= 1022

2. Planing Mill Residue

In addition to the residue that occurs in the form of slabwood,
trim ends, and sawdust, there is furthsr residue created in the remanu-
facture of lumber in the planing mill where the lumber is dressed to
various patterns and dimensions, This residue occurs in the form of
resaw sawdust, shavings, and trimmings. The quantity of lumber surfaced
varies in the different mills, depending on mill policy, markets, and
other factors, and it is possible to form only a rough estimate of this
quantity. It appears, however, that at the present time about 85 per
cont of the cut is surfaced. In the surfacing of lumber the amount of
wood removed varies with size and pattern, but the average, based on 33
items dressed to British Columbia lumber standards, is approximately 30
per cent of the green lumber.

Previous studies showed that trimming loss totalled 6.9 per
cent of the volume, of which 4.8 per cent was due to manufacturing
defects, including scasoning, It is probable that this loss is less
under present conditions of improved manufacturing and seasoning practice.

The surfacing of lumber to obtain a pleasing appearance and
uniform size is a necessity, and shavings are not classified as avoidable
residue, However, it is a product which must be disposed of and as such
often creates a problem for the mill, There is no doubt that the volume
of shavings produced could be reduced considerably if the green lumber
was cut to closcr margins of size tolerance, At the present time it is
used as a fuel for the mill boilers, or, where steam power is not used,
burned in refuse burners, left in piles to disintegrate, or burned during
winter months.

Planing mill trimmings are generally sold as kindling for
domestic use.

%3.- Relation of Wood Residue to Log Diameter
g

At three mills a study was made by individual logs so that the
percentages of lumber, solid residue, and sawdust could be determined
for each diameter of log. The figures varied as much as 10 per cent
between individual mills. However, they showed similar trends and when
averaged are indicative of the general average for the area. Figures
are shown in Table III and Figure l.