Clean Air Branch

The Department of Health has established the Hawaii Greenhouse Gas (GHG) Program to combat the threat of climate change and sea level rise.  The program utilizes the Air Pollution Control Permit process of the Clean Air Branch to regulate GHG emissions statewide.  The Hawaii GHG program works in conjunction with other Federal and Hawaii State programs to mitigate GHGs.

Related Legislation

Act 234 of the 2007 Legislature established the foundation for the Hawaii GHG Program.  It declared a policy to reduce GHG emissions statewide to 1990 levels by 2020.  Act 15 of the 2018 Legislature established a statewide carbon net-negative goal by 2045.  Act 238 of the 2022 Legislature established a goal for the level of statewide GHG emissions to be at least 50 percent below 2005 levels by the year 2030 (including airplane emissions).

On June 30, 2014, Hawaii Administrative Rules (HAR), Chapter 11-60.1 was amended to adopt the new Hawaii GHG program.  The main requirements of the program are set forth in Subchapter 11, Greenhouse Gas Emissions. During promulgation, public comments were solicited and received and a response to comments was provided.

Emissions Cap for Large Existing Covered Sources

To reduce GHGs, the rules specify a 16% GHG emission cap for large existing stationary sources (“affected sources”) with potential carbon dioxide equivalent (CO₂eq) emissions at or above 100,000 tons per year.  Each affected source must submit a GHG emission reduction plan for establishing measures that will be used to meet the emission cap.  The approved GHG emission cap and associated monitoring, recordkeeping, and reporting provisions will be made part of the facility’s covered source permit.  The deadline for submitting GHG emission reduction plans was June 30, 2015. See the Instructions for GHG Emission Reduction Plan (PDF). The Clean Air Branch has received GHG emission reduction plans from all affected facilities for incorporating GHG emission caps into the air permits pursuant to HAR §11-60.1-204(d)(6)(C).

GHG Annual Fees for All Covered Sources

Beginning in 2015, GHG emissions must be included in the calculations to determine annual fees for all facilities holding a covered source permit. Utilize GHG emissions factors and global warming potentials to calculate your CO2e emissions for covered source permit fees.

Greenhouse Gas Emission Inventories

HAR §11-60.1-204(k) requires the Department of Health to provide reports with updated GHG emissions inventories showing progress towards achieving statewide GHG reduction goals.

Emission inventory reports for Hawaii showing statewide CO₂eq emissions and sinks (GHG removals) are provided in the links below. The most recent 2022 report dated April 2025 was prepared by ICF and the University of Hawaii Economic Research Organization (UHERO) for the Department of Health. The GHG emission inventories serve as a basis for decision making and provide direction in future GHG reduction efforts.

Per Act 234 from 2007 Hawaii Session Laws (Act 234 of 2007), energy sector emissions from aircraft (domestic aviation and military aviation) were quantified and subtracted from net emissions for comparison to Hawaii’s CO₂eq emissions limit that is equal to, or below 1990 statewide GHG emissions. Per Act 15 from 2018 Hawaii Session Laws (Act 15 of 2018) and Act 238 from 2022 Hawaii Session Laws (Act 238 of 2022), aircraft emissions were added in the net emission total for comparison to Hawaii’s CO₂eq emissions limits. Biogenic carbon dioxide and international bunker fuel CO₂eq emissions were excluded from the statewide GHG totals in accordance with IPCC guidelines.

The statewide GHG emissions limit of 15.40 million metric tons (MMT) CO₂eq as specified in Act 234 of 2007 was met in 2020. Additionally, the statewide GHG emissions are projected to continue to meet this GHG emissions limit with emissions (excluding aviation emissions) of 11.35 MMT, 7.02 MMT, and 3.94 MMT CO₂eq projected for the years 2025, 2035, and 2045, respectively.

The statewide GHG emissions limit of 11.39 MMT CO₂eq as specified in Act 238 of 2022 is projected to not be met in 2030 with emissions (including aviation emissions) of 15.51 MMT CO2 Eq projected for the year 2030.

The statewide GHG emissions goal of carbon net-negative goal as specified in Act 15 of 2018 is projected to not be met in 2045 with emissions (including aviation emissions) of 10.35 MMT CO₂eq projected for the year 2045.

The largest quantity of statewide GHG emissions were from Transportation sources, which made up 49.8% of Hawaii’s statewide GHG emissions. The second largest quantity of statewide GHG emissions were from Stationary Combustion sources, which made up 36.6% of Hawaii’s statewide GHG emissions.

Inventories from Previous Years

• Hawaii Greenhouse Gas Emissions Inventory for 2020 and 2021: Final Report | Summary of Key Results
• Hawaii Greenhouse Gas Emissions Inventory for 2005, 2018, and 2019: Final Report | Summary of Key Results
• Hawaii Greenhouse Gas Emissions Inventory for 2017: Final Report | Summary of Key Results
• Hawaii Greenhouse Gas Emissions Inventory for 2016: Final Report | Summary of Key Results
• Hawaii Greenhouse Gas Emissions Inventory for 2015: FinalReport | Summary of Key Results
• Hawaii Greenhouse Gas Inventory (Revised): 1990 and 2007: Final Report
• Hawaii Greenhouse Gas Inventory: 1990 and 2007: Final Report

If you have any questions, please contact Mr. Scott Takamoto or Mr. Mike Madsen of the Clean Air Branch at (808) 586-4200.

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