Search Results (18)

To promote renewable energy sources, we focus on optimizing the design of solar–biomass pyrolysis systems. This study suggests the best reactor orientation that creates effective thermal–solar systems for pyrolysis. Solar–biomass pyrolysis uses solar energy to create valuable products like syngas, tar, and char from biomass. This process promotes energy sustainability. We analyze different solar reactors based on their design, operation, heat transfer rate, efficiency, residence time for biomass retention inside the reactor, and biomass conversion efficiency. A thorough analysis of the existing technologies helps to pinpoint the difficulties and most recent developments in the sector, making decision making more manageable and providing information on the viability and sustainability of biomass conversion technologies. Full article

The reliance on fossil fuels poses significant challenges to the environment and sustainable development. To address the heating requirements of the pyrolysis process in a biomass gasification-based multi-generation system, this study explored the use of low-grade solar energy across the full solar spectrum to supply the necessary energy for biomass pyrolysis while leveraging high-grade solar energy in the short-wavelength spectrum for power generation. The proposed multi-generation system integrates the full solar spectrum, biomass gasification, gas turbine, and waste heat recovery unit to produce power, cooling, and heating. A detailed thermodynamic model of this integrated system was developed, and the energy and exergy efficiencies of each subsystem were evaluated. Furthermore, the system’s performance was assessed on both monthly and annual timescales by employing the hourly weather data for Hohhot in 2023. The results showed that the solar subsystem achieved its highest power output of around 2.5 MWh in July and the lowest of 0.7 MWh in December. The annual electrical output peaked at 10 MWh, occurring around noon in July and August, while the winter peak was typically 2–3 MWh. For the wind power subsystem, the power output was maximized in April at 5.17 MWh and minimized in August at 0.7 MWh. Additionally, considering the overall multi-generation system performance, the highest power output of 14.9 MWh was observed in April, with lower outputs of 10.9, 11.3, and 11.4 MWh from August to October, respectively. Overall, the system demonstrated impressive annual average energy and exergy efficiencies of 74.05% and 52.13%, respectively. Full article

In this work, a biochar catalyst was developed from residual brewery spent grain (BSG) biomass and iron oxide to be applied in the counter electrode (CE) in dye-sensitized solar cells (DSSCs). The composite was obtained using a two-stage methodology based on microwave-assisted hydrothermal carbonization and pyrolysis, evaluating the influence of the pyrolysis temperature (700, 800 and 900 °C) on the properties and performance of the material. As result, composites with a high carbon and iron oxide content were obtained in a magnetite state attached to the surface. Furthermore, the physicochemical characteristics of the biochar showed similarities to those of reduced graphene oxide (rGO), which was attributed to the incorporation of iron oxide and the pyrolysis temperature. Electrochemical analysis showed that the composite pyrolyzed at 800 °C presented better catalytic activity and lower charge transfer resistance. Its application in the CE of a DSSC presented a current density of 10.44 mA/cm² and an efficiency of 3.05%, values close to the conventional Pt catalyst in DSSCs (Pt = 4.43%). This study validates the use of a composite based on residual brewery biomass with iron oxide in a CE, making it an alternative that contributes to the recovery of residues and the generation of sustainable technologies. Full article

The urgent need for sustainable strategies to mitigate climate change has spurred the development of efficient carbon sequestration methods with minimal greenhouse gas emissions, presenting promising opportunities to produce biochar and, with this bioproduct, enhance crop productivity. Therefore, this research aimed to evaluate the carbon footprint produced by the low-temperature slow pyrolysis of biomass obtained from the pruning residues of four tree species present in parks and gardens of the southern Andean region of Ecuador. An electric reactor (ER), powered by 44 solar panels of 535 W each, was used to perform the pyrolysis process at 350 °C over four hours. For each species—Persea americana, Polylepis spp., Acacia spp., and Prunus salicifolia—three replicates of the process were conducted using 1.5 kg of biomass per trial. The results showed that Acacia spp. residues produced biochar with higher bulk density (0.303 g/cm³), organic matter (82.85%), total organic carbon (71.21%), oxygen (27.84%), C/N ratio (120.69), and potassium (459.12 ppm). The biochar produced from Prunus salicifolia exhibited the highest levels of pollutant gas emissions and carbon footprint (5.93 × 10⁻⁶ ton∙m⁻³ CO₂ eq and 0.001067 ton∙m⁻³ CO₂ eq, respectively). In contrast, the biochar produced from Polylepis spp. was the least polluting (0.001018 ton∙m⁻³ CO₂ eq), highlighting its potential as a source for biochar production from tree species found in the southern Andean region of Ecuador. Meanwhile, the pyrolysis of Persea americana (avocado) resulted in very low gas emissions, although it exhibited the second-highest carbon footprint due to the high energy consumption associated with the process. In conclusion, this study identified Persea americana and Polylepis spp. as the best options for biochar production through pyrolysis, positioning them as viable alternatives for developing sustainable strategies to mitigate climate change. Full article

In this industrialized world, in which the daily consumption of fossil fuels occurs, companies seek to prioritize energy generation through renewable energy sources with minimal environmental impact to improve their energy efficiency. The research objective was to calculate CO₂ emissions for the pyrolysis process (conventional low-temperature pyrolysis) in two types of reactors, electric and traditional, where solar panels power the electric reactor. In addition, the amount of polluting gases and the energy consumption necessary to convert biomass into biochar were compared. Residual lignocellulosic biomass (RLB) from various species present in the southern region of Ecuador (eucalyptus, capuli, and acacia) was used, with three replicates per reactor. The electrical reactor (ER) consumed 82.60% less energy than the primary forest biomass fuel “traditional reactor (TR)” and distributed heat better in each pyrolytic process. The TR generated more pollution than the ER; it generated 40.48% more CO, 50% more NO₂, 66.67% more SO₂, and 79.63% more CH₄. Undoubtedly, the pyrolysis process in an ER reduces environmental pollution and creates new bioproducts that could replace fossil fuels. This study provides relevant information on the residual biomass pyrolysis of plant species. These species are traditionally grown in the southern Ecuadorian region. In addition, an analysis of polluting gases for the TR and ER is presented. Full article

The state of Sonora, Mexico, stands as one of the leading producers of pecan nuts in the country, which are commercialized without shells, leaving behind this unused residue. Additionally, this region has abundant solar resources, as shown by its high levels of direct normal irradiance (DNI). This study contributes to research efforts aimed at achieving a synergy between concentrated solar energy technology and biomass pyrolysis processes, with the idea of using the advantages of organic waste to reduce greenhouse gas emissions and avoiding the combustion of conventional pyrolysis through the concentration of solar thermal energy. The objective of this study is to pioneer a new experimental analysis methodology in research on solar pyrolysis reactors. The two main features of this new methodology are, firstly, the comparison of temperature profiles during the heating of inert and reactive materials and, secondly, the analysis of heating rates. This facilitated a better interpretation of the observed phenomenon. The methodology encompasses two different thermal experiments: (A) the pyrolysis of pecan shells and (B) the heating–cooling process of the biochar produced in experiment (A). Additionally, an experiment involving the heating of volcanic stone is presented, which reveals the temperature profiles of an inert material and serves as a comparative reference with experiment (B). In this experimental study, 50 g of pecan shells were subjected to pyrolysis within a cylindrical stainless-steel reactor with a volume of 156 cm³, heated by concentrated radiation from a solar simulator. Three different heat fluxes were applied (234, 482, and 725 W), resulting in maximum reaction temperatures of 382, 498, and 674 °C, respectively. Pyrolysis gas analyses (H₂, CO, CO₂, and CH₄) and characterization of the obtained biochar were conducted. The analysis of heating rates, both for biochar heating and biomass pyrolysis, facilitated the identification, differentiation, and interpretation of processes such as moisture evaporation, tar production endpoint, cellulosic material pyrolysis, and lignin degradation. This analysis proved to be a valuable tool as it revealed heating and cooling patterns that were not previously identified. The potential implications of this tool would be associated with improvements in the design and operation protocols of solar reactors. Full article

The pyrolysis process is a thermochemical conversion reaction that encompasses an intricate array of simultaneous and competitive reactions occurring in oxygen-depleted conditions. The final products of biomass pyrolysis are bio-oil, biochar, and some gases, with their proportions determined by the pyrolysis reaction conditions and technological pathways. Typically, low-temperature slow pyrolysis (reaction temperature below 500 °C) primarily yields biochar, while high-temperature fast pyrolysis (reaction temperature 700–1100 °C) mainly produces combustible gases. In the case of medium-temperature rapid pyrolysis (reaction temperature around 500–650 °C), conducted at very high heating rates and short vapor residence times (usually less than 1 s), the maximum liquid yield can reach up to 85 wt% (on a wet basis) or achieve 70 wt% (on a dry basis), with bio-oil being the predominant product. By employing the pyrolysis technique, valuable utilization of tobacco stem waste enriched with lignin can be achieved, resulting in the production of desired pyrolysis products such as transportation fuels, bio-oil, and ethanol. The present review focuses on catalytic pyrolysis, encompassing catalytic hydropyrolysis and catalytic co-pyrolysis, and meticulously compares the impact of catalyst structure on product distribution. Initially, we provide a comprehensive overview of the recent pyrolysis mechanism of lignin and tobacco waste. Subsequently, an in-depth analysis is presented, elucidating how to effectively design the catalyst structure to facilitate the efficient conversion of lignin through pyrolysis. Lastly, we delve into other innovative pyrolysis methods, including microwave-assisted and solar-assisted pyrolysis. Full article

New 3D micro-nanostructured composite materials have been synthesised. These materials comprise SiO₂/CaCO₃/C_org/NdVO₄NPs and SiO₂/CaO/C_org/NdVO₄NPs, exhibiting strong upconversion luminescence. The synthesis was accomplished by metabolically doping diatom cells with neodymium and vanadium. Subsequently, the biomass of these doped diatoms was subjected to pyrolysis at 800 °C. The morphology, structure, and physicochemical properties of the doped diatom biomass as well as dried (SiO₂/CaCO₃/C_org/NdVO₄NPs) and pyrolysed (SiO₂/CaO/C_org/NdVO₄NPs) samples were characterised using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), thermal analysis (TG), and fluorescence spectroscopy (FS). Studies have shown that the surface of diatom shells is covered with trigonal prismatic nanocrystallites (nanoparticles) of NdVO₄ with dimensions of 30–40 nm, forming the crystallite clusters in the form of single-layer irregular flakes. The synthesised composites produced intense anti-Stokes fluorescent emission in the visible region under xenon lamp excitation in the near-infrared (λ_ex = 800 nm) at room temperature in an ambient atmosphere. Such materials could be attractive for applications in solar spectrum conversion, optical sensing, biosensors, or photocatalysts. Full article

Lithium–sulfur batteries (LSBs) with a high energy density have been regarded as a promising energy storage device to harness unstable but clean energy from wind, tide, solar cells, and so on. However, LSBs still suffer from the disadvantages of the notorious shuttle effect of polysulfides and low sulfur utilization, which greatly hider their final commercialization. Biomasses represent green, abundant and renewable resources for the production of carbon materials to address the aforementioned issues by taking advantages of their intrinsic hierarchical porous structures and heteroatom-doping sites, which could attribute to the strong physical and chemical adsorptions as well as excellent catalytic performances of LSBs. Therefore, many efforts have been devoted to improving the performances of biomass-derived carbons from the aspects of exploring new biomass resources, optimizing the pyrolysis method, developing effective modification strategies, or achieving further understanding about their working principles in LSBs. This review firstly introduces the structures and working principles of LSBs and then summarizes recent developments in research on carbon materials employed in LSBs. Particularly, this review focuses on recent progresses in the design, preparation and application of biomass-derived carbons as host or interlayer materials in LSBs. Moreover, outlooks on the future research of LSBs based on biomass-derived carbons are discussed. Full article

An alternative to mitigate the consumption of fossil fuels is the use of biomass as an energy source. In this sense, the rural sector in Latin America has great potential due to its multiple biomass sources. For this reason, this study aims to analyze potential technologies related to the production of energy from biomass and its application in the Latin American rural sector. To achieve this, four key processes are analyzed. First is biomass conditioning through solar dryers. Next are the thermochemical processes that allow for their transformation into biofuels, for which the pyrolysis and the hydrothermal methods were selected due to the flexibility of the products obtained. Subsequently, cogeneration is studied to produce electrical and thermal energy from biomass or its derivatives. Finally, to close the CO₂ cycle, a balance of CO₂ fixation in a forest plantation is presented as an example of carbon accumulated in biomass. The literature systematic review allowed us to determine that the technologies mentioned in this work have different degrees of implementation in the Latin American rural sector. However, they have great potential to be applied on a large scale in the region, making it possible to adapt energy production to climate change and improve the life quality of its inhabitants. Full article

The main factors influencing biochar properties are feedstock biomass and pyrolysis operational conditions. A solar parabolic dish collector was proposed as a new green approach to the pyrolysis process. The technique of this reactor was designed to produce biochar from sesame feedstock (SF) by concentrating solar radiation. This research aims to compare the main physical and chemical properties of biochar produced by the solar reactor to those of the conventional reactor (muffle furnace, SB-3). Biochar produced by the parabolic dish collector was a heterogeneous brown color. Depending on color intensity, biochar was divided into the biochar formed around the inner sidewalls of the internal chamber (SB-1) and the biochar formed in the upper part of the internal chamber (SB-2). Generally, the physiochemical properties of the SB-2 biochar were similar to the SB-3 biochar, while SB-1 biochar was similar to SF. This was because the temperature distribution was not uniform in the solar reactor. The proposed solar parabolic dish collector needs some modifications to upgrade the biochar production to be close to that produced by the electric instrument. SB-2 is preferred as a soil amendment depending on its pH, cation exchange capacity (CEC), elemental composition, ion molar ratio (H/C, O/C, and (O+N)/C), and acidic functional groups. Full article

Solar pyrolysis is a promising technology as it combines use of biomass and solar energy to generate transportable and storable fuels, as well as chemicals of interest. The most desired product of rapid pyrolysis of microalgae is bio-oil, a liquid and viscous mixture composed of hundreds of chemicals. Among these compounds are many oxygenates that usually bring some undesirable properties to bio-oil, e.g., instability. This study aimed to investigate the potential of Spirulina platensis to produce bio-oil from catalytic solar pyrolysis assisted by Fresnel lens. The performance of the mixed oxides derived from hydrocalumite was evaluated, aiming to improve the yield and quality of the liquid product. The effects of reaction time and percentage of catalyst on the product distribution and bio-oil composition were quantified. An optimization study was performed using the differential evolution (DE) algorithm in order to maximize the bio-oil yield. The results showed that the highest liquid yield (43.4%) was obtained in 23.4 min using a catalyst percentage of 58.6%. The mixed oxides derived from hydrocalumite contributed to the improvement in the bio-oil quality, which presented in its composition a low quantity of oxygenated compounds and a higher percentage of hydrocarbons. Full article

Intermediate pyrolysis can be used to obtain high-quality biofuels from low-value residues such as sewage sludge or digestate. A major obstacle is the high water content of sludgy biomass, which requires an energy-intensive and expensive drying step before pyrolysis. Solar greenhouse drying is an efficient and sustainable alternative to a thermally heated belt dryer. In this study, a techno-economic assessment of intermediate pyrolysis with solar drying is carried out. Marketable products of the process are bio-oil, a substitute for diesel or heating oil, and bio-char with various possible applications. Chile is chosen as the setting of the study as its 4000 km long extension from north to south gives the opportunity to evaluate different locations and levels of solar irradiation. It is found that solar drying results in higher capital investment, but lower fuel costs. Depending on the location and solar irradiation, solar drying can reduce costs by 5–34% compared to belt drying. The break-even price of bio-char is estimated at 300–380 EUR/ton after accounting for the revenue from the liquid bio-oil. Full article

Agro-industrial waste valorization is an attractive approach that offers new alternatives to deal with shrinkage and residue problems. One of these approaches is the synthesis of advanced carbon materials. Current research has shown that citrus waste, mainly orange peel, can be a precursor for the synthesis of high-quality carbon materials for chemical adsorption and energy storage applications. A recent approach to the utilization of advanced carbon materials based on lignocellulosic biomass is their use in solar absorber coatings for solar-thermal applications. This study focused on the production of biochar from Citrus aurantium orange peel by a pyrolysis process at different temperatures. Biochars were characterized by SEM, elemental analysis, TGA-DSC, FTIR, DRX, Raman, and XPS spectroscopies. Optical properties such as diffuse reflectance in the UV−VIS−NIR region was also determined. Physical-chemical characterization revealed that the pyrolysis temperature had a negative effect in yield of biochars, whereas biochars with a higher carbon content, aromaticity, thermal stability, and structural order were produced as the temperature increased. Diffuse reflectance measurements revealed that it is possible to reduce the reflectance of the material by controlling its pyrolysis temperature, producing a material with physicochemical and optical properties that could be attractive for use as a pigment in solar absorber coatings. Full article

Energy access and waste management are two of the most pressing developmental and environmental issues on a global level to help mitigate the accelerating impacts of climate change. They are particularly relevant in Sub–Saharan Africa where electrification rates are significantly below global averages and rural areas are lacking a formal waste management sector. This paper explores the potential of integrating solar energy into a biomass pyrolysis unit as a potentially synergetic solution to both issues. The full design of a slow pyrolysis batch reactor targeted at biochar production, following a strict cost minimization approach, is presented in light of the relevant considerations. SPEAR is powered using a Cassegrain optics parabolic dish system, integrated into the reactor via a manual tracking system and optically optimized with a Monte-Carlo ray tracing methodology. The design approach employed has led to the development an overall cost efficient system, with the potential to achieve optical efficiencies up 72% under a 1.5° tracking error. The outputs of the system are biochar and electricity, to be used for soil amendment and energy access purposes, respectively. There is potential to pyrolyze a number of agricultural waste streams for the region, producing at least 5 kg of biochar per unit per day depending on the feedstock employed. Financial assessment of SPEAR yields a positive Net Present Value (NPV) in nearly all scenarios evaluated and a reasonable competitiveness with small scale solar for electrification objectives. Finally, SPEAR presents important positive social and environmental externalities and should be feasibly implementable in the region in the near term. Full article