Decarbonization and Energy Innovation

A priority for Hawaiʻi Gas will be maintaining a stable energy infrastructure for consumers by using a fuel mix that is safe and resilient. On Oʻahu, a diverse fuel mix allows Hawaiʻi Gas to make use of our vast infrastructure; primarily our 1,100 miles of pipeline network and production plant. The existing pipeline network currently accommodates a mix of synthetic natural gas (SNG), renewable natural gas (RNG), liquid natural gas (LNG), and up to 15% hydrogen. That is more utility hydrogen than any other utility company in the nation.

Hawaiʻi Gas is also evaluating projects and new technology that could further diversify and decarbonize our fuel mix. As we better understand the capability of delivering a modified mix of fuel, Hawaiʻi Gas will continue to invest in adapting the existing infrastructure as needed.

Renewable Natural Gas

Renewable natural gas (RNG) is natural gas or methane that is created using the biogas generated by organic matter as it decomposes. RNG is an ultra-clean fuel and can be considered carbon-negative depending on the source because it potentially converts more greenhouse gases than it emits.

Hawai‘i Gas was the first in the state to capture and process biogas from the City and County of Honolulu’s Honouliuli Wastewater Treatment Plant on O‘ahu. This facility produces up to 800,000 therms of energy per year, enough gas for more than 6,000 homes¹. At the same time, this RNG project reduces the need for approximately 15,000 barrels of oil and reduces greenhouse gas emissions by the amount produced by 400 cars annually. Additionally, since 2018, the City and County of Honolulu generated approximately $1.85 million of revenue by selling the biogas to Hawai'i

1. Based on average household use of 11 therms/month by Hawai‘i Gas customers.
Liquid natural gas tanks and silos

The Honouliuli RNG Facility equipment, painted an eye-catching bright green, takes the gases that are a by-product of wastewater treatment and turns them into clean-burning biomethane

Biogas upgrading to biomethane diagram.

The wastewater feedstock is upgraded through a multi-step process to create renewable natural gas in the form of biomethane.

“Ensuring that all families have access to affordable and reliable energy, our RNG project is an important step toward achieving Hawaiʻi’s clean energy goals. RNG leverages existing infrastructure to deliver cleaner fuels to our customers while providing jobs and revenue source to the City.”– Alicia Moy, President & CEO, Hawai‘i Gas

Other RNG Projects

Hawaiʻi Gas is also actively pursuing new RNG projects in the near future with a priority on locally produced RNG and increasing the percentage of carbon-negative natural gas sources in our fuel mix. The Hawaiʻi Natural Energy Institute of the University of Hawaiʻi recently issued a study exploring local production resources for RNG, which is a first step in cataloging the potential opportunities in the state. While there is still more work that needs to be done to bring into focus the many factors that impact RNG production. Benefits include:

  • Economic growth: capital investments, new income source for counties, new jobs in the green energy industry
  • Environmentally friendly: eliminates/reduces the state’s dependency on oil; RNG is carbon negative thus can play a significant role in reducing greenhouse gas emissions
  • Positive consumer impact: gas appliances could save customers an average of 30% on utility bills


There is worldwide recognition that hydrogen—a clean, zero-emissions fuel—will be the clean energy source of the future. Hawaiʻi Gas has been using hydrogen in our utility fuel mix for many years and we are excited to explore new opportunities to improve clean energy options for the state. Our vision is to be an industry leader in transitioning to zero-emissions fuel sources, like hydrogen, safely, affordably and reliably.

Hydrogen has the potential to go beyond gas replacement to be a clean alternative fuel for transportation, to power electric generators, and provide long-lasting energy storage for the electric grid. Recently, Hawaiʻi Gas has embarked on several hydrogen research and development projects to try and overcome the technological challenges of increasing renewable natural gas and hydrogen into our supply mix.

Synthetic Natural Gas

We will continue to use SNG to satisfy consumer demand and stabilize our energy portfolio until such time that newer technologies can make replacement fuels, like RNG and hydrogen, more viable. Since our state has no naturally occurring source of natural gas, Hawaiʻi Gas produces SNG from a petroleum by-product called naphtha. While SNG is created artificially, its properties are like that of natural gas and has considerably less impact on the environment than other energy sources like oil and coal.

How is SNG Made and Distributed?

Remove Sulfur

To produce SNG, the sulfur contained in the naphtha feedstock must be removed. To accomplish this, naphtha is blended with hydrogen gas, heated to 700 degrees Fahrenheit and sent through a reactor vessel where a chemical reaction takes place to remove the sulfur.

Produce Methane, Hydrogen And Carbon Dioxide

The purified feedstock is then sent to a series of reactors where it is blended with super-heated steam and passed through a catalyst of nickel pellets. The result of this process is gas composed of primarily methane, hydrogen and carbon dioxide. After the reactors, the gas flows in two separate directions.

Direction 1: Carbon Dioxide Absorber

One flow goes to a carbon dioxide absorber to remove the carbon dioxide. Then, an odorant is added so its presence can be detected if it leaks or if an appliance is turned on when it is not in use. Next, butane is added to give the SNG additional heating value so that it can properly burn in appliances. Finally, the SNG is channeled into the pipeline delivery system traveling through our transmission and distribution lines to homes and business along our Greater Honolulu Utility System.

Direction 2: Hydrogen Gas Production Plant.

The other flow of SNG is sent into the hydrogen gas production plant. The products of this plant are hydrogen and carbon dioxide gas. The hydrogen flows back into the desulfurization step that began the whole process. The left over carbon dioxide is captured and sent to a regenerator and prepared for sale to other companies.

Liquid Natural Gas

LNG is liquefied natural gas, which is natural gas that has been converted to liquid form. Natural gas is made mostly of methane (CH4), the simplest hydrocarbon compound. Natural gas changes to a liquid state at about minus 259 degrees Fahrenheit (-259°F) and in that state, LNG takes up 1/600th the physical space required when in gaseous form. Thus, LNG provides an economical way to transport natural gas from one location to another. LNG is odorless, colorless, non-toxic and non-corrosive.  Like with other SNG and RNG, Hawaiʻi Gas adds an odorant to gas supplied by LNG as part of its standard safety procedures.

The liquefied natural gas industry has an impeccable safety record. Comprehensive safety practices and procedures for handling, transporting and storing LNG are well established and regulated. According to a Department of Energy report, LNG transports experienced no serious accidents at sea or in port in the past 40 years. In large part this is due to comprehensive safety and security programs for LNG equipment and transportation.

LNG Gas Silos


The use of propane (LPG) is a part of everyday living for many homeowners and businesses. Moreover, it is critical to the stability of essential functions during emergencies and severe weather as it is used to operate emergency command centers, fire stations, hospitals, shelters and other essential services statewide. When the electrical grid is damaged or not functioning properly, gas energy is readily available and easy to set up to cook, heat water for showers or sanitation, and backup power.

  • Propane is used all over Hawaiʻi:
  • For residential water heaters, air conditioners, furnaces, outdoor grills, fireplaces and appliances
  • On farms to control pests, dry crops and power irrigation pumps
  • To power forklifts and industrial vehicles
  • For heating, cooking and much more at thousands of businesses - including restaurants and hotels

Propane is not regarded as a greenhouse gas and is even listed as an approved clean energy source by the 1990 Clean Air Act and Energy Policy Act of 1992. Like any natural gas, propane has some level of emissions, but it is fairly low compared to other fuels. Technology, science and research continues to evolve; however, to date there is no feasible alternative to propane that can offer comparable affordability and resiliency. While propane will continue to be a part of our energy portfolio, we are committed lowering our carbon footprint by investing in initiatives that offset the impact of propane use.

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