In the scramble to find domestically available energy resources, the old standby — wood — has received a heck of a lot of attention lately. Unfortunately, the rampant and injudicious use of this combustible hangs like a double-edged sword above the head of humankind: Burned directly, especially on a large scale, wood could be a serious source of air pollution and its widespread unchecked consumption could have an impact on the environment in more direct ways as well. (After all, it takes a good many years to produce a single hardwood tree.)
Still, "woodburning" doesn't have to be a dirty word. In fact, the people at Wood Power Energy Corporation — in concert with the nursery firm of Miles W. Fry & Son — are taking some pretty impressive steps to demonstrate that cellulose combustion, when managed properly, can be both a practical and an economical alternative for "power hungry" Americans.
The Fry nursery folks, who are part of the "WoodPEC" group, are no strangers to long-time MOTHER EARTH NEWS-readers. (See "Hybrid Poplars" and "Homemade Motor Fuel ... From Firewood.") But the wood-powered, on-site energy system recently demonstrated by the WoodPEC organization takes the group's experiments in wood gasification one step further and actually provides a sizable portion of the nursery's everyday energy requirements!
Greenhouses, you see, are costly to maintain, particularly throughout the winter months. So, the Pennsylvania-based group decided to modify its hothouse's existing oil-fired water-heating system to burn wood gas, by way of an automatically stoked, 1-1/2-million-BTU gasifier. Its 49-horsepower boiler easily supplies two 5,000-square-foot greenhouses (it's been designed to handle four such units), and a secondary heat recovery system insures that any normally wasted thermal energy gets recycled rather than dumped.
Economically speaking, the concept makes good sense: Not only did the new fuel source require, for the most part, minimal equipment changes (a gas-fired furnace would've required even less modification), but between 10 and 25 percent of its content is burnable hydrogen derived from moisture in the wood, a resource that's not used in direct combustion. As a result, the gasifier system's efficiency may approach 90 percent, while conventional wood-burning furnaces and boilers generally function at two-thirds that level (or less). Translated into dollars, the conversion means that the nursery's managers should be able to replace their current annual consumption of $55,000 worth of fuel oil with 300 tons of hybrid poplars, grown at a cost of $15,000. (This amount of furnace feed can be raised on two 25-acre "energy plantations" of marginal land, harvested in alternating years to allow regeneration.)
In addition to the wood-gas-fired hydronic heating system, the WoodPEC folks have been testing a 650,000-BTU downdraft gasifier that's coupled to a 140-horsepower, 70-kilowatt AC generator. Without taking by-product credits for secondary heat recovery into account (and that salvaged energy amounts to 40 percent of the thermal requirements for one greenhouse), they've been able to produce electricity at about 8¢ per kilowatt-hour and hope to reduce that figure, eventually, to less than 6¢.
And, on a more conventional level, a direct-combustion, wood-fired, hot-air furnace is currently being used to deliver up to 800,000 BTU per hour — through a double-shelled exchanger and a simple network of perforated plastic-tube ducts — to a 30-by-170-foot hothouse structure while maintaining stack temperatures as low as 150 degrees Fahrenheit!
By taking their energy needs "into their own hands," so to speak, the people at WoodPEC are well on their way to proving that self-sufficiency can work well, especially when the goal is backed by a bit of plan(t)ing.