Integrated thermochemical conversion process for valorizing mixed agricultural and dairy waste to nutrient-enriched biochars and biofuels.

Hydrothermal carbonization (HTC) and pyrolysis are two promising thermochemical conversion strategies to valorize agricultural wastes, yet neither process can be implemented alone to sustainably upgrade both wet and dry feedstocks. HTC is ideal for wet feedstocks, such as manure, but its solid hydrochars suffer from low surface area and stability. Pyrolysis is well suited to dry agricultural residues, but pyrolysis biochars have low nutrient contents and bio-oils are often highly oxygenated. We propose an integrated process that co-pyrolyzes a nutrient-rich cow manure hydrochar with raw agricultural residues, which effectively reduces the environmental impact of these wastes while producing value-added bioproducts. Biochars produced from the proposed process are more suitable for soil amendments due to their enhancement in bioavailable nutrients and surface area than the manure hydrochars and raw biomass. Co-pyrolysis of blends enriched with cow manure yield oils higher in alkanes and alkenes with fewer oxygenated compounds.

Pyrolysis of oil extracted safflower seeds: Product evaluation, kinetic and thermodynamic studies.

In this study, pyrolysis kinetics and thermodynamic parameters of Safflower residues (SR) obtained from oil extraction were investigated by using TG/DSC-FTIR and py-GC/MS. Thermal analysis was performed from ambient temperature to 750 °C under a nitrogen atmosphere. The first-order reaction kinetics model was applied to thermal analysis data to determine apparent kinetic parameters. Activation energy and pre-exponential factor were calculated as 76.60 kJ.mol-1 and 1.89x106 min-1, respectively. The thermodynamic parameters such as the change in Gibb's free energy, the difference in enthalpy and the entropy change were calculated to be 201.36 kJ mol-1, 71.79 kJ mol-1, and -0.196 kJ mol-1, respectively. TG/FTIR analysis revealed that CO2, C6H5OH, and CC functional group as the main pyrolysis gas products. According to Py-GC/MS results of SR, the presence of high energy-containing compounds among the pyrolysis products was proved. All these results show that SR is suitable for pyrolysis to produce biofuel and/or chemicals.

Demonstrating the suitability of canola residue biomass to biofuel conversion via pyrolysis through reaction kinetics, thermodynamics and evolved gas analyses.

The identification of biomasses for pyrolytic conversion to biofuels depends on many factors, including: moisture content, elemental and volatile matter composition, thermo-kinetic parameters, and evolved gases. The present work illustrates how canola residue may be a suitable biofuel feedstock for low-temperature (<450 °C) slow pyrolysis with energetically favorable conversions of up to 70 wt% of volatile matter. Beyond this point, thermo-kinetic parameters and activation energies, which increase from 154.3 to 400 kJ/mol from 65 to 80% conversion, suggest that the energy required to initiate conversion is thermodynamically unfavorable. This is likely due to its higher elemental carbon content than similar residues, leading to enhanced carbonization rather than devolatilization at higher temperatures. Evolved gas analysis supports limiting pyrolysis temperature; ethanol and methane conversions are maximized below 500 °C with ∼6% water content. Carbon dioxide is the dominant evolved gas beyond this temperature.

Thermokinetic analysis and product characterization of Medium Density Fiberboard pyrolysis.

This study investigates the pyrolysis of Medium Density Fiberboard (MDF) as a potential waste management solution. Thermal behaviour of MDF was analysed via TG/DSC. The primary decomposition step occurred between 190 °C and 425 °C. Evolved gaseous products over this step were evaluated by a FTIR spectrometer coupled with TGA. Peaks for phenolic, alcohols and aldehydes were detected at the maximum decomposition temperature. Py-GC/MS analysis revealed phenols, ketones and cyclic compounds as the primary non-condensable pyrolysis products. The kinetics of pyrolysis were investigated by the widely applied Distributed Activation Energy Model, resulting in an average activation energy and pre-exponential factor of 127.40 kJ mol-1 and 8.4E+11. The results of this study suggest that pyrolyzing MDF could potentially provide renewable fuels and prevent environmental problems related with MDF disposal.

Pyrolysis reaction models of waste tires: Application of Master-Plots method for energy conversion via devolatilization.

Land applied disposal of waste tires has far-reaching environmental, economic, and human health consequences. Pyrolysis represents a potential waste management solution, whereby the solid carbonaceous residue is heated in the absence of oxygen to produce liquid and gaseous fuels, and a solid char. The design of an efficient conversion unit requires information on the reaction kinetics of pyrolysis. This work is the first to probe the appropriate reaction model of waste tire pyrolysis. The average activation energy of pyrolysis was determined via iso-conversional methods over a mass fraction conversion range between 0.20 and 0.80 to be 162.8±23.2kJmol-1. Using the Master Plots method, a reaction order of three was found to be the most suitable model to describe the pyrolytic decomposition. This suggests that the chemical reactions themselves (cracking, depolymerization, etc.), not diffusion or boundary layer interactions common with carbonaceous biomasses, are the rate-limiting steps in the pyrolytic decomposition of waste tires.

Improved prediction of higher heating value of biomass using an artificial neural network model based on proximate analysis.

As biomass becomes more integrated into our energy feedstocks, the ability to predict its combustion enthalpies from routine data such as carbon, ash, and moisture content enables rapid decisions about utilization. The present work constructs a novel artificial neural network model with a 3-3-1 tangent sigmoid architecture to predict biomasses' higher heating values from only their proximate analyses, requiring minimal specificity as compared to models based on elemental composition. The model presented has a considerably higher correlation coefficient (0.963) and lower root mean square (0.375), mean absolute (0.328), and mean bias errors (0.010) than other models presented in the literature which, at least when applied to the present data set, tend to under-predict the combustion enthalpy.

Application of artificial neural networks to co-combustion of hazelnut husk-lignite coal blends.

The artificial neural network (ANN) theory is applied to thermal data obtained by non-isothermal thermogravimetric analysis (TGA) from room temperature to 1000°C at different heating rates in air to study co-combustion of hazelnut husk (HH)-lignite coal (LC) blends of various composition. The heating rate, blend ratio and temperature were used in the ANN analysis to predict the TG curves of the blends as parameters that affect the thermal behavior during combustion. The ANN model provides a good prediction of the TG curves for co-combustion with a coefficient of determination for the developed model of 0.9995. The agreement between the experimental data and the predicted values substantiated the accuracy of the ANN calculation.

Pyrolysis kinetics and thermal characteristics of microalgae Nannochloropsis oculata and Tetraselmis sp.

In this study non-isothermal thermogravimetric analysis were used to investigate pyrolysis behavior and kinetics of microalgae Nannochloropsis oculata (NO) and Tetraselmis sp. (TS). TG/DTG experiments at different heating rates were carried out. Heating rates had slight effect on the decomposition trend, however the maximum temperature and peak of weight loss rate in the DTG curves shifted towards higher temperature with the increase in heating rate. The average activation energy and pre-exponential factor for pyrolysis of NO and TS were estimated by distributed activation energy model. The highest activation energies were observed as 152.20 and 334kJ/mol for NO and TS, respectively, at various conversions. The pre-exponential factors for the corresponding activation energies were observed to be in the order of 10(8)-10(13) and 10(12)-10(25)s(-1) for NO and TS, respectively. Calculated kinetic parameters were used to predict devolatilization curves and results were in well agreement with experimental data.

Kinetic analysis on the non-isothermal degradation of plum stone waste by thermogravimetric analysis and integral master-plots method.

In this study, pyrolysis of plum stone was investigated by thermogravimetric analysis in a nitrogen atmosphere at heating rates of 5, 10, 20 and 40 °C min(-1). Pyrolysis characteristics and the thermal-decomposition rate were significantly affected by variation in the heating rate. However, the heating rate slightly affected the total yield of the volatile matters. Activation energy of the pyrolysis reaction was evaluated by model-free methods, Friedman and Kissingere-Akahirae-Sunose. Results of the Master-Plots method indicated that the most probable reaction model function was the nth order reaction model function as f(x) = (1-x) (3.11), A = 8.02x10(12) under a mean activation energy of 150.61 kJ mol(-1). Proximate and ultimate analysis showed that plum stone can be considered as a favourable source for energy production owing to its low moisture and ash content, and high volatile matter ratio and moderate heating value.

Thermal behaviour and kinetics of alga Polysiphonia elongata biomass during pyrolysis.

The pyrolysis characteristics and kinetics of Polysiphonia elongata were investigated using a thermogravimetric analyzer. The main decomposition of samples occurred between 225 °C and 485 °C at heating rates of 5-40 °C/min; owing to release of 78-82% of total volatiles. The heating rate effected pyrolysis characteristics such as maximum devolatilization rate and decomposition temperature. However, total volatile matter yield was not significantly affected by heating rate. The activation energy of pyrolysis reaction was calculated by model free Friedman and Kissenger-Akahira-Sunose methods and mean values were 116.23 kJ/mol and 126.48 kJ/mol, respectively. A variance in the activation energy with the proceeding conversions was observed for the models applied, which shows that the pyrolysis process was composed of multi-step kinetics. The Coats-Redfern method was used to determine pre-exponential factor and reaction order. The obtained parameters were used in simulation of pyrolysis process and results were in a good agreement with experimental data.

Pyrolysis kinetics of hazelnut husk using thermogravimetric analysis.

This study aims at investigating physicochemical properties and pyrolysis kinetics of hazelnut husk, an abundant agricultural waste in Turkey. The physicochemical properties were determined by bomb calorimeter, elemental analysis and FT-IR spectroscopy. Physicochemical analysis results showed that hazelnut husk has a high calorimetric value and high volatile matter content. Pyrolysis experiments were carried out in a thermogravimetric analyzer under inert conditions and operated at different heating rates (5, 10, 20°C/min). Three different kinetic models, the iso-conversional Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) models and Coats-Redfern method were applied on TGA data of hazelnut husk to calculate the kinetic parameters including activation energy, pre-exponential factor and reaction order. Simulation of hazelnut husk pyrolysis using data obtained from TGA analysis showed good agreement with experimental data. Combining with physicochemical properties, it was concluded that this biomass can become useful source of energy or chemicals.

Interplay of adaptive capabilities of Halomonas sp. AAD12 under salt stress.

In the present study, osmoadaptive mechanism of Halomonas sp. AAD12 was studied through analysis of changes in its proteome maps and osmolyte accumulation strategy to understand how this euryhaline microorganism masters osmotic stress of saline environments. Under salt stress, there were significant variations in the expression of proteins involved in osmoregulation, stress response, energy generation and transport. This was accompanied by an increase in proline and hydroxyectoine but a decrease in ectoine accumulation. The major osmolyte at high salinity was proline. Unexpectedly the size of the total ectoines' pool was smaller at elevated salinity. Experimental findings were then integrated with a metabolic model to get insight into carbon trafficking during osmoadaptation. Simulations predicted that the total flux through energy generating pathways, namely gluconeogenesis and the pentose phosphate pathway, was significantly lower and carbon source that entered the system as citrate was mainly diverted to osmolyte synthesis at high salinity. Overall these results suggested that the moderately halophilic Halomonas sp. AAD12 pursued a different osmoregulatory strategy than the two well known moderate halophiles, Chromohalobacter salexigens and Halobacillus halophilus. The climbing value of osmolytes such as ectoine in health care and skin care products places significant attention to halophilic microorganisms hence an understanding of the osmoadaptive mechanism and osmolyte accumulation strategy of this isolate is very valuable to be able to manipulate its metabolism towards desired goals.

Proteomic insight into phenolic adaptation of a moderately halophilic Halomonas sp. strain AAD12.

A gram-negative, moderately halophilic bacterium was isolated from Çamalti Saltern area, located in the Aegean Region of Turkey. Analysis of its 16S rRNA gene sequence and physiological characteristics showed that this strain belonged to the genus Halomonas ; hence, it was designated as Halomonas sp. strain AAD12. The isolate tolerated up to 800 mg⋅L(-1) phenol; however, at elevated concentrations, phenol severely retarded cell growth. The increase in lag phase with increasing phenol concentrations indicated that the microorganism was undergoing serious adaptative changes. To understand the physiological responses of Halomonas sp. strain AAD12 to phenol, a 2-dimensional electrophoresis approach combined with mass spectrometric analysis was used. This approach showed that the expression of 14 protein spots were altered as phenol concentration increased from 200 to 800 mg⋅L(-1). Among the identified proteins were those involved in protein biosynthesis, energy, transport, and stress metabolism. So far, this is the first study on phenolic adaptation of a gram-negative, moderately halophilic bacteria using proteomic tools. The results provided new insights for understanding the general mechanism used by moderately halophilic bacteria to tolerate phenol and suggested the potential for using these microorganisms in bioremediation.

Preliminary phenotypic characterization of newly isolated halophilic microorganisms by footprinting: a rapid metabolome analysis.

The emerging need for rapid screening and identification methods for microbiological purposes necessitates the combined uses of high-tech instruments. In this work, electrospray ionization mass spectrometry was used to visualize the relation of ten newly isolated moderately halophilic microorganisms, to Halomonas salina DSMZ 5,928 and Halomonas halophila DSMZ 4,770. The method was based on the global analysis of the metabolites in culture media and is termed as metabolic footprinting. Since it was not possible to gain insight into the similarities solely based on the visual inspection of the chromatograms, principal component (PC) analysis was applied on the data. Three PCs alone were able to explain 99% of the information in the data set. The score plots revealed the relation of the new isolates to the two type strains whereas the loading plots gave important clues on the significant ions responsible for the observed clustering. Loading plots also indicated inversely correlated ions that give clues on differing metabolic pathways. The work described here offers a potentially useful way for preliminary rapid phenotypic characterization of new and closely related isolates and a method for screening of similar microorganisms for different and valuable secondary metabolites.