Wood Terms for Dry Kilns by Global Container Kiln

Global Energy Container Kiln

Wood Terms for Dry Kilns

Glossary of Wood Terms

Backhaul

A delivery by tractor-trailer originates from where the trailer is loaded, the load is delivered to a destination, then the trucker returns home. If the return is also a paying load to be delivered to the vicinity of the trucker’s home, that load is called a backhaul. If the trucker returns home empty, that run is called a “deadhead.”

Band sawmill

An evolution in sawmill technology that uses a thinner band saw blade (less kerf therefore less sawdust waste) than a circular saw. It also has teeth on both sides that allows cuts to be made in two directions instead of just one, improving efficiency and productivity.

Bark

The outer protective layer of the tree. Severely damaged bark on a tree is a defect that can lower the value of the its logs. At the sawmill, logs are first debarked, then slabs are cut off leaving a rectangular or square cant to be cut into lumber. There are two main types of debarkers: Rosserhead and Ring debarkers. Before raw bark is sold as bark mulch, it is ground in a tub grinder (hammermill) to give it the proper texture and consistency. Bark quality is a function of color.

Board foot

An volume of lumber that measures 1″ x 12″ x 12″. The number of board feet in a log is estimated using one of three log scales: Scribner, Doyle, or International Rule. The standard used in Massachusetts is the International Rule. The actual yield of a log after sawn into lumber is often greater than the estimated yield. Both logs and lumber are sold by the thousand board feet or MBF.

Bole wood

The lower section of the trunk of a tree from the ground to the first limb or branch. Some loggers and whole tree operations delimb trees leaving only the bole or stem portion of the tree. If chipped in a whole tree chipper, the result a “cleaner” chip with fewer leaves, sticks, or pine needles.

Cant

A log is first debarked then the rounded slab or outside portion of the log is cut off by the sawyer. The remaining square or rectangular portion of the log is called a cant. Lumber is cut from the cant. The more pieces of lumber cut, the more sawdust (waste byproduct ) is produced, reducing the log yield of marktable board feet.

Carriage

The sawmill device on which a debarked logged is placed which moves the log back and forth through the saw blade creating slabs, cants and lumber. The log is also turned on the carriage before making the next cut.

Circular sawmill

The traditional sawmill that uses a circular saw (large version of hand held power saw). Circular saws are thicker (larger kerf) than band saws and produce more sawdust. Logs can be cut moving on the carriage in only one direction, then the carriage returns and turns the the log for the next cut.

Co-Gen Operation

Refers to the simultaneous production of steam and electricity.

Construction and demolition (C&D)

Though lumped together to refer to wood waste produced by construction or by demolition, the products can be quite different. Construction wood waste can be clean dimensionally cut lumber such as board ends or cutoffs. Demolition wood waste is often contaminated with nails, sheetrock, paint, etc. Markets for C&D are limited by how “clean” and free of contaminants the wood is. Some business specialize in processing and disposing of C&D.

Cord

Stacks of hardwood 4′ high by 4′ wide by 8′ long. It is the measure by which firewood is customarily sold , sawdust is sometimes sold, and small diameter logs sometimes bought. One cord is the equivalent of 128 cubic feet, 4.7 cubic yards. The weight of a cord varies if it is green (freshly cut), seasoned (partially air dried), or dry.

Cut to length (CTL)

New timber harvesting equipment allows loggers to fell trees, delimb them, and cut them to market length specifications before loading them on forwarders bound for the landing. CTL equipment is a recent trend in logging operations.

DBH (Diameter breast height)

The diameter of a tree at breast height (4.5 feet above ground) together with the estimated height of the usable logs in a tree is used to determine the volume of lumber likely to be yielded in a log depending on the log scale used (Scribner, Doyle or International Rule).

Doyle Log Rule

In use since about 1870, this scaling method deducts a full four inches for slabs. It grossly underestimates the yield on small diameter logs (less than 14″) . Every fourth Doyle load could be considered free in comparison to International rule, if the logs are within 14 to 20″ inches in diameter and the prices per MBF for both scales were identical. The variance between Doyle rule and other rules is based on diameters, rather than lengths. (Also see Scribner and International Rule.)

Flatbed trailer

Used to haul lumber. Flatbed operators may haul logs if they carry portable stakes. The number of stakes, stake height and distance between stakes determines the number of log tiers and length of logs in each tier a flatbed may carry. Flatbed operators will carry sawlogs before they will carry pulp logs, because the higher value of sawlogs ensures they are more likely to receive an acceptable rate. Lower value pulp logs may require quibbling over nickels and dimes in the rate.

Green Certification

Landowners who actively manage their woods can apply for green certification. Two agencies perform reviews and issue green certification: the non-profit Smartwood and the for-profit SCS (Scientific Certification Systems). Both agencies charge to ensure that land is properly and sustainably managed and that loggers employ best management practices (BMP) to cut wood on certified woodlots.

To maintain its green certification status from landowner to consumer, lumber mills must also be certified in chain of custody arrangements, that is, they ensure that certified logs are stored and milled separately from non-certified logs.

It was originally thought that certified logs would sell at a premium but that has not been the case in New England.

The Quabbin Reservoir managed by the Metropolitan District Commission in Massachusetts was the first publicly land to be green certified.

Ground wood chips

Ground wood is usually produced from a hammer mill or tub grinder and appears shredded and fibrous with irregular sizes, depending on the screen or grate used. Ground wood is easily distinguished by their geometry from wood chips produced from mill chipper or a whole tree chipper (WTC). WTC and mill chips appear square and evenly cut rather than fibrous and irregular.

Hardwood

Hardwood comes from deciduous trees that lose their leaves during the winter.

Heartwood

In a cross section of a log, the heartwood is the center and dead portion where growth rings appear. Also see bark and sapwood.

High-Grading

The practice of “high-grading.” is logging to cut only the higher value trees and leaving the lower value trees in the woods. It is frowned upon in this era of sustainability, and much effort is being made to find suitable markets for lower grade logs.

International Log Rule

In use since about 1906. Generally regarded as the most accurate of the three scaling methods, International log rule deducts only 2.12 inches for slabs and 1/4 inch for kerf. (Also see Scribner and Doyle Rules.) It is the standard rule used in Massachusetts.

Kerf

The width of the sawblade (circular or band) and the source of sawdust. The more traditional circular sawblades are wider than the newer band saw blades and produce more sawdust, a waste byproduct of sawmills.

Kiln

Freshly cut green lumber may be sold green or first dried in a kiln to accelerate removal of the moisture in the wood. Drying wood in a kiln is an art to ensure that the wood dries evenly to retain its strength and aesthetic properties. Different species dry at different rates. Kiln dried lumber commands a higher price than green or air dried lumber.

Laminated Veneer Lumber (LVL)

Structural grade timber veneers glued together under pressure to form a dimensionally stable and uniform product. An engineered (man-made) wood product that is a substitute for dimensional lumber. LVL can be made from small diameter logs thus creating a market for lower value trees.

Landing

That part of a wood lot to which fresh cut logs are skidded or forwarded, accumulated, cut to length (if not cut to length in the woods) , stacked, and loaded onto trailers for delivery or chipped and blown into trailers.

Log defects

Defects affect the log scale and value for which the log may be sold or bought. Deductions for defects are subjective depending on the scaler and a source of confusion in the buy-sell transaction. Defects may include red knots, black knots, rot, burned area of a log, crook, sweep, or doglegs.

Log scales

Determines the value of a log by estimating number of board feet of lumber it will yield (less allowances for bark, slab and kerf). Helps log sellers understand what they are getting for the product of their labor. Log buyers can usually predict the actual yield of board feet from a log depending on the log rule used.

Three major log scales are used: Scribner Log Rule, Doyle Log Rule and International Log Rule, although there are others (Maine and Roy). It is vital that sellers understand the differences between the scaling methods so as not to be taken advantage of. Savvy buyers are flexible in the rules they use.

A common rule of thumb is that International is always 25% better than Doyle, and Scribner is always 15% better. Doyle and International are dramatically different for small diameter logs, yet very similar for large diameter logs.

If the average diameter range of logs is 14″ to 20″, you can convert Doyle to International by multiplying 1.2 and Scribner to International by multiplying 1.11. For example, if logs for a particular site scaled about 5,000 board feet in Doyle, this would convert to 6,000 board feet in International and 5,500 board feet in Scribner.

Log trailer

Built with permanent stakes to carry sawlogs or pulp logs. Log trailers may have a grapple loader mounted front or rear in which case the operator can load himself. The increased cost of a loader on a log trailer means the trucker’s rate will likely be much more. Without a loader, the logger must use his equipment to load the log trailer.

MBF

See thousand board feet.

Mill chips

After debarking and before a sawmill cuts lumber, it saws off the outer four slabs to reduce the log to a square or rectangular cant. The slabs are mostly the sapwood portion of the log and may be resawn to save low quality boards (e.g., pallet boards), or the slabs are sent to the chipper. Most chippers pass their chips over a two-deck vibrating screen to separate the “overs,” “accepts” and “fines.” The “overs” are re-circulated through the chipper again and the “fines and sawdust” are blown into their own pile. The chip “accepts” are blown into a chip van trailer, blown into a pile on the ground to be loaded over the top of an open top trailer with a front-end bucket loader, or they are conveyed into an overhead bin which drops chips into an open top trailer.

Moisture Content

Weight of the water within a piece of lumber measured as a percentage of the weight of the dry wood. Typical moisture content for kiln dried construction lumber is 15%. Wood absorbs or gives off moisture depending on the ambient moisture in the air. The percentage of wood that is not moisture is referred to as “dry solids” that is dried construction lumber would be 85% dry solids.

Mud Season

The period of weeks between winter and spring or summer and fall when the ground in a forest is largely mud, thawing or freezing between warmer days and colder nights. During mud season, heavy logging equipment is not permitted in the woods nor are trees cut during this time. Industry professionals that depend on a continuous supply of logs must account for these seasons and stockpile sufficient quantities to process during mud season. Truckers are usually available during mud season to haul logs from distant concentration yards which may have accumulated logs for mud season.

Mulch

Raw bark peeled from a tree and ground in a hammer mill (tub grinder) and sold as a landscape ground cover. Mulch functions to reduce weeds, retain moisture by reducing evaporation, and insulates the ground in cold weather, in addition to providing an aesthetic appearance for one’s garden.

Procurement forester

A forester employed by and accountable to a sawmill or paper mill and who is responsible for providing a continuous supply of logs for his/her employer. Also referred to as industrial foresters, they purchase trees on the stump or at the landing from landowners or loggers.

Pulp logs

Logs of lesser value (smaller in diameter with acceptable defects) than sawlogs, of greater value than cordwood. Pulp logs are usually bought by the ton to be debarked, reduced to chips, and used to manufacture pulp and paper.

Sapwood

The layer of new wood surrounding the denser, dead heartwood of a tree and under the cambium and bark layers.

Scientific Certification Systems (SCS)

One of two independent organizations that certify landowners engaged in active forest management. SCS is based in Oakland, CA and is a for profit operation. The other agency is Smartwood based in Manchester, VT.

Scragg mill

A special sawmill designed to saw small diameter logs. Not all sawmills have a scragg capability and so are limited to purchasing only larger diameter sawlogs.

Scribner Log Rule

In use since before 1846. This scaling rule is based on a diagram of the size and number of 1″ boards that could be sawn from it allowing for 1/4″ kerf.

Softwood

Evergreen trees, conifers, cone-bearing trees or wood cut from these trees.

Stem Wood

See Bole Wood.

Stumpage fee

Price paid for trees before they are cut. University of Massachusetts publishes a stumpage fee report quarterly based on responses to a survey of local landowners and loggers.

Sustainable Forestry Initiative (SFI)

The program and polices formed by the pulp and paper industry members in response to criticism from environmentalists aimed at logging practices that did not promote forest sustainability. SFI is the industrial counterpart to programs promoted by Smartwood (non-profit) and Scientific Certification Systems (for profit) which promote and certify landowners engaged in proactive and sustainable forest management.

Tare Weight

Tare weight is the weight of tractor-trailer with no load. A tractor trailer typically weigh 30,000 to 35,000 pounds leaving a legal load weight of 45,000 to 50,000 (22 to 25 ton). The heavier overweight loads not only pay the trucker more, but are also more wear and tear on trucking equipment.

Thousand Board Feet (MBF)

One board foot is wood that measures 1″ x 12″ x 12″. Logs and lumber are measured by MBF or thousand board feet. MBF is determined by one of three major scaling rules: Scribner, Doyle, or International Rule. The board feet scaled for logs is an estimate only. The actual board feet yield depends on how the sawmill cuts the log. It is possible for a log to produce more board feet than was estimated producing an overrun.

Veneer Logs

Although veneer logs are sold by the board foot, they are never converted to lumber. Veneer logs are turned and rotary cut, that is, the wood is peeled off the log by turning it against a stationary knife. the sheets of wood may be laminated into plywood or laminated veneer lumber (LVL) products.

Whole tree chips (WTC)

Some mechanized loggers reduce trees that are not otherwise marketable as logs to whole tree chips to be sold to wood energy plants. Whole tree chips differ from mill chips in that they include the bark, sapwood, and heartwood of the tree, as well as branches and leaves (from deciduous or hardwood trees) or needles (from evergreen or softwood trees).

Wood energy plants

Electric generating plants that burn wood chips as fuel to produce steam and electricity. A number of these plants were built in the 1970’s subsidized by the federal government and electric utilities when the price of foreign oil rose dramatically.

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