Feedstock Composition Research Articles

Compositional Changes of Volatile Organic Compounds in Biogases and Biomethanes Depending on the Feedstock in Sweden

Biogas usually contains volatile organic compounds such as terpenes, siloxanes, halogenated hydrocarbons, ketones, alcohols, furans and esters whose presence in the biogas is highly dependent on the feedstock. These trace components can affect the integrity of the materials they come into contact with, e.g., equipment, pipelines and engines, and their presence in the gas may pose health, safety and environmental risks. Understanding the composition of gases is a prerequisite to ensure the correct function of gas infrastructure, appliances and vehicles. This study examined how volatile organic compound (VOC) content in biogas varies depending on the feedstock and evaluated the efficiency of different upgrading processes in removing VOCs. The data, primarily collected in Sweden, include biogases produced in digesters and landfills. The selection of VOCs included in this study was based on extensive analysis of samples collected from numerous biogas and biomethane industrial facilities over an extended period, providing a comprehensive overview of VOC composition. The conducted research is intended to serve as a basis for more systematic studies on the influence of process parameters and feedstock composition on the formation of VOCs. The data have multiple potential uses, including predicting which VOCs would be found in biomethane for a given feedstock and upgrading techniques. Additionally, these data can also be used in standardization discussions to assess the plausibility of the proposed limit values and the need to regulate additional compounds.

Influence of feedstock composition on the pressure drop buildup in gas oil hydrotreater

In this work two samples of solid particulates obtained from the intergranular space of the guard beds catalyst of industrial gas oil hydrotreating reactors were investigated. The hydrotreating reactors were operated on feedstock of different composition. One of the samples of solid particulates was obtained during hydrotreating of feedstock containing a large amount of sodium and calcium. The compositions of the samples of solid particulates were determined. Quantitative elemental and structural analyses were carried out. As a result, the formed solid particulates contained a large amount of sodium chloride, sulfate and calcium sulfide. The qualitative calculations show that the pressure drop in the guard bed of five-segment rings with a diameter of 16.0 mm, due to the deposition of solid particulates in the intergranular space, increases by 108% more than the pressure drop during hydrotreating of feedstock not containing calcium and sodium compounds (under the same operating modes of the hydrotreating reactors and operating time). The obtained results on the effect of the feedstock composition on the pressure drop buildup can be used in optimizing the loading of reactors and in other oil refining processes.

Kinetic modeling and optimization of biogas production from food waste and cow manure co-digestion

As global efforts to reduce reliance on fossil fuels and improve waste management practices intensify, the development of efficient biogas production methods offers a promising solution. This study addresses the urgent need for renewable energy and effective waste management by investigating biogas production from the anaerobic digestion of food waste and cow manure. Optimal conditions for mono-digestion of cow manure were identified at 8 % total solid in 38 °C. In co-digestion experiments, varying food waste ratios were tested, with a 6:2 ratio based on total solid achieving the highest biogas yield of 325 mL/g VS. The synergistic effects of co-digestion led to enhanced nutrient balance and biogas production, significantly outperforming mono-digestion. The experimental data were analyzed using first-order kinetics, modified Gompertz, modified logistic, and transference models, with the modified Gompertz model providing the best fit (R²=0.999). Results showed improved biogas production and higher rates of volatile solids and COD removal. This study focuses on maintaining a constant optimized total solids concentration for optimizing feedstock composition to enhance biogas production and compares four kinetic models on predicting performance, providing insights into anaerobic digestion system improvement. The study's limitations, such as the lack of post-optimization TS adjustments, absence of pH control, fixed temperature conditions, highlight areas for future work to provide more insights and improve co-digestion efficiency.

Biochar-induced changes in soil microbial communities: a comparison of two feedstocks and pyrolysis temperatures

BackgroundThe application of a biochar in agronomical soil offers a dual benefit of improving soil quality and sustainable waste recycling. However, utilizing new organic waste sources requires exploring the biochar’s production conditions and application parameters. Woodchips (W) and bone-meat residues (BM) after mechanical deboning from a poultry slaughterhouse were subjected to pyrolysis at 300 °C and 500 °C and applied to cambisol and luvisol soils at ratios of 2% and 5% (w/w).ResultsInitially, the impact of these biochar amendments on soil prokaryotes was studied over the course of one year. The influence of biochar variants was further studied on prokaryotes and fungi living in the soil, rhizosphere, and roots of Triticum aestivum L., as well as on soil enzymatic activity. Feedstock type, pyrolysis temperature, application dose, and soil type all played significant roles in shaping both soil and endophytic microbial communities. BM treated at a lower pyrolysis temperature of 300 °C increased the relative abundance of Pseudomonadota while causing a substantial decrease in soil microbial diversity. Conversely, BM prepared at 500 °C favored the growth of microbes known for their involvement in various nutrient cycles. The W biochar, especially when pyrolysed at 500 °C, notably affected microbial communities, particularly in acidic cambisol compared to luvisol. In cambisol, biochar treatments had a significant impact on prokaryotic root endophytes of T. aestivum L. Additionally, variations in prokaryotic community structure of the rhizosphere depended on the increasing distance from the root system (2, 4, and 6 mm). The BM biochar enhanced the activity of acid phosphatase, whereas the W biochar increased the activity of enzymes involved in the carbon cycle (β-glucosidase, β-xylosidase, and β-N-acetylglucosaminidase).ConclusionsThese results collectively suggest, that under appropriate production conditions, biochar can exert a positive influence on soil microorganisms, with their response closely tied to the biochar feedstock composition. Such insights are crucial for optimizing biochar application in agricultural practices to enhance soil health.

Evaluating the role of feedstock composition and component interactions on biomass gasification

Biomass gasification offers a solution to waste concerns while generating clean energy. This study examines the gasification of pine sawdust (PS), used ground coffee (UGC), and wheat straw (WS) under identical conditions. The compositions of the biomass samples are determined, and the gasification of individual components (hemicellulose, cellulose, and lignin) are conducted to understand the process’ dependency on the biomass characteristics. The results suggest cellulose and cellulose-rich biomass (PS) produces more tar and less hydrogen than lignin and lignin-rich biomass (UGC and WS). High lignin and hemicellulose content leave more char. Gasification of PS, UGC, and WS yields 12.7, 15.7, and 17.2 vol% hydrogen, respectively. Additionally, cellulose, hemicellulose, and lignin gasification yield 10.5, 22.1, and 30.4 vol% hydrogen, respectively. Comparing experimental and theoretical values for the three biomass samples reveals significant differences due to component interactions. Thermogravimetry analysis (TGA) indicates significant degradation interactions between hemicellulose-lignin, cellulose-hemicellulose, and cellulose-lignin. It is concluded that high cellulose content biomass shows more predictable results, while high lignin and hemicellulose biomass increases secondary reactions or interactions, exacerbating predictability. These findings assist in estimating gasification performance for better biomass selection.

Feedstock-temperature interactions in anaerobic digestion with focus on psychrophilic regime

While feedstock composition and temperature are known to affect anaerobic digestion (AD) performance, their combined effect remains unexplored. By characterizing the response of AD kinetics to temperature across mesophilic and psychrophilic regimes for different agricultural residues -ranging from lignocellulose-rich crop stover to readily biodegradable potato waste–, this study aimed to study their interactive effects on AD kinetic parameters and biodegradability. Lignocellulosic material exhibited increasing biomethane potential (Bmax) with increasing temperature, while easily degradable substrates reached higher Bmax values at lower temperatures. AD rate sensitivity to temperature was lower for lignocellulose-rich feedstocks. Under mesophilic conditions, these feedstocks achieved the highest biodegradability (BD), while BD of easily degradable substrates increased with decreasing temperatures. Our findings revealed significant temperature-feedstock composition interaction effects on AD performance that holds significance for both laboratory and field-scale applications and could be used to improve the performance of psychrophilic AD in temperate-to-cold regions of developing countries.

Thermogravimetric study on thermal degradation kinetics and polymer interactions in mixed thermoplastics

AbstractPotential interactions during thermal degradation of polymer blends significantly influence product yields and their composition. Therefore, chemical recycling of plastic waste requires fundamental understanding of feedstock dependency for effective process design. This study investigates the pyrolysis of polymer blends (HDPE, LDPE, PP, PS, ABS, PET, PA6, PVC) through thermogravimetric experiments at different heating rates. Sample homogeneity’s impact on interactions is analyzed using particles, powder, coextruded blends, and samples in crucibles with separated compartments. A kinetic model is presented to support the experimental findings, assuming linear superposition of individual polymer kinetics. A proposed grouping of thermoplastics, reflecting their degradation behavior and potential interactions, correlates with the polymer structure. Observed interactions, particularly in blends of heteroatom-containing polymers (N, O, Cl), are accelerated reactions and coke formation. Hence, the model accurately predicts the degradation of heteroatom-free polymer mixtures but encounters challenges with more complex blends. This comprehensive study emphasizes the importance of feedstock composition for future pyrolytic polymer recycling. Graphical abstract

Mechanical Recycling of PET Multi-Layer Post-Consumer Packaging: Effects of Impurity Content

The recycling of PET trays is highly challenging. The aim of this paper was to investigate the issues related to the mechanical recycling process and, the correlation between feedstock composition and the quality of the produced rPET. Four feedstocks with different degrees of impurity were mechanically recycled at a laboratory pilot scale. The optical and thermal properties of the rPET products were examined to determine the quality and to seek relations with the starting level of impurities. The final products of the PET trays’ mechanical recycling were found to be affected by the presence of impurities (organics) and multi-material (non-PET) elements in the feedstocks. The rPET products crystallised faster for contaminated feedstocks showed lower molecular mass and higher yellow index values due to thermal degradation. Yellowing is a crucial parameter in assessing the thermal degradation of rPET. Injection moulded samples corresponding to higher contamination levels, reported values of Yellow Index equal to 179 and 177 compared to 15 of mono-PET sample. The intrinsic viscosity decreased from 0.60 dL/g to just above 0.30 dL/g, and losses were more significant for soiled or multi-material feedstocks. A method of improving the final quality would involve the purification of the starting feedstock from impurities.

Optimizing pyrolysis and Co-Pyrolysis of plastic and biomass using Artificial Intelligence

The rapid increase in biomass and plastic waste poses significant environmental challenges. Co-pyrolysis of biomass with plastic wastes offers a promising avenue for sustainable waste management and renewable energy generation. This study covers several novel aspects: First, it investigates the impacts of feedstock composition and operating conditions in pyrolysis (individual feedstock) and co-pyrolysis (biomass and plastic wastes). The study reveals that synergistic effects, specifically improved yields and optimized temperature, exist in the co-pyrolysis of biomass and plastic wastes compared to individual feedstock. Secondly, a suitable blended machine learning predictive model (with Random Forest, Gradient Boosting Regressor, and XGBoost) and robust optimization framework are developed to address model accuracy, non-linear interactions, and uncertainties in pyrolysis such as temperature, heating rate, and biomass-to-plastic ratio. This study predicts the bio-oil yield quantitatively (amount) and qualitatively (composition) with high accuracy (R2 > 0.97). Thirdly, key factors contributing to yield include plastic content (18 %) and biomass type (13 %) have been identified through Gini feature importance and Shapley Additive Explanation (SHAP) analysis. Furthermore, multi-objective optimization techniques reveal the most optimal bio-oil yield under specific conditions, supported by uncertainty analysis, which confines bio-oil yield to a range of 30–50 %. Finally, it also demonstrates a case study to find the optimal bio-oil yield and quality conditions using co-pyrolysis of local resources, i.e., biomass (wood and bagasse) and plastic wastes. The case study suggests optimal conditions like > 50 °C heating rate, <50 min pyrolysis time, and > 60 % plastic content in a blend of wood and HDPE. This study assists industries and policymakers to assess and understand the viability of co-pyrolysis, optimal design parameters, and process impacts.

Foreign experience in determining the group hydrocarbon composition of petroleum feedstock and petroleum products

Determination of the group hydrocarbon composition (saturated and aromatic hydrocarbons, resins, asphaltenes) of petroleum dispersed systems is predominantly carried out using chromatographic analysis methods: liquid adsorption chromatography, high-performance liquid chromatography, thin-layer chromatography with flame ionization detection. The specificity of standard methods developed for the analysis of petroleum feedstock and petroleum products using a particular method often results in the incompatibility of results both in terms of the nomenclature of the identified hydrocarbon groups and the determined concentration values. This review provides a comparative assessment of chromatographic methods for analyzing the group hydrocarbon composition of petroleum feedstock and petroleum products, their features, advantages, and disadvantages. The main options for modifying standard methods aimed at achieving correlation between the results obtained by different analysis methods are described.

Assessing the potential of cow dung and carpet grass as feedstock for biogas production to power a generator

This study investigates the potential of cow dung and carpet grass as feedstock for biogas production, aiming to provide a sustainable energy source for powering generators. A digester was fabricated to produce biogas from a mixture of cow dung and carpet grass under controlled anaerobic digestion conditions. The composition and energy content of the biogas were analyzed, and the biogas yield was measured over a 30-day period. Key parameters such as pH, system temperature, and total dissolved solids (TDS) were monitored to understand their influence on biogas production. Results showed that the pH values ranged from 4.1 to 5.2, which is lower than the optimal range for methanogenesis, yet biogas production was still feasible, peaking at pH 5.0. System temperature ranged from 28°C to 36.8°C, with the highest biogas yield observed at the upper end of this range. TDS levels fluctuated between 1,331 ppm and 3,060 ppm, indicating variations in the feedstock composition and microbial activity. The purified biogas successfully powered a 2.5 KVA generator for 30 minutes, demonstrating its practical application as an alternative energy source. This study highlights the potential of using cow dung and carpet grass for biogas production, contributing to sustainable energy solutions and waste management strategies.

Hydrothermal Liquefaction of Organic Waste Model Compounds: The Effect of the Heating Rate on Biocrude Yield and Quality from Mixtures of Cellulose-Albumin-Sunflower Oil.

Hydrothermal liquefaction (HTL) is a promising technology for the conversion of high-moisture biomass into a liquid biofuel precursor without predrying treatment. This study investigated the effects of the heating rate (20-110 °C/min) and feedstock composition on phase repartition of the HTL products. HTL tests were carried out using as feedstocks cellulose, egg albumin, and sunflower oil as model compounds for carbohydrates, proteins, and lipids, alone and in binary mixtures. The biocrude, solid residue, and aqueous phase were characterized in terms of composition and elemental percentage. The effects of binary interactions were studied in terms of product yields and compositions. It was observed that higher heating rates resulted in lower solid yields from all the cellulose-containing feedstocks and, in most cases, in higher biocrude yields and higher energy recovery. The results showed that the heating rate influences also the oil composition. Biocrude and solid yields were compared with their prediction based on the combination of the yields of single model compounds, showing a general increase in biocrude yields and a decrease in solid yields. The most significant deviation is observed with the mixture cellulose-albumin both for the biocrude and solid yields. In fact, the main interactions were recognized for carbohydrate-protein mixtures followed by carbohydrate-lipid and protein-lipid mixtures.

Comparative Analysis of Biochar Derived from Rice Straw and Soybean Straw

Aim: Recycling agricultural postharvest waste and re-introducing it again into farmland is one of the tangible ways to address zero waste dream, soil infertility and climate change. Pyrolysis of crop leftovers into biochar remains the most acceptable alternative for proper management of crop waste. The possibility of sustainable biochar production practices and multi-functionality features makes it promising to fufill an increasing demand for soil amendment, agricultural sustainability, environmental protection, cutting-edge materials and mitigation of climate change. Methodology: Same amount (14450 g) in feedstock of rice straw (RS) and soybean straw (SS) undergo slow pyrolysis separately to produce biochar. Physical (percentage yield, moisture, ash, volatile matter, bulk density, pH, electrical conductivity), chemical characterization (Microwave Plasma Atomic Emission Spectroscopy (MP-AES), Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX), Fourier Transformed Infrared (FTIR) and Thermogravimetric Analysis and Derivative Thermogravimetry (TGA and DTA)) and evaluation of bochar was determined. Results: Rice straw biochar (RSB) recorded a higher char yield of 42.1%. Both lignocellulosic biochars were black and porous with a higher silica (10.6%) content in RSB and higher carbon (82.2%) content in SSB as was revealed by SEM-EDX. Higher ash 27.1%, volatile matter (VM) 31.3% and moisture 29.4% content was seen in RSB compared to SSB because of feedstock composition. Rice straw biochar show higher peaks of macro and micro mineral elements K(14561.21mg/kg), Ca (2401.28 mg/kg), and Na(1735.27 mg/kg) than soybean straw biochar. FTIR was used to identify functional groups that might act as cation adsorbents. As the temperature increased, the TGA and DTG graphs showed mass loss and sample breakdown. Conclusion: Rice and soybean crop wastes were converted into biochar, a nutrient-rich material that maybe utilized to balance acidic soils promoting healthy plant growth and also protecting the environment.

Tailor-made green composts with suppressive properties against tracheofusariosis of wild rocket (Diplotaxis tenuifolia): Useful option for sustainable circular horticulture

Intensive cultivation systems of wild rocket (Diplotaxis tenuifolia) are threatened by the outbreak of tracheofusariosis caused by the soil-borne fungal pathogen Fusarium oxysporum f. sp. raphani. The disease is difficult to eradicate by curative methods due to the endophytic progression of the pathogen. Suppressive composts can help to prevent this adversity by providing organic matter carrying chemical and biological components that can directly and/or indirectly interfere with the plant-pathogen system. In this study, a collection of seven promising composts from different selected green feedstocks were investigated for their suppressive properties towards wild rocket Fusarium wilting. In planta assays identified two composts, obtained from olive tree pruning + plant and tomato residues, and from olive waste + straw + wool residues, with the highest levels of suppressiveness, influenced by both application dose and plant development stage. These active composts showed overlapping 13C NMR profiles as in vivo suppressiveness, being positively correlated with the organic aliphatic alkyl, O-Aryl and carboxyl C fractions and subsequently with the hydrophobic index and alkyl ratio, and negatively with the lignin ratio. On the contrary, although biotic compost components showed antifungal effects, biological properties did not correlate with in planta wilting suppression. Consistently, reflectance spectroscopy in the Vis-NIR-SWIR highlighted the clustering of samples depending on their feedstock and chemical composition. The results allow the hypothesis of a plant-mediated suppression mechanism. The composting of crop residues improves the circularity of horticulture and makes it possible to produce, from selected matrices, tailored compost towards the sustainable cultivation of wild rocket.

Exploring Biomass Conversion Technologies: From Raw Materials to Valuable Products

The global demand for eco-friendly energy has propelled biomass into the spotlight. This report delves into biomass conversion technologies, including biochemical and thermochemical processes, with a focus on hydrothermal conversion. It highlights challenges related to cost-effectiveness and commercial viability. Thermochemical conversion processes, such as pyrolysis and combustion, unlock energy from organic matter. Hydrothermal processing's three approaches and their efficiency are discussed, particularly in biofuels, chemicals, and biochar production. The review analyzes hydrothermal gasification, emphasizing its efficiency and minimal processing time. Carbon and hydrogen gasification efficiencies are crucial in determining gas yields in supercritical conditions. Yield distribution and the influence of feedstock nature and composition on product yield are examined. In conclusion, this report offers insights into biomass conversion technologies and their sustainability for energy and chemical needs.

Food waste: analysis of the complex and variable composition of a promising feedstock for valorisation

There are global concerns about the environmental, social, and economic consequences associated with the generation of food waste. To effectively address this challenge, and particularly to develop food waste valorisation approaches, it is necessary to acquire understanding of the physicochemical and biochemical characteristics of food waste. This study comprises a systematic overview and quantitative assessment of the characteristics of food waste biomass, and this was achieved through a comprehensive literature review. The resulting database encompasses the physicochemical, biochemical, and elemental composition of food waste. The study evaluates food waste variability, analyses correlations between components, and highlights patterns in composition. Overall, food waste is a rather variable material. Typology, collection source and geographical origin of food waste streams are the main contributing factors to variation in physicochemical, biochemical and elemental compositions of food waste, while collection season and storage temperature appear not to be contributing substantially to variation. A clear distinction between plant-based and animal-based food waste biomass can be observed with animal-matter enriched food waste having high contents of protein, lipid and ash, but a low starch content. On the other hand, plant-based food waste can be either high in lignin and low in starch or high in carbohydrates, starch and higher heating value. Fibre content appears an indicative parameter, distinguishing plant from animal enriched food waste, and correlating strongly with lignin-rich, starch-poor plant biomass. The heterogeneity of food waste biomass composition will create challenges in developing and scaling up appropriate food waste management. The current study shows that the analysis of specific food waste parameters, such as fibre content, can be used, to inform the choice of the most appropriate valorisation route.

Single-step and stepwise pyrolysis to recover high-value chemicals from mixed polyolefins and polylactide

Biodegradable plastics are increasingly utilized due to environmental concerns but are typically disposed of together with conventional plastics. Valuable chemicals could be recovered from waste plastics by chemical recycling, but the mixing of different types of waste plastic affects the efficiency of the process. In this study, high-value chemicals were produced from a mixture of polyolefins and biodegradable polylactide by single and stepwise pyrolysis processes. The pyrolysis of polyolefins yielded fuel-like hydrocarbons, and the pyrolysis of polylactide yielded lactide and lactic acid. In the stepwise process, oxygenated compounds were only produced in the low-temperature step, and fuel-like hydrocarbons produced in the high-temperature step were not contaminated by oxygenated compounds. The influence of different catalysts on yields was investigated in the single-step and stepwise processes. The yield and selectivity of each product were significantly influenced by the type of catalyst and the composition of the plastic feedstock. Using a mixed feedstock of polyolefins and polylactide, low-temperature pyrolysis with a zeolite LTA catalyst favored the formation of lactide and lactic acid, while diesel-range hydrocarbons were obtained in the second step at a higher temperature. Aromatic and gasoline-range hydrocarbons were preferably produced from the single-step pyrolysis of polyolefins with spent FCC catalyst.

Separation Study of Magnesium–Lithium from Low‐Mg/Li Brine

The lithium present in salt lakes constitutes a significant and valuable resource. There are various methods for extracting lithium from salt lake brine, but currently, they all face challenges such as high energy consumption and low utilization efficiency of lithium resources. One prominent issue is the composition of feedstock during lithium extraction, specifically determining the optimal concentration ratio (nMg/nLi value). This constitutes a critical aspect in the later stages of the extraction process, influencing the cost and efficiency of lithium extraction processes. The fundamental reason for this prominent issue is the effective control of the evaporation and concentration process of lithium‐containing brines, which is caused by the disconnection between the evaporation process and the subsequent processing and extraction stages. Therefore, considering the concentration variation patterns of Li+ and Mg2+ in brine during the evaporation process, paper employs a combination of experimental research and computational simulation. It investigates the variation of Li‐Mg concentrations and their interactions during the natural evaporation enrichment process. The research investigates changes in lithium and magnesium concentrations and their interactions during natural evaporation enrichment process of salt lake. Elucidates the mechanism of lithium migration and proposes a new lithium extraction process ‐ the ‘3 Steps 2 Units’.

Investigating the properties and agronomic benefits of onion peel and chicken feather-derived biochars

Biochar production from unconventional biomass, specifically onion peel (OP) and chicken feathers (CF), was investigated in this study. Two distinct biochars were produced by doping each biomass with the other, with the aim of exploring the synergistic effects of different feedstock combinations on biochar properties. The biochar production process was conducted using a retort heating method and characterized using several techniques. A yield of 36 % was obtained for OP-doped biochar (OP92CF8-BC) and 23 % for CF-doped biochar (F92OP8-BC). Fourier Transform Infrared Spectroscopy analysis revealed characteristic functional groups from cellulose, hemicellulose, and lignin in OP92CF8-BC, while CF92OP8-BC displayed keratin-related peaks. Scanning Electron Microscopy imaging showed surface morphology differences, with OP92CF8-BC exhibiting a rougher and more porous structure compared to CF92OP8-BC. Energy-Dispersive X-ray Spectroscopy analysis confirmed the elemental composition, with OP92CF8-BC having higher carbon, calcium, and sulfur contents and CF92OP8-BC having higher nitrogen and oxygen contents. The biochar had specific surface areas of 342.4 and 200.80 m2/g for OP92CF8-BC and CF92OP8-BC, respectively. According to the results, using biochar treatments-more especially, CF92OP8-BC-can significantly enhance cob weight. This could be good for agricultural productivity. These findings highlight the influence of feedstock composition on the properties of biochar and provide insights for its potential applications in soil amendment and pollutant removal.

The Fate of Fluorine Post Per- and Polyfluoroalkyl Substances Destruction during the Thermal Treatment of Biosolids: A Thermodynamic Study

Per- and polyfluoroalkyl substances (PFAS) are a group of fluorinated synthetic chemicals that are highly recalcitrant, toxic, and bio-accumulative and have been detected in biosolids worldwide, posing potential risks to humans and the environment. Recent studies suggest that the organic C-F bond in PFAS can be destructed and potentially mineralised into inorganic fluorides during thermal treatment. This study focuses on thermodynamic equilibrium investigations and the fate of fluorine compounds post-PFAS destruction during biosolid thermal treatment. The results indicate that gas-phase fluorine compounds are mainly hydrogen fluoride (HF) and alkali fluorides, whereas solid-phase fluorine compounds include alkaline earth fluorides and their spinels. High moisture and oxygen content in the volatiles increased the concentration of HF in the gas phase. However, adding minerals reduced the emission of HF in the gas phase significantly and enhanced the capture of fluorine as CaF2 spinel in the solid phase. This study also investigates the effect of feedstock composition on the fate of fluorine. High ash content and low volatile matter in the feedstock reduced HF gas emissions and increased fluorine capture in the solid product. The findings of this work are useful in designing thermal systems with optimised operating conditions for minimising the release of fluorinated species during the thermal treatment of PFAS-containing biosolids.