In an effort meet new federal requirements for cleaner-burning freight engines, Union Pacific unveiled at its Roseville yard Wednesday the UP 9900 – an experimental locomotive utilizing three different filtering technologies.

The UP 9900 – which sacrifices one-quarter of the standard engine's power to make room for the three onboard filters – is part of a $20 million Union Pacific investment toward meeting the Environmental Protection Agency's requirements.

"New locomotives starting in 2015 will have to have some of this equipment," said Mike Iden, Union Pacific's general director of car and locomotive engineering.

Under the EPA requirements, engines purchased after 2015 will be required to meet a Tier 4 emission standard – a 90 percent reduction in emissions from uncontrolled engines.

The power-washed UP 9900 on display Wednesday doesn't quite reach the Tier 4 requirement, but officials called it a critical step in that direction.

The plan is to test the performance, power, fuel-efficiency and maintenance requirements of the engine over the next 18 months while it's in use between Roseville and the Bay Area.

The emissions reduction – achieved with the help of engine manufacturer Electro-Motive Diesel – has left the engine without the power needed for long hauls or to cross the Sierra Nevada, officials said.

Ultimately, new Tier 4 engines will need to match the power of the 16-cylinder engines commonly used now and make room for the emissions filters without making the engine significantly larger.

Existing UP engines are already at the maximum allowable width of 10 feet, 3 inches and the maximum height of 16 feet. Iden said the engines can get slightly longer, but there are limits to that, too.

The UP 9900 emissions systems include exhaust gas recirculation, which recycles 10 percent of the engine exhaust, reducing the amount of oxygen the engine runs on; diesel oxidation catalysts; and diesel particulate filters, which are in place in most modern diesel vehicles.

UP is investing $20 million on 25 experimental locomotives, 16 of which will operate out of the Roseville railyard. The other nine will be based in the San Bernardino County community of Colton.

The experimental locomotives are intermediate line-haul units, with an operating range of about 200 miles. They will be used exclusively in California. Testing on all 25 locomotives is scheduled to last through 2014.

Union Pacific has previously experimented with hybrid locomotives for use around the railyard, but battery problems have limited the success of that program, Iden said.

The company has also employed technology to reduce the amount of time engines idle and increase fuel-efficiency by adjusting train configurations.

"The Roseville railyard has become a center of innovation," said Tom Christofk, of the Placer County Air Pollution Control Board.

Liisa Stark, UP director of public affairs, said Union Pacific was proud of its efforts to reduce emissions and comply with the requirements.

She noted that moving freight by train is far more energy-efficient than moving it by truck.

Roseville City Councilman John Allard noted the city's long history with the railroad and thanked UP for its presence.

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