LISTENING STUDY Question 49:
Are there limits on making tree free pulps into paper on certain machines?

Yes

We would certainly expect so, depending on the design of the machine and the nature of the agricultural fiber. - International Paper

Yes. Every paper machine has its own specific characteristics. - Living Tree Paper Company

Once again, this is not an issue of replacing wood fiber directly with agricultural fibers. So no, the current wood infrastructure is not suitable (without modifications) for materials that are lower in density, have different structures, etc. There are also some problems (ie: silica in rice straw) that causes problems for machinery.
      On a limited scale, some perennials such as Arundo donax and bagasse can run through existing machinery. This proposal is a good ideal. For these fibers, the harvesting is the biggest problem - it's hard to know how much it will cost. - Peter A. Nelson, President, AgroTech Communications, Inc.

No

There are no fundamental barriers. There are numerous ways to make paper, even starting from the selection of a single type of papermaking fiber.
      See for example, my article, "Using crop residues to save forests." - Al Wong, Founder, Arbokem

There are differences in moisture level settings that have to occur in high speed papermaking machines - other than this, a pulp is a pulp. - Jeanne Trombly, Fiber Futures

We have successfully run various kenaf pulps on many paper machines at seven different mills. Proper pulp preparation is essential to success, and is easy to achieve with experience and appropriate processing equipment. - Tom Rymsza, President, Vision Paper

No. - Ernett Altherimer, Founder and Chairman, Nile Fiber

It Is Possible If Adjustments Are Made

Once the fibers turn into pulp, the machines cannot tell the difference between wood pulp and nonwood pulp. Most of the problem is in pulping and not in paper making. One of the general problems with agricultural fibers is high silica content and, according to the pulp and paper industry, the nonwood fibers are hard on machines. However, most of fibers will have impurities and thus undesirable characteristics. - James S. Han, Research Chemist, USDA Forest Service Forest Products Laboratory

In a system that works primarily with tree fiber, there are no special considerations if the tree-free fiber has the same technical characteristics as the wood fibers that were being used. All machines do have limits depending on their primary use and product. A machine producing a hardwood (short fiber) specialty sheet may have to use refined bast fiber (long) to perform create the desired characteristics. - Tom Rymsza, President, Vision Paper

The issue of "sodium chemistry" has already been addressed. The problems of silica in agri-fibers and long-length bast fibers can be overcome by pre-designing the pulping and papermaking facilities appropriately.
      See for example, my presentations, "New Direction in Industry Development and Environmental Protection for Nonwood Pulp Mills in Developing Countries," "Agri-Pulp Development in Alberta," and "Opportunities and limitations of using California rice straw for industrial products." - Al Wong, Founder, Arbokem

Generally plant fibers have lower drainage, water separates more slowly from them than with wood fibers. This can make it necessary to run the paper machine more slowly, reducing the production rate and productivity and increasing costs. Proper design or redesign of the machine can mostly correct this but there is an economic penalty. - Michael Jackson, Consultant, Tolovana Park, OR

For various reasons, wheat straw appears to be most appropriately used in combination with other fibers. Because of its short fibers, wheat straw makes weak paper that drains slowly. However, in combination with long-fiber pulps, these shortcomings can be alleviated. - Environmental Defense Fund Paper Task Force, White Paper 13, "Non-Wood Fiber Sources"

For the most part, nonwood raw materials contain higher amounts of silica than wood. During pulping, the silica is dissolved and enters the black liquor. High silica content in the black liquor results in various problems in the chemical recovery loop including:
a) increased black liquor viscosity at high solids concentrations
b) hard scales in the evaporator and hard deposits at various points in the recovery boiler
c) formation of colloidal gels in the recausticizing system that lower the settling rate
d) formation of glassy material in lime kilns
e) reduced slaking rate
With proper design throughout the pulp mill, all of the above problems can be addressed for most nonwood raw materials with the exception of rice straw which has an exceptionally high silica content. - Hurter 1998