Crotched Mountain > Foundation > Woodchip Plant

Fact Sheet

Fact Sheet

Campus Central Heat
Hot Water Plant

Benefits of Using Wood Chips

Wood chips come from a renewable, sustainable resource base. Fossil fuels will eventually run out, but with proper forestry practices, the biomass resource base can be sustained indefinitely.
The fuel is available in great quantity in New Hampshire and other northeastern states.
Biomass fuel dollars stay in the local and state economy. Biomass fuel comes from in-state businesses that use local labor for cutting, hauling, chipping and delivering fuel. The raw material - hardwood trees - is purchased from local landowners.
Biomass fuel prices have been stable historically and are not directly linked to national or global energy markets. Over the last 15-20 years biomass prices have stayed level or decreased.
Biomass pricing is not subject to monopolistic control.
Biomass has negligible sulfur content, so its combustion does not contribute to the atmospheric buildup of oxides of sulfur, a cause of acid rain.
When biomass is burned for energy, using wood from sustainable forestry practices, there is no net increase in the greenhouse gases that cause climate change so it can be viewed as "carbon neutral".
Using wood wastes from sustainable forestry as fuel increases the health of the forest resource. The Society for the Protection of New Hampshire Forests supports the use of biomass energy production as a way of practicing sustainable forestry.

The Crotched Mountain Wood Chip Plant

Chip Supply

In the 2007-08 heating season we estimate we will use 1500 tons of green wood chips/year. At about 30 tons/trailer load yields 50 deliveries over the year. With full build-out of the campus over the next ten years, we are predicting we will use twice this amount.
The chips are supplied by D.H. Hardwick, a local family run logging business located in Bennington, NH. Through conversion to this fuel source, we are keeping dollars locally and supporting the forest products economy.
We have a five year contract for our chip supply with a certain fixed price and only a modest increase in cost over this contract.
At the current price for the chip supply we are paying the equivalent of 61¢ per gallon fuel oil for the same heat production.
The chips are a "bole" chip. Essentially a bole chip is a cordwood quality chip made from the chipped trunk of a tree bark included with no top branches.
We estimate we will save over $250,000 in fuel costs annually during our first full heating season with estimated annual savings increasing to nearly $1 million over time.

Equipment

The central plant includes 2 wood boilers – 4 MMBtu and 8 MMBtu for a total of 12 MMBtu. We also have a 4.9 MMBtu oil boiler as back-up. (There are additional back-up oil boilers distributed on the campus.)
We have a chip storage bin with truck bridge capable of storing about 150 tons of chip (5 or 6 trailer loads). This should keep us supplied for a week in mid winter with full build-out (2x current load).
The longest pipe run in the district heat system is 2100' (X2 = 4200') with a vertical rise of 100'.
System design is based upon a 30°F ΔT.
Water temperature in district pipe leaves boiler at 190°F - 200°F.
2-15 HP pumps in parallel with VFDs (variable frequency drives) pump water through the district pipe.
We have a 4 module baghouse with automatic jet pulse cleaning.
We have a Cor-ten stack 75' tall. (Cor-ten has a bit of copper in the steel. It is allowed to rust to form a protective coating and patina. No further finishing is required. Similar to some guard rails on roadways.)

Heated Area

Currently we have about 250,000 square feet of building area heated with the wood-fired boilers. We still have about 100,000 square feet of existing buildings to add to the system. We have the capacity to heat all the existing space plus about 250,000 of new construction for a total of 600,000 sf.

Emissions

We will have a two stage system for particulate control. A cyclone separator is a standard control technology to remove fly ash. In addition, we are using a bag house which will remove about a 10 fold increase in small particulates (PM 10). Any visible white plume seen emanating from the stack on a cold day is condensing water vapor from our fuel which is about 40% water. With these emissions controls in place, DES is not requiring monthly testing, an indication of the emissions air quality and an additional cost savings.

Unique Features

There are 3 features of our wood chip system that are remarkable and unique to this location. They are: our chip storage utilizing a truck bridge, tandem wood boilers of different sizes with capacity for different burn settings to achieve maximum efficiency and the bag house for maximum emissions control.