Concentration of CO2 in the Atmosphere

UNH Biomass Boiler Project Is Underway

Rendering of the completed Northwest Biomass Heating Plant at UNH in Durham, NH. Image: Weller & Michal Architects, Inc

Jim Van Valkenburgh

After a long summer of construction, Froling Energy is now finishing up the University of New Hampshire’s (UNH) first large-scale biomass boiler system. The new Northwest Heating Plant will provide heat and hot water to four buildings and ten greenhouses in the Thompson School neighborhood. The new plant is located on the Durham campus, on the back side of Putnam Hall, directly across the street from Wildcat Stadium.

For decades, UNH’s central Combined Heat and Power Plant provided heat to these buildings and most of the campus, but the long pipe run out to the Thompson School area was failing. Instead of spending money on replacing the old buried pipes, the UNH Facilities Department decided to make this an opportunity to create and test a biomass-fired district heating system fueled by one of New Hampshire’s most important renewable fuels, wood.

A key part of the project is the creation of a small area district heating system that will provide heat to Putnam Hall, Barton Hall, Cole Hall, the Veterinary Diagnostic Lab and the ten MacFarlane Greenhouses. By the time snow flies this winter, the new wood chip boiler will be the main source of heat for these buildings, sending it out through newly buried insulated steel pipes. Two new liquid propane gas boilers will act as a back-up source of heat and provide additional heat needed during extremely cold weather.

The biomass boiler is a 2.45 million BTU-per-hour output Viessmann Vitoflex 300-UF which employs gasification technology, oxygen-sensor-based combustion controls and a multi-cyclone in the stack, making it incredibly clean burning. The intended fuel, screened semi-dry wood chips, called PDCs, are a key element in making the Vitoflex 300 one of the most automatic, reliable and efficient wood chip-fired boiler systems available. PDCs are screened wood chips with 25% to 30% moisture content, made from sustainably harvested trees sourced locally from forests in southwest New Hampshire and central Massachusetts. Locally sourced means fuel dollars stay in our region which is important for the New England economy.

Northwest Biomass Heating Plant under construction. Image: Weller & Michal Architects, Inc.

The UNH Facilities Department calculates that the new district will consume 750 tons of PDCs. This is the equivalent of over 70,000 gallons of No. 2 fuel oil (or over 91,000 therms of natural gas). PDCs are delivered a bit like oil: from a truck that pumps it through a hose and into a tank. But with PDCs a blower truck blows them through a five inch diameter hose into the silo. The simplicity of this delivery method significantly reduces the project’s cost. A vertical storage silo is being built inside the boiler house that is able to hold 45 tons of PDCs—that’s the same heat value of about 4300 gallons of fuel oil. PDCs are locally sourced and nearly carbon neutral with a very low cost of about $5.65 per million BTUs.

At this writing, in mid-September, the boiler building and silo are complete, all of the long pipe runs are in place, and the boilers, tanks and pumps are all installed. The next steps are to complete control wiring and begin the system commissioning process. The plant is expected to be fully operational by November.

Froling Energy is acting as the general contractor on this project. The project engineering firm is Wilson Engineering of Medville, PA. The architectural firm is Weller & Michal Architects, Inc. of Harrisville, NH.

Froling is the supplier of the PDC dry wood chips and boiler-service company during the coming winter. For the last nine years, Froling Energy has been focused on the installation of commercial biomass boiler systems in schools, manufacturing plants, municipal buildings and homes throughout New England. They also deliver PDCs to a growing list of customers, and the screened semi-dry wood chip fuel made at their plant in Peterborough, New Hampshire.

Jim Van Valkenburgh is VP Sales & Marketing for Froling Energy. He can be reached at 603-924-1001 x2. For more information on Froling Energy go to

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