In the last century, the economic growth and the petrochemical industry rise have been accompanied by a worldwide diffusion of polymers for a large variety of applications. However, only recent years have seen a growing attention on the consequences, in terms of environmental pollution and energy consumption, of the unconditional use of plastic. In the present work, exergy is used as a measure to quantify the resource consumption during the life cycle of polymers, from their production to their mechanical or chemical recycling. Nine of the most used polymers are chosen and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) of polymers is calculated as the sum of the contribution of each step of the chain, including the production process (i.e. polymerization and production of molecules from petrochemical by-products) and the Exergy Replacement Cost (ERC) of the fossil fuel (the “naphtha to coal” and the “coal to biomass” steps). A comparison with the thermodynamic rarity of abiotic materials is also reported, using a vehicle as reference product. Then, the most suitable recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the new crude polymeric material (primary product) and the oil derivatives or structural molecules (secondary products). The main results show that some commonly used polymers have a higher than expected impact in terms of embodied exergy (e.g. PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. For some polymers (e.g. PA, SBR, EPDM) the invested exergy appears not as high as for justifying the extremely low diffusion of recycling practices in the world.

Exergy-based approach to evaluate the life cycle of polymers: from production to recycling / Russo, Sofia; Valero, Alicia; Valero, Antonio. - ELETTRONICO. - (2020). (Intervento presentato al convegno THE 33RD INTERNATIONAL CONFERENCE ON EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS tenutosi a OSAKA, JAPAN nel JUNE 29-JULY 3, 2020).

Exergy-based approach to evaluate the life cycle of polymers: from production to recycling

Sofia Russo;
2020

Abstract

In the last century, the economic growth and the petrochemical industry rise have been accompanied by a worldwide diffusion of polymers for a large variety of applications. However, only recent years have seen a growing attention on the consequences, in terms of environmental pollution and energy consumption, of the unconditional use of plastic. In the present work, exergy is used as a measure to quantify the resource consumption during the life cycle of polymers, from their production to their mechanical or chemical recycling. Nine of the most used polymers are chosen and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) of polymers is calculated as the sum of the contribution of each step of the chain, including the production process (i.e. polymerization and production of molecules from petrochemical by-products) and the Exergy Replacement Cost (ERC) of the fossil fuel (the “naphtha to coal” and the “coal to biomass” steps). A comparison with the thermodynamic rarity of abiotic materials is also reported, using a vehicle as reference product. Then, the most suitable recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the new crude polymeric material (primary product) and the oil derivatives or structural molecules (secondary products). The main results show that some commonly used polymers have a higher than expected impact in terms of embodied exergy (e.g. PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. For some polymers (e.g. PA, SBR, EPDM) the invested exergy appears not as high as for justifying the extremely low diffusion of recycling practices in the world.
2020
978-1-7138-1406-1
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2853797