ANCHORAGE, Alaska - Oil cooked out of piscine heads, entrails and skeletons is generating heat and electricity for fish processors on the Aleutian Island of Unalaska.

Alaska companies are among the first in the world to use fish oil on a large scale as a cheaper, cleaner-burning substitute for diesel fuel.

At Unisea Inc., in Dutch Harbor, thousands of gallons of pollock fish oil are mixed each day with diesel and used to power the seaside plant's electrical generators and boilers.

Replacing diesel with fish oil cuts costs, as well as harmful emissions such as sulfur and particulates, Unisea officials said.

The seafood company, one of the largest in the world, also saves on the expensive shipping rates it would otherwise pay to send the fish waste to buyers outside Alaska, such as aquaculture companies who use the oil as fish feed.

Unisea officials would not share the company's savings figures, or the costs of its truckloads of diesel.

Don Graves, research and development manager for Unisea, said only that processing and burning the fish oil is worthwhile.

"You have to figure the fish oil is equivalent in value to the diesel fuel, so there's some benefits savings-wise and environmentally to doing this," Graves said. Depending on the fishing season, Unisea generates 4,000 to 15,000 gallons of fish oil a day and uses all of it in-house.

The orangish hue of pollock oil comes from the tiny krill the fish feast on in the Bering Sea. Blending the oil with diesel yields a pale yellowish liquid that leaves no fishy odors.

"There's no smell at all," he said.

Unisea and fish processors in Dutch Harbor, Kodiak, Cordova and several sites in Bristol Bay have used fish oil to run their boilers for years, but in 2001 Unisea, with the help of state funding, became the first to power its electrical generators with the renewable fuel.

Other companies, the state and the National Park Service are all running tests to see how well fish oil biodiesel works in engines that are more complicated and delicate than those at Unisea.

U.S. Seafoods, based in Seattle, is considering a processing facility on board one of its fishing vessels. The 297-foot boat would use the guts of flatfish, cod and atka mackerel for oil to power its engines while hauling in its catch from Alaska waters.

"We want to be able to utilize our fish waste," said Jonathan Spool, a partner in the company. "With the price of diesel fuel these days, we have to think economically." The company hopes to conclude tests by the end of the year.

Researchers this year are also testing fish oil biodiesel in engines at the University of Alaska Fairbanks and in trucks and electrical generators at Denali National Park and Preserve.

Park officials say a fish oil spill in the Alaskan wilderness would dissipate and be consumed by microbes more quickly than a diesel mishap.

"In higher-risk or more pristine areas, a spill means clean-up is short-term and residual effects are much less," said Tim Hudson, a Park Service officer at Denali.

On the whole, fish oil biodiesel is less destructive to air quality than diesel. Compared to emissions from diesel used in most road vehicles, fish oil showed significant drops in carbon monoxide and particulate levels, said John Steigers, a Colorado-based consultant for Unisea.

Sulfur levels in the biodiesel are similar to ultralow-sulfur diesel, Steigers said. However, fish oil's release of nitrogen oxides, a source of respiratory problems, is higher than diesel by a few percentage points.

Alaska's lack of an in-state refinery and frigid temperatures are a challenge to the fledgling technology.

Denali receives free fish oil biodiesel through the study, but would otherwise pay about $5 a gallon, Hudson estimates. About $2 of that covers the cost to send the fish oil for processing at one of Alaska's nearest biodiesel refineries - a plant owned by Pacific Biodiesel in Hawaii.

Fish oil and its biodiesel product thicken at a higher temperature than conventional diesel and just below the freezing point of water, Steigers said.

Chemical treatments to prevent the oil from gelling would not alter its emissions levels, but would likely bump up the price, Steigers said.

Fish oil also generates up to 15 percent less energy per gallon than diesel, but the economics "have still been very favorable," Steigers said.

About 8 million gallons of fish oil are produced by Alaska's major fish processors each year, according to Peter Crimp of the Alaska Energy Authority, a state corporation that works to reduce energy costs.

The technology could help ease dependence on expensive diesel for the many impoverished villages scattered along Alaska's coasts and Interior region. Rural residents, most of whom are Alaska Natives, rely on diesel for heat, electricity and fuel for vehicles used on hunting and fishing expeditions.

About 28.3 million gallons of diesel fuel were imported into Alaska's rural communities for the fiscal year from 2004 to 2005 at a cost of $51.4 million, Crimp said. That's an increase of 36 percent over the last two years.

Salmon swim by the millions up Alaskan rivers each year and possess a fat content of up to 30 percent. The fish are used for subsistence by many Alaska Natives, but are a virtually untapped source of power generation.

"We'd like to see what local energy sources there are in any area to reduce the amount of cash exported for diesel," Crimp said.

As the state and other processors research fish oil's possibilities, Unisea plans to continue burning all of its stock.

"They can go out in the marketplace and say 'We're processing and using green energy,"' Steigers said.

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On the Net:

Unisea Inc.: http://www.unisea.com/

Alaska Energy Authority: http://www.akenergyauthority.org/