ECO-RUBBER: Crumb recycled rubber as a raw material for new urban furniture products

Every year, more than 3.2 million tons of used tyres are generated in Europe. There are significant adverse environmental impacts of landfilling tyres: apart from taking up a disproportionate amount of valuable landfill space, it can be a breeding ground for vermin, a source of contaminated leachate, and a considerable fire hazard causing major environmental impacts, including effects on air, water, and soil quality. Consequently, the European Union banned landfilling of whole tyres since 2003 and shredded tyres since 2006 (EC Directive 1999/31) having emerged a new end-of-use-tyre managementNowadays, among the applications made of tyre recycled crumb rubber chips,  horse arenas for dressage, animal pens, and fillers for sports equipment are included. Crumb recycled rubber is also used together with binders to manufacture children’s flooring that provides protection in playgrounds. Up to 20% of binders (adhesives), generally polyurethane prepolymers reacted with diisocyanates, are added for manufacturing agglomerated rubber products. Other ingredients (fillers) such as carbon black, softeners and surfactants are used to stiffen or strengthen the rubber, to improve the workability of the material or to enhance some properties such as UV or fire resistance. The use of chemicals may prevent further recycling of products and it may cause problems in some applications (children contact) when products are used.

So far, there was no crumb recycled rubber application in high quality products using recycled rubber as a main raw material, but now the first crumb recycled sintered product, a bollard, was manufactured. To develop this product AIMPLAS, Instituto Tecnológico del Plástico, is coordinating ECO-RUBBER project, together with Instituto de Biomecánica de Valencia (IBV) and the enterprises RECIPNEU - TYRE RECYCLING NATIONAL ENTERPRISE LTD and BERLÁ, S.A.

The main goal of ECO-RUBBER has been to adapt the current industrial rubber recycling process to supply innovative recycled rubber urban furniture products manufactured by an innovative sintering process as an alternative to virgin rubber, wood or concrete products.

The crumb recycled rubber obtained in current grinding plants is not suitable for the sintering process. It has been necessary to adapt a grinding line to obtain a crumb recycled rubber with the appropriate requirements for the sintering process; a narrow distribution, rough surface and zero contaminants (textiles fibber, steel, sand…). This adaptation has been the first step in the project. Currently, the design, selection and assembly of grinding ferrous and textile decontamination and size separation equipment are completed. The optimization of the grinding process is nearly finished and partner RECIPNEU is starting the industrial production of optimized crumb recycled rubber.

A bollard was chosen as the urban furniture application to develop within the project due to the fact that a bollard made of recycled rubber represents the advantages of an urban application made of recycled rubber, mainly because the material’s elasticity might reduce the risk of injuries as a result of hits or accidents against them and it is believed to exist a high potential market demand of this product. Furthermore, due to the variety of materials bollards are made of, it will be possible to obtain the advantages of the recycled rubber bollard from a virgin one and from a bollard made of other material such as concrete, steel, etc. Once all specifications regarding standards and emotional aspects were obtained, a preliminary bollard design was proposed, being optimized by means of a Finite Element Analysis (FEA) by partner IBV. Based on this, the final bollard design was selected and the mould design and construction was fulfilled.

In the sintering process proposed in the ECO-RUBBER project, high pressure and temperature is applied over a closed mould filled of pre-heated ground recycled rubber and some additives to make the rubber molecules become cross-linked and obtaining a consistent material. Referring to the sintering plant facilities, nearly all the equipments have been designed, selected and assembled, having manufactured the first production series in order to assess the production line and start with the optimization phase. Furthermore, it was demonstrated that the addition of additives to the base crumbing material improves their properties and currently the final formulation at industrial level is being developed at partner BERLÁ’s plant.

To eliminate the emotional barriers from the use of urban furniture made of recycled rubber, an eco-label was foreseen to be implanted in the bollard, showing the benefits of the use of this kind of recycled material. However, there is no recycled rubber eco-label at European level so, after reviewing all the existing rubber eco labels throughout the world and based on their requirements, it was agreed to complete an environmental self-declaration of the bollards and to apply for a new eco-label group to include a European eco-label of recycled rubber products.

From an environmental point of view, the ECO-RUBBER project will contribute to divert the end-of-use tyres from landfilling and incineration to recycling and to reduce the quantity of natural resources to be used in the rubber manufacturing process. Crumb recycled rubber, developed within ECO-RUBBER project, could be a valuable alternative to the use of natural or synthetic rubber for obtaining a wide range of commercial and industrial products with not very high requirements such as some types of rubber wheels, rubber buffers or cycle track separators, allowing to manufacture sustainable products decreasing the final price and as a consequence, being more competitive in the market.

Based on previous Life Cycle Assessment, where recycled rubber was compared to Styrene-Butadiene Rubber (SBR), it was sorted out that the new products developed according to the ECO-RUBBER project sintering process, will have a lower environmental impact compared to those made of rubber, reducing around 88% in energy consumption and 72 % in greenhouse gases emission. Furthermore, the products made of recycled rubber will present recycled properties. This means that the used product could enter again the grinding /sintering process proposed in ECO-RUBBER obtaining a new product with similar properties to the previous one used as a raw material for the grinding process.

These environmental advantages together with market expectations encouraged the consortium to implement the industrialization process that is described in this article.

ECO‐RUBBER “Innovative used tyres recycling and rubber sintering process for eco-friendly urban equipment fabrication” is a CIP Eco-innovation Pilot and market replication project. (ECO/08/239112/SI2.535300). The project has a total duration of 36 months (from July 2009 to December 2011).

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