In Austria, 50.000 tonnes of scrap tyres are generated every year, about 30.000 of which are used as refuse derived fuel in cement kilns.
According to the EU waste directive 2008/98/EG, the treatment of waste is prioritised in a rigid hierarchy: Avoidance – reuse – mechanical recycling – energetic recovery – disposal. In Austria, 50.000 tonnes of scrap tyres are generated every year, about 30.000 of which are used as refuse derived fuel in cement kilns. Despite the utilisation of the iron contained in tyres for the production of cement, this treatment is regarded as energetic recovery and therefore only on the fourth place of the waste hierarchy.
The Austrian Ministry of Environment is aware that this hierarchy does not always lead to the ecologically most advantageous solution, and allows overruling the waste directive for the sake of an ecological benefit. In order to assess the ecological expedience of energetic recovery of scrap tyres in cement kilns in comparison with two different ways of mechanical recycling, a study was commissioned.
The method of Cost-Benefit Analysis (CBA) is a widely used tool for the assessment of public decisions. It allows to compare two or more scenarios and leads to a result expressed in monetary units.
Welfare-Cost-Benefit Analysis is a modification of CBA, which is foreseen to include environmental and social aspects to comprise all three pillars of sustainable development. These aspects are quantified, converted into monetary units which allows to add up all effects into a single integrated result. Amongst different possible ways of monetizing environmental effects, avoidance costs are used; social effects are not considered in this study.
The study shows that there is at least no proof that the two mechanical recycling options considered for scrap tyres (additive in asphalt and material for sports flooring) are better than the energetic recovery in cement kilns from the ecological point of view. Whereas the environmental effects of scrap tyres in cement kilns are well defined and published yearly, there are uncertainties about the health and safety risks of the mechanical recycling options. Moreover, using potentially hazardous material (like scrap tyres are) as a substitute for new material can lead to a dissipation of the material and a postponement of the actual problems. Altogether, at the moment there are too many open questions regarding mechanical recycling of scrap tyres to tell which recycling or recovery path is the most advantageous one.
What was the concret benefit?
The study provides arguments why the two considered options of mechanical recycling are not necessarily better than energetic recovery of scrap tyres, if the whole life cycle and environmental aspects are considered. It also comprises a summary of the most important open questions that need to be answered in future research before a final decision can be made