Seattle is converting its garbage-truck fleet from diesel to compressed natural gas, in new hauling contracts starting March 30.

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For years, Seattle has operated an aggressive curbside recycling program to reduce the need for expensive landfill space.

Now the city seeks to despoil less of the atmosphere by converting its garbage-truck fleet from diesel to compressed natural gas (CNG) under new hauling contracts starting March 30.

One contractor, Seattle-based CleanScapes, is buying 40 CNG trucks and building a fueling stop in Georgetown. The other, transcontinental giant Waste Management, is buying 106 trucks to be fueled in South Park.

Waste Management’s territory will be South and Northwest Seattle, while CleanScapes will cover the northeast and central areas of the city.

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This is the second municipal-waste contract for CleanScapes, which runs diesel-powered trucks in Shoreline. President Chris Martin founded his cleaning company in 1997, inspired by the debris in his Pioneer Square neighborhood.

A 2008 city ordinance requires the two firms to use either biodiesel or CNG.

Martin said the new engines make less noise than diesel engines, especially in the hilly central city. “CNG allows us to operate more quietly at night in those dense, mixed-use areas.”

Waste Management has more than 600 natural-gas trucks in California, and the Seattle program is part of its national environmental initiative, said Susan Robinson, regional director for public-sector services. “We have a goal of reducing emissions associated with our fleet by 15 percent,” she said.

CNG trucks are likely to reduce air-polluting particulates at least 90 percent compared with older diesel trucks. New diesel trucks are so clean that they roughly match CNG, said Dennis McLerran, executive director of the Puget Sound Clean Air Agency.

But the CNG trucks still have an advantage in greenhouse gases, releasing 20 percent less than even the best diesel engines, he said.

Natural gas, once thought to be running out, is making a comeback because of better extraction technologies and the discovery of new reserves, McLerran said.

Waste Management showed off a new truck last week at a city-owned fueling depot beneath Interstate 90. “It’s like filling up a big propane tank,” said a supervisor, Steve Aiton. It took less than 20 minutes to fill four tanks atop the green truck to 3,600 pounds per square inch.

The company says it will spend $29 million for trucks and $7.5 million to build the fueling yard at South Park — a “slow fill” station where gas is pumped for several hours or overnight. Slower pumping causes less friction and therefore less heat, allowing more gas to reach the tanks.

Meanwhile, garbage costs for the public are going up because of a combination of inflation and a mandatory food-recycling program.

Monthly rates will increase from $23 now to $29.65 in April, a 29 percent boost, for a typical single-family home using a 32-gallon trash can and a 96-gallon yard-waste container. City leaders urge people to save by recycling, but a 20-gallon can will be costlier too, going from $13.55 now to $17.55.

It’s unclear how much of a role the fuel switch played in the increase.

Because the firms made competitive bids, there was no city analysis of their internal costs, said Hans Van Dusen, a contracts manager for Seattle Public Utilities. A phone survey found residents were willing to pay more for quieter, cleaner trucks, he said.

Both haulers predict that over the entire 10-year contract, their costs for CNG versus diesel will even out. Waste Management’s trucks in Seattle are due for replacement anyway, Robinson said.

CleanScapes is predicting the fuel will be cheaper than diesel. Pierce Transit burned the equivalent of $1.21 a gallon to run its all-CNG bus fleet last spring, while other bus agencies paid $4 for diesel.

Mike Lindblom: 206-515-5631 or

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