BEST - Bioenergy and Sustainable Technologies (Austria)

This study evaluates different alternative bed materials, sourced from waste materials, to replace quartz sand in fluidized bed incineration of wood. Using alternative bed materials is not only beneficial in terms of the circular economy, but it also aims at tailoring the chemical and mineralogical composition of the resulting bed ash to enable its use as supplementary cementitious material (SCM) in sustainable cements. Seven alternative bed materials were investigated: Construction and demolition waste fine-fraction (CDW-ff), Electric arc furnace slag (EAF slag), Steel Refinement slag (SR slag), two types of used foundry sands, and Municipal solid waste incineration bottom ash. These materials are likely to present more latent hydraulic or pozzolanic properties than the commonly used quartz sand. The study focuses on (i) the physical and mechanical properties of the alternative bed materials relevant to fluidization, and (ii) their chemical and mineralogical properties relevant for upcycling as SCM. The developed testing scheme involves three stages from the laboratory to the pilot scale. First, materials were characterized using XRF, XRD, and particle analysis, followed by XRD-heating-stage, rotary kiln experiments, and cold-flow fluidization. Finally, the most promising materials (CDW-ff and EAF Slag) were tested in bench scale wood incineration reactors. The produced bed ash contains cement-reactive phases, indicating a high potential for use as SCM. This reuse option will help closing material cycles in the sense of a circular economy. These promising findings should be validated at industrial scale, through cement performance testing and critical evaluation of the composition of the resulting ash regarding heavy metal content.

Butanol is currently produced on an industrial scale, primarily from fossil-based raw materials. An alternative method involves gas fermentation. To improve the efficiency of microbial processes, one promising approach is electrofermentation, which involves the application of an electric current to stimulate microbial growth or modulate metabolic pathways. This study examined the production of biobutanol from gas fermentation supported by electrofermentation, as assessed through a Life Cycle Assessment (LCA). The LCA was conducted for a biobutanol production technology developed within the framework of the BesTECH project, funded in the ERA-NET Bioenergy programme. Two environmental impact assessment methods were applied: ReCiPe 2016 and IPCC 2021 GWP 100 (with CO2 absorption considered). The results of the LCA indicated that the most significant environmental impact is associated with greenhouse gas emissions from fossil fuel combustion used to generate electricity (based on Austria’s energy mix). An additional environmental burden is related to the production of the fermentation medium. Sensitivity analysis revealed that the environmental performance of the process is strongly influenced by the source of electricity used in biobutanol production.

This study explores the impact of enzymatic (ENZ), microwave (MW), and ultrasound (US) pretreatments on supercritical CO2 (scCO2) extraction efficiency, chemical composition, and cytotoxic activity of Tetraselmis sp., Tetradesmus obliquus, and Chlorococcum sp. Pretreatments significantly enhanced extraction yields, with ENZ being most effective for Tetraselmis and Chlorococcum, and MW for T. obliquus. UPLC-HRMS profiling revealed species- and pretreatment-specific shifts: ENZ and US improved pigment recovery in Tetraselmis, while MW enriched carotenoids and chlorophyll derivatives. In Chlorococcum, MW boosted pigment diversity, whereas ENZ and US favored fatty acid derivatives in the extracts. Multivariate analysis confirmed significant compositional changes, particularly after ENZ and MW pretreatments. Tetraselmis extracts, especially those pretreated with MW, exhibited the strongest cytotoxic activity and highest selectivity indices against HeLa and MDA-MB-453 cancer cell lines. Correlation analysis identified compounds such as 2,3-dihydroxypropyl stearate, fucoxanthin, and (3β)-3-hydroxystigmast-5-en-7-one as strongly linked to cytotoxicity. Molecular docking further showed that abundant compounds in Tetraselmis extracts have high predicted affinities for cancer-related targets (e.g., BCL2, EGFR, PDK1). The results suggest that cytotoxic effects arise from both specific bioactive compounds and their synergistic interactions. These findings show that pretreatments can purposefully tune scCO2 extracts and provide a data-driven basis for designing more sustainable microalgal extraction workflows.

Abstract Building and district energy management increasingly requires advanced control strategies. For several tasks that arise, Machine Learning (ML) and Artificial Intelligence (AI) have found widespread application, but often the interaction with existing elements and the integration into the productive system are done in a rather unsystematic way. Thus, one faces problems concerning interface design, data requirements and reliability/trustworthiness. In order to improve this situation, we outline the general control structure of such systems, review key concepts from ML/AI and discuss approaches for conventional high-level control. This is followed by a literature review on ML/AI applications for energy management. Based on the systematics and the literature findings, we establish a taxonomy for the integration of ML/AI methods for energy management, which leads as a main result to a comprehensive guide for such applications, taking into account both characteristics of the method and the affected elements of the system. This is supplemented by a quick guideline for choice of an appropriate method and for subsequent evaluation. The target readership are control engineers who would like to get a systematic overview of ways to integrate ML/AI methods in their work, and data scientists who want to get a better understanding for main tasks and challenges for applying their tools for control tasks.

Abstract This paper explores the inconsistencies in nut factors of PTFE-coated studs, particularly focusing on the effects of manufacturing processes such as over-tapping. Hamilton’s 2022 “K-Factor Testing of PTFE-Coated Studs” demonstrated wide variability in nut factors across different manufacturers. While lubrication was found to improve consistency, many end-users report an inability to use lubricants due to specific process requirements, such as those involving chlorine, leading to challenges in maintaining reliable bolted joint assemblies. To address these concerns, this study evaluates the nut factors of a new PTFE-coated stud manufacturer compared to industry standards. As in the previous study, a Skidmore-Wilhelm Bolt Tension Measuring System was used to measure torque and bolt load. Results showed that the new manufacturers’ studs achieved a highly consistent nut factor of 0.12, both lubricated and unlubricated, with significantly reduced bolt scatter compared to other manufacturers. This consistency held true in both Skidmore and flange tests, suggesting that the new manufacturing process produces more reliable and repeatable results. The study concludes that the newly analyzed PTFE-coated studs present a viable solution for environments where lubrication is restricted, offering better reliability in joint assembly. These findings underscore the importance of manufacturing quality and process consistency in achieving accurate nut factors for PTFE-coated studs.

Despite extensive research on the bed particle layerformationand characteristics of ilmenite bed particles in fluidized bed combustionand gasification of woody biomass (characterized by high Ca and Kcontent), a significant knowledge gap exists when P-rich fuels areused. Chicken litter, as a P-rich biomass, presents a promising alternativebiomass for energy conversion processes. Therefore, this study aimsto investigate the bed particle layer formation and characteristicsof ilmenite bed particles during fluidized bed combustion of chickenlitter. The bed particle layer formation process and characteristicsfor ilmenite bed particles utilized in a 5 kWth bubblingfluidized bed combustion of chicken litter were studied in this work.Bed samples were taken after 4, 8, 12, and 16 h from the start-upand were analyzed via SEM/EDS. The findings highlighted that the initialstage of bed particle layer formation is similar to what was observedin fluidized bed combustion of woody biomass and is driven by thereaction of fuel-derived Ca-rich particles with the bed particle,leading to the formation of the inner layer. As time progresses, thedeposition of fuel-derived bed ash, containing mainly Ca, P, Mg, andK, forms an outer layer that uniformly covers the entire bed particlesurface, irrespective of the bed particle’s surface morphologies.Additionally, the outward migration of Fe from ilmenite bed particlesis significantly constrained when utilizing chicken litter, a Ca-and P-rich fuel, due to the formation of a bed particle layer thatuniformly covers the bed particle surface.

As the iron and steel industry needs to cut its CO2 emissions drastically, much effort has been put into establishing new—less greenhouse-gas-intensive—production lines fueled by hydrogen and electricity. Blast furnaces, as a central element of hot iron production, are expected to lose importance, at least in European production strategies. Yet, blast furnaces could play a significant role in the transitional phase, as they allow for the implementation of another CO2-reducing fuel, carbonized wood reducing agents, as a substitute for coal in auxiliary injection systems, which are currently widely used. Wood carbonization yields vastly differing fuel types depending on the severity of the treatment process, mainly its peak temperature. The goal of this study is to define the lowest treatment temperature, i.e., torrefaction temperature, which results in a biogenic reducing agent readily employable in existing coal injection systems, focusing on their conveying properties. Samples of different treatment temperatures ranging from 285 to 340 °C were produced and compared to injection coal regarding their chemical and mechanical properties. The critical conveyability in a standard dense-phase pneumatic conveying system was demonstrated with a sample of pilot-scale high-temperature torrefaction.

Polyhydroxyalkanoates (PHA) are a promising bio-based alternative to traditional plastics derived from petroleum. Cyanobacteria are photosynthetic organisms that produce PHA from CO2 and sunlight, which can potentially reduce production costs and environmental footprint in comparison to heterotrophic bacteria cultures because (1) they utilize inorganic carbon sources for growth and (2) they do not require intensive aeration for oxygenation. Moreover, supplementing precursors such as propionate, acetate, valerate, etc., can be used to obtain various copolymers with plastic customizable properties in comparison to the classical homopolymers, such as polyhydroxybutyrate, PHB. This critical review covers the latest advances in PHA production, including recent discoveries in the metabolism interplay between PHA and glycogen production, and new insights into cultivation strategies that enhance PHA accumulation, and purification processes. This review also addresses the challenges and suggests potential solutions for a viable industrial PHAs production process.