OREGON STATE UNIVERSITY

Western Juniper Composites

Development of Composites from Western Juniper Residues
(last updated 5/6/2021)



Key Documents


Significant efforts have been made to develop markets for solid wood products from western juniper.  For example, engineers require published design values for a species before they can specify the species in a structure.  Such design values have now been developed for western juniper.  However, profitability of sawmills often hinges on their ability to achieve ‘full utilization’ of their resource.  That is, viable markets are needed for solid wood as well as residues like edgings and trim ends (material removed in trimming a board to width and length, respectively), slabs (half-round shapes produced as logs are first sawn from round shapes into squares), sawdust, and shavings.  There are however, still quite limited market opportunities for such residues from western juniper.  Common residues and their current market options are shown below.  

Explored in this project

Residue

Description

Current Market(s)

Yes

Slabs

From outer diameter of tree, predominantly sapwood with bark

Firewood

Yes

Edgings

Generated as boards with rough edges are trimmed to width; heartwood and sapwood, some bark

Often burned as fuel at sawmills

Yes

Peeler shavings – with bark

Sapwood

Garden mulch

?

Peeler shavings – without bark

Produced by pole peeler, primarily sapwood

Can be sold to particleboard mills

Yes

Sawdust

Includes sapwood, hardwood, and some bark

Note: the geometry of these particles varies with the type of saw used

None

No

Planer shavings

Sap heart

Very limited production (from secondary manufacturers using juniper)

No

Limbs

Generally left in the forest when the trees are harvested

Firewood

Not directly (leaf oil used in durability testing)

Foliage

Generally left in the forest when the trees are harvested

Essential oil

The primary objectives for this project were to develop and test the material properties of prototype panels (conventional particleboard and strandboard) from a variety of western juniper residues, i.e., those noted in column 1 of the table. 

Details and results for each type of panel were as follows:

Particleboard
Phase Species & materials Properties tested

1
Pilot

Douglas-fir;
Juniper sawdust: bandsaw, circular saw (w/ & w/o bark),
heartwood, sapwood

Particle size
Density, moisture content, thickness swell,
water absorption

2
Refining the recipe

Same as Phase 1
Differing levels of wax (0, 0.5, 1%)
Particle screening (to mimic Douglas-fir panels)

Density, thickness swell, water absorption

3
Blends

Douglas-fir, ponderosa pine
Blended with juniper (5, 10, 20%)
(bandsaw, edger, circular saw sawdust)

Density, thickness swell, water absorption,
linear expansion

4
Mech. props. of
3-layer panels

Douglas-fir, juniper

Density, thickness swell, water absorption,
bending (MOR/MOE), internal bond

Results:

•Juniper sawdust particles can be used to produce particleboard, mixed-species or 100% juniper panel
•Juniper sapwood and edger dust:  TS > than DF panels
•Bandsaw & circular saw sawdust (mostly heartwood) - comparable moisture behavior to DF panels
•Blends - no difference in thickness swell compared to control panels (i.e., 100% fir and pine panels) after 24-hour water soak
•Acceptable to include small fractions of bark

 

Strandboard  
Phase Species & materials Properties tested

 1
vs Aspen

Aspen
Mixed juniper heartwood and sapwood

Density, internal bond, thickness swell,
water absorption, linear expansion

 2
vs. pine

Southern yellow pine
Juniper - sapwood, heartwood, sap/heart mix (w/bark), sap/heart mix (w/o bark)

Density (inc. x-ray profile), thickness swell,
water absorption, bending (MOR/MOE), internal bond,
screw withdrawal (face & edge)

 3
Durability

Southern yellow pine
Juniper sapwood - panels from strands impregnated w/juniper leaf oil
Panels impregnated w/juniper leaf oil post-pressing

Resistance to fungal decay (2 brown rot fungi,
1 white rot fungus)

Results:

•Heartwood & sapwood strands can be used to produce panels even w/approx. 10% bark
•Panel properties - equivalent or slightly better than SYP panels w/one exception –
•bending stiffness higher for high-density SYP than all-heartwood juniper panels 
•Durability – heartwood strandboard highly decay resistant
•Decay resistance - impregnating sapwood (strands or finished panels) led to increased decay resistance
to one of the two brown rot fungi tested but not other brown rot fungus or a white rot fungus.
•IB strength - impregnating strands prior to pressing resulted in panels with reduced internal bond strength compared to panels impregnated after pressing; bond strength for all juniper panels (w/ & w/o essential oil) exceeded SYP panels

Recommendations

Small Residues (sawdust, shavings)

  • Collect and segregate residues by process (for example, primary breakdown saw vs. edger)

Larger Residues (slabs, edgings)

  • Entrepreneurial venture needed to acquire materials, produce strands, and produce decorative panels

Future Research

  • Test insect-resistance of panels (as closet liner) with and without oil impregnation
  • Explore economic feasibility and supply
    • Assess haul distance and value of alternative uses
    • Develop detailed estimates of potential supply of material by region

 

Sample product images  
   
   

 

 


Acknowledgements:

This project was managed by Sustainable Northwest via funding received as a Business Oregon High Impact Opportunities Project (HIOPs).