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Ex-ante life cycle assessment framework and application to a nano-reinforced biopolymer film based on mango kernel

https://doi.org/10.1016/j.resconrec.2022.106637Get rights and content

Highlights

  • Ex-ante LCA has great potential to drive sustainable biopolymers development.

  • A framework for ex-ante LCA of biopolymers at low TRL (3–5) is proposed and applied.

  • Starch nanocrystals and film production upscaled using process calculations.

  • Environmental hotspots identified: starch drying, use of acid and plasticiser.

  • Change of reactant and yield gains show substantial impact reduction potential.

Abstract

This article proposes a framework for ex-ante life cycle assessment (LCA) of biopolymers at low TRL, including: (i) scale-up; (ii) scenarios for processes and modelling choices; (iii) comparison with a fossil-based polymer, considering material substitution factors. The framework was applied to analyse a mango kernel starch (MKS) film and compare it with low-density polyethylene (LDPE). Mango seeds (feedstock) were modelled as burden-free since they do not have economic value (baseline). An industrial-scale model was built for the production of starch nanocrystals (SNC) and MKS film using process calculations based on experimental data. Most impacts occur at starch and SNC extraction due to steam and acid consumption. Compared to LDPE, MKS performs better in non-renewable energy use but worse in climate change, freshwater eutrophication, and terrestrial acidification. Scenario analysis showed that yield enhancement and acid shifting could considerably reduce impacts. The proposed framework shows potential to support sustainable innovation of biopolymers.

Introduction

Single-use plastic films are produced and discarded in enormous amounts each year; consequently, they often end up accumulating in landfills (Barlow and Morgan, 2013; Chen et al., 2021). Researchers have been looking for new ways to produce bio-based polymer films at a laboratory scale to find sustainable alternatives (e.g., Leceta et al., 2014; Silva et al., 2019). Promising examples are thermoplastic starches synthesised from food wastes (e.g., fruit peels and pits), which are biodegradable and compostable, and may divert biomass from landfills, delaying methane emissions (Hottle et al., 2017; Lambert and Wagner, 2017).

Various life cycle assessment (LCA) studies focused on biopolymer films at early R&D stages using laboratory-scale inventory data (Deng et al., 2013; Leceta et al., 2014) or a combination of both lab- and industrial-scale data (De Léis et al., 2017). However, researchers have shown that LCAs based on lab-scale data do not necessarily represent a future industrial-scale production and may give misleading results (Gavankar et al., 2015; Hetherington et al., 2014; Piccinno et al., 2018).

Ex-ante LCA can be defined as studies that upscale an emerging technology (at a low technology readiness level) and compare them to an established one (Cucurachi et al., 2018). A few ex-ante LCAs have focused on novel biopolymers (Durkin et al., 2019; Fernández-daCosta et al., 2015; Tecchio et al., 2016). However, to our knowledge, none assessed novel thermoplastic starches (TPS), biopolymers produced from agri-food wastes, or nano-reinforced biopolymers (bionanocomposites).

Mango seeds have been used to produce biopolymer films in the laboratory (Cordeiro et al., 2014; Oliveira et al., 2018; Silva et al., 2019). Oliveira et al. (2018) obtained a mango kernel starch (MKS) film reinforced with starch nanocrystals (SNC) with promising mechanical properties (e.g., tensile strength: 17.5 MPa) intended for application in food packaging and coatings. MKS extraction has also been assessed in an ex-ante LCA (Pereira da Silva et al., 2021), but so far, no LCAs have been performed on MKS films.

Some notable methodological contributions include ex-ante LCA and eco-design frameworks for novel bioproducts (de Araújo e Silva et al., 2020; Pereira da Silva et al., 2021). These authors have inserted LCA in the TRL scale and proposed a sequence of steps to carry out within TRL 3, 4, and 5. However, both studies focused on the scale-up procedure using process simulation software, which is not always accessible and demands much time and expertise in chemical or process engineering. Consequently, such approaches are less easily applicable to other product systems. Furthermore, both studies do not address matters critical to biopolymers, such as functionality and comparability between novel biopolymers and their (mature) fossil-based counterparts.

This article proposes a framework for ex-ante LCA of biopolymers at low TRL (3–5), i.e., produced at lab scale. The framework includes: (i) scale-up approach; (ii) scenario analysis to cover process changes, manufacturing techniques, and modelling choices; and (iii) a comparison with a fossil-based polymer on a same-weight (1 kg) basis and using material substitution factors. The framework is applied to assess the environmental impacts of the future production of a biopolymer film produced from mango seed kernels (waste from mango processing) and to find improvement opportunities. Scenarios for yield, acid shift, film manufacturing techniques, as well as modelling choices (concerning waste burdens and allocation), are analysed. The results for this novel film are compared with low-density polyethylene (LDPE), its fossil counterpart.

This paper contributes to the limited knowledge on the environmental impacts of waste-based and nano-reinforced biomaterials, sheds light on the methodological challenges of conducting ex-ante LCA for novel biopolymers and discusses some ways to address them.

Section snippets

Material and methods

The proposed framework for ex-ante LCA of biopolymers is presented in Fig. 1. This framework aims to advance the LCA methodology (from ISO, 2006) by adjusting the LCA stages for novel biopolymers at early development stages, as follows. In the goal and scope, functional unit, system boundaries, allocation procedures, and scenarios are defined. In the inventory analysis, for components (materials and processes) at low TRL, data can be retrieved from simulation studies when available in the

Results

This section presents the main results of this study, including the laboratory and industrial-scale life-cycle inventory obtained (section 3.1); impact assessment and hotspot analysis results (section 3.2); scenario analysis – combining model (M1-M3) and improvement (P0-P4) scenarios–, as well as a 1-kg basis comparison to LDPE (section 3.3).

Discussion

This section discusses the functionality of the biopolymer film and its comparison to LDPE (4.1), compares our results to other LCAs on biopolymers (4.2), and recognises some limitations of the study (4.3).

5 Conclusions

This article presents a framework for ex-ante life cycle assessment of novel biopolymers at early research and development stages. The framework includes three major components: (i) scale-up modelling, (ii) scenario analysis, and (iii) comparison with a fossil-based polymer considering material substitution factors. The main advantage is a combination of modelling approaches. Scale-up modelling based on process calculations methods is suggested to facilitate inventory and scenario building.

CRediT authorship contribution statement

Jade Müller-Carneiro: Conceptualization, Writing – original draft, Visualization, Methodology. Maria Cléa Brito de Figueirêdo: Conceptualization, Writing – review & editing, Resources. Carla Rodrigues: Conceptualization, Visualization, Writing – review & editing. Henriette Monteiro Cordeiro de Azeredo: Investigation, Validation. Fausto Freire: Conceptualization, Writing – review & editing, Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was supported by Fundação para a Ciência e a Tecnologia, Portugal (FCT) and the European Regional Development Fund (FEDER) under project SET-LCA (CENTRO-01-0145-FEDER-030570). This research was developed in the scope of the Energy for Sustainability Initiative of the University of Coimbra. The first author is grateful for the financial support from the FCT through the MIT-Portugal PhD grant PRT/BD/152836/2021. The authors also thank the support of the Empresa Brasileira de Pesquisa

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