TECHNICAL PAPER # 47
 
                        UNDERSTANDING NON-FUEL
                          USES OF WOOD WASTES
 
                                  By
                              Jon Vogler
 
                                 VITA
                   1600 Wilson Boulevard, Suite 500
                     Arlington, Virginia 22209 USA
                 Tel: 703/276-1800 . Fax: 703/243-1865
                      Internet: pr-info@vita.org
 
            Understanding Non-Fuel Uses of Wood Wastes
                        ISBN: 0-86619-261-1
           [C] 1986, Volunteers in Technical Assistance
 
                              PREFACE
 
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details.  People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
 
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Marjorie Bowens-Wheatley
as editor, Suzanne Brooks handling typesetting and
layout, and Margaret Crouch as project manager.
 
VITA Volunteer Jon Vogler, the author of this paper, is widely
published in the field of recycling.   His book Work From Waste,
published by the Intermediate Technology Development Group, Ltd.,
London, England, describes how to recycle paper, plastics, textiles,
as well as metals.  Mr. Vogler, an engineer, worked in
Oxfam's "Wastesaver" program in developing countries. He has done
much research in the field of recycling waste materials.
 
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations.  VITA maintains an international Inquiry Service,
specialized documentation center, and a computerized roster of
volunteer technical consultants; manages long-term field projects;
and publishes a variety of technical manuals and papers.
 
            UNDERSTANDING NON-FUEL USES OF WOOD WASTES
 
                   by VITA Volunteer Jon Vogler
 
I. BACKGROUND
 
We can define wood wastes as wastes arising from human operations
on wood: extracting it from forest, woodland, and plantation;
converting it into planks and other "stock"; fabricating these
into products--buildings, furniture, tools, and thousands of
other items; and, finally, discarding these when broken or even
just "out of fashion."   To this definition may be added "nature's
wastes," such as leaves, twigs, and branches that fall from the
tree due to natural causes such as ageing, wind, lightning, or
animal disturbance.
 
With this broad definition in mind, tree and wood wastes can be
categorized as follows:
 
Forest Wastes       Converting Wastes        User Wastes
 
Thinnings(*)                            Bark                      Sawdust
Reject Trees                            Sawdust                   Shavings
Leaves                                 Slabs(*)                    Sander Dust
Bark                                    Edgings(*)                End Trim(*)
Branches(*)                             Rejects(*)                Off Cuts(*)
Topwood                                                          Veneer Clippings
Stumps and Roots(*)
 
The use of waste wood is as old as humankind.   Stone-age people
probably used wood waste to fuel fire since greenwood is very
difficult to burn.  Manufacture of items from wood also began
very early.  Wood was used for tools and weapons and, no doubt,
cut-offs from the production of long implements were used for
short axe-handles or pegs, while chips and shavings served for
fire kindling.
 
This paper focuses on non-fuel uses of wood wastes.   However, the
reader must remember that by far the most important use of wood
wastes in large areas of the world is as fuel.   This aspect of
the use of wood wastes is covered in a separate paper, "Understanding
the Use of Wood Wastes as Fuel."   People throughout the
 
---------------
(*) Widely used directly as domestic fuel, as kindling, and as the
raw material for charcoal.
 
developing world, both urban and rural, consume fuel wood and
charcoal faster than it can be renewed.   Meanwhile, an insatiable
demand for paper made from woodpulp, wooden building components,
furniture, and other goods also contributes to deforestation.
Economical use of wood wastes instead of new wood helps to preserve
forest and woodland in developed countries and is becoming
essential to the survival of the poor in many parts of the Third
World, as fuel becomes more scarce.
 
II. BUILDING MATERIALS FROM SAWDUST AND WOOD WASTES
 
Rapid changes in manufacturing technology, particularly the development
of plastics and lightweight foams, have reduced the use
of wood wastes in building technology in many countries.  However,
because the new products are often expensive, imported, or
unavailable outside major metropolitan areas, many uses of wood
wastes that have been replaced in some regions may still be cost-effective
and useful in other regions.   In villages all over the
world, such products may remain invaluable for decades to come.
 
FIBERBOARDS AND PARTICLE BOARDS
 
There are two common processes in making these products:
 
      o    Dry Particle Bonding - The dry and semi-dry processes
          consist of mixing graded material with bonding resins
          and forming them into the finished product, using a
          power press and molds.  This process produces material
          with superior hardness and better nail and screw
          holding properties, desirable in boards used as timber
          substitutes.  These are generally referred to as particle
          boards or chipboards.
 
      o    Wet Process - The wet process reduces sawdust and chips
          to, a semi-liquid state of wood fiber.  This is mixed
          with bonding resins and a fiber mat formed in a decklebox,
          similar to those used in hand papermaking.  From
          this point on, a variety of different kinds of board
          can be produced, but all may be classed as fiberboards.
 
Hardboard
 
To produce the most dense hardboard for interior partitioning or
dense ceiling boards, the matted fibers are pressed between the
platens of a hot press.  Existing plywood presses may be used to
avoid a new capital investment.
 
Fiberboard
 
Medium density fiberboards are produced when binders are introduced
into the fiber mat and the board is hot pressed to a
density of 26 to 50 pounds per cubic foot.   After partial drying,
they may be laminated with one or more plies of low-grade veneer,
to produce a wood-faced panel.
 
Insulation Board
 
Insulation board is produced when such mats are dried without
further hot pressing.  The board is held together by the normal
fiber bonding.  Insulation board plants usually must be large-capacity
because of the cost of continuous dryers.   There may not
be sufficient whole wood waste to justify the installation of
conventional insulation board plants competitive with existing
plants using pulpwood.  Insulation boards require little or no
resin, but resin and alum are added to decrease water absorption.
Asphalt may be added to increase wet strength.   It is reported
that dried mats, unpressed, may be soaked in molten sulphur and
cooled to a fiber-reinforced product, sometimes called poor man's
fiberglass, with good strength and water resistance.
 
PARTICLE BOARDS
 
Panels, doors, furniture, and wallboard can be made from sawdust
and woodchips, bonded with resin.   The materials and processes
for fabricating panels, doors and wallboard are similar.  Most of
them can only be operated on an industrial scale as heavy presses
are required.
 
Materials - The Wood Waste
 
Particles are produced by hammer milling planer shavings and
chips, chipped or hogged veneer, or slab wood.   Because of their
higher moisture content, green planer shavings are damaged less
by the planer and when hammer milled, break into sliver-like
components.  The properties of board made from them are better
than those of boards made from dry shavings.   Little bark is
included in either fiber or particle board because (a) Dirt and
grit are almost always present; (b) Pulping bark may require
different conditions than wood; (c) Particle bark may be stringy
or flaky.  This creates problems in screening, resin distribution
and mat formation; (d) Bark is dark colored and shows up in the
finished boards, either as dark flecking or as a uniform dark
tinge.
 
Equipment that will reduce whole wood to fiber and fiber bundle,
suitable for insulation and hardboard such as hammer mills,
chippers, grinders, defibrators, continuous steam cookers, and
disc refiners can be obtained from manufacturers of wood pulping
machinery.
 
Materials - Resins
 
The bond in particle boards is produced by the cured (hardened)
resin.  The small amount or resin required, even though only 6
to 10 percent, is by far the most expensive ingredient of
particle board.  The amount depends on the size and shape of the
wood particles, so selection of an optimum particle size is
economically very important.   However, the quality of the resin
binding agent has more influence than that of the sawdust and
chips on the quality of the finished product.   Conditions of use
determine choice of resins.  Hygroscopic resins (water absorbing)
should not be used for products that will serve in damp
conditions.  Thus, urea-formaldehyde resins are used only for
interior wallboard where moisture is no problem, because they are
lower in cost than phenolic resins (pheno-formaldehyde) but
cannot withstand high temperatures and moisture.   Phenolic resins
are most suitable for exterior use products or where water
resistance or surface hardness must be increased.   However, even
this product is not suitable for exterior use in damp climates.
Resins that dehydrate (lose water) completely are not suitable
when the finished product is to be used in warm, dry climates.
 
Phenolic and urea-formaldehyde resins and casein glue are known
as synthetic binders; they do not occur naturally.   There are
also a number of naturally occurring binders that are cheaper
and, if selected with the service conditions of the board in
mind, may be equally good.  These include animal glues, blood
glue, starch glue, and, for some uses, the resinous properties of
naturally occurring materials such as tannin (tannin formaldehyde
resin), lignin, and the products of wood decay.   In addition,
binders such as Portland and magnesite cements may be used to
produce building products such as wall ceiling slabs or hollow
building blocks.
 
Manufacturing Operations
 
Commercial board manufacture involves receipt of the raw wood
waste.  Particle or solid material passes through a hogger or
hammer mill, then rejoins small size waste (chips, flakes, and
sawdust) to pass through grinding mills and screens for final
sizing.  The milled material is conveyed, often by air blowers
along ducting systems, to a cyclone separator, which removes
dust, then into dryers (usually of the rotary drum type) to
adjust the moisture content to 6 or 7 percent.   It is then stored
in bins until needed.
 
Dry wood material is weighed into a mixing vat and the required
quantity of liquid or powder binders added.   Liquid binder may be
sprayed on the particles in a continuous operation or mixing may
be carried out in batches, by tumbling the particles and binder
in a drum or mixer.  The moisture content of the particles must
be controlled while the resin is being added.   The mixture is
measured out in measuring boxes, then conveyed to trays that are
loaded into the press.  Presses are multi-daylight, that is to
say, many boards can be pressed in each operation.   Pressing time
depends on thickness, temperature, and whether or not a preform
is used.  For 1/4-inch thick board, pressure is maintained for 15
minutes; for 5/8-inch thick board: 35-45 minutes.   Pressures vary
from about 200 pounds per square inch to 450 pounds per square
inch, depending on the final board density required and the type
of waste material used.  Pressing temperatures used are 250 to
300 degrees Fahrenheit.  After pressing, the boards pass through
trimming saws and go to storage awaiting dispatch.
 
In some particle board plants, an extrusion press is used--a
continuous operation in which the board is squeezed out between
heated rollers.  The particle board produced in this way has
X-definite directional properties.   It is weaker or less rigid in
one direction than in the other.   Cost of the equipment may be
less than for hot presses.
 
After manufacture, boards may be either (a) dipped in moisture
repellents, such as asphalt; (b) humidified (placed in racks in
humid chambers); (c) oil tempered--passed through a bath of oil,
then baked until the oil diffuses through the board (tempering
improves both strength and water resistance); or (d) painted,
scored, sanded, or embossed to improve appearance.
 
Economics of Particle Board Manufacture
 
Particle board manufacture requires an expensive capital plant--grinding
mills, dryers, trough mixers and multi-daylight hot
presses, conveying equipment (conveyor belts, exhaust fans, and
cyclone separators), storage floors and bins, and, where dryers
or press are steam heated, a steam raising boiler.   Also needed
are plates and trays for the pressing operation, trim saws for
sizing the processed sheet, pump and piping to convey liquid
binder to the mixer.  For this reason, particle board plants are
usually large and require large quantities of wood waste to feed
them.
 
A production rate of approximately one ton of half-inch board
per hour can be obtained from two 25-HP grinding mills, two 6-foot
by 20-foot rotary drum dryers, three 8-foot by 4-foot mixing
troughs and two 10- or 12-daylight, hot presses. Consumption
of electricity is 80 to 150 kilowatt-hours per ton of production.
Labor required, with a batch process, is 20 person-hours per ton
of production and with a continuous process, six person-hours per
ton of production.
 
Authorities differ on what is the minimum size of an economical
plant and in practice this will vary from place to place.  One
U.S. source states that:
 
     A one-ton per hour plant, manufacturing medium density board
     (equivalent to some 1,200 square feet of 1/2-inch thick
     board, or 960 square feet of 5/8-inch board per hour) is
     regarded as the smallest.  In special circumstances a plant
     with a production rate of 1/2 ton per hour could operate
     effectively.
 
Another source, on the other hand asserts that:
 
     The minimum daily required of all necessary to produce
     wallboard ranges from 50 to 100 tons per day.  Hand-operated
     facilities produce 35 kg of panel per day, while machine
     powered, semi-automated plants are producing 10 to 20 tons
     per day.
 
Another expert has yet a different view.
 
     Conventional hardboard mills are economical for installations
     of about 35 tons per day.  Such a plant, with a 4-foot
     by 16-foot, 20-opening press, will use about 70 tons of
     raw wood each 24 hours.  Wood can be used for fuel to
     generate power and to provide steam to heat the platens of
     the hot press.  Fuel requirements amount to two to three
     tons of wood waste per ton of board.
 
The cost of dry processing plants is about two-thirds that of wet
processing plants, but the cost of resin binders makes the
product more expensive.
 
OTHER BUILDING MATERIALS
 
Blocks
 
 
Sawdust can be used as a cheap, lighweight aggregate for building
blocks.  Such blocks are light and porous, hold nails and screws
well, and have fair insulation properties.   However, there is a
disadvantage of using sawdust in masonry.   It undergoes comparatively
large movements with changes of moisture content that
result from changes in humidity or wetting and drying.   When
using it with Portland cement, it is necessary to ensure that
materials in the sawdust, such as resins and acids, do not upset
the hardening qualities of the the cement.   Adding hyrdrated lime
to the mix, between one-sixth and one-third volume of lime per
volume of cement, will normally guard against this, but certain
sawdusts give setting difficulties even with lime present.  Other
special treatments include immersion of the sawdust in boiling
water for ten minutes, followed by washing with water, followed
by further immersion in boiling water containing two percent
ferric sulphate, more washing and draining.   Alternatively, use
of 4 or 5 percent by weight of a setting accelerator, such as
calcium chloride, has been found useful.   However, to avoid
expensive additives, first check test whether the proposed mix
hardens satisfactorily using only hydrated lime.
 
Use of the correct quantity of water is most important.   The
strongest mix will be that on which it is impossible to draw a
cement "skin" to the surface during trowelling, while a smooth
surface can still be produced.   It should have a moist earth
consistency with no appearance of free mositure.   For a 1:3 mix
(by volume) of cement, and sawdust, the weight of water should
be from 80 to 140 percent of the weight of cement.   (The variation
is due to the degree of dryness of the cement).   Excess water
causes shrinkage during setting, deep crazing several months
after laying, and lower strength as well.
 
The practical ratio of cement to sawdust is from 1:1 to about 1:5
by volume, ranging from heavy, strong, and dense products from
the former to lighter products from the 1:5 mixes, low in
strength and fire resistance and prone to increases in movement
with moisture changes.  Leaner mixes can be cut and nailed
readily but the richer ones become difficult to nail as drying
proceeds.  Addition of an inert aggregate, such as sand or granite
chips, reduces shrinkage but also reduces insulation properites
and nailability.  Methods employed to minimize movement include
water proofing by tar or bitumen after installation and designs
that allow movement to be taken up within the building.   Manufacture
is by the same processes as for cement-sand blocks,
ranging from hand molding into wooden molds to the use of fully
automated block-making machinery.
 
Concrete
 
Mineralized sawdust (treated with zinc chloride) can be used to
produce a light-weight concrete.   With sawdust forming one third
to one half of the mix by weight, the resulting product is reported
to be wear-resistant, a non-conductor of sound, comfortable
to walk on, and can be sawed, nailed, screwed, and polished.
 
Porous Bricks and Tiles
 
Beautifully mottled wall and floor tiles can be produced by
incorporating a high percentage of shavings in the tile mix.  The
use of attractively grained hardwoods is particularly successful.
Test tiles should be done before mixing a batch to ensure
substances of shavings in the tile mix.   The use of attractively
grained hardwoods is particularly successful.   Test tiles should
be done before mixing a batch to ensure substances in the wood do
not affect the curing properties of the binder used in the tile
mix.
 
Flooring Compounds
 
Fine hardwood sawdust (of 24 to 40 mesh) can be used as a filler
in magnesium oxychloride flooring.   The proportion of sawdust may
be varied 4 to 70 percent.  Sawdust makes the floor light and
porous, so nails can be readily driven into it.   It is
particularly used for composition floors to which a covering is
to be nailed.  A more economical formula is to use 20 mesh, kiln-dried
hardwood sawdust for the top layers and coarse softwood
sawdust for the base.
 
Roofing Felt
 
Forest and mill waste is shredded by "defibrators" to yield a
coarse wood fiber.  This is used as a filler in rolls of roofing
felts and composition shingles.   The preferred species are maple,
birch, and aspen, but other wood types can also be used, in
proportions of up to 50 percent.
 
Gypsum Products
 
Sawdust can be used in the manufacture of gypsum commodities to
decrease weight and increase sound and heat insulation qualities.
This can also make them porous and soft so they can be nailed and
sawn.  Such products are used for interior partitions, floor
insulation, wall boards, and roofing material.   Composition stuccos
and plasters also use sawdust as fillers to make them lighter
and more porous than normal, able to be nailed, and higher
quality insulators.  Shavings can also be mixed with limestone
during burning to produce lime.   The resulting product is said to
be of high quality.
 
Protection of Fresh Concrete
 
Sawdust, spread in a layer three or four inches deep, thoroughly
wet down, provides the moisture needed for proper curing and
reduces the rate of evaporation and the impact of the sun's heat.
 
Insulation
 
Sawdust can be used in wall construction--mixed with asphalt and
resins, then rolled into sheets and used as insulation on the
sides of buildings or floors.   Alternatively, it can be packed
into a sandwich between corrugated galvanized sheeting, commonly
used as roofing for low-cost dwellings, but very hot under direct
sunshine.  Sawdust serves as an effective insulator in construction
of ice-houses, refrigerated trucks, and cold storage
sheds.  When properly packed it does not add to the fire risk and
can be additionally protected against fire and insects by the use
of low cost chemicals.
 
Paths and Sport Facilities
 
Sawdust forms a practical covering for paths over muddy fields
and a soft, yielding surface for jump pits at sports grounds and
other such facilities.
 
III. AGRICULTURAL USES
 
LIVESTOCK AND KENNEL BEDDING
 
Coarsely ground shavings or sawdust make excellent bedding for
small animals such as chickens or rabbits.   It is cheap, soft,
warm, and free from dust associated with straw.   It absorbs urine
and excreta, and especially from fowl has some fertilizer value.
By adding superphosphate and permitting this to rot, an even
better grade of fertilizer can be produced.
 
MULCH
 
A mulch is a layer of material laid of top of (or mixed with the
top layer of) soil, often around young plants, for the purpose of
reducing water evaporation from the soil, controlling surface
temperatures (protection from frost or strong sun), or preventing
weed growth.  Mulches may serve to prevent soil splashing during
heavy rainfall and resulting erosion and may improve the rate of
water movement into the soils.   The action of a mulch is physical;
organic mulches also break down chemically to provide necessary
elements and humus to the soil. Sawdust is considered to be an
excellent mulch for fruit orchards, tobacco and similar seedlings,
and for soft-fruit, vegetables, and flower gardens.   However,
if the sawdust mulch is mixed in with the soil, it is
essential that adequate nitrogen be added also.
 
THE USE OF SAWDUST IN SOIL CONDITIONERS
 
Wood contains only small amounts of inorganic chemicals valuable
as fertilizers: 31 pounds of nitrogen, 21 pounds of phosphate,
and 2 pounds of potash per ton of dry material.   Only when
composted with other materials is the nutrient value of wood
waste raised.  The principal organic compounds present in wood
that are of agricultural interest are cellulose, the pentosans,
and lignin (the tough fibers that make a material "woody").
When sawdust is added to soil, the cellulose and the pentosans
are attacked most rapidly by bacteria and fungi.   The lignin and
its degradation products and the residue of micro-organisms tend
to remain in the soil as humus, the network of fibrous and
granular material that is important for improving the physical
condition of the soil.
 
When undecomposed sawdust is mixed with soil, however, a temporary
harmful effect on crops may occur, indicated by yellowing
plants.  This is caused by depletion of the available soil nitrogen,
which takes place because the decomposition of wood particles
by bacteria and fungi requires more nitrogen than the
small amounts provided by the sawdust.   This extra nitrogen is
drawn from the soil, decreasing the amount of nitrogen available
to plants.  The effect seldom extends beyond the first season if
no more than three to four tons of dry material per acre are
added to the soil, but the addition of larger amounts may result
in nitrate depression over several years.   Ultimately, the nitrogen
used by the microorganisms is released as they die and
becomes available to plants.
 
Factors that influence nitrogen removal:
 
     o     The resistance of the material to decomposition (hardwoods
          and resinous timbers decompose far more slowly)
 
     o     The size of wood particles
 
     o     The nature of the soil: coarse-textured soils allow air
          to penetrate, speeding up the action of the bacteria,
          so they require a greater amount of nitrogen.  In heavy
          soils, micro-organic activity will be less and the
          nitrogen drain will be less swift.
 
     o     Whether the woody material is mixed into the soil; it
          will decompose more rapidly than if only spread on the
          surface.
 
A number of methods are possible to overcome this effect of the
sawdust:
 
     o     Chemical nitrogen can be added, often with limestone
          and phosphate: 10 to 20 pounds of elemental nitrogen
          per ton of sawdust during the first year (equal to 30
          to 60 pounds of ammonium nitrate, or 50 to 100 pounds
          of ammonium sulphate).  Half this amount should be
          added during the second and third-years.
 
     o     The wood can be decomposed before addition to soil,
          usually by composting.  An organic material used to
          decompose woody composts should contain 2 percent or
          more nitrogen content and be mixed one part of sawdust
          to one part of organic material, by volume.  A high-protein
          material, such as fish meal, can be added to
          sawdust in a ratio as low as one to ten.  Animal and
          chicken manures, wastes from fruit, vegetable, and fish
          canneries, spent hops from breweries, pea vines or
          other legume waste, and sewage sludge are all suitable.
          Addition of a small amount of superphosphate or gypsum
          pounds of dry compost) saves nitrogen lost (as ammonia
          gas) from the actively decomposing compost pile.  Under
          conditions of adequate moisture, sawdust compost should
          be ready to use in three to six months.  Inocculation
          of the sawdust composting material with a cellulose-decomposing
          fungus may speed up the process.
 
     o     Using woodwastes that have served as bedding for
          animals and poultry.  The sawdust acts as an absorbent
          for liquid manure, which contains 90 percent of the
          total nitrogen in manure.  As above, the nitrogen in
          the liquid manure should be "fixed," so that it does
          not readily evaporate, by adding slightly more superphosphate
          (50 pounds per ton of dry wood).
 
     o     Use wood chips instead of sawdust.  These support a
          smaller microbe population so nitrogen is not noticeably
          depleted when the material is added to the soil,
          yet the soil still gains many of the advantages
          described above.
 
It is also possible that phosphate deficiency may be brought
about by sawdust addition.  Most kinds of sawdust are acid but,
unless the sawdust is applied to lime-requiring crops, the acid
is of minor importance.  In the case of acid-requiring plants
such as blueberries and azaleas, the resulting acidity is
beneficial.
 
INSECT CONTROL
 
Sawdust has been employed as a carrier for arsenic and other
poisons.  It has also been described as an excellent repellent of
fleas, moths, and other insects.   In Mexico it is used to control
certain tree-destroying worms.   Flies are imported that eat the
worms and are, in turn, trapped on beds of sawdust treated with
insecticide.
 
IV. INDUSTRIAL USES
 
DEALING IN SAWDUST
 
The many uses described here for sawdust, chips, and shavings
mean opportunities exist in some places for traders to become
dealers--to buy from sawmills, furniture factories, and other
large-scale producers, and to transport, grade, store, and market
to  small-scale users.  Shavings and sawdust are generally
classified by dealers as softwood, hardwood, or mixed softwood
and hardwood.  This product can also be purchased as green, air
dry, or kiln dry sawdust.  It may also be graded by size. Common
grades of sifted sawdust are: eight mesh, 20 mesh, 40 mesh, etc.
(Eight mesh sawdust will pass through a wire sieve having eight
wires to the inch.)  Softwood sawdust is low in value and is
seldom sifted.
 
MISCELLANEOUS INDUSTRIAL USES
 
Anti-slip Covering for Floors
 
In workshops where liquids such as blood or oil may be spilled,
sawdust absorbs the liquids and improves the floor friction.
 
Floor-sweeping Compounds
 
There are two general types of sweeping compound that contain
sawdust.  One, containing oil, is for use on cement, terrazzo,
wood, and other floors not affected by mineral oil.   In the other
type, the oil is replaced by a water-wax emulsion.   This is
suitable for use on linoleum, rubber, asphalt, tile, and mastic
floors.  Usually finer grades of sawdust, well aired and dried to
absorb oil and wax, are used.   Types of oil used in sweeping
compounds vary: heavy refined mineral oils, medium grades of
mineral oil with a high boiling point (cylinder oil), low-grade
lubrication oils, and paraffin oil may all be used.   Paraffin wax
is melted in small quantities in hot paraffin oil to improve its
dust-gathering properties.  Sweeping compounds are usually
colored with low-cost dyes, such as vermillion, bluing, iron
oxide, or water-soluble dyes like malachite green. The amount of
dye required is very small.  Cedar oil, oil of sassafras, or oil
of mirbane are sometimes added for fragrance.   The principal
equipment required is a mixer (a clean concrete mixer would
serve), a tank or steel drum for heating the oil, and a sieve for
screening the sand and sawdust.
 
A typical recipe might be:
 
    15 pounds          Sawdust
 
    1 ounce           Powdered wax
 
    1/2 pint           Paraffin oil
 
    1/2 ounce          Oil of mirbane
 
    as desired         Analine dye
 
    1/2 pound          Common salt
 
     5 pounds           Fine sharp sand
 
To prepare:
 
    Melt the wax and add it to the warm paraffin oil.  Add the
    oil or mirbane and any analine dye desired.  Saturate the
    sawdust with this mixture and stir; then add the salt and
    sand.   Adjust the dampness by adding more sawdust if
    required.
 
Hand Soaps
 
Soaps for mechanics often contain sawdust, which serves as a
gentle abrasive, carrying the soap in to the folds and creases of
the skin. Usually very fine grade hardwood sawdust is used.
 
Fire Extinguishers
 
Sawdust can be more effective than sand as an extinguisher of
oil, gas, and lacquer fires.   Because it is light, it remains on
the surface of the liquid and smothers the fire.   It is more
effective if mixed with soda.   Pine sawdusts with high resin
content should not be used.
 
Filters
 
Lubrication oil containing sludge can be passed through a sawdust
filter to remove impurities.
 
Packing
 
Wood shavings are widely used for packing fragile objects.
Clean, dry shavings are essential.   Fragile articles, such as
glass bottles of chemicals, are packed in wood wastes.   Others
may require insulation from heat or cold.   In other cases,
staining liquids (like ink) might damage other goods if the
container is broken.  Because sawdust absorbs moisture, it prevents
rusting of iron and steel goods (such as nails and screws)
in damp climates.  Sifted sawdust without smell or taste, preferably
light colored such as spruce, is preferred.
 
 
Fur Cleaning and Dyeing
 
Sawdust is used in cleaning, glazing, and dyeing fur pelts and
garments by dusting and brushing.   Dry, raw furs are first
moistened by covering with damp sawdust.   They are cleaned by
tumbling in drums with dry sawdust, which absorbs the grease and
dirt.  Often the sawdust is treated with solvent that cuts the
grease.  After the pelts have been tanned, they are again tumbled
with sawdust to give the hair a light, fluffy appearance and to
restore luster reduced in the dyeing process.   Sawdust for
furriers is fine, clean, granular, and absorptive, commonly
kiln-dried hard maple and other hardwood stock.
 
Leather Working
 
Tanneries use sawdust to moisten the hides for stretching.  Wet
sawdust is evenly distributed over the surface and the stretching
done with minimum loss from tearing.   The sawdust must be free of
splinters, foreign matter, and grease.
 
Metal Finishing
 
Ground very fine, sawdust is used in the plating industry to
clean, dry, and polish metals after removal from plating solutions.
Coarse, sifted eight-mesh sawdust is used.   Softwood
sawdust contains objectionable pitch, resins, and oils so only
kiln-dried acid-free hardwood sawdust (18 to 24 mesh) is employed.
Woods containing acid, such as oak, stain the polished
surfaces and are not used.  metals that have been cleaned in a
pickling bath are dried and polished by tumbling in sawdust.
Greasy components made in large volume on automatic machine tools
can be cleaned, dried, and polished by agitation in a tumbling
barrel with sawdust.  Aluminumware is cleaned and polished by
sawdust after degreasing in a solvent solution.
 
Wallpaper Manufacture
 
Sawdust and fine chippings are included in the pulp from which
"oatmeal" or "anaglypta" wallpapers are made, with various distinctive
embossed surfaces.
 
Molded Products
 
Sawdust bonded with resin has been used to manufacture molded
wooden items such as breadboards, cups, bowls, or similar items.
Artificial wood is made of sawdust, paper waste, casein glue, and
limestone or chalk.  The ingredients are ground together,
moistened with water and molded.   The finished product is said to
possess many of the properties of natural wood.
 
Toys
 
Fine dry sawdust is also used to stuff dolls and toy animals.
 
FOOD PROCESSING INDUSTRIES
 
Poultry Picking
 
After the main wing and tail feathers are removed, the carcass is
partially scaled, then covered in fine, dry sawdust.   In three or
four minutes most of the water is absorbed, making picking, and
removal of the pin feathers easier, without injury to the skin.
 
Smoking Meat and Fish
 
Raw hardwood sawdust and chips are used to smoke meat and fish.
Meats that have been pickled or cured (such as ham, bacon, fish,
and sausage) are smoked to give flavor and increase their keeping
qualities.  Usually a smoldering fire of hardwood blocks and
sawdust is built and meat hung over the smoke for four or five
days at about 75 F.  A quicker method of curing can be done in
one day, but requires a higher temperature.   Hickory, maple,
mahogany, oak, and walnut are all commonly used in the smoking
process.
 
Packing for Ice
 
Sawdust used in packing ice helps to keep the ice clean,
insulates it from heat, and makes it less slippery for handling.
 
WOOD FLOUR
 
Wood flour is not the same as sawdust.   It is a uniform, fine
powder of much smaller grain size.   Commercially, it is used as
an absorbent, a chemically reacting substance, a chemically inert
filler, a modifier of physical properties, a mild abrasive, and a
decorative material.
 
Uses of Wood Flour
 
Wood flour can be used as an absorbent to remove water, oils, or
greases from delicate machinery parts, jewelry, and furs.  In the
manufacture of dynamite, the sensitivity of the explosive can be
reduced by absorbing it in wood flour, thus solidifying the
liquid nitroglycerine.
 
The chemically reactive property of wood flour is utilized in
incense and in the coatings of arc-welding rods where it provides
a neutral gas to protect the weld puddle from air.   In reaction
with polyurethane foaming resins it produces a rigid foam-in-place
structure.  Wood flour is also used in fireworks intended
to burn for a time rather than explode.
 
As a chemically inert diluting agent or filler, wood flour is
used in the manufacture of plastic products.   When utilized in
this manner it increases impact resistance or toughness, reduces
stresses, and minimizes shrinkage on cooling after molding.  Wood
flour is sometimes added to make transparent plastics opaque.  It
is also used in the manufacture of patching materials, cements
and glues, insecticides, soap powders, and rubber.   The natural
resins in wood flour are used for their binding properties,
notably in linoleum manufacture.
 
In foundries, wood flour is used as an anti-binding agent to
modify the physical properties of an item--for example, to help
ease castings out of their molds.   In chinaware and fire-brick
manufacture, it is used as a burn-out material to increase
porosity.  In special paints, it gives sound insulating properties
and in electrical equipment, wood flour improves insulation.
 
As a mild abrasive, wood flour is sometimes added to soaps and is
used in cleaning furs.  It is also used to polish soft materials
such as buttons and for removing the flash (material that sweeps
out at the mold joint) from newly molded plastic articles.
 
Wood flour is also used decoratively in interior decorating.  In
velvet or raised wallpaper for example, colored wood flour is
sprinkled over the sized surface.
 
Wood flour has also been used in biochemical processes as a
culture medium for the growth of bacteria, for example.   This
produces valuable organic acids such as acetic, lactic, gluconic,
and citric.
 
Manufacture of Wood Flour
 
Light colored flour is required for many applications.   Since
bleaching is not practiced, light woods such as spruce, pine and
fir teak, beech, mahogany, and cedar are the most desirable.
The chief source of raw materials for wood flour is the residue
of other wood processing industries.   Wood flour can be produced
by a variety of method:  recovery of dust from sanders;
screening, using meshes as fine as 350 to 400; abrasion by
corrugated metal discs revolving in opposite directions; cutting
and shock, using impact hammermills; and crushing by passing the
material between a moving roll and a stationary surface.
 
A plant that produces one ton per hour of fine mesh wood flour
from hardwood shavings and coarse sawdust requires the following:
 
     o   the raw material is reduced in an 18-inch hammer mill,
        driven by a 75-HP motor, then conveyed directly to a
        35-inch double head attrition (grinding/wearing) mill
        with two 75-HP motors;
 
     o   the material falls through a sifter mill with 80-mesh
        screens;
 
     o   the overage from the sifter is recycled back to mill
        and the accepted fraction goes to the bagging
        equipment.
 
Prices charged for wood flour increase with the mesh number:
100-mesh is more valued than 40-mesh and finer meshes will bear
higher prices.
 
INDUSTRIAL CHEMICAL PRODUCTS
 
Most wood waste still retains the fibrous structure of the original
wood.  Wood is composed mainly of cellulose and lignin, and
from the standpoint of chemical utilization these are the main
constituents.  They are highly complex and relatively inert substances,
closely held together by chemical bonds.   They can only
be separated by drastic chemical treatment.   In addition, wood
contains small amounts of extractable materials such as resins,
fats, tannins, and essential oils.   The main processes for chemical
utilization of wood are manufacture of chemical pulp, destructive
distillation, and wood hydrolysis.   None of these processes
fully utilize the chemical properties of wood waste.
 
In the production of wood pulp, both mechanical and chemical, the
wood is converted to fibers and the products derived from the
wood pulp are in general dependent on the properties of these
fibers.  In the production of chemical pulp, there is a loss of
approximately 50 percent of wood substances in the form of
lignin, hemicelluloses, and degraded cellulose.
 
Manufacture of wood pulp from waste is usally more expensive than
using roundwood or complete tree trunks.   Some mills that employ
the kraft or sulphate process, however, in which the presence of
varied wood and bark is not objectionable, add waste to the
roundwood.
 
The process of distillation involves heating the waste in a
limited supply of air so that gases are given off that can be
collected and condensed, leaving a char behind.   The products of
.distilling hardwoods are charcoal, hardwood tars, acetic acid or
calcium acetate (also called acetate of lime), methanol, and wood
alcohol.  In the case of soft woods, distilling products include
charcoal, turpentine, pine oil, and pine tar.   Products of dry
distillation of resinous pine are wood turpentine, tar oils, tar,
and charcoal.
 
Shavings and sawdust are also heated with a mixture of caustic
soda and lime.  Approximately 20 percent of the gases given off
are oils, of which 50 percent are ketones, and 25 percent hydrocarbons
that can be used as solvents and plasticizers.
 
Oxalic acid, which also can be produced by other processes, may
be made according to the Othermer method.   This yields a quantity
of oxalic acid equal to 75 percent of the dry weight of the
wood plus considerable quantities of acetic and formic acids and
methanol.  The general materials and yield are as follows:
 
Material Used - Pounds               Product Formed - Pounds
 
     100          dry sawdust                      44.5  [oxalic acid]
 
       9          sodium hydroxide                 11.7   [acetic acid)
 
    34.7          lime                              2.48 formic acid
 
    61.1          100% sulfuric acid                5.5   methanol
 
                                                 85.5   calcium sulfate
                                                       (waste)
                                                  3.0    wood oil
 
Acid Hydrolysis
 
Hydroloysis (chemical combination with water) of a cellulosic
material such as wood results in carbohydrates, chiefly glucose,
with lesser quantities of sugars such as xylose, mannose, galactose,
and arabinose.  Fermentable carbohydrates convert to yeast
or ethyl alcohol.  Other fermentation products such as butylene
glycol, butanol, acetone, and organic acids can also be produced.
 
To manufacture industrial alcohol from sawdust and other mill
waste, the wood is placed in rotary digesters and treated with
dilute acid at high temperatures, converting the cellulose into
fermentable sugars.  These substances are then separated and
fermented into alcohol, which is distilled and rectified to make
a product equivalent to grain alcohol.   The commercial success of
Wood hydrolysis depends on the demand for alcohol, the availability
and price of molasses (a competive raw material), and the
extent to which alcohol is produced more cheaply from petroleum
refinery by-product gases.
 
Potash
 
Potash is manufactured from wood ashes.   Hardwood ashes are
desirable and will yield 10 percent of potash.
 
OTHER USES FOR WOOD WASTES
 
In the manufacture of softwood lumber, material in lengths under
eight feet is often wasted.  Such short length stock (or off-cuts)
constitutes five percent of the total volume of stockwood
lumber.  Even smaller sawed pieces from sawmills, furniture manufacturers,
and carpentry shops often still have value and may be
used to make boxes, children's toys, beehives, brooms, cable
reels, dowels, drying racks, farm equipment, furniture, handles,
hardwood flooring, picture frames, seating, signs, step
ladders, or other goods.
 
Slabs are strips of wood removed from the outside of the tree
trunk before it is converted into planks.   They are often about
six inches wide and six to eight feet long, with one flat side,
and when the other covered with bark.   Slabs can be used as
lumber and the other covered with bark.   Slabs can be used as
lumber, whenever the finished product does not have to be uniform
and tight-fitting.  Appropriate usage of slabs include animal
pens, shed shelves, loose storage bins, or rustic furniture.
Slabs will rot quickly if exposed to the ground, to they need to
be preserved with creosote.  Slabs nailed to posts, with the
bark side facing outward has the appearnce of rustic fencing.  In
gentle climates, slabs can be used as roof boards if tar paper is
spread under them.  A slab sandwich consists of a layer of slabs,
nailed to cross pieces with the bark side down, then a double
layer of tar paper, another layer of slabs, with the bark side up
overlapping like shingles.  Such a roof is not permanent, but may
last about five years, so it is suitable for storage or other
temporary uses.
 
Forest wastes such as leaves make the finest compost, and should
be used for this wherever possible.   Wood bark protects the tree
but it is harmful to many forms of life.   Therefore waste bark
has in the past, had little commercial value other than for fuel.
Chopped bark can be used as animal bedding and in chipbaord.
Because of its color, however, it may not always be acceptable.
Recently composed bark has been used for soil conditioning after
processing to remove any danger to plant life.   Some tree barks
have special uses including the following:   The cork oak tree for
cork mats, lifebelts, or bottle stoppers; oak bark for the
production of tanning extract for leather tanning, and as a brown
dye; birch bark for canoe building; cinnamon bark as food
flavoring; and cinchona bark for quinine medicine.
 
V.  THE COCONUT TRUNK:  AN UNEXPLOITED RESOURCE
 
Unlike other parts of the coconut tree, the trunk has been underutilized.
With shortages of timber in many parts of the world,
there is increased interest in taking fuller advantage of coconut
timber.
 
Huge amounts of the wood are available, and in some areas such as
Jamaica, due to the spread of yellow leaf disease, a vast number
of trees have been destroyed.   Because of this, coconut tree
trunks must be utilized within a few years if they are to be used
at all.  Otherwise, this resource will be vulnerable to rotting.
 
Given the widespread shortage of hardwoods and the high price of
hardwood timber, why is this attractive commercial opportunity
not exploited? There are two principal reasons.
 
First, extraction is difficult.   Coconuts often grow interspersed
with other crops such as bananas.   The trunk is very heavy due to
its high moisture content.  It contains a high amount of silica,
making it extremely hard, and its unique fiber structure makes
it very tough.  The tree trunk can be cut down with a chain saw
or an ax, but because of its hardness, the saw wears rapidly.  An
additional burden is that the lower trunk must be disposed of
because it serves as a breeding point for insects, principally
the palm beetle and the coconut rhinoceros beetle.   Disposal of
the lower trunk can be accomplished by digging around the roots
of the tree, then using a rope to transport it away.   If a
quicker method is desired, a bulldozer or a cable winch may be
used.  If bulldozing standing trees, caution should be taken to
guard the driver from falling coconuts.   Waste wood should be
burned.
 
The second major reason coconut trunks are under utilized is that
in selecting timber only the outer material is suitable for
cutting.  The inner core is very weak, low density wood, and the
higher portions of stem bear a weaker product.   However, the
trunk is nearly parallel and free from knots, so sawing is easy
to plan.  Because of the differing strengths of timber, a good
plan is to use the bottom portion as timber and the upper stem
for posts.  All material except that next to the bark should be
discarded.
 
Machinery
 
 
The timber is extremely hard due to its high silica content and
tough fibers.  Normal timber saws will become blunt rapidly, but
their sharpness can be prolonged by depositing stellite on the
teeth by arc-welding with a special electrode.   The stellite is
then sharpened with a very hard carborundum stone, a long process.
An alternative is to use circular saw blades and planer
cutters tipped with tungsten carbide (often used in the machining
of steel).  These are expensive compared to normal blades and
need special sharpening, but their life between sharpening will
be .50 times that of ordinary tool steel.   They are brittle and
may break if used on a saw mill without enough power, so it is
best to use slightly oversize machines.
 
Timber Products
 
Coconut wood products are attractive and strong due to the
absence of knots, provided the correct parts of the tree are
selected.  The wide range includes sawed lumber for house walls,
frames, and roof trusses; tongue-and-groove flooring; furniture
with an attractive natural polished finish; doors, windows, and
shingles; parquet flooring (small rectangular blocks laid in
attractive patterns; rough sawed items such as fork truck pallets,
fencing, or roadside guard rail posts.
 
To produce these products, a medium-sized workshop would need
the following equipment:  one 34-kw sawmill driving a 75-cm
diameter blade; one 15-kw sawmill driving a 64-cm diameter blade;
one thicknessing machine; one saw tooth profiling machine; and
one runway and electrial block for lifting trunks.
 
Value of output can be estimated at US$150,000 a year.   Total
capital cost including a suitable vehicle, chain saws, and other
equipment for extracting trunks will be US$80,000 to US$100,000.
A single shift will employ between 20 and 30 people.
 
Production of Poles and Posts
 
Coconut trunks are widely used for telegraph and other poles in
the Philippines.  The main problem is preserving them against rot
and termites.  The timber is dried for four to five months and
and soaked in hot creosote (93 to 98 C for 8 to 10 hours drying.
For sawed lumber, the times can be reduced by 25 percent.  It is
important to use insectides in the drying shed as newly sawed
timber is very vulnerable to attack by insects.
 
                     REFERENCES AND RESOURCES
 
T. R. D. A., Particle Board in Building, U. K. Timber Research
Development Association.
 
UNIDO, Information Sources on Building Boards from Wood & Other
Fibrous Materials, 1974.
 
Bryant, B S, Fibreboard products from Agricultural Resides and
Wild Grasses, BOSTID, USA National Research Council.
 
New Zealand Forest Service, 1976, Coconut Stem Utilization
Report.  New Zealand ministry of Foreign Affairs, Wellington New
Zealand.
 
New Zealand Forest Service (NZFS), Private Bag, Wellington, New
Zealand.
 
Tropical Products Institutes (TPI), 56 Grays Inn Rd, London WCX
8LU, England.
 
South Pacific Bureau for Economic Cooperation (SPEC), Box 856
Suva, Fiji.
 
Asian and Pacific Coconut Community (APCC), Box 343, Jakarta,
Indonesia.
 
Forest Products Research and Industries Development Commission,
(FORPRIDEECOM), NSDB College, Laguna 3720 Philippines.
 
Wood Stove Group, Eindhoven University, Post Bus. 513 5600MB,
Eindhoven, Netherlands.
 
Department of Agriculture, Box 14, Nuku'alofa, Tonga
 
Forestry Division, Ministry of Agriculture, Fisheries and
Forests, P O. Box 358, Suva, Fiji.
 
The Principal, Kristian Institute Technology of Weasisi, (KIOW)
P O Box 16, Isangel, Tanna, New Herbicides.
 
ITDG, Wood Stoves Project, 9, King St., Covent Garden, LONDON
WC2E 8HW or Applied Research Station, Shinfield Road, READING,
RG2 9BE, Berkshire, U K.
 
Timber Research and Development Association, Hughenden Valley,
High Wycombe, Bucks, U K.
 
Fibre Building Board Development Organization Ltd, 1 Hanworth
Road, Feltham, Middlesex, TW13 5AF, U K
 
UNIDO, P O Box 707, A-1011, Vienna, Austria
VS Machine Factory, 90/20 Ladprao Soi 1 Road, Bangkok, Thailand.
 
Aldred Process Plant, Oakwood Chemical Works, Sandy Lane,
Worksop, Notts, S80 3EY.
 
Air Plant (Sales) Ltd (Spanex), 295 Aylestone Road, Leicester,
LFI 7PB, U K.
 
CeCoCo, Chuo Boeki Goshi Kaisha, PO Box-8, Ibaraki City, Osaka
567, Japan.
 
Universal Wood Limited, 11120 Roselle Street, Suite J, San
Diego, California 99121.
 
Fred Hausmann AG, Hammerstrasse 46, 4055 Basel, Switzerland
 
Woodex International Ltd, PO Box 400, Terminal A, Toronto,
Ontario, Canada, M5W
 
IMATRA-AHJO Oy, Sukkulakatu 3, SF-55120, IMATRA 12, FINLAND
 
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