ROCKLAND, Maine — FMC, the community’s largest taxpayer and a major employer, has filed an application with the city to convert its fuel from oil to compressed natural gas.

The conversion is expected to cost $2.5 million and take a year to complete, according to paperwork filed with the city’s code enforcement office.

The company has been looking to make its carrageenan plant in Rockland more energy efficient. In April, FMC officials announced plans to convert from oil to liquefied natural gas. That project would have consisted of four 35-foot-tall, 18,000-gallon tanks to store the fuel.

Last month, FMC Plant Manager Jeff LaBrozzi said that since that meeting, the company has decided to pursue compressed natural gas, or CNG, rather than liquefied natural gas, or LNG. Switching to CNG will eliminate the need for the large tanks that had been considered with LNG, he said. It also will cut the conversion cost to about half the original estimated expense of switching to LNG.

The company has not indicated who would supply the fuel.

But in January, Dead River Co. and Boston-based Xpress Natural Gas announced a partnership to make CNG available to commercial customers in Maine.

CNG is essentially the inverse of liquefied natural gas, and is easier to store and transport by tractor-trailer. With the liquid product, gas is cooled to lower than minus-238 degrees, but is pressure neutral, and expensive equipment is necessary to use the fuel.

Compressed gas is stored at room temperature, but under high pressure. And there’s no need for the costly machinery required to store and use its frigid counterpart, according to officials with Xpress Natural Gas.

LaBrozzi said in November that the conversion to CNG would create a win-win situation by reducing energy costs for the manufacturing plant while dramatically cutting emissions.

FMC currently employs 130 people and nearly a third of them are in specialized scientific and technology jobs. The company also is the largest property taxpayer in Rockland, putting $435,000 into municipal coffers last year. The company also is the largest user, by far, of the city’s wastewater treatment plant.

The manufacturing plant’s sole product is carrageenan, which is derived from various types of seaweed and is used as a gelling, thickening and stabilizing agent in products such as chocolate milk, yogurt, salad dressing, Listerine pocket packs, toothpaste and frozen turkeys.

The Rockland Planning Board will review FMC’s proposal on Jan. 7.

Telephone messages left for FMC this week were not returned.