Energy and environmental assessment of solid recovered fuels valorisation: Waste-to-Chemicals options vs co-combustion in cement plants

Abstract

The increasing interest in Waste-to-Chemical (WtC) technologies operating with Solid Recovered Fuels (SRF) from non-recyclable plastic streams requires a quantitative analysis on the actual convenience of this alternative valorization pathway.

This study assesses SRF in selected WtC technologies for hydrogen and methanol production and compares it with the well-established practice of co-combustion in the cement industry. Two case studies are considered: the first one represents the current scenario where SRF is used in co-combustion for cement production meanwhile the chemical is produced by steam reforming; in the second scenario, the cement plant is fed with pet-coke only, leaving SRF as a feedstock for WtC.

WtC performance assessment has been carried out in Aspen Plus®, whereas cement production and steam reforming have been characterized based on literature information.

The two scenarios have been assessed for two SRF qualities (different LHV and biogenic content) calculating primary energy and fossil CO₂ emissions.

The results show that SRF from plastic waste as a feedstock in WtC is less effective than its utilization in cement plant: when WtC technology for hydrogen production is adopted, additional 9.1% (SRF-1) and 8.6% (SRF-2) of energy consumption is estimated and 25.8% (SRF-1) and 24.1% (SRF-2) additional fossil CO₂ is emitted with respect to the corresponding conventional cases (i.e., chemical from steam reforming and SRF burnt in the cement kiln). When considering methanol production, WtC technology requires 6.2% (SRF-1) and 5.6% (SRF-2) increase of primary energy and 30.2% (SRF-1) and 28.4% (SRF-2) additional fossil CO₂ against the conventional cases.