Wood chips are already starting to pile up in a storage building at Schiller Station in Portsmouth while construction workers put the finishing touches on a boiler that will burn the chips to generate electricity.

The wood-burning power project, which is owned by Public Service Co. of New Hampshire, is a model of the type of plant North Country lawmakers would like to see in Berlin to help offset the closing of the pulp mill. The $75 million Seacoast project is expected to begin generating electricity in August.

Lawmakers ruled this week that PSNH can go ahead with plans for a similar wood-burning power plant in the North Country.

Other independent power producers, like Hanover-based New Energy Capitol, have said they are interested as well.

Wood-burning power plants have been championed as a more environmentally friendly way to generate electricity; proponents say they will help wean the state from reliance on foreign oil and other fossil fuels. PSNH's 50 megawatt wood-burning unit at Schiller Station will be the largest of its kind in the state. It will burn roughly 450,000 tons of wood chips a year and produce enough electricity to power 40,000 homes, according to station manager Richard Despins.

The Portsmouth project

Schiller Station is one of a cluster of power plants built along the Piscataqua River, just beyond the Fox Run Mall on the Portsmouth-Newington line. The 150 megawatt plant was built in the 1940s, and it makes electricity by burning a mixture of coal and oil.

PSNH wants to build more power plants because the company can produce electricity more cheaply than it can buy electricity on the open market. Right now, PSNH can only produce enough electricity to serve 70 percent of its 475,000 customers. And by burning wood instead of fossil fuels, the company earns valuable renewable energy credits that will be used to pay for the project.

In December 2004, construction started on a wood-burning boiler at the plant.

The technology of wood-burning power plants is nothing new. Wood chips are burned to boil water and generate steam. The steam then turns a turbine generator to produce electricity.

At Schiller Station, trucks carrying roughly 30 tons of wood chips each will drive onto hydraulic ramps, be lifted into the air and dump their chips into a 35-foot-tall storage building.

Once the wood chips are machine-sifted to sort out chunks that are too big for the boiler, they are sent along a 1,000-foot conveyor over the top of the coal yard and into the boiler building. The steam generated there will be piped into the turbine generator building, where the electricity will be produced.

It will release 70 percent less nitrogen oxide, 95 percent less sulfur dioxide and 90 percent less mercury than the coal-burning boiler, Despins said.

The wood supply

On a typical logging site, the trees are cut down, the tops are cut off and the branches are stripped. The low-grade wood includes tops, branches, rotten pieces and other leftovers: It is fed into a chipper and loaded into trucks for shipping, said Richard Roy, PSNH's wood chip buyer.

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