originally published as WOOD FUEL IN WARTIME
by Robert T. Hall & M.B. Dickerman
Farmers’ Bulletin No. 1912, US Dept Of Agriculture, July 1942
Editor’s Note: Today, with rapidly escalating fuel oil prices and suspect petroleum supply, more people are already thinking about heating with wood. It has become an important option. Such concerns were also prevalent during World War II. The materials we reprint below illustrate this and approach the subject, sans the ubiquitous chainsaw, from the standpoint of self-sufficiency. There is good stuff to glean from this. LRM
WOOD FUEL AND NATION-WIDE PRODUCTION FOR VICTORY
To provide power for manufacturing and transporting the munitions and materials necessary to defeat the enemies of the United States and at the same time to keep homes, schools, office buildings, and thousands of new factories warm enough for health, the requirements for fuel will soon be the largest in our history. Though industrial production was then greater than ever before, the President announced in January 1942 that the armament program would be at least doubled. This calls for more and more raw materials, raw materials, power and heat to process them, and fuels to generate the power and heat.
Railroads and shipping must carry an enormous additional traffic. Troops and their supplies must be moved, as well as lend-lease shipments, raw materials, and fuels. A large part of the total tonnage to be carried is fuel. Fortunately, pipe lines now transport large quantities of certain fuels – natural gas, oils, and gasoline – relieving the burden on railroad and maritime traffic to that extent. But coal is still the major source of energy for generating electricity and steam. The increased demands for power are suggested by the fact that consumption of bituminous coal by electric utilities was a third more in the fall of 1941 than in the fall of 1940.
Other factors further complicate the problem of supplying fuel to homes. The railroads and the tanker fleet are already operating at near the capacity of their equipment. Because of the shortage of iron and steel, it appears doubtful that enough gondola and coal cars and locomotives will be built to fill the needs of expanding rail traffic, nor are many additional pipe lines likely to be constructed during the war. Instead of transporting coal for ordinary domestic use, more and more trains and boats will be hauling coal to new blast furnaces, for example, besides additional quantities of ores and metals. Wartime strain on shipping is at least as severe as that on railroads.
During the first World War the railroads soon became overburdened with traffic and it became difficult and sometimes impossible to obtain deliveries of coal in some sections of the country. Some factories in New England were forced to burn cordwood instead, and local fuel committees, State foresters, and the United States Fuel Administration urged the public to substitute wood fuel for coal. The situation today is not entirely the same, because oil and gas are in more general use, and there are means of delivering greater quantities of fuels than was possible 20 years ago. On the other hand, the emergency requirements during the present war will be far greater, and there is a limit to the tonnage the railroads can handle. Hauling capacity must be devoted first of all to war materials and services for the armed forces. The domestic consumer may have to take care of himself as best he can.
Unlike the people of Europe, Americans are not likely to suffer from lack of heat in their homes. In many parts of the country there is an ample reserve of fuel in the form of wood in the forests. Although the volume of high-grade timber is decreasing year by year, inferior and waste wood is so plentiful that there is more than enough for most fuel purposes (fig.1). Since coal and oil shortages appear likely in some sections, householders and public authorities may well consider a return to the use of wood. In any case, it is wise to lay in some emergency fuel. Many families can make an important cash saving, besides, by cutting a few cords of firewood for their own use. In view of the expanding need for power and heat, even a large-scale substitution of wood is not likely to bring about any decrease in the total consumption of coal and oil. Production of mineral fuels, however, is concentrated in relatively small areas; these fuels must usually be transported hundreds of miles to consumers by rail, ship, or pipe line. The difficulty in supplying coal, for example, is not in production at the mines, but transportation to the consumers. Fuel wood, on the other hand, is available in most sections of the United States and requires hauling only very short distances. With reasonable cooperation on the part of the public, more of our coal and other industrial fuels can be allotted to war purposes and the deficiency made up by use of wood fuels.
Delivering coal to consumers on farms and in the smaller towns is in general comparatively wasteful of railroad and truck service. If such consumers would temporarily abandon or reduce their use of coal and burn wood from nearby timberlands delivered in light trucks or wagons, it is clear that a considerable number of railroad cars and heavy, long-distance trucks could be released for war-production service. This bulletin, prepared in collaboration with the Northeastern and Lake States Forest Experiment Stations and the Forest Products Laboratory, is intended to point out the best sources of wood fuel, its heating value, and some recently developed techniques in producing, transporting, and utilizing fuel wood.
INCREASING THE USE OF WOOD FUELS
Sources of Supply
Several classes of material make up the potential supply of fuel wood. Because of the widespread practice of leaving poor trees uncut, there has accumulated in American forests a vast number of culls unfit for sawlog use either now or later. On an average, an acre of forest land bears at least a cord of cull material good only for fuel.
In logging and in milling forest products, a large volume of wood is cast aside, in such forms as tops, limbs, slabs, edging, and ends. Much of the debris from milling operations is already being utilized, for many mills either burn this material in their own power plants or sell it as a byproduct. Little of the waste in the forest, however, is now recovered. Removing and utilizing this wood not only is economical (fig. 2), but will reduce forest-fire hazards.
Not all of our timber crop reaches maturity. Each year more than 2 billion cubic feet of timber is killed by such destructive agencies as fire, insects, and disease. A high proportion of these trees would make excellent fuel wood if used before decay advanced very far. In the section of the Northeast where a hurricane struck in 1938, many thousands of cords of usable seasoned wood remain on the ground, awaiting salvage.
Another excellent way to obtain fuel wood is to weed the undesirable trees from the woodlands and thin out the overdense stands. Inferior species and suppressed trees are often entirely satisfactory as fuel. The better trees that are left after these improvement cuttings and thinnings are made will grow faster, produce more useful timber, and earn higher profits for the owner.
Production of fuel wood can therefore be made to yield twofold returns in connection with the good forestry practices of making improvement cuttings and thinnings and salvaging dead and down trees promptly. Properly carried out, these operations would do more to conserve the values in American forests as a whole than any other measure except fire protection. Similarly, the use of mill waste as fuel not only increases opportunities for immediate profit but tends to conserve natural resources.
The regions of the country that have the highest fuel-consumption rates and are probably in the most danger of rail traffic difficulties are those that are most highly industrialized and to which orders for the largest volumes of war production have been allocated – namely, the Central and Lake States, New England, and the Middle Atlantic States. It is in these areas that the substitution of wood for other fuels can be of greatest help. Fortunately, stands of timber containing the best species for fuel are concentrated in these regions, as well as in the Southeast. About one-fourth of our total volume of hardwoods is in the northeastern section of the country, comprising New England and the Middle Atlantic States. The Lake States, Michigan, Wisconsin, and Minnesota, together contain nearly 12 percent of the hardwood volume, and five Central States – Ohio, Indiana, Illinois, Iowa, and Missouri, have 8 percent. Thus these three lake regions, where fuel consumption is heavy, have more than 44 percent of the total hardwood stands of the Nation.
Who Can Use Wood Fuel
When other fuels are obtainable and moderately priced, regular use of wood fuel is rarely feasible if it must be transported more than about 20 miles to the consumer by motortruck. To bring wood more than 20 miles in sufficient quantities for consumers in the larger cities could easily cause serious traffic congestion. Wood is bulky in proportion to its heating value and takes relatively more shipping space than other solid fuels. If, however, there are sawmills or woodworking plants within a radius of a few miles or accessible by barge lines, local use of wood waste from such plants tends to be more economical of the Nation’s transportation facilities than the use of coal. The people who are nearest the source of supply can render a service to the war effort, and perhaps also to themselves, by preparing to use more wood fuel during the emergency. Many who live in the smaller towns and on farms will find that fuel wood can be cut almost at their very doorsteps.
Users of wood fuels may be grouped mainly in three classes. First are the householders who can burn wood for heating and cooking, or in fireplaces for supplementary heat. Many schools, churches, and businesses such as processors of farm products fire their furnaces with wood, or could do so. In the third class are the larger plants, which are generating electricity; these plants usually have apparatus for automatic stoking of sawdust or other waste wood, sometimes in combination with pulverized coal. Ordinary household use, nevertheless, accounts for at last two-thirds of our present consumption of wood fuels. Householders have the best opportunities to substitute wood for other fuels in wartime; accordingly this bulletin is devoted mainly to wood fuel for domestic use.
Advantages in Use of Wood
Wood has certain advantages as a fuel, which many people nowadays have not considered. Wood is clean and free from disagreeable dust; it produces little smoke or soot when properly burned. A cord of hardwood leaves only 60 pounds of ashes, while a ton of hard coal will make 200 to 300 pounds. The wood ashes, moreover, have fertilizing value. Wood begins to burn at a comparatively low temperature, so that a wood fire is easy to start and can be maintained at a lower ebb than a coal fire, when only a small output of heat is needed. For cooking, a wood fire need not be kept burning so long as a coal fire and is less likely to overheat the kitchen in warm weather.
For churches, community halls, summer cottages, and other buildings where heat is requried only occasionally, wood is more satisfactory than coal for providing a large volume of heat quickly. There is considerable economy in using wood in stoves and hot-air furnaces during the more variable spring and fall weather, or when a fire is needed only to remove the chill of evening and early morning. Wood burned part of the time is cheaper than coal burned all the time. Finally, most people appreciate the pleasant aspect of a few logs glowing in a fireplace, which can have a practical value in warming a living room on mild days or in supplying extra heat in colder weather.
Heating Value of Wood
Wood that is well seasoned, or thoroughly air-dry, contains about 15-20 percent moisture by total weight. A pound of such wood, from most species of trees, has a little more than half the heat value of a pound of good coal. A cord of one of the heavier hardwoods weighs about 2 tons and has approximately the same heating value as a short ton of coal of high quality, or 200 gallons of domestic fuel oil (table 1).
Stacked wood occupying 128 cubic feet of space makes up 1 cord, usually considered as a pile 4 by 4 by 8 feet. The content of solid wood in a cord varies considerably, depending on the length, size, and form of the individual sticks as well as the care exercised in fitting them together, but a fair advantage is 80 cubic feet of solid wood to the cord, which is used as the basis for table 1. In some parts of the country wood is sold in “stovewood,” “face,” or “running” cords, “runs,” or “ricks” composed of 12-, 16-, or 24-inch pieces in piles 4 feet high and 8 feet long. Three such piles of 16-inch wood actually contain somewhat more than one pile of 4-foot wood.
The presence of considerable quantities of resins or oils, as in long-leaf pine and eucalyptus, tends to raise the heating value of wood, but causes it to be consumed faster. Pound for pound, resin gives about twice as much heat as wood; it also produces more smoke. Resinous woods named in table 1 are considered as containing 15 percent, or an average amount of resin. The bark of some species, such as birch, Douglas-fir, ponderosa pine, and shagbark hickory, has a higher heat value than the wood, but the bark of some other trees, such as the “cedars” or junipers, has low fuel value and leaves much ash. Generally the softwoods (from cone-bearing trees) burn more readily than the hardwoods, and the lighter hardwoods are consumed faster than the heavier species. The pines, for example, make a quicker, hotter fire and last a shorter time than birch, but birch gives a more intense flame than oak. Oak and hickory burn more slowly and give a steady heat.
American beech has long been a favorite fuel wood in the northeastern and central regions of the country, having heating value nearly equal to that of the best oaks. Eastern hophornbeam, sometimes called ironwood, is also very heavy and yields much heat per cord. Red mulberry and hawthorn, though small trees are highly esteemed as fuel. Of about the same fuel value as sycamore is black tupelo (known also as “sour gum” and “blackgum”), which is widely distributed in the Eastern States. For open fires, chestnut, butternut, tamarack, and spruce are not generally in favor, because they throw off sparks.
Moisture in the wood is the most important factor in the heating value. When wood is burned, the water in it must be raised to the boiling point, converted into steam, and finally superheated to the temperature of the flue gases. Hence the heat required to drive off the moisture does not serve to warm the stove or furnace. Generally from 25-45 percent of the weight of green wood is water, and in such species as cottonwood and willow it may be even 55 or 60 percent. By drying out much of this water, the heating value of the wood is considerably increased. For example, green shagbark hickory weighs about 800 pounds more per cord than airdried wood of the same species, the difference representing mostly water. This extra moisture reduces the heat value about one-sixth, as shown in table 2.
Drying the wood for a short time is much better than not drying it at all; if air is allowed to circulate freely about the wood (fig. 3) for 3 months in reasonably dry weather, seasoning will be about half complete, and the fuel value will then be about 90 percent of that of thoroughly airdried wood. Dry wood kindles much more readily than wet wood, and in a stove or domestic furnace a fire of dry wood is generally easier to tend and regulate. It is said, however, that some species such as gray birch and aspen give better results if not too dry, being consumed less rapidly.
DOMESTIC USE OF STOVE AND FURNACE WOOD
How to Burn Wood
When wood is used for fuel, certain rules should be applied in adapting and operating the heating equipment. To do this will be of benefit in getting as much heating value from the wood as possible and will make its use generally more satisfactory.
#1. Stove wood and furnace wood must be cut short enough to lie flat in the fuel chamber. If the firebox is rounded or oval in shape, it is best to have the pieces somewhat shorter than its inside length. Several sticks should be packed in closely, side by side, with only very narrow air spaces between them, if a hot fire is wanted. The heat reflected from one to the other aids in driving off moisture and maintaining the proper rate of burning.
#2. The simplest and most effective way of using wood in a coal furnace is to combine it with coal. A layer of good-sized sticks of wood should be placed in the firebox; then a layer of coal should be added, filling most of the crevices between chunks of wood but leaving an open flame burning in at least one place. From 25 to 50 percent of the coal normally used can be saved in this way, but refueling will be required slightly more often. Seasoned wood will have less tendency than green wood to cause deposits of creosote in the flues.
#3. If wood alone is to be burned in a coal furnace, a few minor changes in the equipment are desirable. Openings in a coal grate are larger than necessary for wood, but it is not difficult to remedy this; simply keeping a layer of ashes on the grate helps considerably. For temporary conversion about two-thirds of the coal grate may be covered with a piece of sheet iron or flattened gallon-size cans, perforated if desired. Many stoves and furnaces are provided with duplex grates, which need only reversing in order to burn wood. In other cases a special wood grate can be obtained from dealers. Even a furnace that has been converted into an oil burner can in an emergency be adapted for wood by removing the oil-injecting mechanism. If the former grates have not been kept available, a wood fire can be built on the floor of the furnace, which may be insulated with firebrick. The furnace thus becomes a “Wilson heater,” one of the more efficient wood burning devices.
#4. Because wood burns with a long flame and intense heat, various measures should be taken to keep flames from going up the pipe and wasting the heat. Fuel should not be piled up near the level of the smoke outlet. With dry wood, the problem is to hold down the rate of release of combustible gas from the wood and at the same time to admit enough oxygen to burn all the gas that is released. The draft from below the grate should therefore be restricted carefully, while about four-fifths of the air is admitted around and above the fuel, usually through slots int he fuel door. Some wood-burning stoves of conventional design are provided with special tubes to admit air at the top of the fuel level. For the sake of efficiency a check damper in the smoke pipe should be used; wood does not need as much chimney draft as coal.
#5. Holding a wood fire overnight requires extra fueling with the largest chunks, preferably of heavy hardwood, and special attention to closing the draft dampers tightly.
#6. In managing a fireplace, the ashes should be kept to the level of the andirons, forming a bed for the accumulation of glowing charcoal. This yields steady heat and aids in igniting fresh fuel as it is added. To check the fire, cover the burning logs lightly with ashes. Since a banked fire will keep 10-12 hours, the fireplace can be used, continuously if desired. If a fireplace supplements an automatic heating system, the thermostat regulating the latter should not be placed so that the fireplace radiates heat upon it. An ordinary fireplace takes nearly 10 times as much wood as a stove to heat a room equally well. More efficiency is gained by an arrangement that permits the warming of outside air that enters the room to replace the air drawn up the chimney. The fresh air is routed behind a metal shield at the rear of the fireplace and may then be led through ducts and discharged into any room.
#7. Wood requires about two-thirds more burning space and one-third more grate surface than coal, to provide the same amount of heat. The same stove or furnace fired with wood therefore cannot yield the maximum heat of which it is capable when coal is used. In steam boilers, it is sometimes possible to overcome this difference in part by removing the grate and maintaining a wood fire on the ash-pit floor or on a layer of firebrick, as suggested previously. The ash-pit casing may be insulated with firebrick also. With an arrangement of this kind, the ash-pit door is kept tightly closed, and all air is admitted through the damper in the fuel door. Such a conversion is somewhat similar to that for use of domestic gravity-feed sawdust burners. For a hot-water heating system, the use of wood is not recommended. At low temperatures in the boiler, larger deposits of creosote are likely to result, necessitating frequent cleaning.
#8. In stoves and furnaces, green wood should not be used in a slow fire, because it will tend to cause deposits of soot, creosote, and acetic acid in the smoke pipe and flue. Burn the green wood in a hot fire and save well-seasoned sticks for use in starting the fire or maintaining it at a low rate. A small hot fire is better than a large smoldering one.
Improved Wood-burning Stoves
Modern devices can add much to the efficiency and convenience of wood-burning equipment. Slow-combustion stoves and furnaces have been developed with considerable success in Europe, and various improved heating stoves of American design are being tested in this country. The principle generally used is to direct the burning gas from the wood downward and then by a roundabout route through the stove, so that it can be well mixed with preheated air. In this way combustion can be made nearly complete, and little of the heat is wasted.
With a fairly large fuel magazine, a stove of this type may need refilling only every 8 to 24 hours. The rate of burning is quite even, and damper settings do not require frequent changing.
One stove being tried out is designed to heat a four- to five-room house and use either hogged fuel or wood in the form of small blocks. Other improved stoves have been placed on the market, with such features as downdrafts and thermostatic damper controls to keep room temperatures more constant and save fuel (fig. 4).
A farmer may find it best to construct his own wood-burning furnace of brick, using little new metal material except pipes for smoke outlets and air ducts. One or more large oil drums can serve as the firebox, and other parts can be made from discarded articles. A home-made furnace of this type is shown in figure 5. Circulating by means of inlet and outlet pipes, the air is heated in the enclosed space around the oil drum.
Other Forms of Wood-Fuel Use
If wood is cut to very small pieces, it can be moved more conveniently by means of shovels, chutes, or belt conveyors and becomes suitable for automatic firing. Hogged fuel is of this sort and is produced by a machine called a hog which reduces mill waste or other wood chips and splinters; this fuel is often burned with sawdust and shavings in industrial boilers and large heating plants. Pacific Coast lumber mills, pulp and paper mills, and electric-power plants are the principal users.
These fuels are measured in units of 200 cubic feet, containing about the same quantity of material as a cord of 4-foot wood. Hogged fuel has 10 times the bulk of good coal, in proportion to its heating value, but, with mechanical stoking, efficiencies of 70 to 75 percent can be expected, at least equaling the efficiency obtained in burning steam coal. Where hogged fuel and sawdust are available locally, users have reported large savings, especially in regions that are remote from sources of other fuels. The Dutch-oven or reflecting-arch type of installation is commonly employed. In case of a shortage of the fuel formerly used, small industrial plants such as creameries can build Dutch ovens for burning wood fuel, if hand firing is feasible.
Sawdust has been used successfully also for domestic heating, particularly in the Pacific Northwest and in Maine. A unit with a large hopper and a simple gravity feed is generally used, the combustion taking place in the ashpit of a converted furnace, which has been lined with firebrick. As to economy, sawdust is said to compare very favorably with other fuels, and the use of sawdust burners became so popular in Portland, Oreg., a few years ago that the surplus of sawdust available has tended to disappear.
Another form of wood fuel is the sawdust and wood-waste briquet, which is very clean and convenient and ignites so readily that no kindling is required. Briquets are usually drier than ordinary wood and therefore have a slightly higher heat value per pound of material. They burn uniformly, free of soot and smoke, with little draft, and contain less than 1 percent ash. Only 40 cubic feet to the ton of wood briquets is needed for storage space, as compared with 35 to 45 cubic feet for coal. The briquets must be kept dry. On the basis of fuel value, a ton of them should be worth threefourths as much as a ton of good coal.
Tools and Equipment
At every stage of production and transportation, the uneconomical use of hand labor, such as unnecessary stacking and repeated handling of the sticks, should be avoided. Improved tools should be utilized wherever possible, to make the work easier and more efficient. In the present situation there is not assurance, of course, that it will be possible in every locality to obtain new equipment. Repair parts will probably be available, however, for used tools and machines.
In the felling and bucking of trees up to 10 inches in diameter, one man can do almost the work of two by using the new “pulp saw,” a bucksaw having a highly tapered blade held under great tension in a light tubular steel bow (fig. 6, A). The saws come in lengths of 42 and 48 inches, do not bind or chatter, and tire the hands much less than former designs. Handy for splitting cordwood is the Oregon-type splitting maul (fig. 6, B) with a heavy head combining sledge hammer and blade. For work in large timber various types of power saws offer means of speeding production. One of the newer developments is the power chain saw, operated by two men, which is suitable for felling and bucking both fuel-wood and sawlog trees. It is fairly expensive, but is adaptable to integrated cutting of saw timber and cordwood. The more familiar gasoline-powered dragsaw is cheaper; it is useful in bucking large-sized stems, particularly in case they are to be reduced to stove length immediately.
For green wood freshly cut from the forest, from 6 months to a year is usually required for thorough seasoning. The rate of evaporation of the moisture will depend on such factors as temperature, relative humidity of the air, exposure to rain or snow, and movement of air about the individual sticks. Splitting the pieces helps, and is almost indispensable with some species such as birch and alder, which should also be placed in fairly dry locations. Moreover, cottonwood, for example, is far easier to split when green. The wood should be stacked outdoors where it is exposed to the sun and wind, preferably on a hilltop. Skids or bed pieces may be used to keep the fuel wood off the ground, and for best results either some form of roof or covering should be provided, or the top layer of sticks should be packed closely and slanted, to help prevent rain from reaching the interior of the pile. In order to accelerate the seasoning process, the sticks may be piled crisscross. This provides for the maximum circulation of air. If branches of live trees felled during the summer are left intact for 2 or 3 weeks, considerable moisture will be drawn out through the leaves.
Tree species vary considerably in the proportions of moisture usually contained in their wood at the time of felling, as table 2 indicates. For example, green Douglas-fir heartwood is so dry that it has very little more fuel value when seasoned. Near the opposite extreme are the cottonwoods, which contain a great deal of water. Under emergency conditions it may often be desirable to cut fuel wood for use within a very short time. In such circumstances, if the available woodland offers a choice of several different species, it would be useful to know the kinds of trees from which satisfactory fuel may be produced with only a minimum of seasoning. The following species are improved comparatively little by drying:
- Ash, biltmore
- Ash, blue
- Ash, Oregon
- Ash, white
- Beech, American
- Fir, alpine
- Fir, noble
- Hickory, pignut
- Hickory, shagbark
- Locust, black
- Osage orange
- Pine, lodgepole
- Pine, red
- Spruce, red
- Spruce, white
- Tamarack (eastern larch)
Higher moisture content makes seasoning of the following woods more necessary:
- Ash, red Maples
- Ash, black Oaks
- Birch, paper
- Birch, river
- Elm, American
- Fir, grand
- Fir, Pacific silver
- Fir, white (Abies concolor)
- Hickory, bitternut
- Hickory, nutmeg
- Hickory, water (bitter pecan)
- Pine, jack
- Pine, jeffrey
- Pine, loblolly
- Pine, pitch (Pinus rigida)
- Pine, ponderosa
- Pine, shortleaf
- Pine, sugar
- Pine, Table Mountain
- Sweetgum (redgum)
- Tupelo, water
- Walnut, black
Grades and Sizes of Fuel Wood
It has been pointed out that the value of a cord of wood as fuel may vary a great deal, depending on the species, moisture content, and form of the sticks. For use in the home, the length to which the sticks have been sawed is another important factor. Hiring men with a power saw to cut 4-foot cordwood to length of 16or12 inches, usually the most desirable for stove or furnace fuel, costs approximately $0.75 to $1.25 a cord, and there should be a corresponding difference in prices for the 4-foot and stove lengths. If these differences in values were more clearly recognized in the sale of fuel wood, the consumer would know much better what he was getting for his money. Dealers in coal do not sell merely in terms of weight or bulk, but specify the kind, source, size, and sometimes the heating value of the coal. Similar grading of fuel wood is desirable. Sale of wood by the ton rather than the cord or the load would provide a fairer measure of value if there could be assurance that all the wood offered was equally well seasoned. In most cases, however, it will be more practical to follow tradition and continue buying and selling wood by the cord, classified roughly as hardwood or softwood, well seasoned, partly seasoned, or green; slabwood, dry or green; and mill ends (softwoods). Mill ends or trimmings, useful as kindling, are usually sold simply by the truckload or unit, for it is not feasible to stack them in cords. If possible, there may be a further break-down according to the heat value of the species. (See tables 1 and 2.) Not many separate grades of fuel wood are likely to be required in any one community, and it should not be difficult to work out a practical grading system for local needs. Some States have laws regulating the measurement and sale of fuel wood, with which buyers and sellers should become familiar.
Fireplace wood should be of greater average diameter than stove or furnace wood, and the sticks may be longer. In some sections of the country a distinction between old-growth and second-growth wood is maintained, the former being considered better because it is easier to split, comes generally in larger pieces or chunks, and often has higher heat value. Split pieces from rather large stems are preferable to small round lengths and to limb wood. Moreover, a cord of split wood generally has a greater solid content than a cord of small round wood, if the length of the sticks is the same in both cases.
In places where the use of wood fuel is feasible and will, on the whole, tend to save transportation, effort should be made to interest local wood, coal, and lumber dealers in establishing or expanding the wood-fuel business. The possibility of utilizing waste from nearby sawmills and other wood-using plants should be looked into. Creating a demand and obtaining definite orders for fuel wood will do most to encourage farmers and others to provide a supply. It may be advisable in some instances to organize a wartime community fuel service such as those which proved helpful during the first World War. Action should be taken to get a supply on hand well before an actual fuel shortage can occur.
SELECTION OF MATERIAL TO CUT
The cutting of fuel wood may be done in such a way that the value of the woodland property is improved; if done unwisely, it may be destructive. Unfortunately, a good deal of the forest fuel wood is at present cut from sawlog material that should be reserved for lumber or similar uses. This represents a serious loss to the owner of the timber; from the viewpoint of the public, it is wasteful of a natural resource. Indiscriminate cutting of other classes of trees for fuel is also to be discouraged. Trees near the house that are valuable for shade or windbreaks should not be cut solely to obtain fuel wood. Stripping the woodland completely is not a good practice, except to clear the land for crops or pasture. The habit of cutting all trees large enough for fuel in immature second-growth stands is, in some regions, a greater evil than the misuse of saw timber.
It must be remembered that among the various forest products, fuel wood is one of the lowest in value. In cutting for fuel wood, therefore, individual trees to be removed should be selected carefully, consideration being given to the local market for sawlogs, poles, piling mine timbers, fence posts, or pulpwood; if the operation takes the nature of an improvement cutting or thinning, the profits of the owner will be increased. Timber is a renewable resource, but it cannot renew itself satisfactorily if the better trees are continually cut and the poorer ones left.
The removal of cull and inferior trees, if it can be made to pay returns, will go far toward solving one of the most difficult problems in building up the forest resources. It will provide an income to the timber owner during the period when the best trees are making their most valuable growth, and accelerate this growth by ending the excessive competition of inferior trees. In mixed stands of pines and hardwoods, pines are often taken because they split more easily. Generally the poorly formed hardwoods should be cut instead; their higher fuel value tends to offset the extra labor involved. The pines grow faster than the hardwoods and in most places can be sold at better prices for lumber, poles, or pulpwood. At a time when cordwood can be sold at good prices, the landowner has an excellent opportunity to put his timber stand in better growing condition.
A combined operation for the removal of fuel wood and other products from the forest will often be profitable, especially where the saw-timber or pulpwood material is so scattered that cutting for only one kind of product is uneconomical. Timber stands that have formerly been considered unmerchantable might be utilized if both fuel wood and a small volume of other products could be cut and marketed at the same time. Hardwood trees harvested for sawlogs usually contain much excellent fuel-wood material in their tops.
Opportunities to obtain fuel from nearby logging or other woods operations should not be overlooked. Tops of trees, large limbs, and even rejected sawlogs are usually left on the ground. Sometimes trees are accidentally knocked down in the course of logging or cut to get them out of the way. At present, this material ordinarily goes to waste, but it can easily be worked up into cordwood. The timber owner, in most instances, will be glad to have it removed, to reduce the fire hazard. Cull trees and those of inferior species left standing by the loggers often have no value except as fuel.
Many stands of sapling size are so badly overcrowded that their growth is much retarded or has practically ceased. Thinning out the poorer individuals to make cordwood and leaving those with the straightest, cleanest stems and healthiest appearance will speed up timber capital. The thinning should not be too severe, however; enough trees should usually be left so that their crowns will come together again in about 5 years, to prevent the growth of undesirable branches along the lower and middle parts of the stems. In general, if two trees of equally valuable species stand so close together as to hinder each other’s development, the slower-growing one should be cut.
Before the actual felling is started, it is a good plan to mark the trees to be cut. This takes but little time; better selection will be accomplished if other phases of the work are not claiming one’s attention simultaneously; and inexperienced help may then be employed with less danger of having highly valuable trees felled by mistake. Figure 9 gives an example of the contrast between trees that should be cut immediately and those that should be left to grow because of their higher quality.
In most woodlands a satisfactory improvement cutting or thinning can be made through the application of a few simple rules concerning what to cut. Although no set of rules will exactly fit every situation, the following are the most important classes of material that should be used for fuel wood:
- Tops, large limbs, and other logging waste.
- Dead trees, down or standing, that are sound enough for fuel.
- Diseased or insect-infected trees and those likely to be attacked as a result of injury from fire or other causes; also species that are extremely susceptible to local epidemics.
- Hardwoods of bushy form, with stems too short to make a clear sawlog.
- Crooked or broken trees.
- Trees that are seriously overtopped and stunted by others, so that they are unlikely to reach saw-timber size.
- “Wolf” trees, which have unusually large crowns of foliage and, quality considered, occupy excessive space.
- Trees of species not in demand for lumber, poles, ties, pulpwood, etc., especially if they are interfering with the growth of more valuable trees.