The company behind a proposed biomass-fueled power plant in La Pine is seeking permission to expand the size of its building, including exhaust stacks up to 150 feet tall.

Biogreen Sustainable Energy Co., based in St. Helens, proposes to generate 24.9 megawatts of electricity, according to company President Rob Broberg.

Broberg said his company has not finalized its design for the power plant, but is seeking a series of text amendments from Deschutes County in order to keep its options open.

If approved, the text amendments would expand the maximum building height for Biogreen’s facility on Reed Road from 45 feet to 100 feet, and the maximum exhaust stack height from 100 to 150 feet. The company would also be granted additional use of adjacent properties for parking, storage and loading.

Bill Carlson, a consultant helping Biogreen design the plant, said there are two possible designs under consideration. While both burn woody scraps to fire boilers that in turn produce steam to power electricity-generating turbines, the portion of the plant where the biomass is actually burned varies.

In the “grate system,” similar to old steam generators like those used at early Bend sawmills, biomass is burned atop a series of metal grates.

The grates can turn or vibrate in order to produce even burning, Carlson said, and the fire is fed by air blown in from below.

The alternative “fluidized sand” design blends biomass with sand. Air is injected into the sand from below to stir the mixture during burning.

“It actually acts like a fluid, it’s tumbling, almost like you’re stirring a drink,” Carlson said.

A biomass plant operated by Georgia-Pacific at the Wauna Mill in Clatskanie uses a fluidized sand system, Carlson said, while the Seneca Sustainable Energy plant currently under construction north of Eugene will use a grate system.

Broberg said the fluidized sand system generally requires a taller exhaust stack than the grate system. Carlson said the final decision on the height of the stacks will be made in consultation with the Oregon Department of Environmental Quality, which considers the composition of the exhaust and local weather patterns — among other things — in making a recommendation for stack height.

Deschutes County Community Development Director Nick Lelack said Biogreen’s request presents an unusual situation for the county. Since incorporating in 2006, La Pine has adopted some but not all of the codes and policies needed to approve a request like Biogreen’s. While Deschutes County will be asked to make the decision on the text amendments, La Pine will later be asked to make the decision on Biogreen’s site plan and conditional use permits.

“It’s the only situation where we have that occurrence, so that makes it a unique situation,” Lelack said. “The city of La Pine has a comprehensive plan but has not yet adopted its implementing ordinances.”

Lelack said the Deschutes County Planning Commission and Deschutes County Commission plan to look to the La Pine Planning Commission and the La Pine City Council for a recommendation before making their decisions on the text amendment requests.

A joint meeting of the La Pine City Council, La Pine Planning Commission and La Pine Transportation Advisory Committee has been scheduled for Wednesday in La Pine to discuss the Biogreen proposal.

Broberg said if Biogreen does not encounter any delays, it could break ground on the plant by the end of the year and open during the second quarter of 2012. He expects the plant will employ 22 to 25 people directly, with an additional 65 to 70 people involved in the acquisition, processing and transportation of biomass to fuel the plant.

If you go

Joint Session of La Pine City Council, Planning Commission, Transportation Advisory Committee

Where: 51340 U.S. Highway 97, La Pine

When: Wednesday, 5 p.m.

If You Go

Joint Session of La Pine City Council, Planning Commission, Transportation Advisory Committee

Where: 51340 U.S. Highway 97, La Pine

When: Wednesday, 5 p.m.