A techno-sustainability assessment framework: indicator selection and integrated method for sustainability analysis of biobased chemicals

Abstract

The emerging biobased industry has the potential to tackle some of the sustainability challenges the chemical industry must endure. However, the use of biomass as a feedstock does not imply that technologies and product value chains are always sustainable. Sustainability impacts need to be evaluated and monitored to highlight the advantages and pitfalls of different biobased routes over the product life cycle. This dissertation aims to develop a framework for sustainability assessment, specifically for biobased chemicals, while accounting for technological as well as economic, environmental, and social aspects in an integrated approach. First, a review of the state-of-the-art sustainability indicators for biobased chemicals was conducted and a gap analysis was performed to identify indicator development needs. The results show that existing sets of indicators lack a holistic view on sustainability. There is a clear hierarchy present within the sustainability domains (i.e., environmental, economic, and social) with a preference for certain environmental indicators and ignorance towards social aspects. The existing sets lack focus and are not adapted to case-specific characteristics of biobased chemicals. The review study shows that the need exists to elaborate and enhance a standardized and comprehensive list of sustainability indicators for biobased chemicals. To fill this gap, a Delphi study was performed to select sustainability indicators specifically for biobased chemical value chain assessment, and to reach consensus among experts on prioritization of these indicators. Stakeholders were selected from three core groups: the private, public, and academic sector. Best-worst scaling (BWS) was performed to gather data on a prioritization of sustainability indicators per respondent. Next, a multi-criteria decision analysis (MCDA) was applied to compare the individual rankings of the respondents and develop a consensus ranking among the experts. Greenhouse gas (GHG) emissions, market potential and acceptance of biobased materials are deemed the most crucial indicators for respectively environmental, economic, and social sustainability. Expert consensus was found positive in all three domains, with the strongest consensus measured for environmental sustainability. Next, the practicability of the defined indicator set from the Delphi study was evaluated. An integrated techno-sustainability assessment (TSA) framework was developed, which combines environmental, economic, and social analyses to evaluate the impacts over the life cycle of biobased chemicals. TSA integrates technological and country-specific data with environmental characterization factors, economic values, and social data. Decision makers should be able to assess sustainability from a low technology readiness level (TRL) by identifying potential hurdles and opportunities. A MCDA integrates the sustainability indicators expressed in different units, taking into account stochastic and flexible method options. A stochastic, hierarchical outranking approach for sustainable decision-making was proposed with the aim to structure decisions between different alternative scenarios and to make sustainable choices at low TRL. The developed integrated TSA framework was applied to a case for which the sustainability of a production and harvesting plant of microalgae-based food colorants was assessed. Four possible microalgae scenarios were defined comparing two different red microalgae feedstocks, Porphyridium and Dunaliella salina, and two algae cultivation systems, an open pond and a photobioreactor. The integrated TSA results of the microalgae case showed that cultivating Porphyridium in open pond technology and Dunaliella Salina in a photobioreactor, are superior to the other assessed scenarios, given the assumptions made. The novel integrated techno-sustainability assessment framework developed in this dissertation is the first to focus on a combination of methods for (i) a comprehensive indicator selection, (ii) a dynamic integration of sustainability dimensions in one assessment, and (iii) a multi-criteria decision making tool allowing for data uncertainty. The aim of the integrated TSA is to gain insights in the sustainability performance of technologies, products, and value chains. Integrated TSA enables to assess sustainability already in early development stages, to guide research and development, and to support sustainable investment decisions. The most and least preferred scenarios can be selected and better-informed choices between alternatives can be made by evaluating environmental, economic, and social sustainability impacts in one holistic framework.