People are talking about all sorts of new alternative fuels diesel fuel made from natural gas, coal and even fish. But do they really work?

Alaskans are more interested than most in finding lessexpensive alternatives to petroleum-based fuels these days. But given the state's cold winter conditions, reliability and performance may be more important than cost.

A liquid fuel is useless if it develops the consistency of chewing gum at 30 below.

The Arctic Energy Laboratory at University of Alaska Fairbanks has been testing alternative fuels for the past year. The news surrounding these fuels is mixed.

Some of the information gathered will be useful when Alaskans start using ultra-low-sulfur diesel fuel, a conventional diesel fuel where the sulfur has been reduced to 15 parts per million. The U.S. Environmental Protection Agency will require the 15 ppm diesel fuel to be in use in 2006.

Engine performance tests conducted at UAF used an ultraclean synthetic diesel fuel made from natural gas, as well as a fish oil biodiesel fuel made from Alaska pollock caught in the Bering Sea.

Tests show both fuels work in diesel generator sets similar to those used in many rural Alaska communities, says Dennis Witmer, director of the UAF's energy lab.

The synthetic fuel made from natural gas worked as expected that is, better than conventional diesel. The diesel fuel made from pollock also worked well, but experienced some storage problems. When the blodiesel was stored for an extended period and reheated after freezing, it experienced biodegradation through bacterial action, which caused operating problems.

Synthetic diesel fuel made from natural gas, supplied by Tulsa, Okla-based Syntroleum Corp., showed reduced emissions of air pollutants and good performance, compared to conventional diesel fuel in the engine, Witmer said.

"There were some emissions problems detected during the test but were attributed to things other than the fuel," he added.

The fuel was made using the Fischer-Tropsch process, a chemical reaction that converts gas, biomass or coal into a liquid product through a rearrangement of the chemical structure of the molecules. The process is sometimes called "gas-to-liquids," where gas is used as a feedstock.

Syntroleum shipped 15,000 gallons of fuel from Tulsa to Fairbanks for the tests. For the tests at UAF, Syntroleum had made a batch of Arctic-grade synthetic diesel fuel which is basically jet fuel or kerosene. Arctic-grade fuel must be used in much of Alaska in place of ordinary diesel fuel, which gums up at cold temperatures.

The low levels of air pollutants in the tests were expected and basically confirmed results of other testing. The important finding by Witmer's group is that the engine performed well with the fuel in Fairbanks' cold winter weather. As a part of the tests, two Fairbanks city buses operated with the synthetic fuel, and performed well in temperatures of 50 below and 60 below zero.

When the fuel was stored outside it didn't show degradation, either.

The high cetane rating of the fuel - cetane is to diesel what octane is to gasoline - resulted in improved ignition and even more combustion than conventional diesel fuel, Witmer said.

The cetane rating of the synthetic diesel fuel is 70, compared with 40 for most diesel fuel sold in the United States.

Alternative fuels showsstrengths and weaknesses

The biodiesel fuel made with fish oil worked very well in the diesel engine. In fact, the UAF tests showed the fuel's performance actually matched that of conventional diesel fuel, even though laboratory tests indicated a lower energy content per unit of volume compared to the conventional fuel.

Problems were encountered with one batch of fuel that had been stored through the winter, was frozen and then reheated. The fuel changed color, indicating bacterial action, and when Witmer's graduate students started the engine for a test run it stopped cold.

The lesson from this is that biodiesel works fine but it can't be stored for extended periods. Additives could be put in the fuel to restrict bacterial action, but that may reduce the fuel's lowpollution attributes. The team has yet to run the diesel engine on straight fish oil, so there may be other lessons that will emerge.

What's important is that the research group learned something, Witmer said. Biodiesel, a favorite of environmental groups, may not be a panacea for the energy crisis, he said.

One concern with the Fischer-Tropsch diesel was a potential problem with lubricity created by the lack of sulfur in the fuel. Basically, the sulfur in conventional fuels, while unhealthy for humans, helps lubricate the seals and rings in engines. Without the lubricating sulfur, the Fischer-Tropsch diesel can cause seals and rings to become brittle and degrade.

The solution is to use an additive to do the job of sulfur in lubrication. Witmer said the additives seem to work fine on the engine tests, though he added that more extensive tests are needed than the 2,000 hours the diesel engine was operated with the fuel.