Pyrolysis characteristics and pathways of protein, lipid and carbohydrate isolated from microalgae Nannochloropsis sp

Pyrolysis mechanism and pyrolysis kinetics of yellow wine lees

Yellow wine lees, a by-product produced while brewing yellow wine, can be a helpful biomass resource through pyrolysis. However, there have been very few studies on the pyrolysis of yellow wine lees. The kinetics and mechanism of pyrolysis in yellow wine lees were explored through an extensive study of their chemical and elemental composition. The pyrolysis mechanism of yellow wine lees was further studied using thermogravimetric analysis (TGA) from 30 °C to 900 °C. The TG/DTG analysis showed that yellow wine lees thermally decomposed mainly between 121 °C and 500 °C. The maximum decomposition was observed between 218 °C and 326 °C, with a clear peak at 298 °C. Upon analyzing the 3D-FTIR results, the gas phase products at this stage primarily included inorganic molecules like CO2, H2O, and CH4, along with organic compounds such as esters, alcohols, phenols, amines, ethers, aldehydes, ketones, and acids. The Maillard reaction and ketosis decarboxylation primarily occurred in proteins (amino acids) and carbohydrates. The pyrolysis kinetics of yellow wine lees were analyzed utilizing the distributed activation energy model (DAEM). The results of DAEM were simultaneously verified using the Flynn-Wall-Ozawa (FWO) method. The findings indicated that the pyrolysis of yellow wine lees conforms to the assumptions of infinite parallel reactions and activation energy distribution. As the conversion rate increased during pyrolysis, the activation energy of yellow wine lees initially increased to 210-220 kJ mol-1, then stabilized at 190-200 kJ mol-1 and rapidly decreased to approximately 100 kJ mol-1. This study offers a theoretical basis for the application of yellow wine lees using pyrolysis.

Anaerobic digestion of process water from hydrothermal treatment processes: a review of inhibitors and detoxification approaches

Integrating hydrothermal treatment processes and anaerobic digestion (AD) is promising for maximizing resource recovery from biomass and organic waste. The process water generated during hydrothermal treatment contains high concentrations of organic matter, which can be converted into biogas using AD. However, process water also contains various compounds that inhibit the AD process. Fingerprinting these inhibitors and identifying suitable mitigation strategies and detoxification methods is necessary to optimize the integration of these two technologies. By examining the existing literature, we were able to: (1) compare the methane yields and organics removal efficiency during AD of various hydrothermal treatment process water; (2) catalog the main AD inhibitors found in hydrothermal treatment process water; (3) identify recalcitrant components limiting AD performance; and (4) evaluate approaches to detoxify specific inhibitors and degrade recalcitrant components. Common inhibitors in process water are organic acids (at high concentrations), total ammonia nitrogen (TAN), oxygenated organics, and N-heterocyclic compounds. Feedstock composition is the primary determinant of organic acid and TAN formation (carbohydrates-rich and protein-rich feedstocks, respectively). In contrast, processing conditions (e.g., temperature, pressure, reaction duration) influence the formation extent of oxygenated organics and N-heterocyclic compounds. Struvite precipitation and zeolite adsorption are the most widely used approaches to eliminate TAN inhibition. In contrast, powdered and granular activated carbon and ozonation are the preferred methods to remove toxic substances before AD treatment. Currently, ozonation is the most effective approach to reduce the toxicity and recalcitrance of N and O-heterocyclic compounds during AD. Microaeration methods, which disrupt the AD microbiome less than ozone, might be more practical for nitrifying TAN and degrading recalcitrant compounds, but further research in this area is necessary.

Taguchi approach for assessing supercritical CO2 (sCO2) fluid extraction of polyhydroxyalkanoate (PHA) from Chlorella Vulgaris sp. microalgae

This research explicitly investigates the utilization of Chlorella Vulgaris sp. microalgae as a renewable source for lipid production, focusing on its application in bioplastic manufacturing. This study employed the supercritical fluid extraction technique employing supercritical CO2 (sCO2) as a green technology to selectively extract and produce PHA's precursor utilizing CO2 solvent as a cleaner solvent compared to conventional extraction method. The study assessed the effects of three extraction parameters, namely temperature (40-60 °C), pressure (15-35 MPa), and solvent flow rate (4-8 ml/min). The pressure, flowrate, and temperature were found to be the most significant parameters affecting the sCO2 extraction. Through Taguchi optimization, the optimal parameters were determined as 60 °C, 35 MPa, and 4 ml/min with the highest lipid yield of 46.74 wt%; above-average findings were reported. Furthermore, the pretreatment process involved significant effects such as crumpled and exhaustive structure, facilitating the efficient extraction of total lipids from the microalgae matrix. This study investigated the microstructure of microalgae biomatrix before and after extraction using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Fourier-transform infrared spectroscopy (FTIR) was utilized to assess the potential of the extracted material as a precursor for biodegradable plastic production, with a focus on reduced heavy metal content through inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The lipid extracted from Chlorella Vulgaris sp. microalgae was analysed using gas chromatography-mass spectrometry (GC-MS), identifying key constituents, including oleic acid (C18H34O2), n-Hexadecanoic acid (C16H32O2), and octadecanoic acid (C18H36O2), essential for polyhydroxyalkanoate (PHA) formation.

Pyrolytic mechanisms of typical organic components of sewage sludge in the presence of CaO: Polysaccharides, proteins, and lipids

The addition of CaO could facilitate the conversion of sewage sludge (SS) from waste to high-purity syngas. The pyrolytic characteristics of SS are a comprehensive manifestation of polysaccharides, proteins, and lipids, while the influence of CaO on their pyrolytic characteristics is rarely reported. This study conducted a thorough investigation into the pyrolytic mechanism of starch, protein, and lipid in the presence of CaO by analysing their thermal behavior, gaseous products, liquid tar, and residual char. The findings from TGA, GC, GC-MS, and FT-IR analysis indicate that the addition of CaO catalytically lowers the pyrolysis temperature of starch, protein, and lipid components and promotes their conversion into small molecules, resulting in increased syngas production. Moreover, the combination of char with the carbonation and calcination cycle of CaO leads to a significant boost in syngas (H2 and CO) yield, with up to 3 and 10 times increase from starch and protein, respectively, and a higher syngas selectivity of up to 65 %. The study also identifies those polysaccharides and proteins are the primary sources of syngas. This study can provide further insight into SS pyrolysis for syngas production in the presence of CaO and the necessary parameters to predict the pyrolysis behavior of SS in industrial applications.

Independent parallel pyrolysis kinetics of model components in sewage sludge analyzed by BPM neural network

Analyzing the kinetic behavior of sewage sludge pyrolysis is essential for the design of efficient reactors to produce biofuel and syngas. To understand the complex pyrolysis process of sewage sludge, we pyrolyzed six model components (i.e., cellulose, hemicellulose, lignin, protein, soluble sugars, and lipid) using a thermogravimetric analyzer. The effects of the heating rate on the pyrolysis process were examined at four different heating rates (5, 15, 25, and 50 °C/min). As temperature increased, the derivative thermogravimetric peaks shifted to higher temperature zones. The temperature ranges of the maximum mass loss rate for cellulose, hemicellulose, lignin, protein, soluble sugars, and lipid were within 326.1-368.0 °C, 288.7-315.5 °C, 375.1-429.4 °C, 291.9-308.0 °C, 251.0-314.1 °C, and 410.8-454.1 °C, respectively. The apparent activation energies of the model components were obtained using non-isothermal kinetic analysis methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose). In addition, a back-propagation artificial neural network with a momentum algorithm (BPM) was developed to predict the relationship between the pyrolysis experiment and the activation value. The best BPM model (BPM5) for predicting the cellulose pyrolysis was identified.

Biological calcium carbonate enhanced the ability of biochar to passivate antimony and lead in soil

The mechanism of immobilization of heavy metals in the soil using biochar has been studied extensively. However, the decomposition of biochar by biological and abiotic factors can reactivate the immobilized heavy metals in soil. Previous research showed that the addition of biological calcium carbonate (bio-CaCO3) can significantly increase the stability of biochar. However, the influence of bio-CaCO3 on the ability of biochar to immobilize heavy metals remains unclear. Therefore, this study evaluated the effect of bio-CaCO3 on the use of biochar to immobilize the cationic heavy metal lead and the anionic heavy metal antimony. The addition of bio-CaCO3 not only significantly improved the passivation ability of Pb and Sb but also reduced their migration in the soil. Mechanistic studies have shown that the reasons for the enhanced ability of biochar to immobilize heavy metals can be summarized in three aspects. First, the introduced inorganic component CaCO3 can precipitate and exchange ions with lead and antimony. Second, the N element in the organic component of bio-CaCO3 underwent polycondensation with the organic carbon in biochar to form pyridine N and pyrrole N structures, which can form a strong complex with lead and antimony. Pyridine N complexes more strongly than pyrrole N. Third, bio-CaCO3 increased the degree of aromatization and the surface π-electron density of biochar, which enhanced the ability of biochar to adsorb heavy metals. This study will provide a new concept for the application of biochar as an amendment to remediate heavy metals in the soil.

Synergistic interactions between sewage sludge, polypropylene, and high-density polyethylene during co-pyrolysis: An investigation based on iso-conversional model-free methods and master plot analysis

Sewage sludge (SS) is a hazardous by-product of wastewater treatment processes that requires careful management for minimal environmental impacts and effective resource recovery. Through thermochemical processes such as pyrolysis, clean energy is recovered from SS in the form of bio-oil, biogas, and biochar. To improve the yield and quality of products, the co-pyrolysis of more than two materials is increasingly gaining interest. Here, the thermal behaviour, kinetics, and synergistic interactions during the co-pyrolysis of SS with polypropylene (PP) and high-density polyethylene (HDPE) were comparatively evaluated with thermogravimetric analysis at different mixing ratios and heat rates. Activation energies and reaction mechanisms were determined through iso-conversional model-free methods and master plot analysis. Evolved gases were monitored with thermogravimetric-mass spectrometry. Increased volatile conversion and degradation rates, and reduced activation energies during co-pyrolysis were mediated by synergistic interactions between H-radicals of PP/HDPE and oxygenated intermediates of SS. Contrary to the pyrolysis of SS, PP and HDPE, the co-pyrolysis processes are predominantly diffusion-controlled. Insights into the co-pyrolysis processes of SS/PP and SS/HDPE gained from this work provide the theoretical support for subsequent investigation, facilitate design of waste-to-energy reactor, and aid the adoption of the technology to harness the bioenergy potential of the feedstocks.

Microalgae bio-oil production by pyrolysis and hydrothermal liquefaction: Mechanism and characteristics

Microalgae have great potential in producing energy-dense and valuable products via thermochemical processes. Therefore, producing alternative bio-oil to fossil fuel from microalgae has rapidly gained popularity due to its environmentally friendly process and elevated productivity. This current work aims to review comprehensively the microalgae bio-oil production using pyrolysis and hydrothermal liquefaction. In addition, core mechanisms of pyrolysis and hydrothermal liquefaction process for microalgae were scrutinized, showing that the presence of lipids and proteins could contribute to forming a large amount of compounds containing O and N elements in bio-oil. However, applying proper catalysts and advanced technologies for the two aforementioned approaches could improve the quality, heating value, and yield of microalgae bio-oil. In general, microalgae bio-oil produced under optimal conditions could have 46 MJ/kg heating value and 60% yield, indicating that microalgae bio-oil could become a promising alternative fuel for transportation and power generation.

Phase Behavior and Aggregate Transition Based on Co-assembly of Negatively Charged Carbon Dots and a pH-Responsive Tertiary Amine Cationic Surfactant

We studied the co-assembly of an oppositely changed binary mixture of selenium-doped carbon quantum dots (Se-CQDs) and N,N-dimethyl octylamide-propyl tertiary amine (DOAPA) through turbidity, ζ potential measurement, and cryogenic transmission electron microscopy (cryo-TEM) with the aim of fabricating supramolecular assemblies with multiple dimensions and novel morphologies. The Se-CQD/DOAPA binary mixture exhibited abundant phase behavior, in which an isotropic phase (I₁) was first observed, followed by turbidity (T), precipitation (P), and a second isotropic phase (I₂), as the DOAPA concentration increased. Then we focused on investigating the morphologies of samples. In cryo-TEM observations, spherical aggregates were observed in all phase sequences, whereas the aggregates have different ζ potentials and sizes. In the I₂ phase, interesting nanocapsule-like aggregates and spindle-like aggregates can be identified in addition to spherical aggregates. In combination with the rheological behaviors of the I₂ phase solution and the detailed structure of the aggregates from enlarged cryo-TEM images, it is possible that the Se-CQDs and DOAPA co-assemble with novel network-like building blocks. The turbid solutions were found to be responsive to pH in phase P, and spherical aggregates were obtained at pH 6.5 but turned into vesicles when the pH reached 5.0. On the basis of these findings, CQDs and surfactants can be good structural building blocks for supramolecular structures, and the diverse morphologies of aggregates offer the prospect of multiple applications in the future.

State-of-the-art of the pyrolysis and co-pyrolysis of food waste: Progress and challenges

The continuous growth of population and the steady improvement of people's living standards have accelerated the generation of massive food waste. Untreated food waste has great potential to harm the environment and human health due to bad odor release, bacterial leaching, and virus transmission. However, the application of traditional disposal techniques like composting, landfilling, animal feeding, and anaerobic digestion are difficult to ease the environmental burdens because of problems such as large land occupation, virus transmission, hazardous gas emissions, and poor efficiency. Pyrolysis is a practical and promising route to reduce the environmental burden by converting food waste into bioenergy. This paper aims to analyze the characteristics of food waste, introduce the production of biofuels from conventional and advanced pyrolysis of food waste, and provide a basis for scientific disposal and sustainable management of food waste. The review shows that co-pyrolysis and catalytic pyrolysis significantly impact the pyrolysis process and product characteristics. The addition of tire waste promotes the synthesis of hydrocarbons and inhibits the formation of oxygenated compounds efficiently. The application of calcium oxide (CaO) exhibits good performance in the increment of bio-oil yield and hydrocarbon content. Based on this literature review, pyrolysis can be considered as the optimal technique for dealing with food waste and producing valuable products.

Improving of Pyrolysis Oil from Macroalgae Cladophora glomerata with HDPE Pyrolysis Oil

The slow pyrolysis of macroalgae at moderate temperatures in the reactor used resulted in an oil with a slightly better calorific value than that of the literature, but the other properties were not convincing. Therefore, co-pyrolysis with HDPE offers a way out in this study. However, this did not improve the property profile as a fuel, as the co-pyrolysate was incombustible due to its high water content. Only a mixture of the pyrolysis oil from algae and of the HDPE wax from the initial pyrolysis of HDPE resulted in a diesel-like product: the density was from 807 kg m−3, the viscosity 3.39 mm2 s−1, the calorific value was 46 MJ kg−1, and the oxidation stability was 68 min. The isoparaffin index indicates only a low branching of the paraffins, and therefore a low research octane number of 80. The blend did not need any further stabilizing additives.

N,N-Dimethylformamide solvent assisted hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots

Microalgae are considered as a promising alternative to fossil fuels due to their ease of cultivation, short growth cycle and no occupation of cultivated land. In this study, N,N-Dimethylformamide (DMF) solvent was employed to assist hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots (CDs). The effect of pretreatment conditions on the composition and pyrolysis bio-oil distribution of hydrothermal solid residues as well as CDs characteristic were investigated by varying the temperature (180-220 ℃) and reaction time (1-9 h). The results showed that pretreated residues had higher cellulose. And the yield of sugar and N-contained compounds reached 41.59% and 63.57% in the pyrolysis bio-oil of pretreated algae residues, respectively. Moreover, CDs obtained from hydrothermal solution fluoresced red under 365 nm excitation. The paper provides a new method for the complete utilization of microalgae.

Hydrothermal hydrolysis of algal biomass for biofuels production: A review

Hydrothermal hydrolysis is an energy-efficient and economical pretreatment technology to disrupt the algal cells and hydrolyze the intracellular compounds, thereby promoting the biofuels production of fermentation. However, complex reaction mechanisms, unpredictable rheological properties of algal slurry, and immature continuous reactors still constrain the commercialization of such a process. To systematically understand the existing status and lay a foundation for promoting the technology, the chemical mechanism of hydrothermal hydrolysis of algal biomass is elaborated in this paper, and the influences of temperature, residence time, total solid content, and pH, on the biomethane production of hydrolyzed algal biomass are summarized. Besides, a comprehensive overview of the rheological behavior of algal slurries is discussed at various operational factors. The recent advances in flow, heat and mass transfer model coupling with the generic kinetics model in continuous reactors and the application of energy-saving strategies for efficient algal biomass pretreatment are detailed reviewed.

Biological calcium carbonate with a unique organic-inorganic composite structure to enhance biochar stability

Biochar stability is a key factor affecting the efficiency of soil carbon sequestration. Mineral calcium carbonate (M-CaCO₃) can enhance the stability of biochar, and the mechanism has been extensively studied; however, similar studies on biological calcium carbonate (Bio-CaCO₃), another natural form of calcium carbonate, are lacking. In this work, Bio-CaCO₃ was used as an additive to explore the mechanism by which it enhances the stability of biochar. The results showed that Bio-CaCO₃ improved the stability of biochar at pyrolysis temperatures ranging from 250 to 700 °C, and the enhancement effects increased upon increasing the pyrolysis temperature. The enhancement effects of M-CaCO₃ were better at lower temperatures (250 and 400 °C) while Bio-CaCO₃ was better at higher temperatures (550 and 700 °C). Mechanistic studies showed that the enhanced stability of Bio-CaCO₃ at 250 °C was due to the fact that the inorganic component in Bio-CaCO₃ promoted the deoxidation of the carbon matrix and the aromatization of aliphatic carbon at 400 °C. The reasons for the increased stability using Bio-CaCO₃ at high temperatures included two mechanisms. One is that the inorganic components in Bio-CaCO₃ promoted the aromatization of the carbon matrix. The other is that the unique organic nitrogen-containing functional groups in Bio-CaCO₃ underwent dimerization and cyclization with the organic carbon components in biomass to form a more stable pyridinic-N structure. This work provides novel ideas for enhancing biochar stability using Bio-CaCO₃.

Optical properties of biochemical compositions of microalgae within the spectral range from 300 to 1700 nm

The optical properties of biochemical compositions of microalgae are vital for the improvement of biosensor design, photobioreactor design, biofuel, and biophotonics techniques. A combination method using both the double optical pathlength transmission method (DOPTM) and the ellipsometry method (EM) is called DOPTM-EM, and it is used to acquire the optical constants of protein, lipid, and carbohydrate of Haematococcus pluvialis, Nannochloropsis sp., and Spirulina in both a solid state and a solution state within the visible and near-infrared spectral range. For different types of microalgae, the refractive indices of protein and carbohydrate in the solid state are similar to each other, but show an observed difference from lipid in the solid state. The refractive indices of protein and carbohydrate in the solution state presents a visible distinction in the researched spectral range. The absorption indices of protein, lipid, and carbohydrate in the solid state for these three types of microalgae are close to each other in the spectral range of 300-500 nm. However, an observed difference is shown in the spectral range of 500-1700 nm. For ease of application, the refractive index of biochemical composition of microalgae was fitted based on the Sellmeier equation. We believe this work can provide a reference to obtain the optical properties of biomaterial with high accuracy.

Different pyrolysis kinetics and product distribution of municipal and livestock manure sewage sludge

Thermogravimetric analysis and pyrolyzer-gas chromatography/mass spectrometry measurements were taken to examine the kinetic behavior and product distribution on the thermal and catalytic pyrolysis of different types of sewage sludge. Compared to livestock manure sewage sludge (LMSS), municipal sewage sludge (MSS) had larger ash (30.3%) and lower fixed carbon (7.9%) contents. The peak intensities for the 1^st decomposition region (200-380 °C) on the derivative thermogravimetric curve of MSS were higher than those of LMSS. In contrast, the peak height in the 2^nd temperature region (>380 °C) of MSS was lower than that of LMSS. The activation energy for the pyrolysis of MSS (Avg. 186.5 kJ/mol) was lower than that of LMSS (Avg. 263.4 kJ/mol) over the entire conversion range. MSS produced larger amounts of fatty acids and cholesterol than LMSS. The in-situ catalytic pyrolysis of MSS over HBeta using a pyrolyzer-gas chromatography/mass spectrometry also produced larger amounts of aromatic hydrocarbons than LMSS, suggesting that its better feedstock properties strongly influence the final product oil quality.

Nanomagnetic approach applied to microalgae biomass harvesting: advances, gaps, and perspectives

Microalgae biomass is a versatile option for a myriad of purposes, as it does not require farmable land for cultivation and due of its high CO₂ fixation efficiency during growth. However, biomass harvesting is considered a bottleneck in the process because of its high cost. Magnetic harvesting is a promising method on account of its low cost, high harvesting speed, and efficiency, which can be used to improve the results of other harvesting methods. Here, we present the state of the art of the magnetic harvesting method. Detailed approaches involving different nanomaterials are described, including types, route of synthesis, and functionalization, variables that interfere with harvesting, and recycling methods of nanoparticles and medium. In addition to discussing the overall perspectives of the method, we provide a guideline for future research.

Differential Effect of Anaerobic Digestion on Gaseous Products from Sequential Pyrolysis of Three Organic Solid Wastes

Studies have shown that anaerobic digestion (AD) has an effect on the liquid and solid product property of sequential pyrolysis, but its influence on the gaseous products is lacking. In this study, syngas produced by pyrolysis from three raw organic solid wastes and the corresponding digestates, i.e., food waste, vinasse, and cow manure were investigated. AD causes a decrease in the contents of volatile solid, fixed carbon, C, H, and N and an increase in the S content. The weight loss of the wastes mainly occurs at 200-550 °C during the pyrolysis and the loss of the food waste and vinasse is higher than that of cow manure. In the carbon (C)-containing gas, AD leads to a decrease in the CH₄ content of the syngas, implying that the heat values of the digestates are lower than that of the raw substrates. After AD, the total amount of nitrogen (N)-containing gas from the vinasse increases by 40.1%, while that from cow manure decreases by 14.1%. On the contrary, the total amount of sulfur (S)-containing groups in the syngas from vinasse drop by 22.0%, while that from cow manure increases by 9.1%. In addition, slight changes in the C-, N-, and S-containing gases are found from food waste. The results indicate that AD has a different effect on the N- and S- containing gaseous groups from different organic solid wastes, and the mechanisms deserve further investigation. The findings supply a theoretical foundation for environmental-friendly application of syngas from the digestates.

Pyrolysis of High-Ash Natural Microalgae from Water Blooms: Effects of Acid Pretreatment

Natural microalgae (NA, cyanobacteria) collected from Taihu Lake (Jiangsu, China) were used for biofuel production through pyrolysis. The microalgae were de-ashed via pretreatment with deionized water and hydrochloric acid, and the samples obtained were noted as 0 M, 0.1 M, 1 M, 2 M, 4 M, 6 M, 8 M, respectively, according to the concentration of hydrochloric acid used in the pretreatment. Pyrolysis experiments were carried out at 500 °C for 2 h. The products were examined by various techniques to identify the influence of the ash on the pyrolysis behavior. The results showed that the ash inhibited the thermal transformation of microalgae. The 2 mol/L hydrochloric acid performed the best in removing ash and the liquid yield increased from 34.4% (NA) to 40.5% (2 M). Metal-oxides (mainly CaO, MgO, Al₂O₃) in ash promoted the reaction of hexadecanoic acid and NH₃ to produce more hexadecanamide, which was further dehydrated to hexadecanenitrile. After acid pretreatment, significant improvement in the selectivity of hexadecanoic acid was observed, ranging from 22.4% (NA) to 58.8% (4 M). The hydrocarbon compounds in the liquid product increased from 12.90% (NA) to 26.67% (2 M). Furthermore, the acid pretreatment enhanced the content of C₉–C₁₆ compounds and the HHV values of bio-oil. For natural microalgae, the de-ashing pretreatment before pyrolysis was essential for improving the biocrude yield and quality, as well as the biomass conversion efficiency.

Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective

Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy, which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO, formic acid, and hydrogen. By contrast, a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand, biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts, which significantly governs the reactivity and selectivity of CO2R. However, in biotic CO2R, operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.

Characteristics and Evolution of Nitrogen in the Heavy Components of Algae Pyrolysis Bio-Oil

Algae pyrolytic bio-oil contains a large quantity of N-containing components (NCCs), which can be processed as valuable chemicals, while the harmful gases can also be released during bio-oil upgrading. However, the characteristics of NCCs in the bio-oil, especially the composition of heavy NCCs (molecular weight ≥200 Da), have not been fully studied due to the limitation of advanced analytical methods. In this study, three kinds of algae rich in lipids, proteins, and carbohydrates were rapidly pyrolyzed (10-25 °C/s) at different temperatures (300-700 °C). The bio-oil was analyzed using a Fourier transform ion cyclotron resonance mass spectrometer equipped with electrospray ionization, and the characteristics and evolution of nitrogen in heavy components were first obtained. The results indicated that the molecular weight of most heavy NCCs was distributed in the 200-400 Da range. N_1-3 compounds account for over 60% in lipid and protein-rich samples, while N₀ and N₄ components are prominent in carbohydrate-rich samples. As temperature increases, most NCCs become more aromatic and contain less O due to the strong Maillard and deoxygenation reactions. Moreover, the heavier NCCs were promoted to form lighter compounds with more nitrogen atoms through decomposition (mainly denitrogenation and deoxygenation). Finally, some strategies to deal with the NCCs for high-quality bio-oil production were proposed.

Analysis of condom evidence in forensic science: Background survey of the human vaginal matrix using DRIFTS and pyrolysis-GC/MS

Condom traces are increasingly detected from victims of sexual assault, mostly from vaginal swabs. Protocols have been developed for the analysis of silicone-based condom lubricants using DRIFTS-FTIR and py-GC/MS, but very little research is concerned with the background contribution of the vaginal matrix itself. The present contribution would be an asset for more fundamental research on condom residues in the vaginal matrix, as well as for interpretative purposes in the forensic area. This study investigated vaginal matrix residues using Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS-FTIR) and pyrolysis Gas-Chromatography coupled to Mass Spectrometry (py-GC/MS) to obtain fundamental information about the vaginal matrix's initial composition. Differences between women of a given population were investigated as well as the prevalence of silicone-based residues for natural purposes in the population. Apolar fractions of the samples were investigated after extraction with hexane, as it is the one targeted for silicone-based lubricants used in condoms. Infrared spectroscopy outlined the presence of various proteins and lipids in all the samples, and the spectral regions 1000-1850 cm^-1 and 2700-3600 cm^-1 were identified as the most relevant zones of the spectra. Pyrolysis-GC results confirmed the presence of lipids, more specifically the presence of cholesterol residues. Chemometrics analyses showed that it was not possible to distinguish the samples based on the qualitative nor semi-quantitative content. This suggest that the same type of compounds are extracted regardless of the donor. None of the samples were found to contain any silicones residues. These results are promising from a forensic evidence interpretation perspective. Further research is required to fully validate such models and assess their robustness and limitation in casework conditions.

Optimization of the nitrogen and oxygen element distribution in microalgae by ammonia torrefaction pretreatment and subsequent fast pyrolysis process for the production of N-containing chemicals

In this work, ammonia (NH₃) torrefaction pretreatment (ATP) was developed to optimize the nitrogen and oxygen element distribution of microalgae via the N-doping and oxygen removal reaction, which could obviously improve the potential use of microalgae as a feedstock for the production of N-heterocyclic chemicals through fast pyrolysis technology. The nitrogen content increased from 8.3% of raw microalgae to 11.51% at 300 °C of ATP, while the oxygen content decreased from 35.96% to 21.61%, because of the Maillard reactions. In addition, the nitrogen-doping ratio and oxygen removal ratio of ATP was much higher than the conventional nitrogen torrefaction pretreatment (NTP). With the increase of ATP torrefaction temperature or the pyrolysis temperature, the relative content of the N-containing compounds increased, while the O-containing compounds decreased. For the N-heterocyclic chemicals, higher pyrolysis temperature favored the formation of pyrroles, while inhibited the formation of pyridines and indoles.

Thermally induced gluten modification observed with rheology and spectroscopies

The protein vital gluten is mainly used for food while interest for non-food applications, like biodegradable materials, increases. In general, the structure and functionality of proteins is highly dependent on thermal treatments during production or modification. This study presents conformational changes and corresponding rheological effects of vital wheat gluten depending on temperature. Dry samples analyzed by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and thermalgravimetric analysis coupled with mass spectrometry (TGA-MS) show surface compositions and conformational changes from 25 to 250 °C. Above 170 °C, XPS reveals a decreased N content at the surface while FTIR band characteristics for β-sheets prove structural changes. At 250 °C, protein denaturation accompanied by a significant mass loss due to dehydration and decarbonylation reactions is observed. Oscillatory measurements of optimally hydrated vital gluten describing network properties of the material show two structural changes along a temperature ramp from 25 to 90 °C: at 56-64 °C, the temperature necessary to trigger structural changes increases with the ratio of gliadin to total protein mass, determined by reversed-phase high performance liquid chromatography (RP-HPLC). At a temperature of 79-81 °C, complete protein denaturation occurs. FTIR confirms the denaturation process by showing band shifts with both temperature steps.

Comparative (co-)pyrolytic performances and by-products of textile dyeing sludge and cattle manure: Deeper insights from Py-GC/MS, TG-FTIR, 2D-COS and PCA analyses

Not only does pyrolysis recover energy and value-added by-products but also reduces waste stream volume. The low volatiles and high ash contents of textile dyeing sludge (TDS) limit its mono-pyrolysis performance. This study aimed to conduct an in-depth analysis of its co-pyrolytic performance with cattle manure (CM). The co-pyrolysis enhanced the volatiles emission from the early devolatilization stage whose reaction mechanism shifted from a diffusion model to a reaction-order model. The further cracking of macromolecular materials was mainly elucidated by the reaction-order model. The temperature dependency of the co-pyrolytic gases was of the following order: aliphatic hydrocarbons > CO₂ > alcohols, phenols, ethers, aldehydes, ketones, and carboxylic acids. The main co-pyrolytic volatile products were coumaran and 4-vinylguaiacol. The relative content of guaiacol-type components could be enhanced by co-pyrolysis and lowering the operational temperature to 450 °C. The interaction of co-pyrolysis enriched the char aromaticity. Our findings provide practical insights into the control and application opportunities and limitations on the high value-added energy and products from the co-pyrolysis of TDS and CM.

Study on the nitrogen migration mechanism during penicillin fermentation residue fast pyrolysis based on the substance transformation and canonical variational theory

Antibiotic fermentation residue (AR) is not only a kind of hazardous waste, but also a biomass resource that rich in organic matter. The fast pyrolysis of penicillin fermentation residue (PR) and the model compounds was performed in this study. In PR bio-char, protein nitrogen was mainly converted into pyrrole nitrogen and pyridine nitrogen. When the temperature exceeded 500 °C, pyridine nitrogen further converted into quaternary nitrogen. NH₃, HCN and HNCO were the main nitrogen-containing compounds in the PR fast pyrolysis gas, among which HNCO was mainly the decomposition product of 2,5-piperazinedione (DKP). The yield of PR bio-oil reached 33.1 wt%, and the content of nitrogen was 8.9 wt% at 600 °C. It was found that the decomposition of glutamic acid and aspartic acid resulted in the formation of several cycloamides in PR bio-oil. The decomposition of histidine led to the formation of imidazole and aromatic imidazole. The reaction rate constants in the pathways of DKP decomposition were evaluated by the canonical variational theory (CVT). It was indicated that the pathway of HNCO formation has the highest reaction rate in the PR fast pyrolysis ranging from 400 °C to 700 °C. The DKPs that existed in PR bio-oil were mainly the molecules produced by the condensation between proline and another amino acid, which due to the inhibition of HCNO formation by the proline R-group. With the increase of temperature, the rapid increase in the rate constant of dehydrogenation promoted the formation of indole from aromatic amino acids.

Pyrolysis of food waste over a Pt catalyst in CO2 atmosphere

In this study, a method of disposing food waste is introduced via catalytic pyrolysis under CO₂ condition. The catalyst and CO₂ hindered the generation of condensable compounds, leading to enhancing non-condensable gas generation. However, they did not affect the amount of solid residues left after the thermal reaction. The amount of condensable cyclic compounds was reduced when the catalyst and/or CO₂ were used. The enhancement of non-condensable gas production and reduction of cyclic compounds formation were maximized when the Pt catalyst and CO₂ were simultaneously applied to the pyrolysis of food waste. For instance, approximately 67.3 % less cyclic compounds, including benzene derivatives, were generated at 700 °C in the presence of the catalyst under a CO₂ atmosphere compared to non-catalytic conditions without CO₂. The results suggest that a CO₂-assisted catalytic pyrolysis is as environmentally benign disposal method for food waste.

Reaction engineering and kinetics of algae conversion to biofuels and chemicals via pyrolysis and hydrothermal liquefaction

A state-of-the-art review on pyrolysis and hydrothermal liquefaction of algae to fuels and chemicals with emphasis on reaction chemistry and kinetics.

Emission and conversion of NO from algal biomass combustion in O2/CO2 atmosphere

Environmental impacts of NO emissions from biomass combustion have become an important concern. To address NO emission and conversion from algal biomass combustion in O₂/CO₂ atmosphere, three typical algal biomass, Chlorella (Ch), Enteromorpha (En), and Sargassum (Sa), were used to investigate NO emission characteristics in a one-dimensional tube furnace. The effects of the combustion temperature and O₂ concentration (21%, 25%, and 30%) on the NO emission were examined. It was found that the main peaks of NO positively are correlated to the O₂ concentration and combustion temperature. The NO emission trends of each algal biomass are slightly affected by the O₂ concentration at a given temperature. Roughly, the NO yield and conversion rate for each algal biomass increase with increasing O₂ concentration at a given temperature. They first increase with the increasing temperature and then decrease beyond 800 °C with exception for Sa in 30% O₂/CO₂ atmosphere. However, 21% O₂/CO₂ atmosphere is at least effective to reduce NO emission from most algal biomass combustion compared to air-based atmosphere (21% O₂/N₂), by 8.2-62.0%, 4.9-45.6%, and 22.5-59.6% for Ch, En, and Sa, respectively. The possible conversion pathway of fuel-N implies that the NO emission from algal biomass combustion in O₂/CO₂ atmosphere is the result of the combined effect of the NO formation oxidized from N-precursors and NO reduction by CO (converted from CO₂) and other reductive components. These results may provide a positive reference for the control of NO_x emissions from direct combustion or co-firing of algal biomass for energy utilization.

Bioprospection of biocompounds and dietary supplements of microalgae with immunostimulating activity: a comprehensive review

The objective of this review is to analyze the role of microalgal bioprospecting and the application of microalgae as food supplements and immunostimulants in global and regional aquaculture, highlighting the Brazilian Amazon. This study evaluates the primary advantages of the application of the bioactive compounds of these microorganisms, simultaneously identifying the knowledge gaps that hinder their biotechnological and economic exploitation. The methodology used is comparative and descriptive-analytical, considering the hypothesis of the importance of bioprospecting microalgae, the mechanisms of crop development and its biotechnological and sustainable application. In this context, this review describes the primary applications of microalgae in aquaculture during the last decade (2005–2017). The positive effects of food replacement and/or complementation of microalgae on the diets of organisms, such as their influence on the reproduction rates, growth, and development of fish, mollusks and crustaceans are described and analyzed. In addition, the importance of physiological parameters and their association with the associated gene expression of immune responses in organisms supplemented with microalgae was demonstrated. Complementarily, the existence of technical-scientific gaps in a regional panorama was identified, despite the potential of microalgal cultivation in the Brazilian Amazon. In general, factors preventing the most immediate biotechnological applications in the use of microalgae in the region include the absence of applied research in the area. We conclude that the potential of these microorganisms has been relatively well exploited at the international level but not at the Amazon level. In the latter case, the biotechnological potential still depends on a series of crucial steps that involve the identification of species, the understanding of their functional characteristics and their applicability in the biotechnological area, especially in aquaculture.

Sludge char-to-fuel approaches based on the pyrolysis III: Adding protein without dehydration

Urban expansion has led to the accumulation of sludge, and its disposal has to meet increasingly stringent requirements. Therefore, pyrolysis has become an alternative option. However, it was still unclear which part of the sludge could be pyrolyzed to generate the product with a higher heating value, and therefore we divided sludge into extracellular polymeric substances (EPS) and cell phase and measured their heating values respectively. The obtained results showed that the high heating value (HHV) of the pyrolysis cell phase accounted for 85% of the sludge pyrolysis, and the addition of protein significantly increased the heating value of each component. Although the HHV of the pyrolysis cell phase increased by 1.8 MJ kg^-1 for every 1% increase in protein, the HHV of the pyrolysis sludge and EPS increased by only 1.2 MJ kg^-1. It is therefore suggested that EPS may contain substances that inhibit heat release. Properly increasing the cellular or protein components in the sludge could significantly increase the HHV produced by pyrolysis. Based on the measurement of fatty acids (FAs) and alcohol content and FTIR results, the addition of protein could increase the saturated FAs and accelerate the replacement of oxygen with nitrogen in the pyrolysis product, resulting in higher HHV. If the sludge was not dehydrated, more volatile compounds were carbonized and the HHV increased from 12 MJ kg^-1 to 19 MJ kg^-1. In short, since the HHV of the sludge was mainly derived from the cell phase, the HHV generation could be improved by increasing the cell phase or protein content without dehydration.

Biochemical response of indigenous microalgal consortia to variations in nitrogen concentration of treated effluent

Cultivation conditions influence microalgal cellular components, such as lipid accumulation under nutrient depletion, high light irradiation and salinity stress. In this study, indigenous microalgal consortia were cultivated in batch mode using an actual treated effluent. The temporal response of cellular components to the variations in nitrogen concentration and influence of light irradiation on the response were investigated. Prolonged exposure of indigenous microalgal consortia to nitrogen exhaustion had minor effects on total lipid accumulation and enhancement of energy content. Nitrogen replenishment was followed by immediate crude protein accumulation for growth recovery. Total lipid reduction was observed under light and dark conditions after nitrogen replenishment. A one-day lag after nitrogen replenishment in the total lipid reduction was revealed under nitrogen depletion; meanwhile, under nitrogen exhaustion, lipids were utilised as the primary carbon and/or energy source after replenishment, as represented by the decrease from 10.8% to 9.04% within 6 h after the replenishment.

Characterization of the residual biochemical components of sequentially extracted banana peel biomasses and their environmental remediation applications

After consumption of the inner fleshy fruit, the banana peel like many other fruit peels is usually disposed of unprocessed. For sustainable development, agro-wastes including banana peels need to be converted into valuable products that will be beneficial to human and the environment. In this study, biochemical components including lipids, proteins and structural polysaccharides were sequentially extracted from banana peel, and the residuals were characterized by FE-SEM/EDX, FTIR, XRD, TGA/DSC, XPS and elemental analysis. Owing to rapid industrialization, toxic species such as metals and dyes are consistently released into the aquatic environments. Therefore, the residual biomass samples were evaluated for environmental remediation application. The adsorption performances were outstanding, with uptakes reaching 1034, 279 and 152 mg/g, for methylene blue, lead and platinum, respectively. This study thus suggests that sequential extraction and detailed characterization are useful for identification of key contributing components for development of high-performance agro-waste-based adsorbents for water treatment.

Unraveling the interactions in fast co-pyrolysis of microalgae model compounds via pyrolysis-GC/MS and pyrolysis-FTIR techniques

The pyrolysate composition, product time evolution and kinetics of fast co-pyrolysis of protein, carbohydrate and lipid surrogates are investigated to unravel the interactions among microalgae components.

A review on the production of nitrogen-containing compounds from microalgal biomass via pyrolysis

Nitrogen-containing compounds (NCCs) which may be produced from nitrogen-rich biomass such as microalgae, may find important biochemical and biomedical applications. This review summarizes the recent knowledge about the formation mechanism of NCCs during pyrolysis of microalgae. The key technical and biological aspects of microalgae and pyrolysis process parameters, which influence the formation of NCCs, have been analyzed. The mechanism of formation of NCCs such as indole, pyridine, amides, and nitriles during primary and secondary pyrolysis reactions are elaborated. It has been emphasized that the pyrolysis conditions and the use of catalysts had significant impacts on the yields and compositions of NCCs. The available information shows that the transformation of nitrogen and nitrogen functionalities during pyrolysis are strongly associated with the formation process of NCCs. The challenges in the development of pyrolysis technologies for the production of NCCs from microalgae are identified with future research needs identified.

Combustion behaviors of spent mushroom substrate using TG-MS and TG-FTIR: Thermal conversion, kinetic, thermodynamic and emission analyses

The present study systematically investigated the combustion characteristics of spent mushroom substrate (SMS) using TG-MS (thermogravimetric/mass spectrometry) and TG-FTIR (thermogravimetric/Fourier transform infrared spectrometry) under five heating rates. The physicochemical characteristics and combustion index pointed to SMS as a promising biofuel for power generation. The high correlation coefficient of the fitting plots and similar activation energy calculated by various methods indicated that four suitable iso-conversional methods were used. The activation energy varied from 130.06 to 192.95 kJ/mol with a mean value of 171.49 kJ/mol using Flynn-Wall-Ozawa and decreased with the increased conversion degree. The most common emissions peaked at the range of 200-400 °C corresponding to volatile combustion stage, except for CO₂, NO₂ and NO. The peak CO₂ emission occurred at 439.11 °C mainly due to the combustion of fixed carbon.

Hydrotreatment of bio-oil distillates produced from pyrolysis and hydrothermal liquefaction of duckweed: A comparison study

A comprehensive comparison of hydrothermal liquefaction (HTL) to the pyrolysis of duckweed was conducted to determine the yields and components of the crude bio-oils and their distillates. The upgrading behaviors of the distillates were thoroughly investigated with the use of used engine oil as a solvent. With all other variables fixed, HTL produced crude bio-oil with a lower H/C ratio (1.28 ± 0.03) than pyrolysis did (1.45 ± 0.04). However, its distillates had a higher H/C ratio (1.60 ± 0.05) and total yield (66.1 ± 2.0 wt%) than pyrolysis (1.46 ± 0.04 and 47.2 ± 1.4 wt%, respectively). Phenolics and nitrogenous heterocycles constituted relatively major proportions of the two crude bio-oils and most of their distillates. Obvious differences in molecular composition between the two crude bio-oils and their distillates were ascribed to the distinct impacts of HTL and pyrolysis and were affected by the distillate temperature. Co-hydrotreating with used engine oil (UEO) provided the upgraded bio-oils much higher H/C ratios (~1.78 ± 0.05) and higher heating values (~45.5 ± 1.4 MJ·kg^-1), as well as much lower contents of N, O and S compared to their initial distillates. Aromatics and alkanes constituted a large proportion in most of upgraded bio-oils. N removal from the pyrolysis distillates was easier than from the HTL distillates. Distinct differences in yields and molecular compositions for the upgraded bio-oils were also attributed to the different influences associated with the two conversion routes.

Pressurized entrained-flow pyrolysis of microalgae: Enhanced production of hydrogen and nitrogen-containing compounds

Pressurized entrained-flow pyrolysis of Chlorella vulgaris microalgae was investigated. The impact of pressure on the yield and composition of pyrolysis products were studied. The results showed that the concentration of H₂ in bio-gas increased sharply with increasing pyrolysis pressure, while those of CO, CO₂, CH₄, and C₂H₆ were dramatically decreased. The concentration of H₂ reached 88.01 vol% in bio-gas at 900 °C and 4 MPa. Higher pressures promoted the hydrogen transfer to bio-gas. The bio-oils derived from pressurized pyrolysis were rich in nitrogen-containing compounds and PAHs. The highest concentration of nitrogen-containing compounds in bio-oil was achieved at 800 °C and 1 MPa. Increasing pyrolysis pressure promoted the formation of nitrogen-containing compounds such as indole, quinoline, isoquinoline and phenanthridine. Higher pyrolysis pressures led to increased sphericity, enhanced swelling, and higher carbon order of bio-chars. Pressurized pyrolysis of biomass has a great potential for poly-generation of H₂, nitrogen containing compounds and bio-char.

Effect of Temperature and Mineral Matter on the Formation of NOx Precursors during Fast Pyrolysis of 2,5-Diketopiperazine

2,5-diketopiperazine (DKP) was used as a N-containing model compound to investigate the formation pathway of NOx precursors (HCN, NH3, and HNCO) during biomass pyrolysis. The experiment was carried out using a tube furnace coupled with a Fourier Transform Infrared Spectrometer in an argon atmosphere. The results showed that NH3, HCN, and HNCO were the major N-containing species formed during DKP fast pyrolysis. The largest yield was HCN, followed by NH3 and lastly HNCO. When the pyrolysis temperature was increased, the yield of NH3 increased slowly, but the yield of HCN decreased slightly at 800~950 °C and the change accelerate rapidly above 950 °C. Then NH3 became the main product above 1020 °C. The temperature influence was negligible on the selectivity between HCN and NH3 from pyrolysis of DKP. H radicals played an important role in competitive reactions. It was also noted that the presence of Na+, K+, Ca2+, and Mg2+ exhibited a catalytic effect on nitrogen conversion during the DKP fast pyrolysis process. K+ and Na+ were beneficial to the yield of NH3, but not to the yield of HCN. Ca2+ and Mg2+ could promote the formation of HCN, but prevent the formation of NH3.

LED power efficiency of biomass, fatty acid, and carotenoid production in Nannochloropsis microalgae

The microalga Nannochloropsis produces high-value omega-3-rich fatty acids and carotenoids. In this study the effects of light intensity and wavelength on biomass, fatty acid, and carotenoid production with respect to light output efficiency were investigated. Similar biomass and fatty acid yields were obtained at high light intensity (150 μmol m^-2 s^-1) LEDs on day 7 and low light intensity (50 μmol m^-2 s^-1) LEDs on day 11 during cultivation, but the power efficiencies of biomass and fatty acid (specifically eicosapentaenoic acid) production were higher for low light intensity. Interestingly, low light intensity enhanced both, carotenoid power efficiency of carotenoid biosynthesis and yield. White LEDs were neither advantageous for biomass and fatty acid yields, nor the power efficiency of biomass, fatty acid, and carotenoid production. Noticeably, red LED resulted in the highest biomass and fatty acid power efficiency, suggesting that LEDs can be fine-tuned to grow Nannochloropsis algae more energy-efficiently.

Thermal characteristics and surface morphology of char during co-pyrolysis of low-rank coal blended with microalgal biomass: Effects of Nannochloropsis and Chlorella

In this work, the influence of Nannochloropsis and Chlorella on the thermal behavior and surface morphology of char during the co-pyrolysis process were explored. Thermogravimetric and iso-conversional methods were applied to analyzing the pyrolytic and kinetic characteristics for different mass ratios of microalgae and low-rank coal (0, 3:1, 1:1, 1:3 and 1). Fractal theory was used to quantitatively determine the effect of microalgae on the morphological texture of co-pyrolysis char. The result indicated that both the Nannochloropsis and Chlorella promoted the release of volatile from low-rank coal. Different synergistic effects on the thermal parameters and yield of volatile were observed, which could be attributed to the different compositions in the Nannochloropsis and Chlorella and operating condition. The distribution of activation energies shows nonadditive characteristics. Fractal dimensions of the co-pyrolysis char were higher than the individual char, indicating the promotion of disordered degree due to the addition of microalgae.

Kinetics evaluation and thermal decomposition characteristics of co-pyrolysis of municipal sewage sludge and hazelnut shell

Hazelnut shell, as novel biomass, has lower ash content and abundant hydrocarbon, which can be utilized resourcefully with municipal sewage sludge (MSS) by co-pyrolyisis to decrease total content of pollution. The co-pyrolysis of MSS and hazelnut shell blend was analyzed by a method of multi-heating rates and different blend ratios with TG-DTG-MS under N₂ atmosphere. The apparent activation energy of co-pyrolysis was calculated by three iso-conversional methods. Satava-Sestak method was used to determine mechanism function G(α) of co-pyrolysis, and Lorentzian function was used to simulate multi-peaks curves. The results showed there were four thermal decomposition stages, and the biomass were cracked and evolved at different temperature ranges. The apparent activation energy increased from 123.99 to 608.15kJ/mol. The reaction mechanism of co-pyrolysis is random nucleation and nuclei growth. The apparent activation energy and mechanism function afford a theoretical groundwork for co-pyrolysis technology.

Prediction model of biocrude yield and nitrogen heterocyclic compounds analysis by hydrothermal liquefaction of microalgae with model compounds

The model of biocrude yield and the nitrogen heterocyclic compounds in biocrude of microalgae hydrothermal liquefaction are two of the most concerned issues in this field at present. This study explored a hydrothermal liquefaction biocrude yield model involved in the interaction among biochemical compounds in microalgae and analysed nitrogen heterocyclic compounds in biocrude. The model compound (castor oil, soya protein and glucose) and Nanochloropsis were liquefied at 280°C for 1h. The products were analyzed by GC-MS, element analysis and FTIR. The results suggested that interactions among different components in microalgae enhanced biocrude yield. The biocrude yield prediction model involved cross-interactions performed more accurate than previous models.When the ratio of protein and carbohydrate around 3, the cross-interaction and nitrogen heterocyclic compounds in biocrude would both reach the highest extent.

Biorefining of protein waste for production of sustainable fuels and chemicals

To mitigate the climate change caused by CO₂ emission, the global incentive to the low-carbon alternatives as replacement of fossil fuel-derived products continuously expands the need for renewable feedstock. There will be accompanied by the generation of enormous protein waste as a result. The economical viability of the biorefinery platform can be realized once the surplus protein waste is recycled in a circular economy scenario. In this context, the present review focuses on the current development of biotechnology with the emphasis on biotransformation and metabolic engineering to refine protein-derived amino acids for production of fuels and chemicals. Its scope starts with the explosion of potential feedstock sources rich in protein waste. The availability of techniques is applied for purification and hydrolysis of various feedstock proteins to amino acids. Useful lessons are leaned from the microbial catabolism of amino acids and lay a foundation for the development of the protein-based biotechnology. At last, the future perspective of the biorefinery scheme based on protein waste is discussed associated with remarks on possible solutions to overcome the technical bottlenecks.