Abstract Circularity claims in biomass and waste conversion research often depend on feedstock assumptions, but studies do not report baseline management, hazard-related information, and material status consistently. Here we show a Scopus-based evidence map of feedstock reporting across eight conversion technologies. We extract 152,548 feedstock items and retain 133,832 valid items using a deterministic-first workflow with record-level provenance, versioned dictionaries, and audited validation. The map reveals technology-specific reporting patterns and recurring gaps in the information needed to interpret whether feedstocks are primary biomass, wastes, by-products, or commodity inputs, and whether secondary streams carry hazard-relevant qualifiers. We provide a harmonised feedstock dictionary, a reusable labelling infrastructure, and minimum evidence conditions for transparent interpretation of feedstock claims. These findings characterise reporting patterns in a Scopus-indexed and query-constrained evidence base, not real-world deployment, feedstock availability, or sustainability performance. Together, these outputs support more transparent, reliable, and reusable feedstock evidence, enabling better-grounded interpretation of circularity claims across conversion technologies.

Biomass, organic wastes and by-products are increasingly targeted for low-carbon fuels and value-added chemicals. However, strategic decision-making from a circular economy perspective requires a big-picture view of the relative significance of different conversion technologies in handling diverse feedstock portfolios, and no large-scale, cross-technology mapping of these portfolios is currently available. Thus, we assembled a literature-derived dataset linking eight major waste-to-X valorisation technologies (gasification, pyrolysis, hydrothermal liquefaction, torrefaction, anaerobic digestion, aerobic digestion, fermentation and transesterification) to their reported feedstocks. Using the Scopus database, 121,365 records were retrieved with harmonised search strings, spanning publications from 1887 to 2026, including a small number of early-indexed 2026 records. This constrained yet scalable search strategy facilitates automated extraction and validation while yielding a rich dataset. Further, an LLM-assisted workflow was implemented to extract candidate technology and feedstock phrases, followed by a two-level validation that combines rule-based cleaning with targeted LLM re-evaluation to minimise manual curation. The resulting dataset provides technology-specific, validated feedstock descriptors that support comparative analyses and decision-support applications in a circular bioeconomy context.

The post-fossil transition challenge for the chemical industry is structural: the industry needs carbon as a raw material, and decarbonization frameworks do not fully address this dependence. Syngas is a central platform intermediate, producible from biomass, wastes, and captured CO2, and the entry point to multiple established conversion routes. Comparing thousands of products across many such routes is difficult to address with detailed methods alone, such as life cycle assessment (LCA) or techno-economic analysis (TEA), which require route-specific data assembled only for a few defined configurations. This study addresses that gap by extending the EcoStrategic Index (ESI) with a pathway-aware approach. Pathway-aware means that products are assessed together with the conversion path needed to reach them, using conversion-depth as a positional structural indicator of downstream processing intensity rather than a direct estimate of cost, energy use, or environmental footprint. The framework introduces a Pathway-Aware Efficiency index (PAE) capturing conversion-depth burden. ESI and PAE represent complementary strategic dimensions: portfolio breadth and value potential versus depth-adjusted pathway efficiency. Applied to eleven syngas-to-chemicals routes covering 2,756 product entries across five value levels, ESI and PAE are computed independently and compared on a dual-index strategic map. The five main-route cases show a complete rank inversion (Spearman's rho =- 1.00); methanol sub-routes show a strong negative association (rho =- 0.829, p = 0.042). No assessed route simultaneously achieves high breadth and high depth efficiency. ESI-PAE supports strategic screening of large pathway portfolios upstream of detailed TEA, LCA, and MCDA assessments.

Using green electricity to calcine the raw materials and combining this with storage of the pure CO2 generated in the calcination process can significantly reduce CO2 emissions in the cement industry, which generates around 7 % of the global CO2 emissions.In this study, a lab-scale electrically heated fluidized bed calciner, operating with a mixture of fine meal particles and coarse inert particles, is simulated using CPFD software. The electrification of the reactor is done using several horizontal cylinders, which are electrically heated to provide energy both for heating the raw meal (with 77% CaCO3) up to the calcination temperature and for calcination (CaCO3  CaO + CO2). The reactor design is done based on a specified electrical energy input, the gas velocity required for fluidization of coarse inert particles and the velocity required for entrainment of the fine calcined particles. A fluidization velocity of 0.3 m/s appears to be optimal for the reactor, whereas 0.8 m/s resulted in complete entrainment of the bed. The maximum calcination degree achieved was 90% when operating with preheated meal. The average meal residence time was found to be 24-26 s.

Meat and Bone Meal (MBM) is a CO2 neutral fuel, and hence is a good candidate for substituing fossil fuels like pulverized coal in rotary kiln burners used in cement kiln systems. MBM is used in several cement plants, but the optimum substitution rate has apparently not yet been fully investigated. The present study aims to find the maximum possible replacement of coal by MBM, without negatively affecting the product quality, emissions and overall operation of the process. A full-scale experiment was carried out in the rotary kiln burner of a cement plant by varying the MBM substitution rate from 0 to 7 t/hr. Clinker quality, emissions and other relevant operational data from the experiment were analysed. Additionally, coal and MBM were compared by laboratory experiments. The results revealed that MBM could safely replace more than 40% of the coal energy without giving negative effects. The limiting factor is the free lime content of the clinker. Possible explanations to the free lime increase are given. If 40% of the coal in the rotary kiln burner was replaced by MBM on a long-term basis, the total annual CO2 emissions of the plant could be reduced by 10%.

Electrifying a calciner with clean energy can cut fuel emissions and produce a stream of relatively pure CO2 from the calcination reaction (CaCO3 → CaO + CO2), which can be utilized or stored. A fluidized bed calciner offers a high heat transfer coefficient and requires low gas flow rates for operation. The design of such a reactor is studied in this work. It is not possible to fluidize raw meal directly, so a binary mixture of coarse lime particles and fine raw meal is used. The commercial Barracuda CPFD software is applied. The model was first validated against experimental results and then used to find an optimized design. The results indicate that the suggested pilot-scale fluidized bed calciner can operate between 10 and 16 t/h of raw meal feeding with a calcination degree above 90% and with negligible coarse particle entrainment. The calciner needs 0.05–0.09 kg-CO2/kg-raw-meal for the operation, so the required gas recycling is low. Overall the calciner operation is smooth, and such a design could be used for electrification combined with CCUS.

Over two billion tonnes of municipal solid wastes (MSW) are generated annually from households, industrial facilities, and commercial sites. The non-hazardous fraction of MSW is used to produce solid recovered fuels (SRF), which have an economic and environmental value when used as a substitute for fossil fuel burning in industrial facilities. Cement manufacturing plants are among the SRF end-users. SRF co-processing in cement kiln systems has been tested and evaluated for several years and has shown promising results. Cement companies intend further to improve the co-processing technology, considering the massive and increasing amount of solid waste generation, stringent environmental regulations, and economic benefits. SRF utilization in the cement industry has been experimented with using different tactics. Improving SRF characteristics through different pre-processing methods covers one side of this picture. Investigating the engineering and technical potential of SRF combustion in high-temperature cement kiln systems covers the other side. This review article provides a state-of-art description of SRF co-processing in cement manufacturing plants and discusses challenges in this area.

As the share of renewable energy increases, green electricity may help reduce the carbon footprint in the lime industry. Electrifying the calciner can produce relatively pure CO2 from the calcination process (CaCO3 → CaO + CO2), which may be utilized or stored. All the previous literature studied electrically heated rotary calciner with external heating. This work presents a novel design of an electrical rotary calciner through which internal heating is possible. The design can utilize existing kiln drums made from relatively inexpensive refractory and steel materials. The designed calciner operated smoothly for around four days, and the concept was technically feasible. The outer wall temperature and calcination degree was measured during the condition of a pseudo-steady state in the calciner. A model was developed and implemented in OpenModelica, which was validated by comparing it against measured variables. The modelling results revealed that the current setup had low thermal efficiency, as the heat loss amounted to around 60%, and the average heat transfer coefficient was around 101 W/(m2K). A step-by-step procedure with the help of the model was discussed to improve heat efficiency and reduce heat loss by up to 11% by improving thermal insulation and increasing the residence time of particles. With the improved thermal efficiency, energy intensity and electricity cost per unit CO2 were reduced from 35 to 7 MJ/kg-CO2 and 4.9 to 1 NOK/kg-CO2, respectively. So, improving thermal efficiency can improve both the environmental and economic aspect of the process.

The cement industry can reduce its CO2 emissions by electrifying the calciner. It can avoid emissions from fuel combustion and produce pure CO2 from the calcination reaction (CaCO3 → CaO + CO2) for direct capture. A differential-algebraic equation (DAE) model of an electrified rotary calciner was developed and validated against experimental results. The heat transfer coefficient was around 30 W/(m2K), with the calciner inclined at 15°. This value increased to 80 W/(m2K) by reducing the inclination to 2°. The rotary calciner for producing 1 Mton/yr clinker with an internal diameter of 5 m needs a length of 485 m to reach a calcination degree of 94 %. The large system size suggests that this calciner may not be suitable for full-scale production. However, it can still be used for small-scale green production of calcined limestone.

Around two-thirds of the CO2 emission from the cement industry comes from calcite decomposition (CaCO3 -> CaO + CO2), and most of this reaction happens in the calciner. So, it is possible to reduce the CO2 emission significantly by electrifying the calciner. This possibility is studied in this work through a process simulation model using Aspen Plus. The model is first calibrated with experimental results for a cement calciner heated by coal firing. The validated model is then electrified with three scenarios of gas recycling. Electrifying an existing calciner will require high gas recycling, while some alternative designs require no gas recycling. The results indicate that this method could reduce the CO2 emissions by as much as 78%. The total energy (including fans, calciner and kiln) required in the coal-fired calciner system is around 138 MW. The energy in the electrified system may vary between 154 MW for high gas recycling and 137 MW for no gas recycling. The net excess energy in the electrified calciner per captured CO2 unit varies between 0.6 MJ/kgCO2 for high gas recycling and-0.04 MJ/kgCO2 for no gas recycling.

A cold-flow lab-scale cross-flow fluidized bed classifier was simulated using the CFD software Barracuda VR®. The purpose of the study was to identify the most suitable drag model and make the model adjustments that provide the best representation of the flow situation in the classifier when comparing the results with the experimental data. Two particle types were used in the simulations and in the experiments: zirconia (median diameter 69 µm, skeletal density 3830 kg/m3) and steel (290 µm, 7790 kg/m3). Ten different cases, with different solids loading values, were investigated: three with pure zirconia particles, three with pure steel particles, and four with a mixture of zirconia (28%) and steel (72%). Several different drag models were tried out in the simulations. However, none of the available models were able to predict the classification efficiency observed in experiments with their default settings. Although most of the drag models correctly predicted the inversely proportional behavior of the classification efficiency vs. solids loading, the classification efficiency was overpredicted. It was observed that a combined WenYu/Ergun drag model gave a wide range of accuracy, by being able to capture the behavior of both dense and dilute particle systems. Even though the predictions of the classification efficiency for steel particles were acceptable, a larger deviation was observed with Geldart A zirconia particles. CFD simulations with the WenYu and Ergun combined drag model were used for further validation against the experimental observations. In this case, previously published experimental data for fluidization of pure Zirconia particles were used. The fluidization of zirconia was modelled in Barracuda VR® with adjustment of the combined WenYu/Ergun drag model parameter (k1), to obtain a suitable validation. Furthermore, the effect of adding the blended acceleration model (BAM) for the fluidization simulations is discussed. It was observed that the fixed bed pressure drop was very accurate compared to the experimental observation, but the pressure drop after the fluidization was slightly overpredicted.

The chemical and thermal processes associated with the decarbonation and fuel combustion in the cement kiln process produce a large amount of carbon dioxide (CO 2 ) contributing with around 8 % of the global CO 2 emissions. Utilizing green electricity instead of fossil fuels to decarbonate the raw meal in the calciner can eliminate the CO 2 emissions produced through fuel combustion and also provide a basis for simple capture of the CO 2 generated through calcination because CO 2 is the only gaseous product exiting from the electrified calciner. In the current work, an electrically heated fluidized bed (FB) reactor is being developed to calcine the raw meal. The FB may replace the traditional entrainment calciner used in many plants. The purpose is to enable efficient indirect heat transfer in the bubbling bed and hence obtain pure CO 2 as the gaseous product from the calciner. The minimum fluidization velocity and pressure drop of the particle bed are important characteristics in the design of a bubbling fluidized bed, and these have been measured in a cold-flow lab-scale fluidized bed unit with a bed height of 0.21 m and a circular cross-sectional area of 55 cm². The particle size distribution of the meal ranged from 0.2 – 180 µm, with a median particle size of 21 µm. The experimental results revealed that the regular cement raw meal is difficult to fluidize due to the large fraction of Geldart C particles in the meal (approximately 60%). Based on experimental observation, this may be explained by inter-particular electrostatic forces forming particle clusters. The fluidization process has also been simulated with the commercial computational particle and dynamics (CPFD) software Barracuda® (version 17.4.1). The purpose of using CPFD was to be able to simulate the process at cold-flow conditions and then, based on this, simulate the process at large-scale hot-flow conditions. The simulation results complied quite well with the lab-scale experiments and confirmed the difficult fluidization of the meal.

In the current work, computational particle and fluid dynamics (CPFD) simulations are used to study an electrically heated bubbling fluidized bed (BFB) used as a calciner in a cement manufacturing process, applying a binary-particle fluidization system.Owing to the fine particle size (0.2 -180 µm) of the limestone used as a raw meal in the cement kiln process, a conventional bubbling fluidized bed may be difficult to apply due to particle cohesion causing poor fluidizability of the particles smaller than 30 µm.In the current study, to enhance the fluidization of the raw meal particles, they are mixed with coarse (550 -800 µm), inert particles.The aggregation and clustering of the fine particles will decrease due to collisions with inert coarse particles, and hence a more homogeneous distribution of raw meal particles may be achieved.The inert particles will also provide a thermal energy reservoir through their heat capacity and thereby contribute to a very stable bed temperature, which is advantageous in the control of the process.After the raw meal particles have been calcined, they have to be separated from the coarse, inert particles.This can be done by increasing the velocity of the CO2 used for fluidization to a value sufficiently high to entrain the raw meal particles, but still sufficiently low that the coarse, inert particles are not entrained.The commercial CPFD software Barracuda was used for simulations to investigate suitable operational conditions at 1173 K, such as the particle size distribution of the inert particles and the fluidization gas velocity.The impact of gas velocity variation on the fluidization of the particle mixture was studied, and an appropriate range of velocities for the calcination and entrainment modes could be determined.The simulations revealed that mixing raw meal particles with inert coarse particles can enhance the flowability in the FB reactor indicating that it is possible to apply the concept in a full-scale calcination process.

This article summarizes a detailed scientific study of a particle classification system to be used in a fully integrated regenerative calcium looping (FICaL) system for CO2 capture. In conventional calcium looping, the required calcination heat is provided by a separate oxyfuel combustor, which needs an air separation unit (ASU) to provide the required oxygen for the process. The ASU demands a considerable amount of power, which gives an energy penalty of typically 5 % to the power plant. However, in the FICaL system, the required heat for the calcination is instead supplied indirectly from the main combustor in the power plant, so there is a no need for an ASU in the system. Based on process simulation studies done with Aspen Plus®, this may reduce the energy penalty to values in the order of 1-2 %. The indirect heat transfer is done by using inert heat transfer (HT) particles that are heated up in the combustor and then transferred to the calciner where the sorbent material is heated up after mixing with the hotter inert particles. Thereby the sorbent material is calcined. However, after calcination, the sorbent and heat transfer particles have to be separated. Hence, an efficient classifier is required. The current work has therefore focused on designing, constructing and doing experiments in a novel particle classification system. A novel cross-flow fluidized bed classifier was designed, using computational fluid dynamics (CFD) simulations as a tool, in order to separate the sorbent and HT particles exiting from the calciner. The classifier, which has no mechanical moving parts exposed to very high temperature, can be operated under the required high-temperature conditions prevailing in a full-scale plant. Two different cold-flow lab-scale versions of the classifier was built and used for a large number of experiments. In the classification, the aim is to minimize the loss of sorbent particles via the bottom exit from the classifier, and also to minimize the loss of HT particles via the top exit from the classifier. The second and improved version was able to classify very well a mixture of down-scaled sorbent particles (zirconia) and down-scaled HT particles (steel). The experiments with the improved classifier version gave particle losses in the order of 2-3 %, values that are close to what can be seen as acceptable in a full-scale hot-flow system.Extensive CFD simulations were carried out with the commercial software Barracuda® 17.1 to investigate in detail how the different particle types behave in the classifier. Even if the exact particle losses were not well predicted, Barracuda was able to predict the general gas-solids flow behavior and proved to be a useful tool in the design process. Different drag models were used to reproduce the experimental findings and validate the CFD model. Barracuda was also used to simulate the classification process under hot-flow conditions and indicated that the classifier will also perform well under such conditions. The results of the corresponding research work are promising as the classifier is able to give a high degree of purity of the particle streams leaving the classifier. The iterative design and modelling effort from this research work has produced a functional, high-efficiency classification concept.

Bubbling fluidized beds are simple and attractive means of achieving efficient conversion of biomass if particle segregation and the associated effects are minimized.To improve the knowledge of fluidized bed reactor design, this paper compares the behavior of a hot bed containing a certain amount of biomass with the behavior in a cold bed having the same biomass loads and particle properties.An approach for scaling up a cold bed to a large hot bed for the same volume fraction of biomass is introduced.The proposed scheme uses the bed expansion ratio as an output from the cold bed.This approach provides an accurate means of attaining dynamic similarity in bubbling behavior between two different beds without constraining the fluid and particle properties as well as the bed height.

A one-dimensional unsteady state model is developed for simulation of biomass gasification in a bubbling fluidized bed. The proposed model accounts for the effect of hydrodynamic behavior of the fluidized bed by incorporating the momentum equations of fluid and fuel particles. The model results are validated against experimental data in the literature as well as the results from existing models. The proposed model is capable of predicting the total gas yield and composition of the product gas at different operating conditions. The effect of biomass feeding position is investigated, and the performance of a reactor under nonisothermal conditions is compared with its performance under isothermal operation. As the developed model is computationally less demanding, it can be used to improve design and operational control of bubbling fluidized bed gasifiers.