Paper Recycling

(papermill Steyrermuel AG, Austria)

Flashback: Paper is a thin, flat sheet usually made from plant fiber. It was probably invented around 105 in China, where it was made from a mixture of bark and hemp. The Moors introduced the papermaking process into Spain in 1150. By the 15th century, when printing was developed in Europe, paper mills had spread throughout the continent. The basic papermaking process exploits the ability of plant cell fibers to bond together (H-bonding) when a pulp made from the fibers is spread on a screen and dried.
Today, paper is made principally from wood pulp combined with pulps from recycled paper (for finer grades of paper, with fibres from cotton rags). While paper is a product derived from renewable resources, its manufacture can have a harmful effect on the environment. On the one side, forestry management in the US, Canada include large-scale clear-cut logging. Even more unsustainable is aerial herbicide/pesticide spraying to reduce wood-losses due to endofauna or mycelia; this has widespread impacts on flora, fauna and groundwater. Often, such monocultural forest practices lead to forest devoid of natural life. On the other hand, pulp and paper production processes create some of the most toxic effluents that any industry can produce - especially if they still bleach pulp with bleaching agents other than ozone.
Nowadays, paper manufacturers respond to these environmental challenges by introducing sustainable timber harvesting practices (e.g. plantation timber) and by implementing pollution controls during the manufacturing process.
Compared with producing a ton of paper from virgin wood pulp, the production of one ton of paper from discarded "waste" paper uses half as much energy and half as much water. It results in 74% less air pollution and 35% less water pollution, saves 15% average size pulp trees, and reduces solid waste going to landfills.
Recycled paper can be easily incorporated into a closed recycling loop. Both consumer and producer should keep in mind that paper that left the paper mill, and gone through a printing process, is still a raw material of supreme quality. Furthermore, the removal of paper from the solid waste fraction lowers the total organic carbon content of the remaining solid waste fraction. The lowered gas-building potential results in chemically less reactive landfills.
Currently, household paper in Austria is collected directly from containers stationed in front of each block. Newspaper, wrapping paper, shredded documents, and cartonages are thus easily incorporated into the recycling system.

Collection: Across Austria, periodic pick-up services gather collected paper and deliver it to one of the major paper mills. Having visited the paper mill in Steyrermuehl, it will be the major reference point for the recycling steps referred throughout this page.

Household paper is of course quite heterogeneous in composition; thus, cannot be considered of the same high quality (purity) than office papers collected separately by many businesses. Household paper in average contains a fraction of 12-18% of non-useable ingredients. Indeed, plastic bondage, promotional extras sealed into plastics, or any additional inlay in form of a non-cellulose material (CD-Roms, syringes, blades, etc.) do lower its recycling potential and under extreme conditions must be disposed off separately. Office paper, on the other hand, is very homogenous, hence, can be directly incorporated into the paper making process with less precaution.

Recycled office paper

Preselection: While household paper is primarily used for lower class ingredients, it is reprocessed to obtain packaging or wrapping paper. Office paper on the other hand is a pure raw material and therefore utilized to produce high quality paper products. According to the final product, recycled paper can be added in varying percentage levels to the prime material without lowering its qualitative properties. Before doing so, the recycled material requires manual screening to guarantee that any of the disturbing materials mentioned above, do not interfere with the papers' final properties. Thus, both mechanical and manual preselection is required to make sure that the material fed into the complex process is kept at a preset qualitative level.
Þ For processing of non-reusable contents, refer to the plastic-, metal-, and residual waste section.

Manual preselectron

Processing: Once the paper has passed pre-selection, the material fed into the paper making process is soaked in water until the cellulose fibers become loose. Flotation removes any metallic and other constituents (stapler clamps, etc.), while bleaching (de-inking) yields the required pulp.
In general, newsprint paper contains about 50% recycled paper while the remaining other half originates from virgin timber. According to the final requirements, the content of recycled material can be increased as required to almost 100%.

Deinking process

Similarly, raw materials like tree trunks and wood chips undergo a different preparative process. For newsprint, tissue, and other inexpensive papers, woodchips or recycled papers are used. Here, wood chips are grinded in a separate TMP-process (thermo-mechanical pulp) before mixing with recycled paper and bleaching can take place.
High quality paper requires primarily virgin wood material. The trunks are cut into pieces of preset length, de-barked, shredded (grinder using a steel/stone surface structure), and floated with water. Finally, to remove both the ligneous brownish color, the soaked material is exposed to the bleaching agent - this process destroys the colligative properties of lignin.

Virgin wood and wood chips from wood plantations

Chemical pulp is made by boiling a mixture of wood chips using either soda, sulfite, or sulfate. This process removes lignin. The modern and more environmentally sound method involves the utilization of ozone as the main bleaching agent.

The pulp obtained from these manifold processes has a fibre content of only 1-1.5%. Before feeding it into the paper machine, additives like kaolin are mixed into the pulper. Kaolin is used to reduce the paper's absorptive properties during printing; the higher the Kaolin content, the shinier the paper. Writing papers on the other hand, contain a water-resistant substance such as rosin to prevent the ink from spreading out. Kraft paper, because of its strength, is used for bags and wrapping purposes; the sextra strength is obtained using sulfate as the main additive. Only then is the pulp fed into the machine where it is poured onto a wire screen. Here the water drains away and the fibres begin to mat. The paper layer then passes through a series of rollers and dryers, which squeeze, press, and smoothen the watery sheath to various finishes.

These various finishes can only be achieved when routing the strengthening sheath of paper through several units of such rollers and rotational hydraulic presses. Doing so reduces the aqueous content by 84%. Finally the bonded cellulose fibres are dried by routing the paper band through steam-heated kalander batteries (>100C). These batteries further reduce the water content to a 93% level. The paper is then ready to be collected by the pope roller. The visited paper mill utilizes the Voith DuoFormer tamboure; it has a working speed (paper output) of roughly 1600m/min.
Several packing machines (Streampack-Turbo) unfold the 9m wide pope-rolled paper cylinders and splice it into the dimensions as requested by the customers.

Tamboure Roller

Such a high output has enormous energetic requirements. Based on company information, the requirements of this particular paper mill amount to roughly 600kWh/ton of paper. These are met by several hydroelectric power stations (5 stations situated along the river Traun) which cover about 5% of the total. The use of the fluid bed furnace in which biodegradable matter (bark, etc.) is incinerated, powers an attached thermoelectric generator, which covers another 15% of the electrical demand. About 60% of the electrical demand is covered by steam driven gas-turbines and originates from the combustion of natural gas. The steam exiting the turbines is further utilized in the drying process of the kalander batteries. The remaining 20% in this particular plant are provided by external suppliers.
Þ For energetic demands (electricity, and steam), and its secondary uses (district heating network), refer to the residual waste (incinerator).

The huge amount of water needed to maintain the entire paper-making process (about 1.5 ton water per ton of paper) is re-circulated within the plant. Water contaminated during the deinking process (23×E3m3/day) is reprocessed at the plants own depurator, and operates on a mechano-biological cleansing principle.
Þ For wastewater management during the processing of pulp, refer to the sewage-section.

The Voith DuoFormer paper machine

Finally there remains the question of how much raw material is required to obtain 1kg of wood? Europe manufactures several brands of high quality office papers, and most people are familiar with purchasing these in reams of 500 A4-sized sheets. Speaking of office paper one can calculate that it made of roughly 80% bleached pulp. With each ream (500 sheets) weighing about 2.5kg, this corresponds to about 2kg of air-dried pulp. To make this pulp requires about 3.6kg of oven-dried wood (or around 7kg of "fresh" wood - the yield is strongly dependent on the tree species used and is expressed in the paper-conversion factor; here 1.94). With a 15m tall and 0.5m thick tree (approximate volume of 3m3) and a species-dependent density of ~0.5E3kg/m3 converts to 1.53kg of wood per plant. After harvesting and chipping, this makes about 1.23kg of woodchip (wet weight). Using the above mentioned paper conversion factor of 1.94 yields an average of 617kg of paper per tree. This may seem a lot, but keeping in mind that it takes about 20 years for a tree to reach harvestable dimensions, this number does not at all seem that impressive. With a European per capita consumption of 100 kg ( US: 300kg/yr/head, 1993 data) its easy to calculate how many trees are wasted - especially when printing on one side only.


References: Unser Unternehmen (1999); Steyrermuehl AG, Fabriksplatz 1; A-4662 Steyrermuhl - AT
Umwelterklärung 1999; Steyrermuehl AG, Fabriksplatz 1; A-4662 Steyrermuhl - AT
Fry T. (1992); Green Desires; EcoDesign Foundation Inc.; University of Sydney, NSW - AUS
For additional information visit the Steyrermuehl web-site at, or any of the listed:
http://the history and making of paper
http://www.steyrermuehl.at/
http://www.valmet.com
http://www.voithsulzer.com/
http://Paper Consumption
http://how many trees per kg paper?
http://www.timbercorp.com.au
http:// some calculations/
http://www.tve.org/earthreport/archive/doc.cfm?aid=1315

Intro / Paper / Glass / Plastic / Metal / Compost / Toxic / Residual / Sewage / Landfill