Seattle Steam Company was founded in 1893. It has 18 miles of steam pipes running under the streets of downtown Seattle, which it uses to distribute steam to approximately 200 downtown buildings, and the First Hill neighborhoods. That steam heats the buildings, sterilizes hospital instruments, and creates the hot water to wash mountains of hotel and hospital laundry. The oldest steam pipes are wood. In some ways its business is SO “last century.” But in October it will fire up a new boiler that will cut its use of fossil fuels to heat those 200 buildings in half, and take it from being one of the largest users of natural gas in Puget Sound Energy’s market area, to a relatively small customer as industrial customers go.

It will accomplish that by switching to burning urban wood waste. “Urban wood waste” takes many forms. It can include trees removed when land is cleared for development, wood removed from buildings being demolished, wood pallets that are too expensive to reuse, and clean waste sorted from the waste stream by companies such as Allied Waste, Waste Management and CleanScapes. Historically all that wood has gone to landfills, where it decomposes, releasing methane and carbon dioxide to the atmosphere, as well as consuming the limited space available in the landfill and forcing costs up as new landfills have to be opened.

Instead, approximately 10 to 12 truckloads of wood waste a day will be delivered to Seattle Steam’s boiler plant on Western Avenue. The wood is all cleaned, sorted and chipped to be most combustible before being delivered to Seattle Steam, to minimize paints and other residues that would lead to air pollution and to insure efficient combustion. The new boiler Seattle Steam has installed is engineered to exacting standards to insure that air emissions meet all Clean Air Act requirements for a source in the heart of downtown Seattle. The minor amount of ash residue will be removed and used in industrial applications, making this a zero-waste operation.

The Department of Energy classifies biomass as a sustainable renewable resource. The US Green Building Council recognizes biomass as a renewable fuel source in the LEED certification program. That means that buildings pursuing LEED certification can get credits for using biomass to heat the building.

The new boiler will reduce the CO2 output from fossil fuels at Seattle Steam’s plants by approximately 45,000 tons annually – the equivalent of the CO2 taken up by 1,700 mature trees, the CO2 emissions from the annual energy use of over 3,700 homes, or the emissions from over 4.6 million gallons of gasoline being consumed. The CO2 that results from burning wood waste is CO2 that would otherwise be released from a landfill as the wood decomposed. And unlike fossil fuels, wood is grown in Washington’s forests on millions of acres of commercial forest land, so the fuel is fully sustainable.