Engineers at the U.S. Department of Energy's National Renewable Energy Laboratory have taken a major step in launching a "net-zero energy" facility: They lit a road flare and began burning wood chips. No kidding.It's a tad more complicated than that, of course, but that is how the lab says it fired up its new, smoke-free Renewable Fuels Heating Plant. The $3.3 million RFHP will heat NREL's South Table Mountain Campus laboratory buildings, which will include a 218,000 square-foot Research Support Facilities (RSF), expected to be completed in the summer of 2010. The massive office building will carry LEED Platinum certification and house a 2,500-square-foot data center.

The new heating plant also will warm a 130,000-square-foot Energy Systems Integration Facility, which will house a variety of research that aims to overcome technical barriers to adding new renewable energy generation systems to the electrical grid. The ESIF, which is expected to open in 2012, will house a 15,000-square-foot high-performance computing (HPC) data center

Operating smoke-free and odor-free, the heating plant will offset about 4.8 million pounds of carbon dioxide each year and as much as 75% of the 50,000 million Btus of natural gas used annually to heat the South Table Mountain campus, says the NREL. Instead, the RFHP will burn woody biomass, including wood chips from trees lost to the region's mountain pine beetle epidemic and waste wood.

And those disappearing emissions? How is NREL able to pull that off? It explains:

Throughout metro Denver area, woodburning has been nearly eliminated to meet strict state air quality regulations. But the RFHP's ultra-efficient combustion process allows the facility to meet state requirements while burning biomass to reduce the lab's carbon footprint. The RFHP has a state air emissions permit.

The wood chips are screened to remove rocks and debris. The processed fuel will have less than 30% moisture content and a heat content of about 12 million BTU per ton.

Wood chips automatically feed into a combustion chamber and are roasted to the point where they are gasified. The wood gases then are mixed with air for complete combustion in the heat recovery boiler. Temperatures in the two-stage process reach 1700° F (930°C), and leave very little ash or soot.

The system uses a multiclone separator to remove 85% of the remaining particulates from the boiler flue gas. Inside each of the separator's multiple chambers, dual cyclones are generated to capture and spin dust particles from the gas. The particles are hurled against the walls of the chambers and fall into a hopper.