PROJECT DESCRIPTION
BACKGROUND
Europe produces some 3.2 million tonnes/yr of waste tyres. The properties that make rubber tyres desirable as a consumer product, such as durability, heat resistance and traction, also make their disposal and reprocessing difficult. They are almost immune to biological degradation. When tyres are not properly managed and disposed of, they represent certain risks to public health and to the environment. Although the Landfill and End of Life Directives are having a positive impact on the management of ‘end of life’ tyre waste, over reliance on rubber-derived products, particularly tyres, still continues.
OBJECTIVES
The DEPOTEC project proposed a depolymerisation process which will add
value to the waste tyres by producing products that can be used as
substitute carbon filler materials in the rubber manufacturing process.
The current carbon filler materials have high emissions associated with
their production processes. This would ultimately lead to a reduction in
stockpiling of tyres as they will now become valuable raw materials for
the production of these products. It will also offer an alternative to
burning end of life tyres to produce tyre-derived fuel. The project
aimed to design, plan and construct a demonstration ‘ZeroWaste’ plant for
depolymerisation of end-of-life tyres that is able to recycle a
significant quantity of waste tyres per year and be financially viable
on the basis of its byproducts. This plant would be self sustained, and
new products would be created from waste with minimal energy consumption.
The project aimed to demonstrate the viability of future mainstreaming
of the process by processing a significant volume of end-of-life tyres
into a microporous carbon material with absorbent properties over the
duration of the project. The most effective testing procedures, based
on current best practise, for gauging the technical quality of the
products of this process would be assessed and the project would also
contribute to the development of a comprehensive series of environmental
standards that would facilitate the accreditation of the products of
recycling of end-of-life tyres (e.g. through the European Eco-Label).
The overall end result would be the development of a technology that can
be transferred and utilised throughout Europe to enable value-added
products to be produced from waste.
RESULTS
The DEPOTEC project constructed a tyre depolymerisation pilot plant in the laboratories of the associated beneficiary, AUTH, in Greece. This pilot plant, which produces new value added carbon products that can be used as a replacement filler material in the rubber industry, was then scaled up in Ireland by another associated beneficiary, PGE. This plant used a rotary kiln reactor capable of processing 100 kg of end-of-life tyres every hour. The project team moreover demonstrated that the plant could stably operate for more than 100 hours, thus confirming its replicability. Licensing restrictions, however, meant that the annual capacity of the plant was reduced from 1 000 tonnes to 50 tonnes.
Additionally, the process produced gas with a lower heaving value (LHV) of 24MJ/NM3, which is sufficient to meet the energy needs of the plant, thus decreasing the cost of its operations. External power supply is required only during the initial stages of the process. As well as use as a carbon filler material, the recovered carbon can also be used in the production of activated carbons, but the project’s economic viability requires greater development of the tyre-recycling sector.
The project team cooperated with several pyrolysis companies in Europe and the US to assess the opportunities for exploiting the technology. The dissemination of the know-how built up over the project has led to inquiries from several SMEs that are active in this area. Finally, the project highlighted key areas for improving the current Waste Framework Directive, especially the classification of pyrolysis as incineration. It carried out advocacy work on the 'end of waste' criteria that need to be reviewed.
