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[Display omitted] • An integrated HTC–PY technique was implemented to valorizes CS and YW. • HTC improved carbon content, deoxygenation, and higher heating value. • CSH and YWH hydrochars' co–pyrolysis modeled via hybrid RSM–ANN. • The pyrolysis of blends reduced the average activation energy. • Pyrolysis of hydrochars enriched bio–oil with hydrocarbons and phenols. Hydrothermal carbonization (HTC) presents a promising method for converting carbonaceous waste into renewable fuels, facilitating energy recovery. This study focuses on the HTC pretreatment of microalgae (Chlorella sorokiniana) and yard waste, examining their physicochemical structural changes, component migration, and potential for valorization via integrated HTC and pyrolysis processes. HTC notably enhances the carbon content while reducing oxygen and nitrogen levels in these feedstocks, producing a clean solid fuel with high energy density. The study investigates the pyrolytic behavior of hydrochars and their blends using different analytical techniques, kinetic modeling, and fixed–bed reactor experiments. The blends with 90% and 70% of microalgae hydrochar (CSH) exhibited the most significant synergistic effects during co–pyrolysis, evident in its devolatilization behaviors and reduced activation energies. Integrating artificial neural networks and response surface methodology models facilitated optimization of pyrolysis parameters and accurate prediction of bio–oil, biochar, and gas yields. The analytical techniques enabled characterization of pyrolysis products, revealing notable changes in bio–oil and biochar compositions, suggesting potential enhancements. The study comprehensively evaluates the HTC–pyrolysis approach's potential for converting microalgae and lignocellulosic biomass into eco–friendly biofuels for industrial applications. [ABSTRACT FROM AUTHOR]

In this study, co-pyrolysis of low-lipid Nannochloropsis sp. (NS) and waste polystyrene (PS) was deeply investigated using TG-MS-FTIR and Fixed bed reactor to characterize their thermal behaviors, kinetics, evolved gases, and products distribution. The (D)TG investigation of the co-pyrolysis process revealed two distinct stages of thermal decomposition: the first stage (150–420 °C) was mostly caused by NS decomposition, whereas the second stage (420–550 °C) was attributed to NS-PS decomposition. The difference between experimental and theoretical mass loss (ΔW) was lower than zero when the proportion of NS was 75% and 65%. In addition, the average activation energy of the blends containing 75% and 65% of NS was less than sole NS. Thus, based on thermal behaviors and activation energies, the blends with an NS content of 75% and 65% exhibited the strongest synergistic effect. The results of TG-MS, TG-FTIR, and GC-MS analyses revealed that the co-pyrolysis considerably boosted the production of hydrocarbons, notably aromatic hydrocarbons, while concurrently restricting the production of nitrogenous and oxygenous compounds. This study will contribute to a better understanding of the utilization of low-lipid microalgae. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A zero-waste biorefinery concept was developed by pyrolyzing the residual microalgae biomass. • The pyrolysis process was effectively modeled using an integrated ANN and RSM technique. • The maximum H 2 production of 44.46 vol% was produced at optimal conditions. • At 500 °C, max. hydrocarbons and min. N- & O-containing compounds observed in bio-oil. • With the increasing temperature, the biochar exhibited more cracks and holes. The present work focused on the pyrolysis-based valorization of microalgae biomass residual for the generation of sustainable fuel and value-added chemicals. Key pyrolysis factors, including temperature, residence time, particle size, and heating rate, were modeled via an artificial neural network (ANN) and response surface methodology (RSM) models. The use of such an integrated technique was able to conquer the individual constraints of both modeling approaches. RSM model for H 2 -rich syngas demonstrated that the value; R2 = 0.99, minimum p = 0.00, and maximum F = 3877.16 has close relation among the statistical parameters. The ANN model for H 2 -rich syngas revealed that higher R2 = 0.9985 and lower RSME = 0.1038 were obtained for the training phase, while; the higher R2 and lower RSME values of 0.9862 and 0.2661 were estimated for the training phase hence showed a better agreement among the parameters. Optimum H 2 production of 44.46 vol% was produced at temperature = 516.76 °C, residence time = 17.7 min, particle size = 0.23 mm, and heating rate = 17.37 °C/min. All the pyrolytic products have been characterized in detail and are recommended for high end-use. The GC/MS technique revealed that bio-oil was constituted of various organic complexes, which could be used as a substitute for hydrocarbon fuels after undergoing certain upgradation procedures (e.g., hydrotreating, hydrodeoxygenation, hydrodenitrogenation, and hydrocracking) and extracted into different chemicals. In addition, the biochar was characterized using the SEM technique, which also demonstrated its potential as fuel and in a variety of other applications. The study showed that de-fatted Chlorella sorokiniana residue (De-CR) could be efficiently employed to produce bio-energy precursors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A zero-waste biorefinery concept was developed by pyrolyzing the residual microalgae biomass. • The pyrolysis process was effectively modeled using an integrated ANN and RSM technique. • The maximum H 2 production of 44.46 vol% was produced at optimal conditions. • At 500 °C, max. hydrocarbons and min. N- & O-containing compounds observed in bio-oil. • With the increasing temperature, the biochar exhibited more cracks and holes. The present work focused on the pyrolysis-based valorization of microalgae biomass residual for the generation of sustainable fuel and value-added chemicals. Key pyrolysis factors, including temperature, residence time, particle size, and heating rate, were modeled via an artificial neural network (ANN) and response surface methodology (RSM) models. The use of such an integrated technique was able to conquer the individual constraints of both modeling approaches. RSM model for H 2 -rich syngas demonstrated that the value; R2 = 0.99, minimum p = 0.00, and maximum F = 3877.16 has close relation among the statistical parameters. The ANN model for H 2 -rich syngas revealed that higher R2 = 0.9985 and lower RSME = 0.1038 were obtained for the training phase, while; the higher R2 and lower RSME values of 0.9862 and 0.2661 were estimated for the training phase hence showed a better agreement among the parameters. Optimum H 2 production of 44.46 vol% was produced at temperature = 516.76 °C, residence time = 17.7 min, particle size = 0.23 mm, and heating rate = 17.37 °C/min. All the pyrolytic products have been characterized in detail and are recommended for high end-use. The GC/MS technique revealed that bio-oil was constituted of various organic complexes, which could be used as a substitute for hydrocarbon fuels after undergoing certain upgradation procedures (e.g., hydrotreating, hydrodeoxygenation, hydrodenitrogenation, and hydrocracking) and extracted into different chemicals. In addition, the biochar was characterized using the SEM technique, which also demonstrated its potential as fuel and in a variety of other applications. The study showed that de-fatted Chlorella sorokiniana residue (De-CR) could be efficiently employed to produce bio-energy precursors. [ABSTRACT FROM AUTHOR]