Panama Canal expansion: emission changes from possible US west coast modal shift

Transcription

1 For reprint orders, please contact Mini Focus: Shipping and Carbon Emissions Panama Canal expansion: emission changes from possible US west coast modal shift Carbon Management (212) 3(6), James J Corbett* 1,2, Eric Deans 1,3, Jordan Silberman 1,4, Erica Morehouse 5, Elena Craft 5 & Marcelo Norsworthy 5 Background: We analyzed the potential for the Panama Canal expansion to change CO 2 and criteria pollutant emissions (oxides of nitrogen, oxides of sulfur and particulate matter) from Asia US container flows by estimating the modal shift from landside truck/rail network to larger ships enabled by canal expansion. We develop an intermodal case study comparison within the Geospatial Intermodal Freight Transportation framework, assuming potential diversion of 1.2 million 2-foot equivalent units (TEUs) to 5 origin destination pairs. Results: Potential TEU diversions of land-bridge transport through an expanded canal reduced mode-specific emissions substantially, but land-bridge emission reductions due to cargo diversion to post-panamax vessels, with lower emissions per TEU, cannot offset higher waterborne emissions from longer routes. Conclusion: Green-freight policy measures must consider multimodal network solutions to maximize emission benefits. Lower emission freight transport is an issue of concern for government due to the important contribution of goods movement to GHG emissions and, increasingly, a concern shared by industry due to an apparent synergy between CO 2 energy efficiencies and reduced transport fuel costs. A number of technology efforts within freight modes (truck, rail and ship) aim to improve future in-mode performance, including recent and ongoing studies of energy-saving or lowemission shipping technologies. Additionally, mode rebalancing is a key operational alternative to achieve large-scale CO 2 reductions in freight networks [1 6]. The IPCC Fourth Assessment report concerning transportation and infrastructure noted that freight transport is considerably more conscious of energy efficiency considerations than passenger travel because of pressure on shippers to cut costs, however this can be offset by pressure to increase speeds and reliability and provide smaller justin-time shipments [7]. Modal shifts that may increase the use of waterborne transport were identified as a primary means of large-scale decarbonization of the freight sector [6]. Infrastructure changes such as improved intermodal access to regional shipping are important enablers for reconfiguring freight networks. Perhaps the largest single infrastructure change to occur this decade is the expansion of the Panama Canal, to be completed in 214 [8,9,11,12]. This expansion will enable containerized vessels using the canal route to carry up to three-times more cargo, measured in 2-foot equivalent units (TEUs). Large vessels will be more CO 2 - and energy-efficient, per TEU, than vessels transiting under current canal limits. While larger ships using an expanded canal will likely reduce the CO 2 footprints of cargoes previously carried by smaller ships through the canal, we consider whether GHGs and other emissions may be reduced by some degree of mode shift (cargo diversion) from the so-called North American land bridge to a canal route serving east coast destinations. 1 University of Delaware, Newark, DE 19716, USA 2 GIFT Solutions LLC, Newark, DE 19711, USA 3 Maritime Authority of Jamaica, Kingston, Jamaica 4 GIS Consulting, Unionville, PA 19375, USA 5 Environmental Defense Fund, New York City, NY 11, USA *Author for correspondence: Tel.: ; jcorbett@udel.edu future science group /CMT Corbett et al. ISSN

2 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy Key terms 2-foot equivalent unit: Standard intermodal shipping container unit of volume. Strictly, this represents cargo capacity of a standard intermodal container, 2 feet (6.1 m) long and 8 feet (2.44 m) wide; functionally, this refers to the standard-sized metal box that can be easily transferred between different modes of transportation, such as ships, trains and trucks. Black carbon: The set of strongly light-absorbing components of particulate matter that have disproportionate warming impacts on the sensitive Arctic region. Various terms used to describe this species are defined by the measurement techniques used, and include elemental carbon, black carbon and refractory black carbon. Goods movement emissions pose environmental risks to climate, human health and ecosystems. Summary analyses of the modal emissions contributions of GHGs and other pollutants can be found in various literature, both historically and in global aggregate [1,11]. GHGs in general, and CO 2 specifically, are directly related to combustion of hydrocarbons; for refrigerated cargoes, hydrofluorocarbons (among so-called F-gases ) used by ships are also counted among GHGs [12]. Diesel emissions of particulates and oxides of nitrogen (NOx) contribute to health risks, and the WHO recently acknowledged that diesel exhaust is a carcinogen, confirming what national, state and regional studies have shown previously [13 15]. Moreover, ships using high-sulfur residual fuels also contribute to increased particulate matter (PM) emission rates, leading to greater health risk from marine diesel engine combustion. Lastly, black carbon (BC) particles represent more than a subset of PM that increases health risks; BC can be defined inclusively as a set of species of strongly light absorbing carbon particles emitted by combustion of organic compounds [16]. BC emissions from diesels (including marine diesel engines) are among a set of emissions known to be strong shortlived climate polluters [17 21]. Therefore, two separate questions bear investigation. First, what are the estimated reductions in CO 2 and non-co 2 emissions from larger ships enabled by the 214 Panama Canal expansion? Second, can a mode shift improve CO 2 efficiency of shipping Asian trade destined for the east coast of the USA through an expanded canal from the North American land-freight truck/rail network offer net emission reductions? We develop a case study comparison using a routing model within the Geospatial Intermodal Freight Transportation (GIFT) framework of typical intermodal cargo flows on inbound Asian routes and potential diversion of 1.2 million TEUs through an expanded Panama Canal using approximately 5 origin destination (O D) pairs on intermodal routes. This research provides quantified ana lysis of emissions impacts related to potential diversions of Asia USA container routes to alternative east coast ports as a result of the Panama Canal expansion to be completed in 214. Currently, containerized cargo flows from Asia to North America are conceptually illustrated in Figure 1. Historically, most Asia-originated seaborne containerized cargoes are delivered to west coast ports and conveyed by landside modes (truck and rail) to US destinations, including east coast destinations. In recent years, approximately 4% of containers delivered to the USA from all origins arrive in the top four to five west coast container ports [17,13]. The expanded Panama Canal is expected to facilitate some rebalancing of cargo flows, by allowing larger containerships from Asia to serve east coast ports. Using the GIFT model, this work analyzed containerized volumes from 2 representative Asian ports through US ports to typical commodity destinations [22]. To evaluate how the trans-pacific cargo could be influenced by the expansion of the Panama Canal, a routing model of intermodal flows and potential diversions is created within the GIFT framework. Emissions are calculated for these freight Asia Seattle Oakland Los Angeles/ Long Beach Midwest East coast New York Norfolk Charleston Gulf Savannah Panama Canal Figure 1. Conceptual trans-pacific containerized cargo flows from Asia to the USA. Red arrows depict primary water routes and black arrows represent land-bridge freight flows. 57 Carbon Management (212) 3(6) future science group

3 Panama Canal expansion: emission changes from possible US west coast modal shift routes under current distribution proportions and under a scenario that assumes a 1% diversion in west coast containerized cargoes to five major east coast port locations. We present a brief background motivating our study design, followed by a description of our methodology including port selection, vessel characteristics for the case study, mode-specific emissions rates and an explanation of the GIFT model. Results follow, concluding with a discussion of emissions implications. Background Asia USA containerized traffic grew from 4.4 million TEUs in 1997 to 14.3 million TEUs in 21, representing a compound annual growth rate of 9.5%, despite the global financial crisis of [23,24]. Approximately 75% of this cargo enters through the west coast, while 25% enters through the east coast via the Panama Canal [9,25]. Based on these growth patterns, large investments have been made to expand the Panama Canal by 214, allowing for larger ships to deliver goods from Asian markets directly to US east coast destinations. Although there are mixed views on whether an expanded canal will significantly disrupt existing routing patterns, one expectation is that some cargo previously routed via the west coast will be diverted to east coast routes due to the economies of scale arising from the use of larger vessels [8,9,26,27]. More efficient vessels (albeit on longer water routes) and shorter land routes may result in energy savings and emissions reductions. Other studies challenge this expectation, suggesting lower energy and emissions when east coast-bound cargoes use rail via west coast ports [28]. The Panama Canal is important to US seaborne trade. Containerized carriers on the Asia USA east coast route are expected to exploit the enhancements to the waterway, triggering route rescheduling and redeployment of ships, since these carriers are the single largest users of the Panama Canal, with over 4% of transits [29,3]. More specifically, container traffic between Asia and the USA has increased steadily, as shown in Table 1. Importantly, there has been a market share change of approximately 1% over a decade between east and west coast ports, with much more modest increases in Gulf Coast shares (albeit a tenfold increase for Gulf Coast ports from.1% in the mid- 199s). This trend mirrors a 21 US Department of Agriculture study finding that describes the shift in market share for Asian cargoes delivered to US ports [9]. Methodology This work analyzes container flow patterns between approximately 5 O D pairs connecting cargo volumes from 2 Asian ports (Box 1) on typical waterborne routes with US cargo destinations. These O D pairs were derived from commodity flow survey data in the Freight Analysis Framework version 3 (FAF3), as prepared for use in the GIFT model [22,31]. We construct a base-case scenario using projected cargo volumes for 215, the first year after the planned opening of the expanded Panama Canal. These volumes were estimated by extrapolating 215 cargo flow estimates from 21 values assuming growth of 7.2% per annum. We compare the base-case scenario with diversion scenario where we divert 1% of west coast container volume to east coast ports via the Panama Canal. We then compare emissions from each of these scenarios regionally using appropriate mapping techniques. Details are presented below for east coast port selection, vessel characteristics, cargo volume, short sea route selection, emissions estimation and the GIFT model for routing and emissions ana lysis. Detailed route maps and tables provide geospatial representation of local and regional emissions changes. Table 1. Asia to US container traffic and percent market share ( ). Direction Year Traffic (thousands of 2-foot equivalent units) To west coast To east coast To Gulf Coast Total ,318 11,724 12,81 12,871 Market share (%) West coast East coast Gulf Coast Total Data taken from [25]. future science group 571

4 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy Box 1. Asian ports of origin. US port selection This study models potential Bangkok, Thailand diversion from the dominant Ningbo, China hubs in the west coast of Los Busan, South Korea Qingdao, China Angeles (CA), Long Beach (CA), Dalian, China Seattle (WA), Tacoma (WA) and Shanghai, China Oakland (CA) to dominant ports Fuzhou, China on the east coast, including New Shenzhen, China York City (NY), Savannah (GA), Ho Chi Minh City, Vietnam Norfolk (VA), Baltimore (MD) Taichung, Taiwan and Charleston (SC). The port Hong Kong, China of Baltimore was included in this Tokyo, Japan study scenario because it represents Jakarta, Indonesia a top 2 container port with Xiamen, China deepening plans and illustrates the Kaohsiung, Taiwan Xingang, China potential impacts of diversion along Laem Chabang, Thailand the heart of the I-95 mid-atlantic Yantian, China corridor. Supplementary Table 1 Nagoya, Japan summarizes the top 25 container Yokohama, Japan ports, with shaded rows and cells Data taken from [42]. representing ports included in this work. We analyze nine of the top ten US ports by container volume as well as the port of Baltimore. Ship information Routes for this study depend on the deployment strategies of the competing shipping lines serving the trans-pacific trade routes including those transiting the Panama Canal [32]. As noted in Supplementary Figure 1, there is an upward trend in the size of container vessels calling at US ports [14]. However, the Panama Canal currently constrains vessel size on Asia to east coast service to 5 TEUs. The expanded Panama Canal will accommodate ships up to 12, TEUs; this study models a 1,-TEU containership size. Vessel capacity, speed, engine power and other characteristics for the study are based on information for representative ships of each size. To evaluate the potential co-benefit of coupling canal diversion with short sea shipping, this study uses a short sea containership profile from the recent American Marine Highways design set released by the US Department of Transportation (DOT) Maritime Administration [33]. Cargo volume This ana lysis assumes a 7.2% annual growth rate in containerized imports from Asia between 21 and 215 [34]. The global economic growth rates are not forecast to match the high growth over the last decades, and our estimates are calibrated to expectations for steady growth in the coming years. The Asia North America routes will remain robust because major Asian economies are still expected to continue to grow at levels exceeding the world average by a considerable margin [34]. The forecast for the growth will result in export volume from Asia of 43.4 million TEUs in 215, as projected by the Economic and Social Commission for Asia and the Pacific [34]. The top 25 US ports handled approximately 17 million TEUs in 21. At a 7.2% annual growth rate, the container volume in 215 is estimated to be 24 million TEUs. Approximately 63% of current container cargo is from Asia; therefore we use a volume of 15 million TEUs for the total Asian container volume in the 215 base-case scenario. For our diversion scenario, we model a 1% shift in containerized cargo flows from west to east coast ports. This allows the potential emission impacts from diversions through an expanded canal to be evaluated parametrically. Of the projected 15 million TEUs from Asia, the west coast handles approximately 12 million TEUs and the corresponding 1% diversion results in a 1.2 million TEU shift. Volumes used to develop our base case and diversion flows are shown in Supplementary Table 1 and the 5 O D pairs include a diverse set of ports. Although other diversion amounts may be evaluated, we note that a 1% diversion was observed in the decade (Table 1). However, another 1% shift in port market share may be substantial, given that our review of commodity flow survey data in the FAF3 [15] reveals that up to 3% of the Asian cargo transiting west coast ports is destined for areas east of the Mississippi River [35]. In other words, 1.2 million TEUs represents roughly one-third of Asian cargo volumes delivered to west coast ports that are destined east of the Mississippi, which might be considered an upper bound for diversions in the near term. Moreover, the diversion route is a slower logistics path than using truck and rail across continental USA, and many commodities transported in containers from Asia are time-sensitive consumer goods, which might suffer from the time penalties imposed by an all-water route to the east coast. For simplicity, we divide Asian flows uniformly from Asian ports; this allowed us to consider variation effects in voyage distance, but imposed a uniformity assumption to avoid over-specifying the scenario and to keep the model design focused on the objectives. These container volumes were diverted from west coast ports and routed to the previously mentioned five east coast ports in proportion to their relative market shares. This avoided imposing potential distortion in our study design where ports with limited current Asian volumes might be assigned greater diversions, although it also ignores the potential for asymmetric shifts to be realized through port investment. On the destination allocation, Asian volumes shipped to US port destinations are 572 Carbon Management (212) 3(6) future science group

5 Panama Canal expansion: emission changes from possible US west coast modal shift allocated proportional to the port-specific Asia USA container volumes; this assures that we can evaluate the intermodal impact from the Canal under the diversion scenario. Seaborne cargo is subsequently carried by truck and rail to its inland destinations; using the FAF3 commodity flow survey data, we identify flows with each of these modes in order to capture an accurate emissions picture. Across the west coast ports, TEU mode splits between truck and rail vary substantially, ranging between 8 and 63% rail mode share. Using a weighted average calculation, this study estimated the mode share between truck and rail for west coast ports to be 6 and 4%, respectively. For simplicity, this study used the same mode ratios when diverting containers through the expanded Panama Canal to the east coast. Specifically, approximately 52, TEUs were diverted to east coast rail routes and approximately 7, TEUs were shifted to east coast truck routes. This assumption can be explored in future research, as more accurate mode split shares may impact local emission estimates depending on the differential in emission factors between truck and rail. Short sea shipping This paper considers the potential for a US marine highway service that could serve a portion of the diverted containerized traffic that would otherwise require the I-95 truck or rail corridors. With improvements to the marine highway system, post-panamax ships could employ a hub-and-spoke strategy to bring large loads through the Panama Canal to major east coast ports. Then, they could dispatch coastwise vessels to smaller ports located closer to the final destination of goods, thereby avoiding the congested highways [8]. The US DOT notes that marine highways can relieve surface transportation congestion, achieving energy savings and environmental benefits [36]. We pose two routes that may provide reasonable insights for further research into mitigating expanded east coast freight volumes if diverted traffic occurs following the expansion of the Panama Canal (note that there are short sea shipping opportunities regardless of potential diversions). Given that the Panama Canal expansion will be completed after the introduction of the North American Emission Control Area (ECA), we presume that the short sea vessel operates on compliant distillate fuels, although advanced alternatives may be modeled that further reduce emissions levels. Emissions estimation The net change in atmospheric emissions from multimodal freight activity in the diversion scenario relative to the base-case scenario is evaluated in terms of CO 2, NOx as NO 2, oxides of sulfur (SOx as SO 2 ), and PM as PM 2.5. Within a given mode, CO 2 and criteria pollutants generally change proportionally to each other. However, this may not hold across modes and where regulatory standards, fuel changes or other innovations result in different combustion/emission relationships. Representative vessels, locomotives and trucks are used to calculate the emission profile of the relevant fleets for each mode. Given that the most common ship size deployed on the Asia to west coast service is approximately 6 TEUs, the emission characteristics of the MV Maersk Kinloss (62 TEUs) are adapted for this ana lysis. However, on the Asia to east coast service the emission profile of the MV Maersk Missouri (48 TEUs) was used for pre-expansion canal service, while the profile of the larger MV Anna Maersk (93 TEUs) was used in the diversion scenario through the expanded canal. Emissions profiles were obtained from the Rochester Institute of Technology University of Delaware-developed, web-based multimodal energy and emissions Key terms calculator [16], and are presented in Table 2 (note that this calculator allows users to modify inputs for a given vehicle/vessel, allowing for inputs that may conform to prior studies describing fleet average emissions in a cargo-mile basis [g/teu-mile]). Given the GIFT model convention, and conforming to typical industry use of TEUs in containerized freight transport, our emissions calculator develops the emission rates from power-based emissions factors reported in grams per TEU-mile (distance in statute miles, consistent with intermodal assessments); the calculations assume ten metric tons of cargo per TEU. All non-co 2 emissions vessel emissions are modeled under MARPOL Annex VI ECA conditions for all Asia to west coast trips. This is not realistic in estimating the true magnitude of criteria pollutant emissions from locations outside the 2 nautical mile North American ECA, because ships transiting outside of the ECA boundaries from Asia and/or along the Mexican coastline can meet less stringent shipping emissions and fuel standards. However, the purpose of this work is to reveal comparisons with intermodal diversions Short sea shipping: Historically, this term referred to coastal trade, coasting trade and coastwise trade, which encompass the movement of cargo and passengers mainly by sea, without directly crossing an ocean. Short sea shipping in general includes domestic and international maritime transport, including feeder services, along the coast and to and from the islands, rivers and lakes. In the US context, short sea shipping is typically narrowed to refer to vessels complying with US cabotage laws such as Section 27 of the Merchant Marine Act, 192. This law mandates that all cargo moving between US ports be carried in vessels that are crewed by Americans, built by Americans and owned by Americans. Post-Panamax: This adjective refers to vessel sizes larger than the current Panama Canal can accommodate. Within the context of this paper, we use the term more narrowly, to mean larger vessel sizes that will fit through an expanded Panama Canal. The paper specifies containership size ranges considered post-panamax today but expected to be included in the new panamax capacity for larger vessels. Emission Control Area: Defined under MARPOL Annex VI, where special mandatory measures are required to control oxides of nitrogen, or oxides of sulfur and particulate matter, or all three types of emissions from ships. future science group 573

6 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy Table 2. Emission rates for case study ocean and canal transit routes. Emission Value Units West coast base case (62 TEUs) Vessel ship 1 Based on Maersk Kinloss CO 2 2 g/teu-mile Energy 236 btu(in)/teu-mile SOx (as SO 2 ).12 g/teu-mile NOx (as NO 2 ) 3.1 g/teu-mile PM.117 g/teu-mile BC.4 g/teu-mile East coast base case (48 TEUs) Vessel ship 2 Based on Maersk Missouri CO g/teu-mile Energy 274 btu(in)/teu-mile SOx (as SO 2 ).14 g/teu-mile NOx (as NO 2 ) 2.66 g/teu-mile PM.1365 g/teu-mile BC.311 g/teu-mile East coast diversion (93 TEUs) Vessel ship 3 Based on Anna Maersk CO g/teu-mile Energy 196 btu(in)/teu-mile SOx (as SO 2 ).1 g/teu-mile NOx (as NO 2 ) g/teu-mile PM.7395 g/teu-mile BC.222 g/teu-mile Vessels use Emission Control Area compliant fuel, per MARPOL VI, including lower sulfur marine fuel or equivalent operation providing 96% sulfur reduction from uncontrolled emissions, 35% reduction in NOx and 85% reduction in PM emissions reductions through engine design or after treatment; uncontrolled emissions would be greater than assumed in this study. BC emissions rates are based on current understanding of ratios of BC:PM as reported in a recent published report; specifically, for vessels that are uncontrolled for PM currently, we use a BC:PM ratio of approximately 3%; for truck and rail, which are controlled for larger particles, we use a BC:PM ratio of approximately 74% [18]. BC: Black carbon; btu: British thermal unit; PM: Particulate matter; TEU: 2-foot equivalent unit. and, assuming ships conform to ECA conditions, is regionally accurate and globally conservative. Moreover, if Mexico (and/or Panama) were to join the North American ECA, future shipping activity would produce emissions more similar to the assumptions chosen here (in other words, this comparison assigns conditions that yield best practice performance for shipping). Emissions rates are based on vessel design parameters assuming full utilization of vessels. While this is a standard practice in the literature for comparison studies, lower utilization rates will necessarily change the per-teu rates, and uncertain or variable utilization throughout a year is not considered here either. Second, these emissions represent the inbound to US voyage and only looks at the emissions of the front-haul voyages (e.g., not including potential backhaul cargo conditions). It is typical for vessels to carry cargoes on return voyages if only partially utilizing the vessel payload capacity although some routes may be mostly empty backhauls and other backhaul volumes may be similar to the so-called front-haul voyage (an empty backhaul might suggest that emissions on return voyages be counted; conversely, a full payload on return would suggest that return voyage emissions be assigned to backhaul cargoes instead). There is no current data to reveal where some routes or some cargoes can establish a backhaul service; therefore, this study scope only looks at the emissions of the front-haul voyage (i.e., imported TEUs). For emissions purposes, these adjustments if applied uniformly affect all differencing comparisons similarly, but result in different emissions estimates (in kilograms or tons mass). Effects of uncertain payload utilization are discussed further in the results section. For landside emissions from truck and rail, emissions profiles were obtained from a web-based multimodal energy and emissions calculator [16], and are presented in Table 3. Rail emissions are based on the EPA line haul tier 2+ emission profile and truck emissions are based on an average of model year group profile and model year 21+ group profile. Emissions represent regulatory limits, where the primary difference between the two groups is lower NOx standards for 21+ trucks. By averaging these, we explicitly assume the fleet mix in 215 (the year after the expanded canal is due to be completed) is a combination of the more recent truck models and that approximately half the fleet will operate at lower NOx emissions. Of course, additional ana lysis could be designed to include older model years or to consider further improvements in truck and rail, including better fuel efficiency measures proposed for trucking by the federal government. The truck profile used here is better than what is found currently in many ports and long-haul routes. Adjusting this profile to an older fleet would result in an emissions increase. For short sea shipping, this study uses a containership profile [17,18] from the recent American marine highways design set, one of 11 designs intended to adequately address the spectrum of vessel types suited for transporting trailers and cargoes normally driven over the road [33]. This vessel carries 8 TEUs at 18 knots speed, with model inputs from the emissions calculator presented in Table 3. Again, the same general assumption of full utilization applied for short sea shipping estimates. GIFT model The GIFT model, developed by the Rochester Institute of Technology (Rochester, NY, USA) and the University of Delaware (Newark, DE, USA), solves routes for the volumes of freight flowing between multiple originations and destinations, and calculates geospatially resolved emissions from freight transport on a regional scale. The 574 Carbon Management (212) 3(6) future science group

7 Panama Canal expansion: emission changes from possible US west coast modal shift GIFT model combines networks for roadways, railroads and the waterways of the USA and Canada, along with the intermodal facilities in the North American continent on the ArcGIS Network Analyst platform. The model uses a generic shortest path algorithm provided in the platform to determine optimal routes to ship goods from one location to another. The shortest path algorithm searches and selects routes that minimize the defined penalties and reports the accumulated totals of other impedances to provide for tradeoff comparison. GIFT not only solves for typical objectives such as least-cost and time-of-delivery, but also for energy and environmental objectives, including emissions of CO 2, CO, NOx, SOx, PM and volatile organic compounds. The transportation network data and the facilities data were sourced from the National Transportation Atlas Database maintained by the US DOT s Bureau of Transportation Statistics, GeoGratis, maintained by Natural Resources Canada and Ship Traffic Energy and Environment Model (an international shipping database describing the ocean shipping lanes) developed by the University of Delaware. GIFT has been applied in a range of applications such as tradeoffs associated with a shift from heavy-duty trucks to ships for freight transport in the Great Lakes region, with particular attention given to cross-border freight flows between the USA and Canada [37]. GIFT can evaluate intermodal shipments. Details on how GIFT was constructed and programmed can be found in previously published literature [22,38,39]. Supplementary Figure 2 presents a map illustrating the portion of the GIFT model network from which scenario routes were solved for this study. In this work, GIFT solved routes according to the least distance algorithm in modal segments, which were then joined to provide full O D connectivity. Leastdistance water routes to west coast ports are joined with least-distance routes for landside transport; for the canal routes, least-distance routes to the canal from the Pacific are joined with least-distance routes from the canal to east coast ports and then joined with least-distance routes to the same landside destinations east of the Mississippi. This allows us to evaluate the same solved routes under different vessel configurations without changing the intermodal (truck, rail) conditions other than route distance for the diversion scenario. Scenario results For large-scale representation of scenarios, CO 2 emissions are depicted in figures and tables, as CO 2 emissions are generally proportional to energy use from freight transportation across modes. Criteria pollutant emissions (e.g., NOx, SOx, PM and BC as a subset of Table 3. Emission rates for truck, rail and short sea shipping routes. Emission Value Units Rail US EPA line haul tier 2+ CO g/teu-mile Energy 47 btu(in)/teu-mile SOx (as SO 2 ).31 g/teu-mile NOx (as NO 2 ) 2.77 g/teu-mile PM.448 g/teu-mile BC.327 g/teu-mile Truck blend of model years CO g/teu-mile Energy 17 btu(in)/teu-mile SOx (as SO 2 ).79 g/teu-mile NOx (as NO 2 ) g/teu-mile PM.176 g/teu-mile BC.13 g/teu-mile Short sea vessel MARAD America Marine Highways 21 design CO 2 38 g/teu-mile Energy 364 btu(in)/teu-mile SOx (as SO 2 ).185 g/teu-mile NOx (as NO 2 ) 4.63 g/teu-mile PM.18 g/teu-mile BC.54 g/teu-mile BC emissions rates are based on current understanding of ratios of BC:PM as reported in a recent published report; specifically, for vessels that are uncontrolled for PM currently, we use a BC:PM ratio of approximately 3%; for truck and rail, which are controlled for larger particles, we use a BC:PM ratio of approximately 74% [18]. Vessel uses emission control area compliant fuel, per MARPOL VI, including lower sulfur marine marine fuel or equivalent operation providing 96% sulfur reduction from uncontrolled emissions, 35% reduction in NOx and 85% reduction in PM emissions reductions through engine design or aftertreatment; uncontrolled emissions would be greater than assumed in this study. BC: Black carbon; btu: British thermal unit; MARAD: US Maritime Administration; PM: Particulate matter; TEU: 2-foot equivalent unit. PM) vary among modes for several reasons, including the nature of combustion conditions and fuels in the engines, and due to different regulatory standards and implementation timelines. The section presents basecase scenario results for CO 2 first, representing 215 cargo volumes with no diversion assumptions and using current vessel sizes. Diversion scenario results, characterized by larger vessel sizes and 1% diversion of west coast volumes to the east coast, are then compared. Next, a brief discussion of uncertainty discusses the importance of back-haul and other payload parameters. Then comparisons for atmospheric pollutants are provided. Lastly, short sea shipping along the east coast is evaluated to scope the potential for further study on the potential for short sea shipping to mitigate increases in regional emissions. CO 2 emission changes Figure 2 and Table 4 present base-case scenario results, using CO 2 emissions to illustrate the geospatial patterns future science group 575

8 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy A All modes B Truck C Rail D Ship North America CO 2 emissions (pre-expansion) 5, tons 5,1 1,, tons 1,,1 1,5, tons 1,5,1 2,, tons 2,,1 2,5, tons 2,5,1 3,, tons E Ship trans-pacific Figure 2. Map of base case depicting typical routes from Asia to US destinations. (A) All modes, (B) truck, (C) rail, (D) Ship North America and (E) Ship trans-pacific. and route intensity. Canal expansion and cargo diversion will change three conditions related to emissions: The amount of total work done due (e.g., more TEU-miles); The efficiency of the cargo movement (e.g., larger vessels); The location of the emissions source (e.g., diversion to alternate routes). All three of these effects must be considered to evaluate the diversion scenario. Although diversion results in more seaborne TEU-miles, landside travel is reduced since goods are delivered on the east coast closer to their final destination. Water route results from the diversion scenario are shown in Figure 3 and Supplementary Table 2. The postexpansion diversion has two important parts: larger vessels due to canal expansion and cargo diversion to east coast ports using the Panama Canal instead of shorter west coast port routes. These results show that the TEU-miles under the diversion scenario are greater than under the base case due to the greater distance traveled through the canal. The net effect is a 6% increase in TEU-miles after diversion of west coast containers through the expanded Panama Canal. However, emissions from these longer cargo routes may be partially offset by more efficient post-panamax ships. An ana lysis of base-case scenario routes was re-run using larger ship sizes to quantify the effect of using instead of the more typical averages of the 576 Carbon Management (212) 3(6) future science group

9 Panama Canal expansion: emission changes from possible US west coast modal shift Table 4. CO 2 estimates for base-case scenario routes. Mode Routes to east coast (metric tons) Routes to west coast (metric tons) Total (metric tons) Vessel 13,, 14,, 28,, Rail 1,, 3,4, 4,5, Truck 1,9, 6,4, 8,3, Total 16,, 24,, 4,, 6-TEU west coast vessel and the 4-TEU east coast vessel. This assumes the same cargo shares, but represents a 215 volume. Figure 3 and the center data column in Supplementary Table 2 confirms that larger vessels provide economy-of-scale benefits for waterborne freight emissions. Some 23% reduction in emissions can be expected due to larger vessel sizes as an expanded Panama Canal will enable the average vessel sizes, destined for east coast ports, to be similar to expected average vessel sizes serving west coast ports. Under the diversion scenario, both effects (longer distances and vessel size differences) must be evaluated together. The combination of less cargo flowing to the west coast and larger vessel capacities results in emission reductions along routes destined for west coast ports, as expected. However, the increased voyage distances for routes to east coast ports results in net increases in emissions. More importantly, the net effect is an increase in waterborne emissions west coast route emissions reductions are smaller than east coast route emission increases. Combining route and vessel-size Change for all sea routes Sea routes to west coast Sea routes to east coast Change (%) % 1,452,7 (77,4) Change in TEU-miles (diversion) -23% (2,45,) (3,818,) Change in emissions (vessel size) 4% 2,412, (1,174,) Change in emissions (vessel size and diversion) 2,, 1,, (1,,) (2,,) (3,,) (4,,) (5,,) (6,,) (7,,) Tens of thousands TEU-miles and metric tons (metric tonnes CO 2 ) emissions Figure 3. Effect of diversion and vessel size on 2-foot equivalent unit-miles and CO 2 emissions by sea route. TEU: 2-foot equivalent unit. future science group 577

10 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy changes, a 4% increase in overall emissions is estimated for water routes in this study. Therefore, Figure 4 presents a map of the absolute estimated CO 2 emissions differences by route segment and provides additional insight into the magnitude of emissions avoided along the major freight corridor from southern California to east coast destinations especially for trucking (Figure 4C). This figure also highlights the substantial increase in emissions along the water diversion route through the canal and along the east coast feeder route serving east coast ports. Generally, relative changes in NOx, SOx and PM may be proportionally similar within a modal route segment, but the route-by-route changes in these emissions would differ from the CO 2 summary presented. The waterborne route findings do not yet consider the avoided emissions of truck and rail transport of containers from west coast ports to east coast destinations. Figure 5 illustrates the percent change in CO 2 emissions expected along multimodal routes (truck, rail and waterway). Warmer colors represent increased emissions and cooler colors represent decreases in emissions. Figure 5 reveals substantial regions in the western USA where potential diversion of west coast containerized cargoes reduces truck and rail activity and emissions. However, east coast landside activity increases due to cargo diversions, along with regional increases in truck, rail and ship emissions. Note that route segments accounting for most of the emissions may differ from routes with relatively greater percent changes. The percentages are increases from A Ship B Rail C Truck 1% TEU shift scenario emissions: tons of CO 2 per mile traveled -45 to to -12 Net decrease -119 to to +1 to to to +2 Net increase +21 to +45 D All modes east coast Figure 4. Absolute change in CO 2 emissions from base-case to diversion scenario where insets illustrate emissions changes by mode. (A) Ship, (B) rail, (C) truck and (D) all modes east coast. TEU: 2-foot equivalent unit. 578 Carbon Management (212) 3(6) future science group

11 Panama Canal expansion: emission changes from possible US west coast modal shift A All modes B Truck C Rail D Ship North America < -6% -59 to -2% -19 to -1% 1 to 2% 21 to 4% 41 to 6% E Ship trans-pacific Figure 5. Percentage change in CO 2 emissions from base-case to diversion scenario. (A) All modes, (B) truck, (C) rail, (D) Ship North America and (E) Ship trans-pacific. the given routes base-case emissions. In other words, if a water route to the Panama Canal is used for cargo diversions, then the percent change in that route s emissions are illustrated in Figure 5. Note that given the model design presents both absolute emissions from diversion (Figure 4) and in percent difference from base case Figure 5, where east coast water routes representing the diversion volumes show near zero or negative percent difference representing decreases due to larger vessel sizes on these routes. In particular, our assumption of very small diversion of east coast cargoes through Gulf ports produces very little percent change in emissions on routes. One may recognize that the absolute emissions on a major route are typically much greater than emissions on a minor route, even if both routes see a similar percent difference under diversion through the expanded Canal. For example, the port of Baltimore was included in our study to explore a smaller volume port with known investment preparing for canal diversion. In this case, the additional TEUs are relatively less impactful than the larger vessel size adjustment, which mitigates the absolute change in emissions on water routes near this port. Note, however, that we do estimate net increases in emissions to Baltimore s water routes, and more significantly, that these diversions contribute to landside (I-95 corridor) emissions. One of the most significant results is the increase in emissions along the I-95 corridor connecting east coast ports with inland freight destinations. According to the Federal Highway Administration, nearly onethird of I-95 is congested, representing some 6% of the miles in urban areas along the route [19]. Projections assuming no improved performance put 1% of future science group 579

12 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy urban miles under heavy congestion, and nearly half of all nonurban miles impacted by increased trucking. Panama Canal diversions aggravate this (Figure 4C & D). A potential source of mitigation is increased use of short sea shipping. Analyzing overall effects, percentage change in total emissions is small. Emissions are estimated to change as little as +.65% for CO 2 (Figure 6) or -.45% for PM/ BC (Figure 7). Comparisons of NOx and SOx emissions show modest increases of 2% (Figure 8) and 4% (Figure 9), respectively. Uncertainty Uncertainty and variability in estimates, and the nonexclusivity of the scenario design construction, suggest that these overall changes in estimated emissions can be considered similar to a no change result for emissions across the entire diversion. Supplementary Tables 3 6 present these results in tabular format. For analyses of this design, many inputs are treated as deterministic when in fact they represent averages of variable and sometimes uncertain parameters. These include average emission rates (Supplementary Tables 4 & 5), which we hold constant (determined) for this ana lysis focused on mode route comparison. Other variables are endogenous to our ana lysis, such as the route choices and distances solved by GIFT. These are a function of the underlying network, which means that uncertainty due to alternate routing may matter if we were using the estimates of our scenarios to compare with, say, other sources of pollutants in a supply chain. However, because we use the same network for both the base-case and diversion scenario, this uncertainty affects only potential network bias on the estimators, not on their difference, which is used to estimate the change in emissions reported here. A third category of variables merit further study but are ignored in this study design. This includes voyage details such as 3 Diversion CO 2 Waterborne CO 2 Rail CO 2 Truck CO 2 21, 132, 3,, 2 17% 2,, Change (%) ,412, -13% (1,174,) (43,) (1,43,) 1,237, (271,) -.65% (1,23,) 1,, (1,,) (2,,) Change in CO 2 emissions (metric tons) -3 (3,,) -4 (4,,) East coast routes West coast routes Total Figure 6. CO 2 emissions changes due to diversion scenario. Please see color figure at: 58 Carbon Management (212) 3(6) future science group

13 Panama Canal expansion: emission changes from possible US west coast modal shift 2 17% Diversion PM/BC Waterborne PM/BC Rail PM/BC Truck PM/BC Change (%) (52) -.45% (55) (38) (26) 1 5 (5) Change in PM emissions (metric tons) (57) -1 (1) -11% (3) -15 East coast routes West coast routes Total (15) Figure 7. Particulate matter/black carbon emissions changes due to diversion scenario. PM on first (left) axis; BC on second (right) axis. BC: Black carbon; PM: Particulate matter. Please see color figure at: vessel payload variability (utilization rates), average tons per TEU, backhaul cargoes (return trip utilization), cargo-handling differences among ports and so on. By observation, one can expect that lower vessel utilization rates and routes that cannot support backhaul cargoes would increase waterborne (and overall) emissions. This observation is true as well for inefficiently used landside modes, and intermodal combination routes that we model would require many iterations to fully explore the effects of system asymmetries in utilization and backhaul. A good review of the maritime components of carbon footprint methods shows that uncertainty in route-average components is important, but is smaller on average for individual voyages [4]; similar approaches apply to landside modes [21] and study design affects the treatment of uncertainty [41,42]. In other words, the uncertainties in underlying inputs are important to study further, although our design controls for, or explicitly holds, these constant to investigate the basic question of diversion emissions comparison. More importantly, in each case, the modal emission changes are consistent. Across all routes, the emissions from cargo transported on US truck and rail routes decrease. This is shown in the red and green bars in the total columns of each pollutant graph and table. Of course, the net decrease in truck and rail emissions results from a larger decrease in longer west coast routes avoided than the increase from additional shorter-haul east coast routes. This is observed in the red and green bars in the east coast routes and west coast routes presented in figures and tables. Atmospheric pollutant changes Looking into some detail with regard to the mode shares of the emissions changes, the ocean leg dominates all the changes in emissions for east coast diversions and, future science group 581

14 Corbett, Deans, Silberman, Morehouse, Craft & Norsworthy Diversion NOx Waterborne NOx Rail NOx Truck NOx 4 4, , Percent change (%) % 27,69-1% (13,438) (35) 2% 14,159 (24) (3) 2, 1, (1,) Change in NOx emissions (metric tons) -2 (45) (2,) -3 (3,) East coast routes West coast routes Total Figure 8. NOx emissions changes due to diversion scenario. Please see color figure at: therefore, is the dominant mode contributing to overall changes across the routes. This is especially true for SOx emissions clearly a function of the difference in fuel standards for on road and marine fuels. With regard to reductions in emissions for routes serving west coast ports and landside transport, fewer trucking trips are dominant sources of CO 2 reductions, and fewer train trips are dominant sources of PM reductions. Fewer west coast ship trips are a dominant source of NOx reductions and are nearly 1% of the reason for SOx reductions again as expected given the sulfur contents of ECA-compliant marine fuels. One should note that this study assigned ECA standards to emissions estimates and that the Panama Canal route falls outside the current North American ECA boundary. In other words, the sulfur, NOx and SOx changes noted here may underestimate actual waterborne cargo diversion emissions, if dual-fueled post-panamax vessels in east coast service choose to operate with lower quality fuel during transits outside the 2-nautical mile ECA region. In reading the graphs and tables, note that the percentage changes overall are not strictly additive because the percentage change on the east coast routes is in terms of the change in emissions change in east coast routes, and the percentage change on the west coast routes is in terms of the emissions difference in west coast routes. The overall percentage change is in terms of all routes. Similarly, percentage changes reported for the different modes are in terms of their mode basis, and the absolute estimates need to be summed to obtain east or west coast, or total route values, from which multimodal percent changes can be evaluated. Short sea shipping The east coast increases in trucking (and to a lesser extent in rail) create an opportunity to consider short 582 Carbon Management (212) 3(6) future science group