Search Results (30)

A novel externally heated retort for Jimsar oil shale resources is proposed, and the symmetrical mathematical model of the transport process in the retort is established through intensively studying the mechanisms of shale gas flows, heat transfer, and pyrolysis reactions in the retort. The descriptions of axial and radial movements and temperature of oil shale and gases, and the distribution of pyrolysis reaction and yielding of gaseous products and semi-coke in various regions of the retort are simulated. The results show that oil shale can pyrolyze gradually from the region near the wall to the core region of the retorting chamber and pyrolyze completely at the bottom of the retorting zone through receiving the heat flux transferring from the combustion channels. The final pyrolysis temperature of oil shale is 821.05 K, and the outlet temperature of semi-coke cooled by cold recycled gas is 676.35 K, which are in agreement with the design requirements. In total, 75 toil shales can be retorted in one retorting chamber per day, and the productivity of the retort can be increased by increasing the number of retorting chambers. The fuel self-sufficiency rate of this externally heated oil shale retort can reach 82.83%. Full article

Water pollution from industrial, municipal, and agricultural sources is a pressing global concern, necessitating the development of sustainable and efficient treatment solutions. Algal biomass has emerged as a promising feedstock for the production of carbonaceous adsorbents due to its rapid growth, high photosynthetic efficiency, and ability to thrive in wastewater. This review examines the conversion of algal biomass into biochar and hydrochar through pyrolysis and hydrothermal processes, respectively, and evaluates their potential applications in wastewater treatment, carbon sequestration, and biofuel production. Pyrolyzed algal biochars typically exhibit a moderate to high carbon content and a porous structure but require activation treatments (e.g., KOH or ZnCl₂) to enhance their surface area and adsorption capabilities. Hydrothermal carbonization, conducted at lower temperatures (180–260 °C), produces hydrochars rich in oxygenated functional groups with enhanced cation exchange capacities, making them effective for pollutant removal. Algal-derived biochars and hydrochars have been successfully applied for the adsorption of heavy metals, dyes, and pharmaceutical contaminants, with adsorption capacities significantly increasing through post-treatment modifications. Beyond wastewater treatment, algal biochars serve as effective carbon sequestration materials due to their stable structure and high carbon retention. Their application as soil amendments enhances long-term carbon storage and improves soil fertility. Additionally, algal biomass plays a key role in biofuel production, particularly for biodiesel synthesis, where microalgae’s high lipid content facilitates bio-oil generation. Hydrochars, with energy values in the range of 20–26 MJ/kg, are viable solid fuels for combustion and co-firing, supporting renewable energy generation. Furthermore, the integration of these materials into bioenergy systems allows for waste valorization, pollution control, and energy recovery, contributing to a sustainable circular economy. This review provides a comprehensive analysis of algal-derived biochars and hydrochars, emphasizing their physicochemical properties, adsorption performance, and post-treatment modifications. It explores their feasibility for large-scale wastewater remediation, carbon capture, and bioenergy applications, addressing current challenges and future research directions. By advancing the understanding of algal biomass as a multifunctional resource, this study highlights its potential for environmental sustainability and energy innovation. Full article

Recycling plastics on an industrial scale is a key approach to the circular economy. This study presents a techno-economic analysis aimed at recycling polypropylene waste, one of the main consumer plastics. Specifically, it evaluates the technical and economic feasibility of achieving a large-scale cracking process that converts polypropylene waste into an alternative fuel. Pyrolysis is considered as a promising technique to convert plastic waste into liquid oil and other value-added products, with a dual benefit of recovering resources and providing a zero-waste solution. This study concerns a fast catalytic pyrolysis in a fluidized bed reactor, with the presence of a fluid catalytic cracking catalyst of low acidity for high heat transmission, for an industrial plant with a capacity of 1 t/h of polypropylene waste provided by the Greek Petroleum Industry. From the international literature, the operational conditions were chosen pyrolysis temperature at 430 °C, pressure at 1atm, heating rate at 5 °C/min, and yields of products to 71, 14, and 15 wt.%, for liquid fuel, gas, solid product, respectively. The plant design includes a series of apparatuses, with the main one to be the pyrolyzer. The catalytic method is selected over the non-catalytic because the presence of catalyst increases the quantity and quality of the liquid product, which is the main product of the plant. The energy loops of recycling pyrolysis gas and char as a low-carbon fuel in the plant were considered. The production cost, annual revenue, for 2023, are anticipated to reach €13.7 million (115 €/t) and €15 million (15 €/t), respectively, with an estimated investment equal to €5.3 million. The Payback Time is estimated to 2.4 years to recover the cost of investment. The endeavor is rather economically sustainable. A critical parameter for large scale systems is securing feedstock with low or negligible price. Full article

In the past few years, wind power has become a viable alternative in Brazil to diversify the energy mix and mitigate pollutant emissions from fossil fuels. Significant wind energy generation potential is inherent in the Brazilian Northeast state of Rio Grande do Norte, due to prevailing strong winds along the coastline and elevated regions. However, clean and renewable wind energy may lead to potential biodiversity impacts, including the removal of native vegetation during plant construction and operation. This case study explores the flash pyrolysis-based valorization of three commonly suppressed species, namely Cenostigma pyramidale (CP), Commiphora leptophloeos (CL), and Aspidosperma pyrifolium (AP), in a wind farm situated within the Mato Grande region of Rio Grande do Norte State. The study centers on determining their bioenergy-related properties and assessing their potential for producing phenolic-rich bio-oil. The investigation of three wood residues as potential sources of high-value chemicals, specifically phenolic compounds, was conducted using a micro-furnace type temperature programmable pyrolyzer combined with gas chromatography/mass spectrometry (Py–GC/MS setup). The range of higher heating values observed for three wood residues was 17.5–18.4 MJ kg⁻¹, with the highest value attributed to AP wood residue. The bulk density ranged from 126.5 to 268.7 kg m⁻³, while ash content, volatile matter content, fixed carbon content, and lignin content were within the respective ranges of 0.8–2.9 wt.%, 78.5–89.6 wt.%, 2.6–9.5 wt.%, and 19.1–30.6 wt.%. Although the energy-related properties signifying the potential value of three wood residues as energy resources are evident, their applicability in the bioenergy sector can be expanded via pelleting or briquetting. Yields of phenolic compounds exceeding 40% from the volatile pyrolysis products of CL and AP wood residues at 500 °C make them favorable for phenolic-rich bio-oil production. The findings of this study endorse the utilization of wood residues resulting from vegetation suppression during the installation of wind energy plants as potential feedstocks for producing bioenergy and sustainable phenolic compounds. This presents a solution for addressing a regional environmental concern following the principles of green chemistry. Full article

Pyrolysis is an excellent method for recovering mixed and contaminated plastics that are no longer recyclable. Special attention must be paid to the stability of the fuel to avoid the formation of undesirable products. This can be achieved by additives such as antioxidants. In this study, high-density polyethylene, polypropylene, and polystyrene plastic waste are slowly pyrolyzed to a maximum of 470 degrees Celsius. A gasoline fraction (0–190 °C) and a diesel fraction (190–320 °C) are then obtained from these. Three antioxidants are added to these fractions: pyrocatechol, phenol, and freshly produced algal pyrolysis oil; the latter is described in the literature as containing particularly high levels of antioxidants. The oxidation stability of these mixtures and the change in the iodine number over time are measured using a newer method than the commonly used method of Wijs. Phenol improves the oxidation stability best, followed successively by algae pyrolysis oil and pyrocatechol. The oxidation stability of the gasoline fraction of the polypropylene pyrolysis oil with phenol is 49% higher than that of the same fraction without antioxidants. Full article

Plum stone stands out as an alternative biomass source in terms of obtaining fuel and chemicals with or without catalysts under different conditions. Under variable heating rates (10, 50, and 100 °C min⁻¹) and pyrolysis temperatures (400, 450, 500, 550, and 600 °C), plum stone was pyrolyzed at a constant rate in a constant sweep gas flow (100 cm³ min⁻¹) in a tubular fixed-bed reactor. According to the results, an oil yield reaching a maximum of 45% was obtained at a heating rate of 100 °C min⁻¹ and pyrolysis temperature of 550 °C in the non-catalytic procedure. The catalytic pyrolysis was carried out with two selected commercial catalysts, namely ZSM-5 and PURMOL-CTX and clinoptilolite (natural zeolite, NZ) under optimum conditions with a catalyst ratio of 10% of the raw material. With the addition of catalyst, the quantity and quality of bio-oil increased, including calorific capacity, the removal of oxygenated groups, and hydrocarbon distribution. In the presence of catalysts, an increase was observed in terms of desirable products such as phenol, alkene, and alkane, and a decrease in terms of undesirable products such as acids. Considering and evaluating all the results, the use of zeolite materials as catalysts in pyrolysis is a recommended option for obtaining enhanced chemicals and fuels. Full article

In order to satisfy the increasing need for renewable chemicals and fuels, it is important to replace petroleum-based products with alternative feedstocks. Lignocellulosic biomass is considered to be the most capable alternative source for producing sustainable biofuels. Catalytic co-pyrolysis (CCP) is a process that involves simultaneously pyrolyzing biomass and plastics to produce a combination of liquid and gaseous products, such as bio-oil and syngas. Catalysts are used to raise the reaction degree and the selectivity of the co-pyrolysis process, with the choice of catalyst dependent on the physico-chemical features of the feedstock. Catalytic pyrolysis is a useful method for producing high-quality biofuels directly from biomass, although it typically yields a modest amount of aromatic hydrocarbons (HCs) and a large amount of coke, even with highly effective catalysts. Adding a co-reactant high in hydrogen to the CCP process can significantly increase the yield of aromatics while reducing coke formation. The use of CCP can help to address the environmental issues related to waste plastic disposal and improve energy security. This review article thoroughly discusses the process and mechanism of catalytic co-pyrolysis, the influence of plastics on the process, and how the addition of plastics can improve the quality and output of bio-oil while reducing the production of oxygenated compounds and coke. The importance of various catalysts (such as biochar, activated carbon, and acid and base catalysts) in improving the production and quality of obtained products is also compared and discussed. Full article

This study aims to improve the economic efficiency of the pitch synthesis reaction on the pilot plant by optimizing the pitch synthesis reaction and utilization of the byproduct. The pitch was synthesized using a 150 L pilot plant with pyrolyzed fuel oil as a precursor. The pitch synthesis reaction is carried out through volatilization and polycondensation, which occur at 300 and 400 °C. Volatilization is terminated during heating; thus, additional soaking time is meaningless and reduces the process efficiency. Soaking time is a major variable when the synthesis temperature exceeds 400 °C. The byproduct is generated through volatilization; thus, its chemical characteristics are only influenced by the reaction temperature. The byproduct consists of various polycyclic aromatic hydrocarbons. The average molecular weight and yield of the byproduct increase with the reaction temperature. Carbon black was synthesized using chemical vapor deposition from the byproduct. The particle size of carbon black was controlled by the used precursor (byproduct), and the electrical conductivity of prepared carbon black has a maximum of 58.0 S/cm. Therefore, carbon black, which is synthesized from the byproduct of pitch synthesis, is expected to be used as a precursor for conductive material used in lithium-ion batteries or supercapacitors. Full article

The increase in industrialization and development has tremendously diminished fossil fuel resources. Moreover, the excessive use of fossil fuels has resulted in the release of various toxic gases and an increase in global warming. Hence, necessitating the need to search for a renewable energy source. In this study, sesame waste biomass (SWB), which is abundantly available in Pakistan, has been used as feedstock for obtaining bio-oil using the pyrolysis technique. Pyrolysis was carried out using thermogravimetry and a pyrolysis chamber. Firstly, thermogravimetric analysis was performed on biomass with/without a laboratory synthesized catalyst Ni/Co/MCM-41 in nitrogen at different temperature programmed rates of 5, 10, 15, and 20 °C/min. A four-stage weight loss was observed that pointed toward the vaporization of water, and degradation of hemicelluloses, cellulose, and lignin. The kinetics parameters were determined using the Kissinger equation. The activation energy for the decomposition reaction of hemicelluloses, cellulose, and lignin, without catalyst, was observed as 133.02, 141.33, and 191.22 kJ/mol, respectively, however, with catalyst it was found as 91.45, 99.76, and 149.65 kJ/mol, respectively. In the catalyzed reaction the results showed the lowest activation energy, which is an indication of the fact that the catalyst is successful in reducing the activation energy to a sufficient level. As the TG/DTG showed active degradation between 200 and 400 °C, therefore, the waste sesame biomass over Ni-Co/MCM-41 was pyrolyzed within the same temperature range in the pyrolysis chamber. Temperature and time were optimized for maximum oil yield. A maximum oil yield of 38% was achieved at 330 °C and 20 min. The oil obtained was studied using GCMS. The physicochemical characteristics of the oil were assessed, and it was found that if the oil was upgraded properly, it could serve as a fuel for commercial use. Full article

The utilization of activated carbon (AC) as a catalyst for a lab-scale pyrolysis process to convert waste cooking oil (WCO) into more valuable hydrocarbon fuels is described. The pyrolysis process was performed with WCO and AC in an oxygen-free batch reactor at room pressure. The effects of process temperature and activated carbon dosage (the AC to WCO ratio) on the yield and composition are discussed systematically. The direct pyrolysis experimental results showed that WCO pyrolyzed at 425 °C yielded 81.7 wt.% bio-oil. When AC was used as a catalyst, a temperature of 400 °C and 1:40 AC:WCO ratio were the optimum conditions for the maximum hydrocarbon bio-oil yield of 83.5 and diesel-like fuel of 45 wt.%, investigated by boiling point distribution. Compared to bio-diesel and diesel properties, bio-oil has a high calorific value (40.20 kJ/g) and a density of 899 kg/m³, which are within the bio-diesel standard range, thus demonstrating its potential use as a liquid bio-fuel after certain upgradation processes. The study revealed that the optimum AC dosage promoted the thermal cracking of WCO at a reduced process temperature with a higher yield and improved quality compared to noncatalytic bio-oil. Full article

Amaranthus retroflexus or redroot pigweed is a second generation lignocellulosic fuel. Each biomass sample (leaves, inflorescences and stems) was pyrolyzed in a lab-scale furnace, in a nitrogen atmosphere under non-isothermal conditions at heating rates of 10 °C/min until the furnace temperature reached 550 °C. The pyrolysis characteristics of the three major components were also studied through thermogravimetric analysis. The thermal decomposition of the biomass samples is similar to the process of pyrolysis of lignocellulosic materials and proceeds in three main stages: dehydration, devolatilization, and carbonation. The highest bio-oil yield was obtained for inflorescences (55%) and leaves (45%). Gas chromatography—mass spectrometry analysis was carried out for oil fractions of the pyrolysis liquid from Amaranthus retroflexus. The composition of the pyrolysis oil fraction from the leaves had an overbearing aliphatic hydrocarbon nature whereas the oil fraction from inflorescences and stems was composed mainly of oxygen-containing components. The use of Amaranthus retroflexus biochars can lead to slag formation in power equipment, so it is advisable to use them to produce composite fuel, for example, mixed with coal. The results would help to better understand the thermal behavior of Amaranthus retroflexus biomass and its utilization for fuels or chemicals. Full article

Energy consumption is rising dramatically at the price of depleting fossil fuel supplies and rising greenhouse gas emissions. To resolve this crisis, barley waste, which is hazardous for the environment and landfill, was studied through thermochemical characterization and pyrolysis to use it as a feedstock as a source of renewable energy. According to proximate analysis, the concentrations of ash, volatile matter, fixed carbon, and moisture were 5.43%, 73.41%, 18.15%, and 3.01%, consecutively. The ultimate analysis revealed that the composition included an acceptable H/C, O/C, and (N+O)/C atomic ratio, with the carbon, hydrogen, nitrogen, sulfur, and oxygen amounts being 46.04%, 6.84%, 3.895%, and 0.91%, respectively. The higher and lower heating values of 20.06 MJ/kg and 18.44 MJ/kg correspondingly demonstrate the appropriateness and promise for the generation of biofuel effectively. The results of the morphological study of biomass are promising for renewable energy sources. Using Fourier transform infrared spectroscopy, the main link between carbon, hydrogen, and oxygen was discovered, which is also important for bioenergy production. The maximum degradation rate was found by thermogravimetric analysis and derivative thermogravimetry to be 4.27% per minute for pyrolysis conditions at a temperature of 366 °C and 5.41% per minute for combustion conditions at a temperature of 298 °C. The maximum yields of biochar (38.57%), bio-oil (36.79%), and syngas (40.14%) in the pyrolysis procedure were obtained at 400, 500, and 600 °C, respectively. With the basic characterization and pyrolysis yields of the raw materials, it can be concluded that barley waste can be a valuable source of renewable energy. Further analysis of the pyrolyzed products is recommended to apply in the specific energy fields. Full article

This study aims to examine the hydrodeoxygenation (HDO) of vanillin, an oxygenated phenolic compound present in bio-oil, into creosol. Biochar residue generated when wood is slowly pyrolyzed is utilized as a catalyst support. To improve biochar’s physicochemical properties, H₂SO₄ (sulfuric acid) and KOH (potassium hydroxide) are used as chemical activators. By means of a wet impregnation method with nickel salt, an Ni/biochar catalyst was prepared and utilized in the HDO of vanillin using a 100 mL Parr reactor, catalyst loading 0.4–0.8 g, temperature 100 °C to 150 °C, hydrogen (H₂) pressures of 30 to 50 bar, and a stirring rate of 1000 rpm. The prepared catalysts were characterized with the nitrogen-sorption isotherm technique, carbon dioxide temperature-programmed desorption (CO₂-TPD), scanning electron microscopy (SEM) coupled with energy dispersed X-ray analysis (EDX), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Based on chemical treatment, Ni/biochar (KOH) pore sizes were found to be dominated by mesopores, with a surface area increase of 64.7% and a volume increase of 65.3%, while Ni/biochar (H₂SO₄) was mostly microporous and mesoporous, with an area increase of 372.3% and a volume increase of 256.8% in comparison to Ni/biochar (74.84 m²g⁻¹ and 0.095 cm³g⁻¹). Vanillin conversion of up to 97% with 91.17% selectivity to p-creosol was obtained over Ni/biochar catalyst; in addition to being highly selective and active for p-creosol, a plausible fuel, the catalyst was stable after four cycles. Chemical treatments of the biochar support resulted in improved physicochemical properties, leading to improved catalytic performance in terms of vanillin conversion and p-creosol yield in the order Ni/biochar (H₂SO₄) > Ni/biochar (KOH) > Ni/biochar. Full article

Endocarp residues remaining after coconut oil extraction from Acrocomia aculeate are traditionally used for combustion as fuel. As an alternative, we propose its conversion into biochar to substitute peat in planting substrates. To test the feasibility of this approach, untreated endocarp residues (particle size approx. 10 mm) and materials shredded into particles of 4 and 1 mm were pyrolyzed at 200 °C, 325 °C and 450 °C and were subsequently characterized. The pyrolysis-induced loss of organic matter increased the ash contents and pH. Nuclear magnetic resonance (NMR) spectroscopy confirmed the aromatization and a loss of carboxyl C with an increasing pyrolysis temperature. This is commonly associated with an enhanced biochemical recalcitrance. The particle size of the feedstock had no significant effect on the chemical composition or microporosity (BET-adsorption with CO_s) of the biochars, but affected their water holding capacity. With respect to macro- and micronutrients, only the potassium and Olsen P levels occurred in concentrations that are optimal for tomato seed growth. The low nitrogen level of the products may be advantageous for hydroponic culturing since it allows for a higher flexibility for the adaptation of nutrient contents based on the needs of the used culture. Full article

Biofuels produced via thermochemical conversions of waste biomass could be sustainable alternatives to fossil fuels but currently require costly downstream upgrading to be used in existing infrastructure. In this work, we explore how a low-cost, abundant clay mineral, bentonite, could serve as an in situ heterogeneous catalyst for two different thermochemical conversion processes: pyrolysis and hydrothermal carbonization (HTC). Avocado pits were combined with 20 wt% bentonite clay and were pyrolyzed at 600 °C and hydrothermally carbonized at 250 °C, commonly used conditions across the literature. During pyrolysis, bentonite clay promoted Diels–Alder reactions that transformed furans to aromatic compounds, which decreased the bio-oil oxygen content and produced a fuel closer to being suitable for existing infrastructure. The HTC bio-oil without the clay catalyst contained 100% furans, mainly 5-methylfurfural, but in the presence of the clay, approximately 25% of the bio-oil was transformed to 2-methyl-2-cyclopentenone, thereby adding two hydrogen atoms and removing one oxygen. The use of clay in both processes decreased the relative oxygen content of the bio-oils. Proximate analysis of the resulting chars showed an increase in fixed carbon (FC) and a decrease in volatile matter (VM) with clay inclusion. By containing more FC, the HTC-derived char may be more stable than pyrolysis-derived char for environmental applications. The addition of bentonite clay to both processes did not produce significantly different bio-oil yields, such that by adding a clay catalyst, a more valuable bio-oil was produced without reducing the amount of bio-oil recovered. Full article