POSSIBILITIES OF INCREASING THE USE 

OF HARDWOODS TO MEET PULPWOOD 

REQUIREMENTS 

May 1946 

No. R1614 

UNITED STATES DEPARTMENT OF AGRICULTURE 

FOREST SERVICE 

FOREST PRODUCTS LABORATORY 

Madison, Wisconsin 

In Cooperation with the University of Wisconsin 
- - - - 

POSSIBILITIES OF INCREASING THE USE OF HARDWOODS TO 

MEET PULPWOOD REQUIREMENTS1 

By 

J. N. McGOVERN, Chemical Engineer 

Forest Products Laboratory, 2 Forest Service 

U. S . Department of Agriculture 

Abstract 

Predictions of increased paper and board demands for 

the immediate future raise questions regarding possible sources 

of fibrous raw material to satisfy anticipated requirements. 

Because the cheapest source of paper-making fiber will probably 

continue to be wood and because readily available supplies of 

preferred long-fibered species are inadequate, new resources of 

pulpwood will need to be developed if domestic supplies are to 

be utilized. A promising pulpwood source lies in currently 

secondary species and low-grade wood. Hardwoods make up the bulk 

of secondary species and their use is necessary to realize a badly 

needed improvement in silviculture in the woods. Although hardwoods have been used to advantage in small amounts in the pulp and 

paper industry for many years, it is only within the last few years 

that advancements in technical knowledge have been made to overcome 

certain difficulties in hardwood harvesting and processing and in 

pulp- and paper-making procedures. Those advances have improved 

the possibilities of increased utilization of hardwoods. 

Nearly 150 years ago the English economic world was introduced 

to the startling theory which predicted alarming poverty if population 

increases did not become commensurate with the more moderate increases in 

means of subsistence. However, advances in agricultural and other technologies and in transportation tended to disprove this famous theory of 

Malthus. Today, serious shortages again confront the United States and the 

world. Of particular interest to the Forest Products Laboratory is the 

shortage of paper and paperboard, since these are chiefly products of the 

forest. The demands for these products are not being met and the predicted 

demands in the near future exceed considerably the readily available supplies of the preferred long-fibered raw material. Although the situation 

is unlike that described by Malthus. It will be shown that technological 

developments can again help meet the present and prospective shortages, at 

least the paper and board shortages. 

1Presented at a meeting of the Wisconsin Press Association at Milwaukee, 

Wis., May 17, 1946. 

2Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 

Report No. R1614 
As you know, the pulp and paper industry in the United States 

has had a rather amazing growth during this century. A large increase in 

paper consumption has been shown in each decade. In the period from 1899 

to 1945 the consumption of paper and board has increased from slightly 

over 2 million tons to about 20 million tons, It has been predicted conservatively that paper and board consumptian will be 24 million tons by 

1950. During the period of 1899 to 1943 the per capita consumption of 

paper and board increased from 58 to 288 pounds, although it reached a 

high of 309 pounds in 1941; it is estimated that this value will be 330 

pounds by 1950. It is of interest, incidentally, to recognize that a 

close correlation exists between consumers' expenditures for nondurable 

goods and services and paper consumption. 

Accepting the predicted increase of 20 percent in paper and 

board consumption by 1950, the question then arises as to where this 

increase is to come from. It seems likely now that the added requirements will be met to a greater or lesser degree by the following alternatives, assuming that wood will continue to be the cheapest source of 

primary fibrous raw material: 

(a) Importing more pulpwood, pulp, and paper. 

(b) Using more waste paper. 

(c) Increasing domestic pulpwood production by going farther 

afield for preferred long-fibered species, by using new species, or by 

using more of the little-used species. 

Part of the increased requirements will undoubtedly be met by 

increased imports, although there arc increasing demands elsewhere for 

Scandinavian pulp and paper products and it will be a few years before 

those countries have recovered from the effects of World War II. In this 

connection it is interesting to note that before the war the amount of 

paper imported or made from imported pulpwood and pulp nearly equaled the 

amount of paper made from domestic pulpwood. Waste paper will continue to 

be used in large quantities in numerous grades of paper but it is doubtful 

if the war-time collection level can be maintained unless the situation 

becomes critical. Thus a large part of the increased requirements for the 

f'uture will probably need to be met by domestic pulpwood. 

During 1945 close to 86 percent of the pulpwood consumed in the 

United States was in the form of the preferred long-fibered species, the 

softwoods. The possibilities of cutting more preferred softwood pulpwood 

and maintaining this high percentage of long-fibered wood appear to he 

limited because additional supplies of the desired species are not readily

available or cutting at an increased rate will impair tho forests. In the 

Northeast, for example, the available supplies of softwoods have been 

inadequate for years and a considerable percentage, 31 percent in 1944, 

of the softwood pulpwood consumed has been imported. A similar situation 

exists in the Lake States. In tho South there is a sufficient over-all 

supply of pine pulpwood for the future, but concentration of mills in 

certain areas has reduced the availability of the pine, or cutting at a 

higher rate is contrary to good forest practice. Finally, the supplies 

Report No. R1614 -2-
of the preferred hemlock in the Northwest have become increasingly less 

available so that an increase under past conditions is improbable. In 

all regions, however, there is a tremendous supply of low-grade wood and 

little-used species whose utilization is imperative if badly needed 

improvements in the conditions and future productivity of the forest are 

to be realized. In the Northeast, Lake States, and the South these unused 

forest resources are largely in the form of the broad-leafed hardwoods. 

This source of wood appears to offer an attractive possibility for increasing 

the supply of pulpwood. Hemlock and Douglas-fir logging and mill wastes 

comprise the probable source of pulpwood in the Northwest. Thus, the most 

likely resources in three of the four major pulping regions exist in hardwoods. 

Before discussing the possibilities of utilizing hardwoods to 

meet a substantial portion of present and future pulpwood requirements, 

it is advantageous to review tho history of the use of wood as a fibrous 

raw material for paper in order to help determine possible future trends 

in pulpwood use. The first wood species used in the pulp and paper industry 

were poplar and basswood, both hardwood species although soft in texture. 

These woods were particularly suited for soda pulping, the first chemical 

pulping process. The invention of the sulfite pulping process and developments in groundwood pulping soon changed the preference to spruce. In 

1899 spruce alone made up 76 percent of all the pulpwood consumed. Because 

the supplies of spruce did not prove inexhaustible and because paper 

demands were increasing rapidly, other species had to be used to meet 

these demands. In this way Eastern and Western hemlock, Southern yellow 

pine, balsam and white fir, and jack pine were added to the list of socalled pulping species. To the original hardwoods, poplar and basswood, 

were added small amounts of yellow-poplar, gum, chestnut, birch, maple, 

and cottonwood, These additions came about as a result of both economic 

pressure and advances in technical knowledge. The importance of spruce 

in the over-all picture has thus diminished and in 1941 spruce represented 

only 22 percent of the U. S. pulpwood consumption. It is inescapable, 

however, that the trend has been for now, long-fibered species like Western 

hemlock or southern pine to satisfy the increasing demands for pulpwood. 

It is now natural to question why hardwoods have been passed over 

in spite of their availability in large quantities. Two reasons stand out 

for this rejection. These are: (1) Hardwoods are difficult to harvest and 

prepare for pulping (particularly bark removal), and (2) hardwood fibers 

are short (on the average 1/25 inch long in comparison with 1/8 inch long 

for softwood fibers) and have been used satisfactorily by conventional 

methods only in a few grades of paper where strength is not important. The 

question then arises as to whether those reasons still limit and will 

continue to handicap hardwoods. The answer to this second question is that 

hardwood harvesting will probably always be more difficult than softwood 

harvesting and that hardwood pulps will probably never find usage where 

the greatest strength is needed, but recent technical advances and developments having considerable future promise are showing the way for a much 

Report No. R1614 -3-
wider use of short-fibered hardwoods than in the past. Discussion of a 

few of those advances and developments will illustrate the possibilities 

of increasing the use of hardwoods in the pulp and paper industry. 

Hardwood harvesting and processing is generally more costly 

than that of softwoods because hardwoods are heavier and more difficult 

to saw, handle, and debark. Improvements in mechanization and integrated 

logging are expected to reduce costs and difficulties. The hardwood 

peeling season is shorter then for softwoods and hardwood bark is removed 

with oonsiderable difficulty at the mill. However, improved methods of 

bark removal which my overcome this object: ion to hardwoods are being 

developed. 

Before the war hardwood pulps were used chiefly as soda pulp in 

certain grades of book, writing, and printing papers, as sulfite pulp in 

printing, writing, and absorbent papers, papers, and as semichemical pulp in corrugating paper. The amounts of pulp made were not large and the use of 

semichemical pulp was the only substantial advance made since 1925. The 

hardwood soda pulp was used because ita soft and bulky nature and its 

short resilient fibers made papers with excellent printing characteristics. 

The sulfite pulp was used as a filler pulp to improve paper formation and 

surface properties, mainly because of its short fibers. The hardwood semichemical pulps imparted a desirable stiffness to the corrugating paper. 

All of these uses of the hardwood pulps depended on specific characteristics of the hardwood fiber. These specific properties at the same time 

limited the use of hardwood pulp to the narrow field where strength was not 

important. There have been recent developments, however, that indicate 

that pulps made from hardwoods can find broader use, and that the possibilities of increasing the utilization of hardwoods in the pulp and paper 

industry are definitely brighter now than at any time in the past. 

One important development in hardwood pulping has been the 

demonstration that many hardwoods can be pulped by the conventional sulfate 

process to produce pulps having considerable strength and wide use possibilities. Heretofore, the sulfate process has been applied chiefly to 

northern and southern pines to produce the strong pine kraft pulps used in 

wrapping paper and container board. The hardwood sulfate pulps are much 

stronger than the soda pulps. One large northeastern mill has proven to 

its own satisfaction that bleached hardwood sulfate pulps can be used for 

a majority of the outlets now served by bleached softwood sulfite pulp 

and has started construction of a mill to produce bleached sulfate from 

birch, maple, and beech. At least two northeastern soda mills plan to 

convert to sulfate pulping to improve the strength and utility of their 

hardwood pulps. During the war a Wisconsin sulfate mill started using 

aspen to furnish part of its wood supply when pine and spruce resources 

failed. The benefits obtained exceeded expectations and the mill is 

continuing tho pulping of aspen. One large southern sulfate mill has 

been pulping southern hardwoods for use in tissue papers; another is 

pulping hardwoods for book paper. It has been shown experimentally at 

the Forest Products Laboratory that certain proportions of hardwoods, say 

10 percent, can be pulped in mixture with pine without sacrifice in pulp 

Report No. R1614 -4-
quality. General use of even small proportions of hardwoods will provide 

a possible outlet of as much as a million cords annually in the pulp 

industry in the South. In a recent contest in Canada for the most practical method to use hardwoods in newsprint manufacture, the prize-winning 

suggestion entailed the use of semibleached sulfate pulp from birch, in 

addition to aspen groundwood pulp to provide a 40 percent portion of 

hardwoods in newsprint. Thus, the sulfate pulping process with little 

change in conventional operation offers several attractive possibilities 

for increasing hardwood utilization. 

With slight modifications, tho sulfite process also offers 

possibilities for increasing hardwood utilization over and above present 

use. During the war period it was recognized that hardwood sulfite pulps 

made according to the best practice had more use possibilities than previously realized. For example, the quality of birch sulfite pulp is not 

far from that of Eastern hemlock sulfite pulp. Hardwood sulfite pulp also 

has certain qualities which makes it a promising material for chemical 

conversion. 

The conventional groundwood pulping process likewise offers 

possibilities for the additional use of hardwoods. During the war several 

Wisconsin groundwood pulp mills used aspen groundwood pulp to great advantage. The product made by one of the mills, a coated book paper, contained 

50 percent aspen. While this usage was compelled by wartime demands, 

certain definite advantages have been recognized and at least a part of 

the wartime gains in the production of aspen pulps by the various methods 

is expected to be continued. Incidentally, the consumption of aspen has 

doubled during the last few years, and the information obtained by its 

forced use will increase the possibilities for its future utilization. 

By modifying the relatively new neutral sulfite semichemical 

pulping of hardwoods through addition of a stage of blenching, it is 

possible to partially overcome the low strength of hardwood pulps. 

Actually, hardwood pulps as strong as standard pulps from many longfibered species have been made in mill-scale demonstrations. Developments in the semichemical pulping process itself are being pursued in 

several places. One large southern mill has started construction of 

pulping facilities to produce hardwood semichemical pulp for wider usage 

than heretofore on the basis of successful wartime operation in a smaller 

southern mill . Experiments at the Forest Products Laboratory have 

indicated the possibility of using hardwood semichemical and groundwood 

pulps in mixture with softwood pulps in the manufacture of newsprint. Other work at the Laboratory has shown that a large number of southern 

hardwoods are suitable for producing an excellent quality of corrugating 

board from semichemical pulp made with sulfate pulping liquor. 

During the last few years the use of printing papers, particularly of the coated type for magazines, has increased astonishingly and 

huge quantities are expected to be used in the future. The hardwood pulps have an excellent possibility of fitting into this expansion because they 

Report No. R1614 -5-
improve printing qualities. Development work recently started has as its 

purpose improving the strength of hardwood papers by use of resin bonding. 

If successful, this will increase the utilization of hardwood pulps. 

Finally, some of the most attractive opportunities for 

utilizing wood waste and low-grade material, including certain hardwoods, 

exist in the field of coarse-fiber materials such as building board and 

paper, insulating board, and roofing felt. Use of these products has 

increased greatly during the past few years and this rapid expansion is 

expected to continue. 

Thus it appears that the possibilities of increasing the use 

of hardwoods in the pulp and paper industry are more favorable now than 

at any previous time. The problems connected with hardwood utilization 

are far from solved, however, and considerable technical advancement is 

still needed before hardwoods may be used to the best advantage. 

Report No. R1614 -6-