fuel penalty between 4% and 29% in fuel significant amounts of data and resources and produces the efficiency. (71) most accurate results. The mid-tier and streamlined methods require less data and resources but produce less accurate re- sults. (9) Exhibit 3-35 lists these three methods. 3.5 Waterborne/Ocean-Going Vessels There are no current publicly available models for calcu- Cargo movements by marine vessels include ocean-going lating OGV emissions at ports. Most researchers use one of vessels (OGVs) and barge movements pushed by tugs or the three methods described here to estimate emissions at tows. OGVs are discussed in this section, followed by a dis- ports. A list of recent mid-tier and detailed inventories is pro- cussion of tug/tow movements at ports and inland rivers in vided in Exhibit 3-36. Section 3.6. Emissions from OGVs are usually determined at and around 3.5.2 Evaluation of Methods and Models ports because these are the entrances and clearances of cargo into the regions of modeling interest. They are estimated using Since all of the current methods and models estimate emis- information on number of calls at a particular port, engine sions at ports, the geographic distinctions (i.e., national, re- power, load factors, emission factors, and time in like modes. gional, and local/project scale analyses) are less meaningful The current practice to calculate emissions from OGVs is than in other sectors. Generally, to estimate national OGV to use energy-based emission factors together with activity emissions, all major ports are modeled and emissions added profiles for each vessel. The bulk of the work involves deter- together. For a regional approach, such as that done by CARB mining representative engine power ratings for each vessel for estimating California marine vessel emissions, a similar and the development of activity profiles for each ship call. approach is taken where emissions at the major California Using this information, emissions per ship call mode can be ports are estimated and then added together. The difference determined using Equation 6. really relies upon whether a detailed or streamlined method is used for the individual ports and the data that are collected. E = P LF A EF (Equation 6) Where Detailed Methodology E = Emissions (grams [g]), In the detailed methodology, emissions from OGVs are es- P = Maximum Continuous Rating Power (kilowatts timated from detailed information on ship calls at a given port [kW]), together with detailed ship characteristics, time and speed in LF = Load Factor (percent of vessel's total power), each mode, load factors, and emission factors. The more de- A = Activity (hours [h]), and tailed the information collected, the more accurate the results. EF = Emission Factor (grams per kilowatt-hour [g/kWh]). Each parameter, as well as its potential biases and errors, is discussed in the following subsections. 3.5.1 Summary of Methods and Models Calls. The most accurate information for the number of There are three basic methods for calculating emissions calls comes from the local port Marine Exchange or Port from OGVs at ports, namely (1) detailed methodology where Authority (MEPA). MEPAs generally record vessel name, IMO considerable information is gathered regarding ships enter- number, date and time of arrival, and date and time of depar- ing and leaving a given port, (2) a mid-tier method that uses ture. Larger MEPAs also record flag of registry; ship type; some detailed information and some information from sur- pier/wharf/dock (PWD) names; dates and times of arrival rogate ports, and (3) a more streamlined method in which and departure from various PWDs, anchorages, next ports; detailed information from a surrogate port is used to estimate cargo type; cargo tonnage; activity description; draft; vessel Exhibit 3-35. OGV methods. Method Geographic Scale Pollutants Freight/Passenger Detailed Methodology All All Both Mid-Tier Methodology All All Both Streamlined All All Both Methodology

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73 Exhibit 3-36. Recent port inventories. Year Data Port Method Pollutants Contractor* Published Year SO2, NOx, PM10, PM2.5, CO, Selected Alaska Ports (92) 2006 2002 Mid-Tier Pechan NH3, VOC Beaumont/Port Arthur (93) 2004 2000 Detailed NOx, CO, HC, PM10, SO2 Starcrest NOx, TOG, CO, PM10, PM2.5, Charleston (94) 2008 2005 Detailed Moffatt & Nichol SO2 Corpus Christi (95) 2003 1999 Detailed NOx, VOC, CO ACES NOx, VOC, CO, PM10, PM2.5, Houston (96) 2009 2007 Detailed Starcrest SO2, CO2 Great Lakes (Ports of Cleveland, Lake Carriers 2006 2004 Detailed HC, NOx, CO, PM10, PM2.5, SO2 OH and Duluth, MN) (97) Assoc. Lake Michigan Ports (98) 2007 2005 Mid-Tier NOx, PM10, PM2.5, HC, CO, SOx Environ NOx, TOG, CO, PM10, PM2.5, Los Angeles (99) 2008 2007 Detailed Starcrest SO2, DPM, CO 2, CH4, N2O NOx, TOG, CO, PM10, PM2.5, Long Beach (100) 2009 2007 Detailed Starcrest SO2, DPM, CO2, CH4, N2O NOx, VOC, CO, PM10, PM2.5, New York/New Jersey (101) 2008 2006 Detailed Starcrest SO2, CO2, N2O, CH4 Oakland (102) 2008 2005 Detailed NOx, ROG, CO, PM, SOx Environ NOx, HC, CO, SOx, PM10, Bridgewater Portland (103) 2005 2004 Mid-Tier PM2.5, CO2, 9 Air Toxics Consulting NOx, TOG, CO, PM10, PM2.5, Puget Sound** (104) 2007 2005 Detailed Starcrest SO2, DPM, CO2, CH4, N2O NOx, TOG, CO, PM10, PM2.5, San Diego (105) 2008 2006 Detailed Starcrest SO2, DPM Notes: * Starcrest = Starcrest Consulting Group LLC, ACES = Air Consulting and Engineering Solutions; Environ = Environ International Corp. ** Includes the Ports of Anacortes, Everett, Olympia, Port Angeles, Seattle, and Tacoma. dimensions; and other information. Generally MEPAs record port, is not accounted for in the database. Ship calls where no every ship that enters or leaves a port but do not record those cargo is loaded or unloaded are also excluded. However, U.S. that stop at private terminals outside the port authority juris- flagged ships carrying cargo from a foreign port to a U.S. port diction. On a national or regional level, not counting these or from a U.S. port to a foreign port are accounted for in the calls can lead to underestimation of emissions related to OGVs U.S. ACE entrances and clearances database since these are for the area. considered foreign cargo movements. Although at most ports A second source of call data is U.S. ACE entrances and clear- domestic commerce is carried out by Category 2 ships, there ances data. The Maritime Administration (MARAD) maintains are a few exceptions, particularly on the West Coast. Unfor- the Foreign Traffic Vessel Entrances and Clearances Database, tunately, there is little or no readily available information on which contains statistics on U.S. foreign maritime trade. Data domestic trips, so determining this without direct port input are compiled during the regular processing of statistics on for- is difficult. Third, the entrances and clearances data does not eign imports and exports. The database contains information always match MEPA data because it does not differentiate on the type of vessel, commodities, weight, customs districts between public and private terminals at a port. This is impor- and ports, and origins and destinations of goods. tant because a port authority may not have jurisdiction over There are several drawbacks to using U.S. ACE entrances private terminals. A recent study found that the U.S. ACE and clearances data. First, it does not contain any call TIM entrances and clearances data accounted for over 90% of the information. Average TIM and speeds need to be used with emissions from Category 3 ships calling on U.S. ports. (107) the U.S. ACE data to perform a mid-tier or streamlined For a national or regional level analysis, not counting U.S. analysis. Second, it only represents foreign cargo movements. Jones Act ships could result in an large underestimation of Thus domestic traffic, defined in the Jones Act (106) as U.S. emissions if the region is on the West Coast. From a local ships delivering cargo from one U.S. port to another U.S. level, including ship calls that are not part of a port authority

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74 jurisdiction could result in an overestimation of emissions for actual speed should be the vessel speed minus the river speed; that port. for vessels traveling against the river current, the actual speed should be the vessel speed plus the river speed. Because of the Power. Determination of ship propulsion power is fairly stall speed of a ship, load factors are assumed not to fall below straightforward using Lloyd's Ship Register data. Lloyd's 2%. There are several assumptions made here. First, the cruise data are produced by Lloyd's Register-Fairplay Ltd., head- speeds listed in Lloyd's data are 94% of maximum speed used quartered in Surrey, England. (108) Lloyd's data contains in Equation 7. Starcrest, in their 2001 Port of Los Angeles information on ship characteristics that are important for inventory (110) determined that service speed varied from preparing detailed marine vessel inventories. These data 83.3% to 100% of maximum speed for 28 ships surveyed. The include the following: average of those surveyed was 94%. Thus, propulsion cruise load factors could vary from 57.8% to 100% resulting in a Name, possible over- or underestimation of emissions. Ship Type, The second assumption is that the Propeller Law holds true Build Date, for all conditions and propeller designs. The basic Propeller Flag, Law assumes a fixed pitch propeller and free sailing in calm Dead weight tonnage (DWT), waters. Wind and water currents, heavy seas, fouling, and Vessel service speed, and other factors can increase the amount of load necessary, while Engine power plant configuration and power. improved propellers, ship hull design and other factors can reduce the power required to move at a given speed. Thus, All data are referenced to both ship name and IMO num- propulsion load factors calculated using the Propeller Law ber. Only the IMO number is a unique identifier for each ship can result in potential errors in emission calculations. Since because the name of a ship can change. Lloyd's insures many the Propeller Law is used to derive main engine load factors of the OGVs on an international basis and, for these vessels, for cruise, RSZ and maneuvering modes, uncertainty in this the data are quite complete. For other ships using a different approach propagates to emissions calculations in those OGV insurance certification authority, the data are less robust. activity modes. Using Lloyd's data to determine propulsion power should Current auxiliary engine load factors came from interviews lead to fairly accurate emissions calculations. conducted with ship captains, chief engineers, and pilots dur- Auxiliary engine power also can be determined from Lloyd's ing Starcrest's vessel boarding programs. (83) Auxiliary load data, but many records are missing this information. Best prac- factors are specified by ship type and time in mode. Because tices dictate using ratios of auxiliary to propulsion power from ships vary in generating needs, auxiliary load factors can vary a CARB survey (109) based upon ship type to determine total from ship to ship. Overstating the auxiliary load factor can re- ship auxiliary power. Although on a large scale this will lead to sult in an overestimation of emissions, while understating the fairly accurate emission determinations, on a local level, ship auxiliary load factor can result in an underestimation of emis- auxiliary power to propulsion power ratios may vary by ship sions. In a large inventory (or several inventories to comprise size and thus be less accurate for a smaller port. a regional or national analysis) it is likely that these factors Load Factor. Load factors are expressed as a percent of balance out. the vessel's total propulsion or auxiliary power. At service or Activity. OGV activity is usually broken into like modes cruise speed, the propulsion load factor is assumed to be 83%. that have similar speed and load characteristics. Vessel move- At lower speeds, the Propeller Law should be used to estimate ments for each call are described by using four distinct TIM ship propulsion loads, based on the theory that propulsion calculations. A call combines all four modes, while a shift nor- power varies by the cube of speed as shown in Equation 7. mally occurs as maneuvering. Each TIM is associated with a speed and, therefore, an engine load that has unique emis- LF = ( AS MS ) 3 (Equation 7) sion characteristics. Although there will be variability in each Where vessel's movements within a call, these TIMs allow an average description of vessel movements at each port. TIMs should be LF = Load Factor (percent), calculated for each vessel call occurring in the analysis year AS = Actual Speed (knots), and over the waterway area covered by the corresponding MEPA. MS= Maximum Speed (knots). TIMs are described in Exhibit 3-37. When ships move against significant river currents, the Cruise speed (also called service speed) is listed in Lloyd's actual speed in Equation 7 should be calculated based upon data and generally taken as 94% of the maximum service speed. the following: for vessels traveling with the river current, the Distances from the maximum port boundary to either the

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75 Exhibit 3-37. Vessel movements and TIM descriptions within MEPA areas. Summary Table Description Field Call A call is one entrance and one clearance from the MEPA area. A shift is a vessel movement within the MEPA area. Shifts are contained in calls. Although many Shift vessels shift at least once, greater than 95% of vessels shift three times or less within most MEPA areas. Not all MEPAs record shifts. Time at service speed (also called sea speed or normal cruising speed) usually is considered to be 94% of maximum speed and 83% of maximum continuous rating (MCR). This is calculated for each Cruise (h/call) MEPA area from the port boundary to the breakwater or reduced speed zone. The breakwater is the geographic marker for the change from open ocean to inland waterway (usually a bay, river, or channel). Time in the MEPA area at a speed less than cruise and greater than maneuvering. This is the maximum safe speed the vessel uses to traverse distances within a waterway leading to a port. Reduced Speed Zone* Reduced speeds can be as high as 15 knots in the open water of the Chesapeake Bay, but tend to be (RSZ) (h/call) about 9 to 12 knots in most other areas. Some ports are instituting RSZs to reduce emissions from OGVs as they enter the port. Time in the MEPA area between the port entrance and the pier/wharf/dock (PWD). Maneuvering within Maneuver (h/call) a port generally occurs at 5 to 8 knots on average, with slower speeds maintained as the ship reaches its PWD or anchorage. Even with tug assist, the propulsion engines are still in operation. Hotelling is the time at PWD or anchorage when the vessel is operating auxiliary engines only or is cold ironing. Auxiliary engines are operating at some load conditions the entire time the vessel is manned, but peak loads will occur after the propulsion engines are shut down. The auxiliary engines are then Hotelling (h/call) responsible for all onboard power or are used to power off-loading equipment, or both. Cold ironing uses shore power to provide electricity to the ship instead of using the auxiliary engines. Hotelling needs to be divided into cold ironing and active to accurately account for reduced emissions from cold ironing. * Referred to as the transit zone in many inventory documents. RSZ or the breakwater are used with the cruise speed to de- age maneuvering speeds vary from 3 to 8 knots depending on termine cruise times into and out of the port (however, not direction and ship type. Outbound speeds are usually greater all ports have a physical breakwater, and for those without, an than inbound speeds because the ship does not need to dock. imaginary breakwater needs to be defined). Some MEPAs Ships go from half speed to dead slow to stop during maneu- record which route was used to enter and leave the port, and vering. Time in mode varies depending on the location of, and this information can be used to determine the actual dis- the approach to, the destination terminal and turning require- tances the ships travel. Determining the actual distance and ments of the vessel. Best practice is to determine maneuvering speed during cruise mode is the most accurate method. times from conversations with pilots. Again, the maneuvering Speeds and locations can be determined using the Automatic time will vary by ship size, currents, traffic, and other factors. Identification System (AIS), which at least two services track. Accuracy in determining maneuvering times can affect calcu- (Lloyd's AISLive and VesselTracker.com). Less accurate meth- lations of hotelling time as discussed in the next paragraph. ods include assuming the ship travels at service speed during Hotelling can be calculated by subtracting time spent the cruise portion and estimating the distance the vessel travels maneuvering into and out of a PWD from the departure time in that mode. minus the arrival time into a port. If possible, anchorage time Reduced speed zone TIM also is an estimation based on (time at anchorage within the port but not at a PWD) should average ship speed and distance. Starcrest refers to this TIM be broken out from time at a PWD. Some MEPAs record as "transit" in their inventory documents. Generally, the RSZ shifts as well and this will allow for further refinements in starts when a ship enters the U.S. coastline such as a shipping maneuvering time. Other methods to determine hotelling channel, river, or bay where speeds need to be reduced for include conversations with pilots. During hotelling, the main navigational purposes. The RSZ ends at the port entrance. propulsion engines are off, and only the auxiliary engines are Pilots can provide average ship speeds for a precautionary or operating, unless the ship is cold ironing. Hotelling times also reduced speed zone. Again, such speeds are estimates and more can be determined from pilot records of vessel arrival and accurate results can be gained from using AIS. departure times when other data are not available. Actual Maneuvering time in mode is estimated based on the dis- hotelling times should be calculated for each individual port tance a ship travels from the port entrance to the PWD. Aver- because hotelling is generally a large portion of the emissions

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76 at a port. Hotelling times should be separated for those ships Exhibit 3-39. Low-load that use cold ironing at a port and those that do not. It is im- adjustment factor derivation portant to also look for outliers (ships with extremely long information. hotelling times) to eliminate those in the average since they may represent ships at a PWD but not with auxiliary engines Pollutant Observations R2 on. Miscalculation of hotelling time can directly affect emis- NOx 291 0.57 sion calculations. Hotelling emissions are generally a signifi- SO2 239 0.78 cant part of ship emissions near ports. CO2 291 0.65 CO 291 0.52 Emission Factors. The current set of marine engine emis- HC 291 0.52 sion factors come from ENTEC (111), which were derived from emissions data from 142 propulsion engines and 2 of PM 31 0.95 the most recent research programs: Lloyd's Register Engi- neering Services in 1995 and IVL Swedish Environmental Research Institute in 2002. ENTEC estimated uncertainties at defined low-load adjustment factors that should be multi- the 95% confidence interval, presented in Exhibit 3-38 for the plied by the propulsion engine emission factors when the ENTEC emission factors. load factor is below 20%. These factors can be large at very New work by IVL (112) shows major reductions in CO and low loads. HC emissions in comparisons with the previous ENTEC study. Although these low-load adjustment factors are used in CO emissions for slow-speed diesel engines (SSDs) are about most of the recent port inventory analyses and are recom- one-third of previous values, while the new study shows HC mended in the EPA guidance (114), they were derived mostly emissions at approximately half of prior values. In addition, on distillate fuels, and much of the data came from Coast PM emissions seem to vary significantly from ship to ship. Be- Guard cutters and ferries. Exhibit 3-39 shows the observa- cause of these observed differences, it is likely that the actual tions and R2 values from the curve fits for the various emis- uncertainty (within the given confidence intervals) on PM, sions. As can be seen from Exhibit 3-39, the curve fits have CO, and HC emissions are much higher than those specified relatively low R2 values. in Exhibit 3-38. These low correlation coefficients and the small sample of Another assumption made in using emission factors is that ship types imply highly uncertain low-load adjustment fac- they are constant down to about 20% load. Below that thresh- tors. It also should be noted that the PM adjustment factors old, emission factors tend to increase as the load decreases. are particularly suspect because they were only estimated This trend results because diesel engines are less efficient at based on smaller engines operating on distillate fuel. Although low loads and BSFC tends to increase. Thus, while mass emis- errors can occur in the determination of the low-load adjust- sions (grams per hour) decrease with low loads, the engine ment factor, the loads at which these adjustments are applied power tends to decrease more quickly, thereby increasing the are very low, and the overall impact of these uncertainties is emission factor (grams per engine power) as load decreases. probably small. Energy and Environmental Analysis Inc. (EEA) demonstrated this effect in a study prepared for EPA in 2000. (113) This study Summary of Strengths and Weaknesses. The analysis of strengths and weaknesses is included in Exhibit 3-40. Exhibit 3-38. Estimated Mid-Tier Methodology uncertainties at 95% confidence interval. Some mid-size ports, or those preparing emission inven- tories with mid-sized resources, could prepare a simplified, Estimated mid-tier version of the inventory. This differs from the de- Pollutant Uncertainty tailed methodology by averaging vessel characteristics and NOx 20% operational data by ship type. Even better resolution can be SO2 10% gained if the average information also is broken down by ship CO2 10% size (DWT range). Load factors and emission factors for each HC 25% ship type and DWT range can be calculated using a method similar to that in the detailed methodology. Annual vessel PM 25% calls for each ship type and DWT range should be determined BSFC 10% at the port. Each call should be divided into the various modes

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77 Exhibit 3-40. Summary of strengths and weaknesses--comparison among methodologies. Criteria Detailed Mid-Tier Streamlined Representation of Strength: Dominant physical processes included. physical processes Sensitivity to input Strength: Method relies on Weakness: Method relies on surrogates for missing parameters detailed user inputs that may inputs; results highly sensitive to quality of inputs not be readily available, but should produce best results Weakness: General, overall uncertainty unknown Flexibility Weakness: Requires detailed Strength: Customizable to data limitations data collection Ability to incorporate Strength: Best information Strength: Highly customizable effects of emission available; effects may be reduction strategies included in use of different EFs Representation of Strength: Projections available in the model and customizable to local information future emissions Consideration of Strength: May be achieved in methodology by using Weakness: Does not alternative vehicle/fuel appropriate EFs consider alternative technologies vehicle/fuel technologies Data quality Strength: Structured from best Weakness: Structured from available information available information Spatial variability Strength: Applicable to any Strength: Applicable to any location; data flexibility location, but data requirements allows multiple spatial scales likely limit to smaller spatial scales Temporal variability Weakness: Most likely limited Strength: Designed for annual inventories, but scalable to annual inventories with appropriate information Review process Strength: Documented in EPA Methodology Guidance Endorsements Strength: EPA endorsed of operation and each mode also should be averaged for the For large ports, the errors are probably small because most of vessel type and DWT range. the detailed inventories done to date were for large ports. The mid-tier approach is detailed in Commercial Marine However, if modeling a small port and using a large port as Port Inventory Development. (115) In this report, U.S. ACE the typical port, the error margins could be large as different entrances and clearances data are married with Lloyd's data. ship sizes service smaller ports and the port efficiency is usu- Emissions for the modeled port were then determined by ally lower. Additional issues in port selection are discussed in mode, ship type, engine type, and DWT range from similar each of the time-in-mode calculations discussed below. categories at the paired typical port for which a detailed in- ventory was done. Cruise Mode. Cruise mode emissions are calculated by The same baseline errors and parameter uncertainties dis- determining ratios of number of calls, average propulsion and cussed in the detailed methodology exist in this method. Ad- auxiliary engine power, and vessel service speed between the ditional uncertainties arise from the selection of the like port modeled port and the typical port. Because this information is and the implications of that choice on the various activity used, uncertainties in the cruise mode emissions for the mod- modes. eled port are related to uncertainties in the detailed port analy- sis, the similarities between distances traveled at the two ports, Like-Port Selection. This process involves determining and the vessel, engine, and fuel similarity at the two ports. The a port for which a detailed inventory has been prepared (typ- bias due to distance may be quantifiable and correctable. ical port) that is similar to the port to be modeled (i.e., like or modeled port). The more similar the port chosen as the typ- RSZ Mode. In the transit, or RSZ, mode, the average dis- ical port is to the modeled port, the more accurate the results. tance and average speed is specified for both the typical and

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78 modeled port. In addition to ratios of number of calls and Streamlined Methodology propulsion and auxiliary engine power, ratios of propulsion A streamlined methodology can be applied if those prepar- load factors and TIM are also calculated and used in determin- ing port inventories do not have sufficient resources to fol- ing emissions. This should provide results similar in accuracy low the mid-tier approach described. In this approach, those to the detailed port analysis as long as the average speeds are preparing port inventories should use an existing emission fairly representative of the ships that call on both ports. If there inventory from another similar port, scaling the emissions up is a disparity of speeds among the ships at the two ports, errors or down based on the ratio of vessel operation data between can result in the emission calculation. the two ports. Two EPA activity guidance documents pro- Maneuvering Mode. For the maneuvering mode, only vide details on estimating emission inventories from other ratios of number of calls and propulsion and auxiliary en- ports. (116117) These documents use U.S. ACE data to gine power are used. It is assumed that the modeled port scale emissions based on the ratio of ship trips from a like and the typical port have the same maneuvering time and port that has an existing inventory compared to the port in load factors. If the two ports are different in distances from question. No adjustments are made, however, for average the port entrance to the PWD or in the number of shifts that propulsion and auxiliary power or vessel speed. This can occur, errors in maneuvering emissions will result. How- result in significant error if the typical port selected is differ- ever, since maneuvering emissions are small compared to ent from the modeled port as discussed in the mid-tier the other activity modes, the contribution to overall error methodology subsection. will probably be small. Summary of Strengths and Weaknesses. Exhibit 3-40 Hotelling Mode. For the hotelling mode, only ratios includes the analysis of strengths and weaknesses for the of number of calls and auxiliary engine power are used. It detailed, mid-tier, and streamlined methodologies. is assumed that the average hotelling time for each ship type is the same between the typical port and the modeled 3.5.3 Evaluation of Parameters port. This can lead to errors if the efficiency at the typical port is different than at the modeled port. Since hotelling Exhibit 3-41 summarizes all parameters relevant for calcu- emissions are significant, the resulting error could be sig- lating emissions from OGVs calling at ports. Each of these has nificant as well. been detailed under the discussion of the appropriate model or method in Section 3.5.2. Also as discussed above, no quantita- Summary of Strengths and Weaknesses. The analysis of tive assessments are provided, because the range of parameters strengths and weaknesses is included in Exhibit 3-40. is essentially unknown. Exhibit 3-41. Parameters. Geographic Pedigree Qualitative Quantitative Parameter Methods/Models Scale Matrix Assessment Assessment Calls All All Engine Detailed and mid-tier All Power Load Factor Detailed and mid-tier All Activity Detailed All Emission Detailed All Factors Port Mid-tier and streamlined All Selection Fuel Type Secondary; used to determine All emission factors Growth Optional and secondary; needed for All Factor future year projections Engine Age Optional and secondary; needed to All Distribution determine average emission factors Key: indicates that a parameter is analyzed in the way denoted by the column: indicates that the parameter is not discussed in the way denoted by the column.

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79 Exhibit 3-42. Pedigree matrix--OGV parameters. Technological Correlation Geographic Correlation Temporal Correlation Representativeness Acquisition Method Range of Variation Impact on Result Independence Parameter Calls 4 1-2 1-2 1-2 1 1 Varies 3 Engine 4 2 1 1 1 Varies 2 2 Power Load Factor 4 3-4 3 2 1 Varies 3 4 Activity 4 2-4 3 3 1 Varies 1 3 Emission 4 2-3 1-2 4-5 3 Varies 3 4 Factors Port 4 4 3 N/A N/A Varies N/A N/A Selection Pedigree Matrix. Exhibit 3-42 shows the pedigree matrix Emission Factors. Emission factors for ships were deter- for the six primary parameters for determining emissions mined for a small subset of engines. Although most ships use from OGVs. Criteria to assign scores in the pedigree matrix similar engines, this set does not represent a large enough are included in Appendix A. sample to be accurate. This is particularly true of PM emis- sions. Measurement techniques of PM emissions vary and Calls. Emissions are linearly related to the number of calls. there is sensitivity to sampling methodology (e.g., tunnel Call data should be determined for each ship type and DWT length). PM emission factors need a more robust data set range. Thus, while accurate assessment of the number of ship to determine them more accurately. In addition, current calls is critical, in many cases there can be errors depending thinking is to estimate PM2.5 emission factors as 92% of upon the source of the data and the geographic boundaries of PM10 emission factors for OGVs. Various studies have esti- the analysis. mated PM2.5 emissions from 80% to 100% of PM10 emissions. Engine Power. In the detailed and mid-tier approaches, Therefore, a more accurate determination of PM2.5 emission propulsion power is determined directly from Lloyd's data. factors is needed. Conversely, auxiliary power is estimated from surveys that Low-load adjustment factors also need reviewing. The cur- produce ratios of auxiliary power to propulsion power by rent methodology is based upon limited data and rough curve ship type. More accurate determination of auxiliary power fits. Improvement of the low-load adjustment factors can would improve emission calculations. result in more accurate emission calculations. Furthermore, the current emission factors were deter- Load Factor. In the detailed approach, propulsion load mined for engines built before year 2000 when IMO set NOx factors are calculated using the Propeller Law. There are emission standards on OGV engines. More testing is needed inherent errors in applying that law to all ships and speed to determine the emission factors for engines built after 2000 ranges. Currently the Propeller Law is universally accepted as well as for future IMO Tier II and Tier III NOx emission as the method to use to determine propulsion load factors. standards. It is doubtful that significant errors would result from these calculations. Port Selection. In the mid-tier and streamlined method- Auxiliary load factors, however, have been determined ologies, selecting a typical port that is like the port to be mod- from surveys and tend to change with each new Starcrest eled is of utmost importance. EPA has provided some guidance inventory. More precise determination of auxiliary engine on how to select the typical port and a list (118) based upon load factors, particularly during hotelling, would provide detailed inventories prepared at the time. As more ports pre- more accurate results. pare detailed inventories, this list should be expanded.