Syngas production from biomass pyrolysis in a continuous microwave assisted pyrolysis system

Bio-Polyethylene and Polyethylene Biocomposites: An Alternative toward a Sustainable Future

Polyethylene (PE), a highly prevalent non-biodegradable polymer in the field of plastics, presents a waste management issue. To alleviate this issue, bio-based PE (bio-PE), derived from renewable resources like corn and sugarcane, offers an environmentally friendly alternative. This review discusses various production methods of bio-PE, including fermentation, gasification, and catalytic conversion of biomass. Interestingly, the bio-PE production volumes and market are expanding due to the growing environmental concerns and regulatory pressures. Additionally, the production of PE and bio-PE biocomposites using agricultural waste as filler materials, highlights the growing demand for sustainable alternatives to conventional plastics. According to previous studies, addition of ≈50% defibrillated corn and abaca fibers into bio-PE matrix and a compatibilizer, results in the highest Young's modulus of 4.61 and 5.81 GPa, respectively. These biocomposites have potential applications in automotive, building construction, and furniture industries. Moreover, the advancement made in abiotic and biotic degradation of PE and PE biocomposites is elucidated to address their environmental impacts. Finally, the paper concludes with insights into the opportunities, challenges, and future perspectives in the sustainable production and utilization of PE and bio-PE biocomposites. In summary, production of PE and bio-PE biocomposites can contribute to a cleaner and sustainable future.

Hyper-Cross-Linked Resin Modified by a Micropore Polymer for Gas Adsorption and Separation

Polymerization confined to the pore was first adapted for the nanoscale structure adjustment of adsorption resin. The self-cross-linked polymer (P-1) formed in the pore of hyper-cross-linked resin (HR) by the Friedel-Crafts reaction of p-dichloroxylene (p-DCX), occupying the macropore of the HR resin and bringing about an external micropore. Compared with the raw HR resin, the volume of the micropore of HR@P-1 in 0.4 < D < 1 nm increased but the volume of the macropore has obviously decreased. After the loading of P-1 in the nanopore of HR, HR@P-1 has better gas adsorption performance. At 298 and 100 KPa, the adsorption capacity of CO2 is almost 30% higher than that of HR, reaching 35.7 cm3/g, due to the increase in the smaller micropore volume. Moreover, HR@P-1 has also been found to be the first C2H6-selective adsorption resin. The uptake of C2H6 is up to 56 cm3/g, and the IAST selectivity of C2H6/CH4 reaches 15.3. HR@P-1 can also separate syngas efficiently at ambient temperature and be regenerated by simple vacuum operation.

Unveiling the microwave heating performance of biochar as microwave absorber for microwave-assisted pyrolysis technology

Microwave (MW) heating has gained significant attention in food industries and biomass-to-biofuels through pyrolysis over conventional heating. However, constraints for promoting MW heating related to the use of different MW absorbers are still a major concern that needs to be investigated. The present study was conducted to explore the MW heating performance of biochar as a low-cost MW absorber for performing pyrolysis. Experiments were performed on biochar under different biochar dosing (25 g, 37.5 g, 50 g), MW power (400 W, 700 W, 1000 W), and particle sizes (6 mm, 8 mm, 10 mm). Results showed that MW power and biochar dosing significantly impacted average heating rate (AHR) from 17.5 to 65.4 °C/min at 400 W and 1000 W at 50 g. AHR first increased, and then no significant changes were obtained, from 37.5 to 50 g. AHR was examined by full factorial design, with 94.6% fitting actual data with predicted data. The model suggested that the particle size of biochar influenced less on AHR. Furthermore, microwave absorption efficiency and biochar weight loss were investigated, and microwave absorption efficiency decreased as MW power increased, which means 17.16% of microwave absorption efficiency was achieved at 400 W rather than 700 W and 1000 W. Biochar weight loss estimated by employing mass-balance analysis, 2-10.4% change in biochar weight loss was obtained owing to higher heating rates at higher powers and biochar dosing.

Comparative study by microwave pyrolysis and conventional pyrolysis of pharmaceutical sludge: Resourceful disposal and antibiotic adsorption

Compared with conventional pyrolysis, microwave pyrolysis has superior heat transfer performance and promotes the decomposition of organic matter. The paper focuses on the harmless treatment and resource utilization of pharmaceutical sludge (PS) by microwave heating and conventional heating methods. The experimental results showed that the conventional pyrolysis gas is dominated by CO2, CO and H2. For microwave pyrolysis gas, the "microwave effect" promoted secondary cracking of volatile fractions and increases the content of CH4, CxHy, H2 and CO through condensation, aromatization, and dehydrogenation. Conventional pyrolysis oils contained the highest percentage of oxygenated compounds. However, high-temperature microwave radiation accelerated the cleavage of polar oxygenated molecular bonds and long-chain hydrocarbons, thereby increasing the aromatics content of pyrolysis oils. The solid residues obtained from microwave pyrolysis is highly graphitized and porous, with a surface area of 146.2 m2/g. Furthermore, the solid residue was rich in pyridine-N and pyrrole-N that could be utilized for adsorption and catalysis. The MA-600 removes up to 99% of tetracycline (TC) in 6 h. It was also found that the adsorption process of TC by the two pyrolysis residues was consistent with the proposed secondary and Freundlich models.

Gasification of biomass for syngas production: Research update and stoichiometry diagram presentation

Gasification is a thermal process that converts organic materials into syngas, bio-oil, and solid residues. This mini-review provides an update on current research on producing high-quality syngas from biomass via gasification. Specifically, the review highlights the effective valorization of feedstocks, the development of novel catalysts for reforming reactions, the configuration of novel integrated gasification processes with an assisted field, and the proposal of advanced modeling tools, including the use of machine learning strategies for process design and optimization. The review also includes examples of using a stoichiometry diagram to describe biomass gasification. The research efforts in this area are constantly evolving, and this review provides an up-to-date overview of the most recent advances and prospects for future research. The proposed advancements in gasification technology have the potential to significantly contribute to sustainable energy production and reduce greenhouse gas emissions.

Microwave-enhanced hydrogen production: a review

Currently, the massive use of fossil fuels, which still serve as the dominant global energy, has led to the release of large amounts of greenhouse gases. Providing abundant, clean, and safe renewable energy is one of the major technical challenges for humankind. Nowadays, hydrogen-based energy is widely considered a potentially ideal energy carrier that could provide clean energy in the fields of transportation, heat and power generation, and energy storage systems, almost without any impact on the environment after consumption. However, a smooth energy transition from fossil-fuel-based energy to hydrogen-based energy must overcome a number of key challenges that require scientific, technological, and economic support. To accelerate the hydrogen energy transition, advanced, efficient, and cost-effective methods for producing hydrogen from hydrogen-rich materials need to be developed. Therefore, in this study, a new alternative method based on the use of microwave (MW) heating technology in enhanced hydrogen production pathways from plastic, biomass, low-carbon alcohols, and methane pathways compared with conventional heating methods is discussed. Furthermore, the mechanisms of MW heating, MW-assisted catalysis, and MW plasma are also discussed. MW-assisted technology usually has the advantages of low energy consumption, easy operation, and good safety practices, which make it a promising solution to supporting the future hydrogen society.

Microwave processing of oil palm wastes for bioenergy production and circular economy: Recent advancements, challenges, and future prospects

The valorization and conversion of biomass into various value-added products and bioenergy play an important role in the realization of sustainable circular bioeconomy and net zero carbon emission goals. To that end, microwave technology has been perceived as a promising solution to process and manage oil palm waste due to its unique and efficient heating mechanism. This review presents an in-depth analysis focusing on microwave-assisted torrefaction, gasification, pyrolysis and advanced pyrolysis of various oil palm wastes. In particular, the products from these thermochemical conversion processes are energy-dense biochar (that could be used as solid fuel, adsorbents for contaminants removal and bio-fertilizer), phenolic-rich bio-oil, and H₂-rich syngas. However, several challenges, including (1) the lack of detailed study on life cycle assessment and techno-economic analysis, (2) limited insights on the specific foreknowledge of microwave interaction with the oil palm wastes for continuous operation, and (3) effects of tunable parameters and catalyst's behavior/influence on the products' selectivity and overall process's efficiency, remain to be addressed in the context of large-scale biomass valorization via microwave technology.

The role of solvent soaking and pretreatment temperature in microwave-assisted pyrolysis of waste tea powder: Analysis of products, synergy, pyrolysis index, and reaction mechanism

This study focuses on microwave-assisted pyrolysis (MAP) of fresh waste tea powder and torrefied waste tea powder as feedstocks. Solvents including benzene, acetone, and ethanol were used for soaking feedstocks. The feedstock torrefaction temperature (at 150 °C) and solvents soaking enhanced the yields of char (44.2-59.8 wt%) and the oil (39.8-45.3 wt%) in MAP. Co-pyrolysis synergy induced an increase in the yield of gaseous products (4.7-20.1 wt%). The average heating rate varied in the range of 5-25 °C/min. The energy consumption in MAP of torrefied feedstock (1386 KJ) significantly decreased compared to fresh (3114 KJ). The pyrolysis index dramatically varied with the solvent soaking in the following order: ethanol (26.7) > benzene (25.6) > no solvent (10) > acetone (6). It shows that solvent soaking plays an important role in the pyrolysis process. The obtained bio-oil was composed of mono-aromatics, poly-aromatics, and oxygenated compounds.

Synthesis of sustainable chemicals from waste tea powder and Polystyrene via Microwave-Assisted in-situ catalytic Co-Pyrolysis: Analysis of pyrolysis using experimental and modeling approaches

In the current study, catalytic co-pyrolysis was performed on waste tea powder (WTP) and polystyrene (PS) wastes to convert them into value-added products using KOH catalyst. The feed mixture influenced the heating rates (17-75 °C/min) and product formation. PS promoted the formation of oil and WTP enhanced the char formation. The maximum oil yield (80 wt%) was obtained at 15 g:5 g, and the maximum char yield (44 wt%) was achieved at 5 g:25 g (PS:WTP). The pyrolysis index (PI) increased with the increase in feedstock quantity. High PI was noticed at 25 g:5 g, and low PI was at 5 g:5 g (PS:WTP). Low energy consumption and low pyrolysis time enhanced the PI value. Significant interactions were noticed during co-pyrolysis. The obtained bio-oil was analyzed using GC-MS and a plausible reaction mechanism is presented. Catalyst and co-pyrolysis synergy promoted the formation of aliphatic and aromatic hydrocarbons by reducing the oxygenated products.

Synergistic optimization of syngas quality and heavy metal immobilization during continuous microwave pyrolysis of sludge: Competitive relationships, reaction mechanisms, and energy efficiency assessment

To realize the efficient resource utilization of sewage sludge, this work explored the competitive relationship and reaction mechanisms between syngas quality optimization and heavy metals (HMs) immobilization. The results showed that continuous microwave pyrolysis (CMP) technology with an instantaneous temperature increase could shorten the pyrolysis time, and the biogas yield and syngas concentration reached 51.68 wt% and 83.6 vol%, respectively. Although a higher pyrolysis (750 °C) temperature could optimize the syngas quality, the HMs immobilization efficiency was reduced due to the deep pyrolysis of the biochar. The moderate pyrolysis temperature (650 °C) facilitated the rapid formation of biochar with abundant surface functional groups and pore structure, thus enhancing HMs immobilization. Furthermore, the HMs could also form more stable crystalline compounds with inorganic components (SiO₂, Al₂O₃, inorganic sulfur). By optimizing the process parameters, the risk factor of HMs in the sludge decreased from 117.36 to 62.5 while obtaining high-quality syngas. The energy utilization efficiency of microwave pyrolysis also increased significantly from 11.20% to 82.01%. This work provided new insight into the efficient resource utilization and environmentally friendly treatment of sludge, and demonstrated that CMP technology has significant potential for future industrial applications as an alternative to traditional pyrolysis.

Preparation of high-value porous carbon by microwave treatment of chili straw pyrolysis residue

Microwave technology is utilized to prepare porous carbon from the chili straw pyrolysis residue in this study. As the pyrolysis temperature increases, the thermal stability of biochar is higher. The carbon speciation of the porous carbon PC500 is closest to that of graphite, and its inorganic-C reaches to 51.21%. Notably, the specific surface area of the activated porous carbon increases with increasing pyrolysis temperature, with a maximum value of 2768.52 m²/g for PC500. Further testing of the electrochemical properties of the porous carbon, PC500 possesses a high specific capacitance of 352F/g at 1 A/g while that of conventional heating is only 226.1F/g. The porous carbon prepared by microwave heating has better electrical properties compared to conventional heating, and the biochar obtained at higher pyrolysis temperature has a richer pore structure after activation.

Recent Progress in Sludge Co-Pyrolysis Technology

With the development of society and industry, the treatment and disposal of sludge have become a challenge for environmental protection. Co-pyrolysis is considered a sustainable technology to optimize the pyrolysis process and improve the quality and performance of pyrolysis products. Researchers have investigated the sludge co-pyrolysis process of sludge with other wastes, such as biomass, coal, and domestic waste, in laboratories. Co-pyrolysis technology has reduced pyrolysis energy consumption and improved the range and quality of pyrolysis product applications. In this paper, the various types of sludge and the factors influencing co-pyrolysis technology have been classified and summarized. Simultaneously, some reported studies have been conducted to investigate the co-pyrolysis characteristics of sludge with other wastes, such as biomass, coal, and domestic waste. In addition, the research on and development of sludge co-pyrolysis are expected to provide theoretical support for the development of sludge co-pyrolysis technology. However, the technological maturity of sludge pyrolysis and co-pyrolysis is far and needs further study to achieve industrial applications.

Concept for Biomass and Organic Waste Refinery Plants Based on the Locally Available Organic Materials in Rural Areas of Poland

The importance of developing efficient and environmentally friendly means of biomass conversion into bioenergy, biofuels, and valuable products is currently high in Poland. Accordingly, herein, two new energy and biofuel units are proposed, namely, POLpec and POLbp, which are used as reference sources for comparing energy consumption and biofuel production in other countries or regions in the world. One POLpec equals 4400 PJ (195.1 Mtoe), reflecting the annual primary energy consumption of Poland in 2020. Meanwhile, one POLbp equals 42 PJ (1.0 Mtoe), referring to the annual production of biofuels in Poland in 2020. Additionally, a new import–export coefficient β is proposed in the current study, which indicates the relationship between the import and export of an energy carrier. More specifically, the potential of biomass and organic waste to be converted into energy, biofuels, and valuable products has been analysed for the rural areas of Poland. Results show that the annual biomass and organic waste potential is approximately 245 PJ (5.9 Mtoe). Finally, the concept of a biomass and organic waste refinery plant is proposed based on the locally available organic materials in rural areas. In particular, two models of biomass refinery plants are defined, namely, the Input/Output and Modular models. A four-module model is presented as a concept for building a refinery plant at the Institute of Technology and Life Sciences—National Research Institute in Poznan, Poland. The four modules include anaerobic digestion, gasification, transesterification, and alcoholic fermentation. The primary reason for combining different biomass conversion technologies is to reduce the cost of biomass products, which, currently, are more expensive than those obtained from oil and natural gas.

Recent advances of thermochemical conversion processes for biorefinery

Lignocellulosic biomass is one of the most promising renewable resources and can replace fossil fuels via various biorefinery processes. Through this study, we addressed and analyzed recent advances in the thermochemical conversion of various lignocellulosic biomasses. We summarized the operation conditions and results related to each thermochemical conversion processes such as pyrolysis (torrefaction), hydrothermal treatment, gasification and combustion. This review indicates that using thermochemical conversion processes in biorefineries is techno-economically feasible, easy, and effective compared with biological processes. The challenges experienced in thermochemical conversion processes are also presented in this study for better understanding the future of thermochemical conversion processes for biorefinery. With the aid of artificial intelligence and machine learning, we can reduce time-consumption and experimental work for bio-oil production and syngas production processes.

Integrating Taguchi method and artificial neural network for predicting and maximizing biofuel production via torrefaction and pyrolysis

Artificial neural network (ANN) is one kind of artificial intelligence in the computing system that aims to process information as the way neurons in the human brain. In this study, the combination of the Taguchi method and ANN are used to maximize and predict biofuel yield from spent mushroom substrate torrefaction and pyrolysis via microwave irradiation. The Taguchi method is utilized to design the multiple factors (particle size, catalyst, power, and magnetic agent) and levels of experiment parameters. The highest total biofuel yield (biochar + bio-oil) is 99.42%, accomplished by a combination of 355 µm particle size, 300 mg·g-SMS^-1 catalyst, 900 W power, and 300 mg·g-SMS^-1 magnetic agent. ANN with one hidden layer shows the outstanding linear regression predictions for the highest biofuel yields (biochar 0.9999 and bio-oil 0.9998). This high linear regression indicates that ANN with a quick propagation algorithm is an appropriate approach for predicting biofuel conversion.

Lignocellulosic biomass-based pyrolysis: A comprehensive review

The efficacious application of lignocellulosic biomass for the new valuable chemicals generation curbs the excessive dependency on fossil fuels. Among the various techniques available, pyrolysis has garnered much attention for conversion of lignocellulosic biomass (encompasses cellulose, hemicellulose and lignin components) into product of solid, liquid and gases by thermal decomposition in an efficient manner. Pyrolysis conversion mechanism can be outlined as formation of char, depolymerisation, fragmentation and other secondary reactions. This paper gives a deep insight about the pyrolytic behavior of the lignocellulosic components accompanied by its by-products. Also several parameters such as reaction environment, temperature, residence time and heating rate which has a great impact on the pyrolysis process are also elucidated in a detailed manner. In addition the environmental and economical facet of lignocellulosic biomass pyrolysis for commercialization at industrial scale is critically analyzed. This article also illustrates the prevailing challenges and inhibition in implementing lignocellulosic biomass based pyrolysis with possible solution.

In-depth exploration of mechanism and energy balance characteristics of an advanced continuous microwave pyrolysis coupled with carbon dioxide reforming technology to generate high-quality syngas

This study firstly coupled advanced continuous microwave pyrolysis with CO₂ reforming technology to recover syngas from cow manure and CO₂. The contribution of CO₂ to syngas, pyrolysis mechanism, and energy balance characteristics were analyzed thoroughly. The results showed that continuous microwave pyrolysis coupled with CO₂ reforming technology has superiorities over other pyrolysis methods in bio-gas generation. The bio-gas yield, syngas content, and heating value of syngas reached the maximum value of 71.02 wt%, 85.70 vol%, and 10.87 MJ/Nm³, respectively. CO₂ strengthened pyrolysis and reacted with pyrolysis products to produce high-quality syngas and reduce H₂S. Due to the limited substances that can react with CO₂ and excessive energy consumption with increasing CO₂ concentration, the utilization efficiencies of CO₂ and energy decreased from 36.31% and 27.27% to 31.16% and 24.24%, respectively. This work provides basic theory and technical support for advanced technology to recover high-quality syngas from biomass with low energy consumption.

Pyrolysis of soybean soapstock for hydrocarbon bio-oil over a microwave-responsive catalyst in a series microwave system

A novel Silicon carbide (SiC) foam ceramic based ZSM-5/SiC nanowires microwave-responsive catalyst was developed to upgrade the pyrolysis volatiles in a microwave-assisted series system (both the pyrolysis and catalytic systems were heated by microwave). The growth of SiC nanowires was helpful for the ZSM-5 growth on the SiC foam ceramic. Because the specific surface area of SiC foam ceramic was improved. The dielectric properties of the composite catalyst were improved due to the growth of SiC nanowires. Bio-oil composition analysis showed that area percentage of hydrocarbons and aromatic hydrocarbons could reach 80.89% and 40.48% at catalytic temperature of 450 ℃and 500 ℃, respectively. The microwave-responsive composite catalyst had good aromatization performance in microwave-assisted series system due to high dielectric properties and specific surface area. The composite catalyst performed well after five-cycle regeneration, and the hydrocarbon content could still reach 76.40%, which is 80.89% for the original catalyst.

Effects of oxygen vacancy defect on microwave pyrolysis of biomass to produce high-quality syngas and bio-oil: Microwave absorption and in-situ catalytic

This paper proposed to use ferric oxide (Fe₂O₃) and ferroferric oxide (Fe₃O₄) as catalysts with both microwave absorption and catalytic properties. Carbon dioxide (CO₂) was introduced as the reaction atmosphere to further improve the quality of biofuel produced by microwave pyrolysis of food waste (FW). The results showed the bio-gas yield and the syngas concentration (H₂ + CO) increased to 70.34 wt% and 61.50 mol%, respectively, using Fe₃O₄ as the catalyst. The content of aliphatic hydrocarbons in bio-oil produced with the catalyst Fe₂O₃ increased to 67.48% and the heating value reached 30.45 MJ/kg. Compared with Fe₂O₃ catalyst, Fe₃O₄ exhibited better microwave absorption properties and catalytic properties. Transmission electron microscopy (TEM) and Electron paramagnetic resonance (EPR) characterizations confirmed that the crystal surface of Fe₃O₄ formed more oxygen vacancy defects and unpaired electrons. Additionally, according to the X-ray photoelectron spectroscopy (XPS) analysis, the content of lattice oxygen in Fe₃O₄ was 14.11%, a value that was much lower than Fe₂O₃ (38.54%). The oxygen vacancy defects not only improved the efficient utilization of microwave energy but also provided the reactive sites for the reaction between the volatile organic compounds (VOCs) and CO₂ to generate CO. This paper provides a new perspective for selecting catalysts that have both microwave absorption and catalytic properties during the microwave pyrolysis of biomass.

Energy optimization of bio-oil production from biomass by fast pyrolysis using microwaves

Microwave fast pyrolysis leads to higher bio-oil production for flax shives than other biomass. An high heating rate and an optimum energy input are required for maximum bio-oil production. Gas and oil composition is stable with operating conditions.

Progress in waste valorization using advanced pyrolysis techniques for hydrogen and gaseous fuel production

Hydrogen and gaseous fuel derived from wastes have opened up promising alternative pathways for the production of renewable and sustainable fuels to substitute classical fossil energy resources that cause global warming and pollution. Existing review articles focus mostly on gasification, reforming and pyrolysis processes, with limited information on particularly gaseous fuel production via pyrolysis of various waste products. This review provides an overview on the recent advanced pyrolysis technology used in hydrogen and gaseous fuel production. The key parameters to maximize the production of specific compounds were discussed. More studies are needed to optimize the process parameters and improve the understanding of reaction mechanisms and co-relationship between these advanced techniques. These advanced techniques provide novel environmentally sustainable and commercially procedures for waste-based production of hydrogen and gaseous fuels.

A review on selective production of value-added chemicals via catalytic pyrolysis of lignocellulosic biomass

Increasing fossil fuel consumption and global warming has been driving the worldwide revolution towards renewable energy. Biomass is abundant and low-cost resource whereas it requires environmentally friendly and cost-effective conversion technique. Pyrolysis of biomass into valuable bio-oil has attracted much attention in the past decades due to its feasibility and huge commercial outlook. However, the complex chemical compositions and high water content in bio-oil greatly hinder the large-scale application and commercialization. Therefore, catalytic pyrolysis of biomass for selective production of specific chemicals will stand out as a unique pathway. This review aims to improve the understanding for the process by illustrating the chemistry of non-catalytic and catalytic pyrolysis of biomass at the temperatures ranging from 400 to 650 °C. The focus is to introduce recent progress about producing value-added hydrocarbons, phenols, anhydrosugars, and nitrogen-containing compounds from catalytic pyrolysis of biomass over zeolites, metal oxides, etc. via different reaction pathways including cracking, Diels-Alder/aromatization, ketonization/aldol condensation, and ammoniation. The potential challenges and future directions for this technique are discussed in deep.

Recovery of renewable aromatic and aliphatic hydrocarbon resources from microwave pyrolysis/co-pyrolysis of agro-residues and plastics wastes

The present study focussed on recovering the valuable carbon resources from agro-residues (wheat straw, rice husk) and waste plastics (polypropylene, polystyrene) using microwave pyrolysis and co-pyrolysis. The main objective of this study is to investigate the effect of the susceptor blending mechanism on the co-pyrolysis product distribution. Graphite was mixed with feedstock in a new approach to achieving homogeneity, and microwave power of 600 W was used. The average heating rate (52-67 (°C/min)), microwave energy required (2267-2936 (J/g)), heat energy utilized (1410-1444 (J/g)), and conductive heat losses (85-110 (J/g)) were analyzed. The selectivity of cyclic alkanes and alkenes (65.5%) was found to be high in polypropylene pyrolysis oil. Polystyrene pyrolysis oil predominantly contained cyclooctatetraene (61%) compound. Bio-oil obtained from wheat straw predominantly contained aromatic hydrocarbons (85%), whereas rice husk oil also contains high selectivity aromatic hydrocarbons (37.8%) along with aliphatic hydrocarbons (54.9%). The co-pyrolysis oils has high selectivity of aromatics.