Abstract
The merits of temporary carbon storage are often debated for bio-based and biodegradable plastics. We employed life cycle assessment (LCA) to assess environmental performance of polyhydroxyalkanoate (PHA)-based plastics, considering multiple climate tipping as a new life cycle impact category. It accounts for the contribution of GHG emissions to trigger climate tipping points in the Earth system, considering in total 13 tipping elements that could pass a tipping point with increasing warming. The PHA was either laminated with poly(lactic acid), or metallized with aluminum or aluminum oxides to lower permeability of the resulting plastics toward oxygen, water vapor and aromas. The assessments were made accounting for potential differences in kinetics of evolution of greenhouse gases (CO2, CH4) from bioplastic degradation in the end-of-life. Results show that: (1) PHA films with high biodegradability perform best in relation to the climate tipping, but are not necessarily the best in relation to radiative forcing increase or global temperature change; (2) sugar beet molasses used as feedstock is an environmental hot spot, contributing significantly to a wide range of environmental problems; (3) increasing PHA production scale from pilot to full commercial scale increases environmental impacts, mainly due to decreasing PHA yield; and (4) further process optimization is necessary for the PHA-based plastics to become attractive alternatives to fossil-based plastics. Our study suggests that multiple climate tipping is a relevant impact category for LCA of biodegradable bioplastics.
Highlights
This study focuses on production of polyhydroxyalkanoate (PHA) from sugar beet molasses
To provide additional insights to the metrics of climate change recommended in the EU Commission's ILCD Handbook (ISO, 2006; EC-JRC, 2010), we present the inclusion of a new life cycle impact category, the multiple climate tipping (Fabbri et al, 2021)
It accounts for the contribution of greenhouse gases (GHGs) emissions to trigger multiple climate tipping points in the earth system
Summary
This study focuses on production of polyhydroxyalkanoate (PHA) from sugar beet molasses. E.g. renewable materials like sugar, industrial waste and by-product streams, as well as CO2, which can be utilized by cyanobacteria types (Koller, 2017; Kookos et al, 2019; Moretto et al, 2020; Wongsirichot et al, 2020) This makes PHA a versatile plastic type within the bioplastics and bio-based plastics. It is necessary to improve the barrier properties to lower permeability if PHA is to be used in contact with food (Struller et al, 2014) This can be done by lamination with (poly)lactic acid (PLA) or metallization with aluminum (Al) or aluminum oxides (AlOx) (Kassavetis et al, 2012). It accounts for the contribution of GHG emissions to trigger multiple climate tipping points in the earth system (up to 13 tipping points)
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