It is estimated that the annual sawdust pile of the world would be several times as large as the largest skyscraper of New York. The sawdust is only about one-fifth of the total waste from the lumber industry. It is estimated that 62 percent of each tree cut for lumber is wasted. This includes the limbs, top, and stump as well as the waste at the mill. From the sawlogs alone the waste is approximately 49 per cent

Arnold, Lionel K.

English

It is estimated that the annual sawdust pile of the world would be several times as large as the largest skyscraper of New York. The sawdust is only about one-fifth of the total waste from the lumber industry. It is estimated that 62 percent of each tree cut for lumber is wasted. This includes the limbs, top, and stump as well as the waste at the mill. From the sawlogs alone the waste is approximately 49 per cent.</p

Arnold, Lionel

Digital Repository @ Iowa State University (ISU)

THE     AMES    FORESTER                      17Wood  Waste  as  a  Raw MaterialLionel  K.  Arnold,  Engineering  Experiment  StationIt  is  estimated  that  the  annual  sawdust  pile  of  the  worldwould  be  several  times  as  large  as  the  largest  skyscraper  ofNew 'York.     The  sawclust  is  only  about  one-fifth  of  the  totalwaste  from  the  lumber  industry.    It  is  estimated  that  62  percent  of  each  tree  cut  for  lumber  is  wasted.    This  includes  thelimbs,  top,  and  stump  as  well  as  the  waste  at  the  mill.    Fromthe sawlogs  alone the  waste  is  approximately 49  per cent.Unbreakable  dolls  and  dynamite  are  only  two  of  the  manyproducts  made  fl-om  wood  flour  which  is  made  from  sawdustand  other  wood  wastes.    In  spite  of  the  immense  quantities  ofsawdust  and  other wood wastes  produced  in  the  United  States,we  are  importing  in  the  neighborhood  of  12  million  pounds  ofwood  flour  every  year  at  a  cost  of  about  90  thousand  dollars.We   are,   however,   producing  a,bout   four  times   this   quantityfrom  our  own  wood  wastes.    Wood  flour  is  made  by  grindingsawdust  and  chipped  trimming`s  in  mills  of  several  sorts.      InEurope  the  old  fashioned  burr  mills  used  for  grinding  grainare used  almost  exclusively.    In  this  country burr  mills,  doubleand  single  attrition  mills,  hammer  mills,  and  roller  mills  areall  used.    The  finerless  of  the  finished  product  varies  with  theuse  to  which  it  is  put,  from  t,hat  passing  through  a  20  meshscreen  to  that  passint,o'  a  100  mesh  screen.    At  least  75  percentof  the  wood  flour  produced  in  the  United  States  is  made  fromwhite  pine,  the  remainder  being  chiefly  from  poplar,  spruce,hemlock,  maple,  ancl  birch.   Woods  of high resin  content  do  notmake satisfactory \l-ood flour for most  industries.    Many indus-tries  require  a  light  colored  wood  flour  which  may  be  coloredby  suitable  dves.uOver  50  percent  of  the  wood  flour  used  in  the  United  State~5goes  into  the  manufacture  of  linoleum,  chiefly  the  inlaid  types.Here  it  is  mixed with  rosin,  linseed  oil,  and kauri  gum  and  ce-mented to a burlap backing. The Tl-'OOd flour used must be light incolor and capable of taking pigments.    The  linoleum manufact-urers use  both  imported  and  domestic  flour,  the  latter  being  ingeneral  the  better  for  this  purpose.A  quite  different  use  of  wood  flour  is  as  a  constituent  ofdynamite.    Nitroglycerine,   due   to   its   sensitiveness   t,o   shock,is  dangerous  I,o  handle.     To make  it less Sensitive tO  Shock,  it  iSdiluted with wood flour.    In this form it can be made into stickso±'  high  explosive  which  are  relatively  safe  to  handle.     Consid-erable  quantlities  of  wood flour  are  used for  filler in the  manu-facture  of  unbreakable  dolls.    The  wood  flour  is  mixed  with18                      TIIE     AMES    FORESTERrosin, gums,  and other binders and molded under pressure withheat   in   bronze   molds.    Light-colored,   semi-fibrous,   import,edgrades  of  wood  flour  are  used  for  doll  manufacture.      Aftermolding,  the  parts  are  dipped  in  a  flesh  colored  gllue  solutionwhich  gives  them  the  proper  color.    Considerable  wood  flour  isused  as  filler  in  phenol-formaldehyde  condensation  resins  suchas  Bakelite.    It  reduces  the  brittleness  of  the  synthetic  resinsso that they may be molded.    The flour used is usually  60 meshor  finer.    A  considerable   amount  of  wood  flour  is  combinedwith  a  variety  of  binders  in  the  production  of  such  things  aspicture   fr`ames,   tenpins,   bowling  balls,  furniture  legs,  brushbacks,  and  phonograph  records.Wood  flour  becomes  a  building material  in  such  caser,  all  Oat-meal  wallpaper  and  composition  flooring.    In  the  productionof oatmeal wa,llpaper the wood flour is  added to the paper pulpbefore  it, is made  into  paper.    When  the  paper  is  formed  fromthe  water  suspension  of  pulp  a,nd  wood  flour,  the  unhydratedwood  flour  floats  oTl  the  Surface  and  appears  finally  as  a  thinsurfacing  on  the  paper  giving  the  "oatmeal"  effect.    Compo-sition  flooring  is  made  from  caustic  maoo`nesia  cement,  sawdust,and  wood  flour.    The  sawdust  is  used  in  the  main body  of  theflooring  with  the  finer  wood  flour  on  the  surface  layer.Numerous   processes   for   the   conversion   of   wood   waste   tosugar  have  been  tried.    The  cellulose  in  the  wood  can  be  con-verted to glucose by heating under pressuye with a small amountof   sulphuric  acid.         Hydrolyzed  wood  waste  has  been  pro-posed as a cattle  food.    Considerable research has been  done  onthe   fermentation   of  the   sugars  formed.    It  has   been  shownthat  one  ton  of  dry  sawdust  or  other  wood  waste  will  yield  asmuch  as  25  gallons  of  190  proof  ethyl  alcohol.     Several  plantsfor  the  production  of  ethyl  alcohol  from  woocT  waste  have  beenbuilt,  but most  of  I,hese  are not  considered  practical.    The  com-petition  of  other  raw  materials  such  as  black  strap  molassesis  keen.    With  improvements  in  the  process  it  may  be  possibleto  produce  the  alcohol more  economically  froln  the  wood  Wastethan from anv other material. It has been shown experimentallythat the pent;se sugars remaining after the fermentation of thehexose  sugars  to  alcohol  can  be  fermented  by  certain  bacteriato  lactic  and  acetic  acids.    If  this  could  be  carried  out  com-mercially   it  might   make   the   industry   profitable.    It   is   alsoT,OSSible to recover small  amounts  of acetic  acid  and  formic  acidfrom  the  b-1o-w-off  liquors,  probably  decomposition  products  ofthe  lignin.    Turpentine   and  pine   oil  are   obtained   from  thebl_ow-off  liquors  when  certain  of  the  southern  pines  are  hydro-1yzed.     These  products  are  obtained  only  in   small  quantitiesso  that  at  pre1=ent  their  recovery  iS  not  Practical.TIIE,     AMES    FORESTER                      19-gtOnPOJd@g_SDA4POOA4.20                     TIIE    AMES    FORESTERGreat quantities of sawdust and other wood waste are burnedas  a  fuel.    Sawdust  requires  specially  constructed  grates  andautomatic  feeding'  devices.    Most  of  the  waste  wood  is  utilizedfor  heat  and  power  at  the  saw  mills  since  it  does  not  pay  toship  it  any  great  distance.    Many  attempts  have  been  made  toform  sawdust  into  fuel  briquettes  using  various  binders  suchas  tar,  resin,  and  waste  sulphite  paper  lic'_uor.  While  good  bri-quettes have been made from sawdust they have not been able tocompete  with  ot,her  fuels.The  destruct,ive  distillation  of  wood  wastes  to  procure  char-coal,  illuminating  gas,  acetic  acid,  wood  alcohol,  and  other  pro-ducts  has  been  the  object  of  considerable  research.    The  wooddistillation  industry  is  one  of  the  large  chemical  industries  butis now facing a  scarcity  of raw  material.    In  addition  the  com-petition  of  other  chemical  industries  producing  the  same  pro-ducts is very keen.    The use of wood wastes would help materi-ally in solving the raw material problem.    Since in the destruct-ive  distillation the wood is broken  down  chemically the  originalsize  and  shape  of  the  wood  pieces  used  would  not  seem  to  beof  importance.    Efforts  to  distill  sawdust  aIld  Other  fire  woodwaste  in  the  usual  equipment  used  in  the  industry  resulted  infailure, due to d'fficulty in uniformly heating the mass, and dueto the formation of a charred layer on the inside of the retorts.Recently a satisfactory process of continuously distilling woodwaste has been put into commercial operation in England.    Thewood  waste  is  fed  into  a  horizontal  rotary  tube  in  which  thewood is heated.    Agitators prevent the sawdust from caking  onthe  sides  of  the  tube  and  keep  it  moving'  to  the  discharge  end.,The  charcoal  and  the  volatile  products  r\f  the  distillation  passut of the tube into a  chamber at the end of the tube.  The char-coal  drops  to  the  bottom  where  it  is  clrawn  off  intermittently.The volatile material is drawn out the top into condensers wherethe  tar  and  pyroligneous  acids  are  liquified.   The  various  pro-ducts  are  separated  and  refined  in  the  usual  manner.    Thisplant is successfully utilizing the waste wood and sawdust froma  large  wood working plant.In  the  Scandinavian  countries  the  waste  slabs  from  the  sawmill are made into paper.    This is made possible by the loggingmethods  used,  which  differ  from  those  in  this  country.    All  ofthe bark is removed from the logs in the forest so that the slabsfrom  the  sawmill  are  free  from  bark.    It,  is  not  practical  tomake  paper  from  slabs  with bark  such  as  come  from Americansawmills.Various  processes  for  the  production  of  wall  board  and  in-sulation  board  from  wood  wastes  have  been  developed.    Mostof  these  processes  depend  upon  the  mechanical  disintegrationof  the  waste  wood  into  fairly  coarse  fiber  by  special  types  ofTIIE     AMES     FORESTER                     21lnachinery  such  as  attrition  mills  or  modified  refiners.    The  in-sulation  board  is made up  of  a  mat  of larger  and  less uniformfibers than are used in paper.    The fibers are hydrated much lessso that a greater number of less-mechanicalL Processes for Produc-tion of pulp are possible. Pulp is formed into a mat on a screen byvarious machines of both the fourdrinier .1nd Cylinder types anddried  in  a  tunnel  dryer,  u~3ually  of  the  roller  type.    A  ratherdifferent  type  of  process  is used  by  the  Masonite  com.pany.    Intheir  process  the  waste  wood  is  heated  under  very  high  steamI,re:Sure until the mt_I,iSture has thoroughly Penetrated the wood.The  I,reSSure  iS  Suddenly  released  and  the  wood  blown  out  of22                     THE     AMES    FORESTERthe gun-like pressure chamber.    The  rapid lowering  of  externalpressure causes the wood to be blown into fibers, which are thenformed  into  a  mat  on  a  modified  fourdrinier  shaker  machine.The  resulting  mat  is  dried  in  a  steam  heated  hydraulic  press.when  dried  with  practically  no  pre;sure  an  insulating  type  ofboard `is  produced.    When  dried  under  high  pressure  a  hard,dense board known as pressed board is formed.    Boards of thesetypes  are  replacing natural lumber  for  certairL  Purposes.      Theinsulating  board  is  used  as  a  wall  board  in  place  of  lath  andplaster,  as  a  plaster  base,  and  as  a  sheathing  material.      Thepressed  board  is  used  as  a  base,  and  as  a  sheathing  material.The  pressed  board  is  used  as  a  panelling  material  in  pullmancars,  truck  bodies  arid  furniture.Wood   in   the   form   of   shavings,   excelsior.,   and   sawdust   isused  as  a  packing  material  for  many  thlr]gS.    Sawdust  is  usedaround  bottled  goods  as  it  ak_o  acts  as  art  absorbent  of  liquidsin case  of breakage.    A considerable  amount  of sawdust  is  usedin  the  packing  and  shipping  of  fruit.    Over  4000  tons  are  con-sumed annually in Cali±'ornia for the packing of grapes.  Groundcork  was   formerly  used  for  this  purpose  but  sawdust  fromsuch woods as spruce  and fir has proved to be both cheaper andbetter.Sawdust,  as  such,  is  used  in  a  variety  of  industries.     Ap-proximately   1100  tons  of  sawdust  are  used   annually  in  therubber  indust_ry.     prdrdbal-1v  the  largest  use  in  the  leather  in-dustry  is  in  Ike  manu£act~ure  of  patent  leathers  and  uppers.After   dyeing   and   tanning,   the   skins   must   be   softened   orkneaded and then stretched.    For these proce-+ses the hides mustbe  moistened.     One  method  is  to  pile  them  between  layers  ofdamp  sawdust.    The  damp  sawdust  provides  just  enough  mois-ture  for  proper  softening.  Different  manufacturers  use  differ-ent  kinds  of  sawdust  varying  ±'rom  fine  maI,1e  to  coarse  pine.For light, colored leathers only sawdust from lig`ht, non-stainingwoods  may be  used.    For  all sorts  it  must  be  free  fI'Om  foreignmatter such as dirt and grease.    Sawdust is also used to a minorextent  in  some  other  tanning  operations.Considerable  sawdust  is  used  in  cleaning  oil  from  manufac-tured  metal  products  such  as  cutlery,  wire  novelties,  aluminumut-,ensils,  and  other  metal  objects.     About  2thrJtO  tons  a  year  areused  in  the  aluminum  industry  alone.    Another  cleaning  useis in the fur industry. Most of the sawdus+u used in these processesis maple sawdust, altllOugh some Other, Such aS Oak and beech, arerised.A  considerable  amount  of  sawdust  is  used  on  concrete  floorsto  prevent  too  rapid  drying  during  the  curing  process.    Onlythe non-staining varieties are suitable for this purpose.   Anotherbuilding use is as a heat and sound insulating material in houses.TIIE     AMES    FORESTER                     23It  is  filled  between  the  studs  in  the  walls  and  between  ceilingsand  subfloors.    It  stops  the  convection  currents  and  drafts  aswell  as  acting  as  a  direct  insulating  ma+uc-rial.     Itl  is  necessarythat the wall be so constructed as to keep the sawdust dry or itsinsulating value will be  low.    Wall stoppings  should be used  toretard fire  and rodents.Sawdust  is  used  in  the  production  of  various  manufacturedproduc,ts.    It  is  used  as  filler  in  gypsum  plaster  board,  in  com-position flooring,  and in  concrete floor tiles and roof slabs.  Saw-dust  is  used  to  give  porosity  to  various  burnt  clay  products.More than 7000 tone a year are used  in the manufacture  of sili-con-carbide  abrasives,,  where it serves to  keep  the fusecl  abrasivematerial`in proper porous  condition to  allow escape of  the  gasesformed.   A minor us,e of sawdust is in the manufacture of sweep-ing compounds in which it is treated with certain oils which  ab-sorb the dust.    Amc,ng other uses are such as a stuffing materialfor dolls and other toys,  as  an insulating material  in storage  ofice,  and in various pyrotechnics.Ida,ho   White   Pi,ne-an   Important   Commercidl   Specke8.

Wood Waste as a Raw Material

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Wood Waste as a Raw Material

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