Papermaking Solid Waste Composition and Characteristics
As shown in Fig. 10.5 most of the German paper industry’s waste is generated in recovered paper processing. To produce recycled fiber pulp suitable for use in the manufacture of different paper and board grades all substances likely to disturb the processing of recovered paper or the quality of the final product must be re¬moved as far as possible from the disintegrated recycled stock. Depending on the contamination of the recovered paper with non-paper components and the paper grade produced, larger or smaller volumes of waste result.
The volume also de¬pends on the amount of effort invested in separation at the different process stages. Table 10.2 shows the percentages of waste amounts related to the recovered paper used and dependent on the paper and board grades produced.
Table 10.3 shows the composition of waste that occurs at different stages of recovered paper processing
Sludges also result from process water clarification and biological treatment of wastewater. The sludge from wastewater treatment plants can be divided into pri¬mary sludge from mechanical treatment and bio-sludge from biological treatment. It is technically possible to return these sludges to the production process in man¬ufacturing paper grades as corrugating medium or testliner. Because the in-mill reuse may affect product quality and process runnability the use as raw material in production processes must always be considered on a mill-by-mill basis.
The amount and characteristics of ash resulting from energy generation and flue gas cleaning depend on the fuel and the combustion technology used. In the Ger¬man paper industry the total amount of ashes in 2001 was 400 000 tons. Like all other wastes from pulp and paper processing, the ashes are non-hazardous and were mainly used in the construction material industry.