The US Environmental Protection Agency (EPA) has ordered the city of Honolulu to pay $16.1 million (£11m) for a solar project.
It will also pay $875,000 (£564k) in fines after violating the federal Clean Air Act which requires the collection and controlling of gases at landfill sites.
The city failed to install and operate the gas collecting system by the set deadline in 2002 at its 215-acre Kapaa Landfill in Kailua, Oahu.
Decomposing refuse in a landfill generates hazardous air pollutants such as methane.
Jared Blumenfeld, EPA’s Administrator for the Pacific Southwest said: “Air emissions from a closed landfill are toxic and can contribute to global warming.
“If the proper systems had been in place at the landfill, over 343,000 tons of methane and 6,800 tons of hazardous air pollutants and volatile organics would not have escaped to the atmosphere.”
The solar panels will be installed at the City’s H-POWER (Honolulu Program of Waste Energy Recovery) facility in Campbell Industrial Park by 2020.
They will have a capacity of 3.1MW and will generate over five million kilowatt-hours of electricity per year, enough to power 800 Oahu homes.