The state Supreme Court on Monday once again dashed Honua Ola Bioenergy LLC’s hopes of bringing its $520 million Hawaii island biomass plant into operation burning trees for renewable energy.

The high court unanimously affirmed the Public Utilities Commission’s May 23 decision denying a power purchase agreement between Hawaiian Electric and Honua Ola, legally known as Hu Honua Bioenergy.

“The reality is that yesterday’s good enough has become today’s unacceptable,” the court concluded in a 20-page decision written by Associate Justice Todd W. Eddins. “The PUC was under no obligation to evaluate an energy project conceived of in 2012 the same way in 2022. Indeed, doing so would have betrayed its constitutional duty.”

In a statement, Warren Lee, president of Honua Ola, expressed disappointment and said the company “is evaluating its options going forward.”

Lee said the court’s decision effectively prevents Honua Ola from providing 24/7 renewable energy that would replace fossil fuel- based energy for the Big Island.

He said the plant is now fully constructed in accordance with the PUC’s previous orders approving the project in 2013 and again in 2017.

“It’s important to remember that it was the PUC that placed Honua Ola in this position by not sufficiently considering greenhouse gas impacts in 2017, which then resulted in several years passage of time,” Lee said.

“We believe this decision sets back Hawai‘i’s renewable energy transition and results in Big Island residents having to continue to pay high energy rates mostly based on expensive fossil fuel oil, while also increasing the likelihood of grid instability and more blackouts,” he said.

The PUC previously approved an agreement between Hawaiian Electric and Honua Ola in 2013. Lee said that decision led to Honua Ola spending $175 million in development and construction costs, while the 2017 approval of an amended agreement called for the company to build the 30-megawatt plant to completion and to begin producing energy as soon as possible, bringing the total investment over $520 million.

But in May the PUC voted 2-1 to reject the amended agreement, saying the project would emit substantially more carbon than it sequestered for at least the first 25 years of operation and would end up raising ratepayer prices during that time.

The commission also found that Honua Ola’s promise of eventual carbon neutrality was speculative at best and, in the end, contrary to the public interest.

In its ruling Monday, the court said: “The people of Hawai‘i have declared ‘a climate emergency.’ Hawai‘i faces immediate threats to our cultural and economic survival: sea level rise, eroding the coast and flooding the land; ocean warming and acidification, bleaching coral reefs and devastating marine life; more frequent and more extreme droughts and storms. For the human race as a whole, the threat is no less existential.

“With each year, the impacts of climate change amplify and the chances to mitigate dwindle,” the opinion said. “A stepwise approach is no longer an option.”

In rejecting the company’s appeal, the court said the PUC had understood its mission to uphold the public’s interest. “It faithfully followed our remand instructions to consider the reasonableness of the proposed project’s costs in light of its greenhouse gas emissions” as well as the project’s impact on the environment.

The court added that the PUC measured the project’s cost and system impact and acted properly in evaluating Hu Honua’s “unconvincing” statements and promises to reach carbon neutrality.

Justice Michael Wilson wrote a concurring opinion.

The company formed in 2008 to convert the old Hilo Coast Processing Co. plant in Pepeekeo into a biomass plant that would burn trees. The plant formerly burned sugar cane waste material and coal.

Honua Ola officials insist that the project is ready to be the state’s first carbon- negative power plant, capable of producing up to 30 megawatts of renewable energy fueled by non-native eucalyptus crops and supplemented by invasive species such as albizia, strawberry guava and gorse.