9.2 Transportation Refrigeration Units
Categories 1652, 1653, and 1654
9.2.1 Introduction
Categories 1652, 1653, and 1654 cover emissions (NOx, CO, PM, PM10, PM2.5, ROG, SO2, and TOG) from the combustion of fuel in internal combustion engines that provide the power to operate refrigeration units on trucks and trailers. These units maintain low temperatures for certain products (e.g., perishable foods) while they are being transported.
9.2.2 Methodology
The Transportation Refrigeration Units emissions are derived by California Air Resources Board (CARB) inventory staff. 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. BAAQMD staff export the emissions data directly from CEPAM into the District’s Base Year inventory package. This calculation approach and collection of categories are internally termed as “CARB Source Categories”.
This base year inventory uses the 2016 CEPAMv1.05344 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.
9.2.3 Changes in Methodology
Emissions data were obtained from the CARB’s 2016 CEPAMv1.051. In comparison, the emissions in the previous inventory methodology involved area source categories derived from the CARB’s OFFROAD2007 model.
There was a CARB regulation in effect in 2000 that stated that Districts that were not in attainment of the Federal one-hour Ozone standard could not allow purchase of gasoline-powered off-road vehicles. Since BAAQMD was not in attainment, the Air District was subject to this rule and emissions from these vehicles decreased through time. The Transportation Refrigeration Unit (categories 1652 and 1653) historical emission data were retained in this emissions inventory.
9.2.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
9.2.5 Trends
(a) Historical Emissions / History
Prior to the 1999 base year emissions, the methodology for the transportation refrigeration units was based on the published report: “Report on Utility Equipment Emissions in the State of California”. The average engine power, hours of use per year and emission factors for each type of unit were taken from a study conducted by Booze, Allen, and Hamilton Inc. (BAH). Total number of refrigeration units was based on the Department of Motor Vehicles’ registration data for regular commercial trucks and trailers by county. The total was distributed to counties using this data. The BAH study showed that all transportation refrigeration units consist of diesel units and there are no longer any gasoline power units.
California Air Resources Board (CARB) developed the Off-road vehicle emission inventory’s OFFROAD2007 model to estimate emissions from off-road motor vehicles for all counties and air basins in California. The OFFROAD model contains a more comprehensive list of equipment from a wider range of categories compared to BAH. The OFFROAD model adds an inventory estimate for engines powered by diesel fuel, compressed natural gas (CNG) and liquid petroleum gas (LPG) which were not previously accounted for. The criteria and GHG emission data for transportation refrigeration unit categories in the Bay Area were obtained from the CARB’s OFFROAD2007 model.
(b) Future Projections / Growth
Emissions forecasting was done by holding the year-2035 emissions data constant through and up to year-2040. For CARB Sources, emissions are forecasted by CARB staff by applying growth profiles to the base year-2012 inventory data (see above in ‘Methodology’ section).
(c) Control
In December of 1990, the CARB adopted two levels of emission standards for small off-road engines. The first phase of standards (Tier 1) was implemented in 1995345 and Tier 2 standards are scheduled for implementation in 1999. The deterioration rates for 4 stroke Tier 1 engines were derived from data supplied by engine manufacturers. Since engines meeting Tier 2 standards are not yet available, engineering judgment was used to estimate the effect of the more stringent standards.
Projected emissions include expected benefits from CARB’s Clean Diesel Regulations in 1993 and Re-Formulated Gasoline Phase II beginning 1999. These benefits were estimated using control factors developed by ARB.
9.2.6 Uncertainties
The estimated Transportation Refrigeration Units emissions for Solano and Sonoma counties under District’s jurisdiction may contribute to an increased uncertainty of the Bay Area Off Road emissions.
9.2.7 Contact
Author: Michael Nguyen
Reviewer: Ariana Husain
Last Update: November 06, 2023
9.2.8 References & Footnotes
CARB. 2016. California Emissions Projection Analysis Model (CEPAM) inventory. https://www.arb.ca.gov/app/emsinv/2016ozsip/2016ozsip/fcemssumcat_2016o3sip105.php↩︎
CARB. 1995. California Exhaust Emission Standards and Test Procedures For 1995 and Later: Small Off-Road Engines. https://ww2.arb.ca.gov/sites/default/files/barcu/regact/sore/test_fin.pdf?_ga=2.97100055.962285900.1646782104-423543219.1584725377↩︎