Life cycle assessment of electricity generation by tire pyrolysis oil

Abstract

The disposal of used vehicle tires at the end of their life time, is a significant environmental concern. There is need for specific legislative framework, regulating their disposal, after these are replaced, however, there are several options for further processing. In the framework of circular economy, recovery methods and new applications for the material are available. This paper examines the life cycle environmental impacts of the pyrolysis of End of Life (EoL) tires and the use of the produced Tire Pyrolysis Oil (TPO) for generation, presenting a Life Cycle Assessment (LCA) for a 17.8 MW designed generation unit in Cyprus. The boundaries of the system under study start from the receipt of shredded used tyres, and include the pyrolysis process, the electricity generation and the management of by-products, pollutants and waste for a case study about a unit designed to operate in Cyprus. Two Functional Units (FU) are used, 1 Kg of TPO and 1 MWh of produced electricity. A detailed Life Cycle Inventory (LCI) is presented and moreover, by applying the CML 2001 impact characterization method, the magnitude of a number of characterization factors are calculated for both of them. These results are compared to the respective of Light Fuel Oil (LFO) and of Cyprus grid electricity as alternatives. While, the TPO found to have lower environmental impact than LFO for all the impact categories, the production of electricity at the unit cause higher potential of depletion of abiotic resources – elements and marine aquatic ecotoxicity potential than the grid electricity. Specifically, the first, for 1 MWh produced in the unit under study, is 0.00026 kg antimony eq. and the second 171666.4 kg 1,4-dichlorobenzene eq., while for 1 MWh of Cyprus grid electricity they are 0.00013 kg antimony eq. and 136095.2 kg 1,4-dichlorobenzene eq., respectively. A contribution analysis, for these two impact categories is presented, showing that the use of urea and the production of solid waste to the unit contributes the most to both plus the exhaust gases to the second, therefore specific suggestions to minimize the contribution are formulated, available to be exploited for similar units. Moreover, concluding that the TPO use for generation could be an advantageous environmental option, recommendations for its strategic adoption are also made.