• Energy Research

We would like to thank Herman Beckers, Metin Bulut, Frans Snijkers, Joris van der Have, Jan Vanderheyden, Leen Bastiaens, and Lies Eykens for the provision of technological and economic data and the useful discussions on the assumptions in the model. We would also like to thank Eva Cordery for proofreading the article and the anonymous reviewers for their valuable feedback and suggestions. Furthermore, we gratefully acknowledge the financial support of the Fundacion Novia Salcedo.

Abstract In recent decades new recycling technologies for mixed plastic waste have emerged. In pyrolysis, the polymer chains are thermally broken (pyrolyzed) to obtain hydrocarbon materials of different molecular weights such as naphtha, oil or waxes, whose yields can be controlled by varying the reaction parameters. Naphtha represents a closed-loop recycling process as it is a feedstock for (poly)olefins; while the co-production of waxes, having several applications in e.g. the construction industry, exemplifies an open-loop recycling process. This paper compares the economic performance of the pyrolysis of mixed polyolefin waste in a closed-loop and open-loop scheme, including a probabilistic approach to the most important variables. From an economic perspective, open-loop pyrolysis as presented outperforms closed-loop recycling, due to the high prices of wax. However, the results present a high dispersion caused by the volatility of the prices of crude oil and its derivates. Considering the current oil price projections, our case study analysis showed that for open-loop recycling there is a future probability of almost a 98% of observing positive results and around 57% of probability in the case of closed-loop recycling, under the assumptions made. Yet, in a future scenario where decarbonized electricity would decrease oil prices, the probability of a positive outcome reduces to 57% for the open-loop case and to less than 8% in the case of closed-loop recycling. To make these pathways attractive to investors, the nameplate capacity should be at least 70 kt/year for open-loop recycling and 115 kt/year for closed-loop recycling. A 120 kt/year plant should operate minimally at 80% of its capacity for open-loop recycling, while closed-loop recycling would demand running close to maximum capacity. Security of feedstock supply therefore is required.

Abstract: Lignocellulosic biomass is the most abundant source of renewable biomass and is seen as a high-potential replacement for petroleum-based resources. The conversion technologies to advanced biofuels are still at a low maturity level, thus allowing for future cost reductions through technological learning. This fact is barely considered in state-of-the-art techno-economic assessments and a structured approach to account for technological learning in techno-economic assessments is needed. In this study, a framework for techno-economic assessments of advanced biofuels, integrating learning curves, is proposed. As a validation of this framework, the economic feasibility of the valorization of corn stover for the production of second-generation bioethanol in Belgium is studied. Process flowsheet simulations in Aspen Plus are developed, with an emphasis on the comparison of four different pretreatment technologies and two plant capacities at 156 dry kt biomass/y and 667 dry kt/y. The dilute acid pretreatment model of the large-scale biorefinery required the lowest minimum learning rate to reach an economically feasible biorefinery by 2030, being 3.9%, almost half as the one calculated for the smaller scale plant. This learning rate seems to be achievable based on learning rates commonly estimated in literature. We conclude that there is a potential for advanced ethanol production in Belgium under the current state of technology for large-scale biorefineries, which require additional biomass imports, when accounting for future cost reductions through learning

Social indicators are not easy to be quantitatively analyzed, although at the local scale, the social impacts might be relevant and important. Using the existing approaches for both quantitative and semi-qualitative measurements, this study aims to assess the social impacts of a company working on algae production systems in Belgium through social life cycle analysis (SLCA). By highlighting the opportunities and challenges on the way of applying the existing SLCA approaches at company level, the objective of this study is to contribute to the development of a suitable and clear SLCA approach when a company is considered as the unit of analysis. Based on the list of potential social impact categories suggested by the United Nations Environment Program/Society of Environmental Toxicology and Chemistry (UNEP/SETAC) guidelines (2009) for SLCA, three stakeholder groups (workers, consumers, and local community) and three subcategories associated with each stakeholder group were identified as the most relevant for carbon capture and utilization technologies. Company and sector level data were collected using existing documents and reports, and the data were analyzed and scored using a combined quantitative and semi-quantitative approach to develop a social assessment model for the case study. The company appears to perform well for all the evaluated social indicators except the one related to the subcategory “equal opportunity/discrimination for workers” for which the share of women employed is lower compared with the sector-level data. The results of our assessment were further discussed regarding the challenges and limitations of performing SLCA at the company level. Based on our experience, the validity of the outcomes is significantly influenced by the data availability, the generality of the indicators introduced within the UNEP/SETAC guidelines, and the subjectivity in data collection for the semi-quantitative assessment among others. By highlighting the difficulties and challenges of applying the SLCA at the company level, our study provides a starting point for improving the quantitative assessment and monitoring social implications at the company level within a regional foreground in Europe.

Abstract: Today, the concept of a circular economy (CE) has become omnipresent. Central to this concept is the term value, however, it is not properly defined, which leads to different interpretations, and hinders implementation of the CE concept. Hence, this article operationalizes the theoretical concept of value into a more practical understanding. First, the meaning of value within the CE context is examined, followed by the development of a framework wherein value is decomposed into two essential types; functional and created value. Next, the framework is applied to an illustrative case study involving four different end-of-life strategies: landfilling, closed loop recycling, remanufacturing and reusing. The framework enables a holistic comparison of the different strategies, represented in a visually compelling way, and clarifies the connection between theoretical CE concepts and practical measures. Consequently, it enhances the understanding of existing CE indicators and serves as a stepstone for the development of new indicators.

Abstract Algal-based bioenergy products have faced multiple economic and environmental problems. To counter these problems, algal-based biorefineries have been proposed as a promising solution. Multiple environmental and economic assessments have analyzed this concept. However, a wide variation in results was reported. This study performs a review to evaluate the methodological reasons behind this variation. Based on this review, four main challenges for a sustainability assessment were identified: 1) the use of a clear framework; 2) the adaptation of the methodology to all stages of technological maturity; 3) the use of harmonized assumptions; 4) the integration of the technological process. A generic methodology, based on the integration of a techno-economic assessment methodology and a streamlined life cycle assessment was proposed. This environmental techno-economic assessment can be performed following an iterative approach during each stage of technology development. In this way, crucial technological parameters can be directly identified and evaluated during the maturation of the technology. The use of this assessment methodology can therefore act as guidance to decrease the time-to-market for innovative and sustainable technologies.

Abstract: Sustainability impact assessments studies combine several indicators to cover environmental, economic and social impacts. These indicators describe different impact pathways and are expressed in different units, which makes comparing alternatives challenging. An aggregated metric is required to facilitate the presentation and communication of sustainability. The presented aggregation framework is based on the distance-to-target method NR-TOPSIS and adapted to a distance-to-sustainability-target approach. A procedure is given for aggregating 12 sustainability indicators into a single score sustainability indicator. Reference points for normalization of diverse impact indicators and weighting factors are investigated. The framework was applied to a wind energy case study comparing one offshore and two onshore alternatives. The case study results were compared using both a dashboard of 12 endpoint indicators and an aggregated sustainability indicator. The indicator was presented on a sustainability scale that indicated the distance of the investigated cases to an ideal (sustainable) solution. A sensitivity analysis of the weighting factors showed that the distribution of weights influenced the ranking of alternatives, especially when the alternatives are positioned close to each other on the sustainability scale, as it is the case for the wind energy scenarios. For most of the weighting scenarios, the onshore wind energy project using permanent magnet synchronous generators appeared to be the most sustainable solution.

Abstract: A transition to renewable energy sources is needed in the EU countries to achieve their goal of a low-carbon economy. This transition may come with potentially negative impacts on the well-being of the population, both globally and locally. Such social impacts are not yet systematically assessed for renewable energy technologies. In this paper, a social impact assessment framework for renewable energy technologies is developed and applied for a wind energy case study. The assessed social categories comprise impacts on human health, human rights infractions, working conditions, local job creation, quality of residential life, landscape quality. In order to cover this broad field of social impacts, four distinct social impact assessment methods were combined in a common social impact assessment framework. The application of the framework was demonstrated by means of the wind energy case study. The results are presented in the form of a social sustainability dashboard comprising 23 social impact indicators covering both global and local well-being impacts. The analysis showed that the life cycle material demand of offshore wind projects has larger impacts on global well-being than the onshore alternatives. For the local dimension, the offshore case was found to be less intrusive for the local population.