9.8 Commercial Harbor Crafts

Categories 1769 - 1786

9.8.1 Introduction

Categories 1769 through 1786 presented herein account for emissions from combustion of fuel from engines of commercial harbor crafts.

The emission estimates for harbor crafts are developed by the California Air Resources Board (CARB) and are described in CARB’s 2007 Technical Support Document:³⁵⁹. The emissions reflected herein include all five criteria pollutants (PM, VOC, NO_x, SO_x, CO).

The definition for commercial harbor craft means any private, commercial, government, or military marine vessels including, but not limited to commercial/passenger fishing vessels, ferry/excursion vessels, crew and supply boats, tug/tow/push boats, work boats, pilot vessels, and others that do not otherwise meet the definition of ocean-going vessels or recreation vessels. The inventory accounts for emissions from harbor crafts that navigate within 3, 24, and 100 nautical miles from the coast line of the San Francisco Bay Area region.

9.8.2 Methodology

Commercial harbor craft emissions data are derived by inventory staff of the state’s chief air quality regulatory agency, the California Air Resources Board (CARB). This significant emissions dataset, sorted by county, is published every few years and is a product of the State Implementation Plan (SIP) emissions document formally known as the California Emissions Projection Analysis Model (CEPAM) inventory. For related sets of categories, such as airport ground support equipment (GSE), ships, structures coatings etc., where independent data collection and derivation of emissions are both cost- and time-prohibitive and likely a redundant effort, BAAQMD staff export the emissions data directly from CEPAM into the District’s Base Year inventory package. This calculation approach and collection of categories is internally termed as “CARB Source Categories”. More information on CEPAM can be found here: California Emissions Projection Analysis Model (CEPAM) inventory³⁶⁰.

The CEPAM provides historical emissions as well as forecasts emissions for major emission source classifications including –

1. on-road mobile sources [from Emissions Factor (EMFAC) model],
2. off-road mobile sources (OFFROAD model), and,
3. stationary and areawide sources - For these major source classifications, CEPAM combines facility level /area source emissions data reported to the California Emissions Inventory Development and Reporting System (CEIDARS) for multiple years by various regional air quality agencies (including the BAAQMD).

The current base year inventory uses the 2016 CEPAMv1.05 to estimate emissions from “CARB Source Categories”. This version of the CEPAM derives emissions from a 2012 base year inventory and contains backcasts and forecasts from year-2000 to year-2035. All applicable regulatory and technological controls are assumed to be built into the CEPAM dataset during CARB staff’s inventory computation work. After the emissions data are exported, the inventory for CARB Source categories is taken through a quality assurance (QA) process.

In the QA process, BAAQMD staff perform a systematic crosswalk between CEPAM’s source category classification (Emission Inventory Code - EICs) and the District’s source category classification (category identification number - cat_ids). Based on the scope of emissions covered, individual EIC or a group of EICs are mapped to a single cat_id. This process also addresses issues when cat_ids have no matching EICs or there are discontinued EICs that need to be investigated. Following this, emissions data are backcasted to year-1990, as well as forecasted to year-2040 using certain mathematical methods, as described in the Trends section. Finally, the emissions trends spanning from year 1990-2040 for each category and pollutant are evaluated, and CARB staff are consulted for explanation of any observed anomalies in trends.

The emission inventory account for nine types of commercial harbor crafts. They are commercial fishing, charter fishing, crew and supply vessel, ferries/excursion vessel, pilot vessel, towboat/pushboat, tug boat, work boat and others. The others category include vessels that do not fit into the other eight categories, such as vessels used to dispose of cremated remains. Most of the information used including engine population, engine hours of operation, and engine load originate from the harbor craft survey. The inventory does not include vessels from the U.S. Navy and/or U.S. coast Guard vessels due to limited data available on them.

For each category of vessels, emissions were calculated based on emission factors specific to the main propulsion and auxiliary engine model year. Adjustments, such as engine deterioration rate, load factor, and fuel correction factor were applied to the emission estimates. These adjustments can have a significant effect on emissions and are used in the calculation to obtain a more accurate estimate of the overall emissions. Data such as load factors were based on U.S. Environmental Protection Agency’s (USEPA) Nonroad model³⁶¹. Deterioration rate was based on ARB’s OFFROAD2007 model³⁶². For this inventory, it is assumed that all harbor crafts operating in the San Francisco Bay Area use diesel engines for both propulsion and auxiliary power. Emission estimates for each category of vessel along with engine type (main and auxiliary) are accounted for the in the inventory.

9.8.3 Emissions

A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.

9.8.4 Trends

Emission trends forecast are based on projected fleet growth, turnover, engine deterioration, and the change of emission rates. It is expected that harbor craft emissions would trend lower going forward. The commercial harbor craft regulation was adopted in 2007 to reduce toxic and criteria emissions to protect public health and environment ³⁶³. It was amended in 2010 and will gradually be phased in and fully implemented by year 2022.

For commercial harbor crafts, monthly activity was assumed to be higher in the summer months and reduced during the winter months. Weekly activity was assumed to be constant on the weekdays and reduced on the weekends. The emissions data from CARB CEPAM inventory only covers year 2000 to 2035. Different approaches were applied to estimate emissions for years 1990 to 1999 and 2036 to 2040 as described below. Please refer to CARB’s CEPAM Inventory Documentation ¹ for more information.

(a) Historical Emissions / History

Three different methods are used for backcasting to project historical emissions prior to year-2000 going back to year-1990, which is the starting year of the current base year inventory (referred to as BY2015). Following preliminary evaluation of the data available for initial years (post-year 2000) in the CEPAM inventory, BAAQMD staff recommends a backcasting approach. The default backcasting approach is defined by a formula here –

\[ \begin{eqnarray} \text{BY2015 emissions for year X for county Y} = \text{BY2011 total emissions for year X} \\ \\ \times \dfrac{\text{BY2015 year-2000 emissions}}{\text{ BY2011 year-2000 emissions}} \\ \\ \times \dfrac{\text{county Y fraction}}{\text{ fractional total}} \end{eqnarray} \]

This calculation is referred to as the BY2011 scaling method (based on the previous base year inventory). The second calculation approach is to derive the linear regression best fit of the year 2000-2008 CARB Sources emissions data for a category, species, and county, and extrapolate that data back in time. If this backcasting results in negative emissions prior to a certain year, the lowest positive emission value is held constant from that particular year back to year-1990. The third possible calculation approach is to use a specific growth profile for the category, provided by the in-house staff expert. These custom growth profiles are often derived from surrogate data provided by another agency or resource, or available activity data that is assumed to scale with the emissions for that specific CARB Source category.

For commercial harbor crafts, the BY2011 scaling method is used to derive emissions for years 1990 through 1999.

(b) Future Projections / Growth

For CARB Sources, emissions beyond base year to 2035 are forecasted by CARB staff by applying growth profiles to the base year-2012 inventory data (see above in ‘Methodology’ section). Emissions forecasting beyond 2035 was done by holding the year-2035 emissions data constant through and up to year-2040.

(c) Control

Emissions include benefits from ARB’s Clean Diesel Fuel Regulations (Beginning 1993) and Re-Formulated Gasoline Phase II (beginning 1996)³⁶⁴. These benefits were estimated using control factors developed by ARB. In 1999, federal EPA enacted the marine engine standard requirements on new commercial marine diesel engines. Dependent on the timeline, new engines put in harbor craft must meet certain tier requirements that must comply with new emission standards³⁶⁵. Also, in 2007, CARB approved of the commercial harbor craft regulation⁵. This regulation became effective in 2009 and places further operation and new engine requirements for all commercial harbor craft operating in California waters. The regulation also put in-use engine requirement for ferries, excursion vessels, tug boats, and towboats. It is expected that NO_x and PM emission will be reduced significantly with these regulatory requirements.

9.8.5 Uncertainties

Please refer to CARB’s CEPAM Inventory documentation ² for more information.

9.8.6 Contact

Author: Tan Dinh

Reviewer: Abhinav Guha, Yuan Du

Last Update: November 06, 2023

9.8.7 References & Footnotes

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359. CARB. Initial Statement of Reasons for Proposed Rulemaking, Proposed Regulation for commercial Harbor Craft. 2007. https://www.arb.ca.gov/msei/chc-appendix-b-emission-estimates-ver02-27-2012.pdf↩︎

360. CARB. Criteria Pollutant Emission Inventory Information (CEPAM) . [accessed 2023 Mar 13]. https://ww2.arb.ca.gov/criteria-pollutant-emission-inventory-data↩︎

361. USEPA. 2017. https://19january2017snapshot.epa.gov/moves/nonroad-model-nonroad-engines-equipment-and-vehicles_.html↩︎

362. CARB. 2021. https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/road-documentation/msei-documentation-road↩︎

363. CARB. 2007. https://ww2.arb.ca.gov/sites/default/files/2020-07/chcfactsheet0516.pdf↩︎

364. CARB. 2020. https://ww2.arb.ca.gov/our-work/programs/alternative-diesel-fuels↩︎

365. USEPA. 2018. https://www.epa.gov/regulations-emissions-vehicles-and-engines/domestic-regulations-emissions-marine-compression↩︎