August 21, 2009

Seattle turns to old heat source: Wood

Photo by Katie Zemtseff [enlarge]

Seattle Steam has replaced an old natural gas boiler with a new wood-fired boiler at the steam plant on Western Avenue and added a new wood storage structure behind the Four Seasons Hotel across the street.

Seattle Steam is completing a $25 million project that will allow the energy company to go from using exclusively fossil-based fuel to using a renewable resource to provide 60 percent of its fuel.

The biomass or wood waste project is set to debut this fall. The company now burns natural gas and occasionally oil to create steam that heats about 190 downtown buildings.

Soon wood will be burned whenever possible to create steam. Natural gas will be burned on cold days when more heat is needed or when wood cannot be delivered due to icy weather. On very cold days, when natural gas is needed in other parts of the city, Seattle Steam will burn oil.

Seattle Steam said the change will reduce the company's carbon footprint, and that of its customers. Rates should not increase directly because of this change.

President and CEO Stan Gent said switching to wood won't save Seattle Steam any money at the moment. But he said the company chose to move in this direction in response to volatile prices for gas and oil, and in preparation for a future where emissions are taxed.

When that happens, Gent said, he will use credits from burning wood to offset energy his company creates from gas. He said he will still have credits left to save or sell. “That's potential revenue.”

The new system

Seattle Steam will use 250 tons of wood waste each day, or about 91,000 tons per year. Wood will come from three sources: land clearing, clean urban wood waste and Cedar Grove Composting, which will collect “wooden bits” left over from its composting, Gent said. Cedar Grove will provide about 100 tons a day.

Local waste haulers CleanScapes, Allied Waste and Waste Management will also collect wood waste from their hauling activities, such as construction debris and wood crates.

Wood waste from those four sources will provide about 80 percent of the wood the plant needs.

Another supplier is collecting urban wood waste and some land clearing debris from the Redmond/Bellevue area. Gent said Seattle Steam is also talking with the city of Seattle to get tree clippings and waste from the city's Parks and Recreation Department. Wood waste will be collected at a staging area near Boeing Field, where it will be chipped and processed.

Chris Martin, president of CleanScapes, said wood waste now is either burned or used for pulp, depending on quality. When CleanScapes sends its wood to Seattle Steam, Martin said he expects wood that can turned into pulp will still be separated. His company will also produce fewer emissions because it will be transporting wood down the street, rather than to Auburn or Fall City where it goes now.

“We try to make sure our products are going to the highest and best use,” Martin said. “I don't see a short end of the stick on this one.”

The Seattle Steam project has two parts:

• a new wood-fired boiler in the steam plant that replaces an old natural gas boiler

• a new storage structure behind the Four Seasons Hotel.

Gent said the storage space was originally used for coal but sat empty for about 50 years when Seattle Steam removed boilers from the space.

Every evening trucks will deliver chipped wood waste to the storage space, where it will be stored in a special silo. Wood waste will be blown under Western Avenue through a tunnel that was built in 1917 for coal, and be burned in the new facility across the street.

University Mechanical Contractors is the general contractor.

A number of control mechanisms have been installed to clean the fumes and protect air quality. A scrubber scrubs flue gasses and takes out sulfur and chlorine. Ammonia is also injected into the mixture to clean it. A dust of dirt and ash from the process is collected to be used in a range of products, from concrete to temporary caps at landfills.

Gent said the cleaning system is more expensive than the wood itself.

“We think we're the cleanest wood burning plant in the Pacific Northwest,” Gent said. “It's easy to say that about the newest one, but our scrubber I think is something that's a first.”

Finding money

Seattle Steam has wanted to start using wood waste for years but had a hard time finding financing for the new equipment. Gent said lending institutions liked the project and thought it would work, but didn't want to finance it.

Gent was discussing the project one day with Seattle Steam's union, the International Brotherhood of Electrical Workers, when he said it would be an ideal project for a union pension fund. The union agreed and decided to fund it, as long as it was built and operated by union members.

Gent said that completed the circle. “It's kind of what Seattle Steam is. It's a small, family company.”

Burning wood comes with challenges. Unlike natural gas, which is pretty consistent, wood varies. It gets dirty and has different moisture content. Pieces can also be different sizes, and that can be tough on machinery. “It's just more complicated.”

But wood has advantages: it's a renewable resource with a stable price. Buying wood locally also puts money back into the region, supporting jobs. The natural gas Seattle Steam uses comes from Canada.

Moving to a renewable resource is just the start for Seattle Steam. A year ago, it founded a subsidiary that Gent also heads — Seattle Community Energy — to investigate how to recover heat that is now being wasted. Gent said Ash Grove Cement is one example: Waste heat from Ash Grove's plant could be captured to warm houses in a community like Yesler Terrace.

Seattle Steam is also investigating turning its Post Alley plant into a combined heat and power plant. Gent applied for an $18 million grant from the federal stimulus to do that work. If it doesn't get the grant, he said the company will try to find other ways to make it happen.

Gent said Seattle Steam draws a lot of inspiration from Scandinavia, but it won't start burning solid waste or garbage as some of those countries do. Gent said burning garbage makes sense from an energy standpoint, but permit requirements would be “enormous” and the topic is politically unpopular.

“Technically, they're clean as a whistle,” he said. “(Politically) it's like a nuclear power plant. It's a nightmare.”

He said the only way garage burning would happen is if the process made financial sense and legislation came from the top down.

Other project members include LMN Architects, architect; HIPP Engineering, early engineering; Precision Energy Services, detailed engineering; and EISI, structural engineering.