Field: Substitution
Global Technical function: Grinding, Manufacturing
Technical Function Unit: Cryogenic grinding, Labelling, Magnetic separating, Mechanical separating, Mixing, Re-manufacturing, Sintering
Geographic Area: Spain

ECORUBBER

Current tire compositions include a wide variety of additives and compounds, including several types of rubber, carbon black, silica, polyester, etc. End-of-life (ELF) tires are considered as non-hazardous waste according to the Waste Directive and the European Waste List, but their landfilling is forbidden according to the Landfill Directive.

In 2007, the EU-27 countries produced around 3.4 million tonnes of ELF tires, but only 38% was recycled for civil engineering applications and rubber grounds. Approximately 32% of ELF tires are used as fuel in cement kilns, thermal powers and other sectors (such as paper mills, steel mills, etc.), thereby increasing the ELF tires recovery rate but leading to harmful emissions. These reuse strategies appear to be insufficient, considering that the ELF Vehicle Directive sets a target of 95% recovery/reuse rate of vehicle components by 2015. So, developing new technologies for remanufacturing ELF tires could be helpful for reducing the amount of waste.

A consortium of technical institutes and industrial companies from Spain (Berlá, Instituto Tecnológico del Plástico and Instituto de Biomecánica de Valencia) and Portugal (Recipneu) has developed an innovative process for recycling ELF tires. ECORUBBER aimed at implementing this eco-friendly process in order to obtain high quality urban street furniture elements (i.e. bollards). The project, funded by the EACI under the CIP Eco-innovation call, was carried out from 2009 to 2011.

Given that vulcanised elements are very hard and resistant, it is difficult to cope with the recycling of ELF tires. A two-step approach has been set up to tackle this issue. In a first step, an improved grinding process (involving both mechanical and cryogenic grinding) for obtaining rubber powder has been developed in the project. After a further mechanical separating step (sieving), the powder which has been obtained was characterised by particle sizes lower than 0.6 mm and high specific surface areas, but they needed to be purified. So, magnetic separating and densimetric separating processes were applied to remove, respectively, ferrous and textile impurities. The powder which was obtained was compounded with substances maximizing tensile strength and elongation of the raw material. These properties were also attained by getting a narrow range of powder size. As a result, from 60 to 89% of recycled rubber powder was incorporated to the final raw material, thereby ensuring the recycling of ELF tires and granting the good performance of bollards.

In a second step, advanced mixing and sintering processes were applied for manufacturing the new bollards. A device comprising a headframe pre-dosifier connected to an automatic timer and a suspended mixer was developed for combining and heating the raw materials and additives. The equipment was modified (adding and modifying Mixers, pneumatic feedings and heating chambers) for obtaining the desired bollards. These new products have been tested via impact tests. They have shown that 89% rubber-based bollards were 4-fold safer than conventional metallic devices. Moreover, they produce less friction and scratch failures when vehicles crash against them. As a consequence, the substitution of conventional metallic bollards with these innovative products could be significantly advantageous.

The environmental feature of this new product has also been validated during the project; a Life Cycle Analysis was carried out, demonstrating that these new bollards are really environmental-friendly.
Furthermore, the labelling of the new bollards was also obtained by conducting a design study.

The project ended in 2011, providing product ready for commercialisation, so it reaches a level 9 on the TRL scale. Although bollards have been selected as a representative product, many other suitable products dealing with various sectors (not only road safety) could benefit from this new tire-recycling technology.