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Engineered fillers: an Agenda 2020 goal.

To improve forest products industry economics, we must learn to leverage resources. That is why the American Forest & Paper Association (AF&PA) created Agenda 2020, a special project designed to enhance the forest products industry's value to society. Agenda 2020 consists of six Technology Platforms [1] as shown in Figure 1.

Agenda 2020 participants have been involved in numerous projects and have conducted two very successful Technology Summit Symposiums. Technology Summit I identified four major opportunity areas in Breakthrough Manufacturing Technology [2]. As a result, one project (Fibrous Fillers) was subsequently funded by DOE [3].

The potential of the fibrous fillers project, and its results, were sufficiently encouraging to include the subject in the "Retaining and Improving Fiber Functionality" discussion at Technology Summit II [4]. This article provides an update on what has occurred in this area since Technology Summit II.


Historically, fillers have been fine particles with a generally round shape and little or no charge. They are used to replace higher cost fiber and to improve desired sheet properties such as opacity.

The filler types discussed in this article have been added to the stock and retained in the sheet through the forming process. The "first pass retention" is often low as many fillers are removed from the slurry by very strong hydraulic forces present in the drainage process [5] [6]. Retention packages have been developed to improve first pass retention and offset the strength loss that often occurs; however, this approach has met with limited success.

The predominate filler used in the U.S. is precipitated calcium carbonate (PCC), which is manufactured on-site at many larger mills. PCC levels can range from 13 to 19% in free sheet grades. Historically, the predominate filler used in Europe is ground calcium carbonate (GCC) because fiber costs are higher and the GCC results in several percentage points of additional filler.

The original concept from Technology Summit I was to develop fillers with an oblate, spheroid shape and some desirable charge, so that the filler content could be increased without the sheet suffering undesirable losses in properties like bulk and strength [2].


Since Technology Summit I, trials on a commercial machine have shown that it is possible to double filler content. As a result of this and other developments, the Breakthrough Manufacturing Technology Task Force has calculated the positive economic impact on the industry that would result from tripling the filler content in some grades.

An 1800 tons/day mill running with approximately 17% filler purchases 300 tons/day filler, and makes or purchases 1500 tons/day fiber. A three-fold increase in filler content (please suspend disbelief until viewing the unique fillers described below) means that this mill could produce the same tonnage by purchasing or making 900 tons/day filler and making or buying 900 tons/day fiber. There are simple and complex ways to look at the change.

The simple and most conservative approach is to calculate the savings on replacing 600 tons/day of fiber with 600 tons/day of filler. Assuming a net cost savings of US$ 100 per ton, than the annual savings for this mill is approximately US$ 65 million per year.

This calculation--applied to 20 million tons of the estimated 50 million tons of paper grades produced in the United States each year [7] --would result in an increased cash flow to the industry of as much as US$ 1.3 billion per year.

We do need to track a few key assumptions. First is that the net cost difference is US$ 100 per ton. Current calculations are higher; however, when a pulp mill scales back from 1500 tons/day to 900 tons/day, the cost of pulp will go up. That is why we must look at the net difference, not the gross difference.


The second assumption is that fiber production is scaled back. If it is not, more complex calculations and evaluations must be made that will significantly improve the economics.

As fillers have no "inter lumen" water, an increase in press solids is also expected and has been demonstrated in pilot runs. This benefit will be additive when quantified in enough detail to be included. It has significant energy savings potential.


A key finding of Agenda 2020 work is that projects without benefit to society often lack the necessary drivers to move them to commercialization at a pace that sustains development. Replacing fiber with filler will result in a net energy savings. The fiber can be saved at that location or some other location (a complex cascading of events).

Using paper industry averages and estimates from one potential supplier [8] the savings are conservatively estimated at 20 MM Btu thermal/ton and 400 kWh/ton. Based on 7 million tons of fiber not produced, this is a gross savings of 140 trillion BTUs and 2.1 trillion kWh. Because half of the power would come from the "recovery" cycle in a mill, this is a net savings of 70 trillion BTUs thermal and 1.05 trillion kWh. Results are the same for integrated and non-integrated mills, as long as any fiber purchased was made in the U.S.


Technology Summit II focused on using novel calcium and silica-based fibrous fillers to significantly increase filler levels while improving product quality. Lab, pilot and commercial trials verified that these fillers could be used at double historical levels while maintaining or improving quality at an estimated cost saving of US$ 50 per ton. Participants generally agreed that the proof of concept was complete; the next step would be proof of process at a semi works or at an actual mill.

Fiber costs are different for an integrated mill than for a non-integrated mill. An interesting benefit would be increased production at larger mills. The ultimate objective and greatest potential would be for products with properties that cannot be achieved with today's raw materials.


These and other issues have been addressed in a series of developments since Technology Summit II and now there are a series of potential products from two sources. The following examples illustrate.

Example 1: The first researchers [9] have developed the following products:

* T2- a patented "super" PCC- where 3 forms are shown (see Figure 2)

* T4-a patented silicate macro particle (SMP)-(see Figure 3)

* T8-a patented silicate nano-fiber (SNF)-(see Figure 4)

Selected properties of T4 and T8 are shown in Table 1.

For a simple replacement application, T2 would be of interest to all mills using PCC. T4 would be of most interest to non-integrated mills, and T8 is a potential replacement for more expensive brightening fillers. Mixtures that can be produced from the same equipment can be engineered to meet specific objectives. Figure 5 shows one proposed arrangement. As shown, we have now emerged from a concept of fibrous fillers to engineered fillers.


It is likely that current economics are inadequate to be a driver in many integrated mills. To reduce filler costs, researchers are developing concepts to integrate the lime kiln with the filler making operations. One version would use lime mud. Another version would eliminate the lime kiln. Both are economically attractive. A discussion of these concepts is beyond the scope of this article but shows the reader continuing progress.


Example 2: A second set of researchers [10] has found that clay coated with starch significantly increases paper strength (versus unmodified clay). The project goal is to develop new bonding fillers to improve sheet properties while decreasing fiber costs. Targets include:

* 35% filler for copy paper

* 15% for newsprint

* 15% for tissue

* 15% for linerboard

Figure 6 shows tensile results for a "control sample" and samples with clay coated with two different starches at two different levels. The starch coated clay produced product with the same tensile strength but about 5 percentage points of additional filler.


The production process for these coated starches is relatively simple. The starch is cooked separately and conventionally, and the cooked starch is mixed under high shear with dry clay and water to the desired solids and starch content. The equipment required is shown in Figure 7.

The industrial partner believes that the research has already proven that:

* modified clay can be economically produced

* characterization of hand sheets shows promise

* modified clay can be produced in large quantities.


To better understand opportunities and challenges, the Breakthrough Manufacturing Technology Task Group of Agenda 2020 is updating and quantifying its roadmaps. So far, this process has involved considerable planning with the U.S. Department of Energy (DOE) as well as consulting firms with extensive roadmapping expertise. A small group of experts met to develop and quantify opportunity areas. A large group including DOE and experts from outside the industry met to refine and add to the information.


While the results are preliminary, it appears that overcoming the obstacles and mastering the opportunities on all goals would result in savings of up to 30% of manufacturing costs while reducing energy use by as much as 67%. It is clear that not all objectives can be fully achieved; however, it is also clear that there is sufficient reason to be excited about our future.


How does all of this relate to engineered fillers? While the prioritization process is not complete, it is likely that engineered fillers will emerge as one of the top three roadmap opportunity areas [10].



Engineered fillers appears to hold great benefit for both industry and society. The idea generated in Technology Summit I is now ready for proof of process at a semi-works or in an actual mill. In one advanced case, a mill could evolve into a forest biorefinery [12]. In this case there would be choices as to how to use the extra capacity. Presumably there would be the opportunity to take it as fiber capacity or as fuel/chemical capacity or the most economical split between the two. This benefit would be very mill specific. Agenda 2020 is developing the tools to facilitate decisions. The tie between Breakthrough Manufacturing technology and the Integrated Forest Biorefinery is very clear.

The most profitable case for industry and society would be to use the properties of the new raw materials to make new and improved products. It is not possible to make accurate forecasts about this goal today, but it is possible to see enough to be excited about our future.
Table 1.

 T4 T8

Diameter (nanometers) 100-200 50-200
Length (microns) 1.0-2.0 1.5-4.0
Aspect ratio 1.15-1.5 1.1-1.5
Brightness (ISO) 91-93 94-96
Water absorption (%) 250-400 400-800


[1.] Role of Agenda 2020 in Stimulating Forest Products Industry Innovation, TAPPI presentation by Del Raymond, Atlanta, Georgia, USA, April 15, 2004.

[2.] Setting the Industry Technology Agenda, TAPPI Press, Atlanta, Georgia, 2002.

[3.] Fibrous Fillers to Manufacturer Ultra High Ash/Performance Paper-Mathur. GR International ID14439,CPS #01872.

[4.] Initial results from Technology Summit II:

[5.] Effect of turbulence during drainage for high filler content paper, Knuts, Ebeling, Laine and Peura, Paperi ja Puu, No. 9, 1982.

[6.] Principles of twin-wire forming, Bo Norman, Svensk Paperstidning, No. 11, 1979.

[7.] 2004 AF&PA Statistics report, AF&PA, Washington, DC. Available to members only.

[8.] Private communication with American Process Inc. and GRI, Inc.

[9.] GRI's Filler Technology Introduction to the Center for Technology Transfer, Feb. 15, 2005 (unpublished).

[10.] High Filler Content of Paper and Board Products TIP 3 2004-2005 Mid-Year Report by IPST.

[11.] Breakthrough Technology Road maps to be published in 2005.

[12.] Agenda 2020 reachable goals can double pulp and paper industry cash flows, Thorp and Raymond, Paper Age, September and October 2004.


* How Agenda 2020 has sparked the development of concepts with high potential for industry-wide cost savings.

* How engineered fillers could increase filler rates for potential average savings of US$65 million per mill.

* Roadmapping progress that could lead to substantial savings in manufacturing costs and energy use.


* "Perspectives on Agenda 2020," A.D. "Pete" Correll, Solutions! May 2004. To access this article, type Product Code 04MAYS032 into the search field at

* The technology platforms of Agenda 2020, Del Raymond and Ben Thorp, Solutions! July 2004. Product Code: 04JULS045.

* Forest products biorefinery: Technology for a new future, Del Raymond and Gerard Closset, Solutions! September 2004. Product Code: 04SEPS049.


Benjamin A. Thorp, III, retired from Georgia-Pacific Corp., works as a consultant to the industry. Before joining Georgia-Pacific, Thorp served in manufacturing technology with Chesapeake Corp., process technology and engineering with James River Corp., engineering with BE&K, and research technology and various positions with Huyck Corp. He serves on the Boards of the Paper Industry Management Association, Besicorp-Empire Newsprint Company, KP Products and Meadowbrook Estates Civic Association, as well as the industrial advisory boards of Peregrine Corporation and ForestWeb. A TAPPI Fellow since 1986, he received the TAPPI Paper & Board Division Leadership Award in 1994, the PIMA Glen T. Renegar Award in 1999, and was named to the PIMA Leadership Council in 2000. Contact him by email at:
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Author:Thorp, Ben
Publication:Solutions - for People, Processes and Paper
Date:May 1, 2005
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Next Article:TAPPI's CorrPak[R] Competition moves to two-year cycle; recommendations sought.

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