The fuel for the plant is a combination of green woodchips, clean wood waste, recycled waste oil and natural gas. We burn no trash, garbage, construction/demolition debris, coal, toxic waste, tires, or medical waste. We purchase about 10,000 barrels of low sulfur oil a year from a New Hampshire energy company, which collects waste lubricating oil and other petroleum waste products from gas stations and industrial plants. The waste oil is put through a process that cleans it and removes all harmful contaminants before it is delivered to our site. We fire the recycled oil in the same boilers in which we also burn the 35,000 tons of woodchips we purchase annually from a dozen local loggers and chip suppliers.
Sulfur-free woodchips are a byproduct of the ongoing logging operations, which harvest timber for sawmills or paper mills. In the past, loggers left behind the tree limbs and tops, called "slash". They also left behind the culls, deadfalls, brush, and non-merchantable species of timber. The seedlings of oak, birch, maple, pine, and the other useful species were left to compete with the weeds. Moreover, the slash presented an extreme fire hazard and hatched the eggs and larvae of beetles and other insects harmful to trees. Selective cutting and whole-tree chipping operations are an established part of New England timber harvesting, and the garden is finally being weeded. Studies sponsored by the U.S. Dept. of Agriculture and the University of NH Extension Service report that this removal of slash, brush, deadfalls, and non-merchantable timber is a net benefit to New England woodlots. New Hampshire's woodlands could easily sustain more than 50 wood-fired steam and power plants.
Our wood fuel is delivered in 40-foot vans, each of which holds about 25 tons. The van is weighed on a scale platform and then self-unloads the chips, which fall into a receiving hopper. A conveyor carries the chips to a screen where branches, scrap lumber (and the occasional chain saw or spare tire) are removed. The chips are processed through the screen and then conveyed to the two fuel storage silos. The silos are constructed of concrete and together hold 1300 ton of woodchips, enough for four winter days. More conveyors carry the chips from the silos to the boilers.
The chips are blown into the furnace where they burn on a stationary, water-cooled, grate. Ash from the boilers is land spread by farmers to enhance the productivity of the soil they use to grow crops.