Sludge and fly ash from paper industry could be reused in plastics production

Up to half of oil-based polypropylene can be replaced with paper industry side streams. Two Finnish companies have made a trial batch of floor tiles and storage containers, of which side streams accounted for 30%.

As part of the European Union’s Reffibre project, Finland’s VTT Technical Research Centre (VTT) examined whether new industrial applications could be developed for various types of sludge and fly ash generated by the paper and board industry.

Large quantities of various side streams are created during the manufacture of paper and cardboard. Part of these can be used instead of natural aggregates as a raw material in concrete or asphalt, or in construction. Large amounts of side streams still end up in landfills and incineration.

However, laboratory tests showed that these side streams can replace up to 50% of oil-based polypropylene. They can be used as a raw material in plastic composites, which are made using injection moulding and extrusion. They could also be used to lower composite manufacturing costs, reduce the environmental impacts of production, and lower the total amount of waste. This would also reduce the production of oil-based plastics.

Laboratory tests showed that 50% of the raw materials in injection-moulded composite could come from paper and board industry side streams. The amount of side streams has an effect on the product’s properties: strength, stiffness, heat resistance, appearance and the texture of the surface.

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During the project, companies produced floor tiles and storage containers, of which side streams accounted for 30%. According to a press release from VTT, new applications are continually being sought, which could include pallets and crates, for example.

However, the press release did say that possible legal restrictions still have to be explored prior to the product-specific use of side streams in composites. There was no mention of how these side streams might be used in Canada or North America.

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