One of Hawaii island’s largest power suppliers and one of the state’s two oil refineries say they can’t meet legal requirements for reducing air pollution as the state moves forward on an eight-year-old law that requires Hawaii to reduce its greenhouse gas emissions to 1990 levels by 2020.

Act 234, signed into law by former Gov. Linda Lingle, affects about two dozen facilities, which are required to reduce emissions by 16 percent.

Hamakua Energy Partners, which supplies up to 30 percent of Hawaii island’s electricity needs, says that there aren’t any cost-effective solutions to reducing emissions at its petroleum-burning plant in Honokaa and that its electricity is too important to the island to cut production.

Meanwhile, Chevron says that the state emission rules are unfair as they relate to its Kapolei refinery because emissions at the facility haven’t increased since 1990.

The companies laid out their objections to state emission rules in greenhouse gas reduction plans that were filed with the state Department of Health in June and obtained by the Honolulu Star-Advertiser through an open records request.

Both companies have asked health officials to exempt them from the 16 percent reduction requirement, according to the documents.

Nolan Hirai, who oversees the Health Department’s Clean Air Branch, said that the department can approve a reduction lower than 16 percent for a facility if the company can show that it is not technically or financially feasible to achieve the reduction. However, no decisions have been made on whether to approve the requests.

Both companies could face fines of up to $25,000 a day for not complying with the state law if they aren’t granted exemptions.

Jeff Mikulina, executive director of the Blue Planet Foundation, a clean energy advocacy organization based in Honolulu, said that the company filings reflect the original need for the law.

“It just shows the current thinking,” he said, in reference to fossil fuel-burning companies. “It really doesn’t reflect that this is a new era and we are going to have to make changes.”

Hawaii ranked 15th among states in per capita greenhouse gas emissions, according to Environmental Protection Agency data for 2014. The 2007 law was passed in response to growing concern by lawmakers about the impact of global warming on Hawaii’s economy and natural resources.

“The potential adverse effects of global warming include a rise in sea levels resulting in the displacement of businesses and residences and the inundation of Hawaii’s freshwater aquifers, damage to marine ecosystems and the natural environment, extended drought and loss of soil moisture, an increase in the spread of infectious diseases, and an increase in the severity of storms and extreme weather events,” according to the text of the law.

Five companies, including Hawaiian Electric Co., Hawaiian Commercial and Sugar Co., Kalaeloa Partners, the Kauai Island Utility Cooperative and Hu Honua, all filed plans that laid out strategies for meeting the state reduction targets, which include adopting more renewables, implementing energy efficiency measures and possibly switching to natural gas.

AES, the state’s only coal plant, and Hawaii Independent Energy, the state’s other oil refinery — both of which operate on Oahu — are expected to file their plans with the Health Department later this year after being granted extensions.

Paul Karaffa, environmental coordinator for AES, told the Star-Advertiser that the company expects to meet or exceed the emission requirements through burning alternative fuels. The company, which supplies about one-fifth of Oahu’s electricity, has been experimenting with burning recycled fuel wood.

Hawaii Independent Energy didn’t respond to specific questions about the refinery’s plans to reduce emissions.

Lance Tanaka, a spokesman for the company, said by email that the refinery “is working hand-in-hand with the state on a path forward.”

Hamakua Energy Partners, which burns naphtha, a petroleum product, said in its filing with the Health Department that the 16 percent emission requirement is “unobtainable” by the facility.

The company argues that its generators already operate at high efficiencies, that carbon capture technologies are not currently available or economically feasible, and that reducing production is not an option because of its contract with Hawaii Electric Light Co. and the importance of its energy production for Hawaii island.

The company’s contract to supply power to HELCO, the Hawaii island utility, runs through 2030.

ACCORDING to its filing, Hamakua Energy Partners proposes an alternative plan: deep-cleaning its generators over the next two years, which could reduce emissions by up to 1 percent.

The company pegs the cost to the facility at $200,000. If the state goes ahead with plans to import natural gas, the company says, it would then evaluate switching to the cleaner-burning fuel.

Allen Hess, manager of the Hamakua plant, declined to comment on the filing.

Blue Planet’s Mikulina said that Hamakua Energy Partners ignores other options for meeting the 16 percent emission reduction, such as using cleaner-burning biofuels, and said that in the larger picture, the island’s ample geothermal resources could make the fossil fuel plant unnecessary.

The state rules also allow companies to work with one another to achieve the same overall emission reductions, similar to a “cap and trade” system.

Chevron, which announced last year that it was soliciting buyers for its Kapolei refinery and gas stations, is also seeking a revised emission requirement from state health officials. Instead of reducing greenhouse gas emissions at its facility by 16 percent, the company requests approval for a 2.2 percent reduction from 2009 levels, which it has already achieved, according to its filing.

Chevron argues that the refinery has actually decreased its greenhouse gas emissions by 7.3 percent since 1990.

The Health Department lacked facility-specific data on emission rates for 1990. So instead, officials used 2010 as a baseline for companies to make 16 percent emission reductions, which the department expects will achieve the state’s overall mandate to reduce emissions to 1990 levels.

CHEVRON spokesman Al Chee said that there aren’t any reduction measures that the company can take to reduce emissions that are technologically or economically feasible.

“We can’t see anything more that we can do at this time, though we will continue to look at ways, as we always have, to reduce greenhouse gas emissions,” said Chee.

He said that the company had not looked into joining with another company to achieve the 16 percent reduction.

Hirai said that the Health Department doesn’t have a deadline for approving the greenhouse gas emission plans. He said the department will begin measuring greenhouse gas emissions beginning in 2016 and every year thereafter to gauge Hawaii’s progress in meeting the 2020 mandate.

While state officials move to implement Hawaii’s greenhouse gas emissions law, the Obama administration finalized rules in its Clean Power Plan on Monday, which require a 32 percent reduction nationally in greenhouse gas emissions from 2005 levels.

Hawaii was one of four states that received a deferral from having to comply with specific federal requirements due in part to its geographic isolation, said Janet McCabe, an EPA assistant administrator, during a media conference call this week.

Hirai said that the state’s own greenhouse gas laws and aggressive renewable energy targets, which require the electric utilities to convert to 100 percent renewable energy by 2045, will likely render the federal requirements moot.