Search Results (23)

Low-carbon liquid fuels are needed for decarbonization of hard-to-decarbonize segments of the transportation sector. This decarbonization can be limited by the amount of renewable carbon. Thermochemical conversion of biomass/municipal solid waste (MSW) through gasification is a promising route for producing low-carbon fuels. There are two major opportunities for increasing the amount of low-carbon liquid fuel that can be produced from gasification in any region. One is to increase the amount of liquid fuel from a given amount of biomass/MSW, particularly by hydrogen-enhancement of gasification synthesis gas. Second is the potential for large expansion of use of biomass feedstocks from its present level. Such biomass feedstocks include agricultural waste, forestry waste, MSW, and specially grown biomass that does not interfere with food production. The use of MSW may provide advantages of an established network for pickup and transportation of feedstock to disposal sites and the avoidance of methane produced from landfilling of MSW. As a case study, we looked at potential expansion of US low-carbon fuel production, considering the recent projections of the 2024 USDOE report, which estimated potential production of a billion tons/yr of biomass/MSW feedstocks in the US. This report included an estimated potential for liquid biofuel production of 60 billion gallons/yr of diesel energy equivalent fuel without the use of hydrogen enhancement. By hydrogen-enhanced biomass/MSW gasification, this projection could be doubled to 120 billion gallons/yr of diesel energy equivalent fuel. Furthermore, the co-location potential of biomass/MSW resources with potential renewable energy generation sites is explored. This overlap of hydrogen production and biomass production in the US are located in regions such as the US Midwest, Texas, and California. This co-location strategy enhances logistical feasibility, reducing transport costs and optimizing energy system integration; and can be applied to other geographical locations. Hydrogen-enhanced biomass/MSW gasification offers a promising route to substantially increase low-carbon liquid fuel production (e.g., methanol) and support increased liquid fuel production and greenhouse gas reduction goals. Full article

This study evaluates the greenhouse gas (GHG) impacts of converting municipal solid waste (MSW) into methanol, focusing on both landfill methane (CH₄) emission avoidance and the provision of cleaner liquid fuels with lower carbon intensity. We conduct a life cycle assessment (LCA) to assess potential GHG reductions from MSW gasification to methanol, enhanced with hydrogen produced via natural gas pyrolysis or water electrolysis. Hydrogen enhancement effectively doubles the methanol yield from a given amount of MSW. Special attention is given to hydrogen production through natural gas pyrolysis due to its potential for lower-cost hydrogen and reduced reliance on renewable electricity compared to electrolytic hydrogen. Our analysis uses a case study of methanol production from an oxygen-fired entrained flow gasifier fed with refuse-derived fuel (RDF) simulated in Aspen HYSYS. The LCA incorporates the significant impact of landfill methane avoidance, particularly when considering the 20-year global warming potential (GWP). Based on the LCA, the process has illustrative net GHG emissions of 183 and 709 kgCO_2e/t MeOH using renewable electricity for electrolytic hydrogen and pyrolytic hydrogen, respectively, for the 100-year GWP. The net GHG emissions using 20-year GWP are −1222 and −434 kgCO_2e/t MeOH, respectively. Additionally, we analyze the sensitivity of net GHG emissions to varying levels of fugitive methane emissions. Full article

ZSM-5 zeolite is a kind of high-value-added porous aluminosilicate zeolite. The use of the coal gasification slag utilization process by-product desilication liquid as a silicon raw material to replace the current raw materials such as water glass will help reduce production costs and achieve high-value utilization of solid waste. ZSM-5 zeolites for volatile organic compounds (VOCs) adsorption were prepared by a one-step hydrothermal method using the desilication solution prepared from coal gasification slag as the main silicon source and sodium source. The effects of crystallization reaction time, the crystallization temperature, the Na₂O/SiO₂ molar ratio, and the SiO₂/Al₂O₃ molar ratio on the relative crystallinity and the specific surface area of the ZSM-5 zeolite were investigated and optimized. The optical reaction conditions were as follows: a crystallization time of 12 h, a crystallization temperature of 170 °C, a Na₂O/SiO₂ molar ratio of 0.2, and a SiO₂/Al₂O₃ molar ratio of 200. The optimal ZSM-5 zeolite synthesized is hexagonal, with regular grains, a relative crystallinity of 101.48%, a specific surface area of 337.48 m²·g⁻¹, and a pore volume of 0.190 cm³·g⁻¹. And the optimal ZSM-5 zeolite was composed of SiO₂ content of 97.52 wt%, Al₂O₃ content of 1.58 wt%, Na₂O content of 0.33 wt%, and SiO₂/Al₂O₃ molar ratio of 104.93. Na₂O/SiO₂ molar ratio is 0.0033. The results of static adsorption experiments show that the static adsorption capacities of ZSM-5 zeolite for p-xylene, benzene, toluene, and butyl acetate were 118.85, 69.98, 68.74, and 95.85 mg·g⁻¹, respectively, which can effectively adsorb VOCs. The synthetic process of the ZSM-5 zeolite is a simple preparation process and short in synthesis time. The results of this study not only help to realize the high-value utilization of silicon components in solid waste, but also provide an economical and effective way to synthesize VOCs adsorption materials. Full article

In recent decades, economic development and population growth has been accompanied by the generation of billions of tonnes of solid residues or municipal “wastes”, a substantial portion of which is composed of plastics and biomass materials. Combustion-based waste-to-energy is a viable and mature method of extracting calorific value from these end-of-life post-recyclable materials that are otherwise landfilled. However, alternative thermochemical methods, such as gasification, are becoming attractive due to the ability to synthesize chemical precursors for supply chain recirculation. Due to the infancy of gasification technology deployment, especially in the context of anthropogenic CO₂ emission reduction, additional systems engineering studies are necessary. Herein, we conduct an attributional life cycle analysis to elucidate the syngas production and environmental impacts of advanced thermochemical gasification methods for the treatment of biomass and plastic wastes obtained from municipal solid wastes, using a comprehensive thermodynamic process model constructed in AspenTech. Feedstock composition, process parameters, and gasification methods are varied to study the effects on syngas quality, yield, power generation potential, and overall greenhouse gas emissions. Steam-based gasification presents up to 38% reductions in CO₂ emissions when compared to conventional thermochemical methods. Using gasifier-active materials, such as metal hydroxides, can also further reduce CO₂ emissions, and realizes a capture load of 1.75 tonnes of CO₂ per tonne of plastic/stover feedstock. This design alteration has implications for reductions in CAPEX due to the mode of CO₂ capture utilized (e.g., solid sorbent vs. liquid SELEXOL). The use of renewable energy to provide a method to generate steam for this process could make the environmental impact of such MSW gasification processes lower by between 60–75% tonnes of CO₂ per tonne of H₂. Overall, these results can be used to inform the guidance of advanced waste gasification methods as a low-carbon transition towards a circular economy. Full article

During recent years, gasification technology has gained a high potential and attractiveness to convert biomass and other solid wastes into a valuable syngas for energy production or synthesis of new biofuels. The implementation of real gasification facilities implies a good insight of all expenses that are involved, namely investments required in equipment during the project and construction phases (capital expenditures, CapEx) and costs linked to the operation of the plant, or periodic maintenance interventions (operational expenditures, OpEx) or costs related to operations required for an efficient and sustainable performance of a gasification plant (e.g., feedstock pre-treatment and management of by-products). Knowledge of these economic parameters and their corresponding trends over time may help decision-makers to make adequate choices regarding the eligible technologies and to perform comparisons with other conventional scenarios. The present work aims to provide an overview on CapEx associated with gasification technologies devoted to convert biomass or solid waste sources, with a view of reducing the carbon footprint during energy generation or production of new energy carriers. In addition, an analysis of technology cost trends over time using regression methods is also presented, as well as an evaluation of specific capital investments according to the amount of output products generated for different gasification facilities. The novelty of this work is focused on an analysis of CapEx of existing gasification technologies to obtain distinct products (energy and fuels), and to determine mathematical correlations relating technology costs with time and product output. For these purposes, a survey of data and categorization of gasification plants based on the final products was made, and mathematical regression methods were used to obtain the correlations, with a statistical analysis (coefficient of determination) for validation. Specific investments on liquid biofuel production plants exhibited the highest decreasing trend over time, while electricity production became the least attractive solution. Linear correlations of specific investment versus time fitted better for electricity production plants (R² = 0.67), while those relating the product output were better for liquid biofuel plants through exponential regressions (R² = 0.65). Full article

The formulation of the CFD-DEM model, CD-MELT, is established in this study to include three-phase non-isothermal processes with simultaneous combustion and melting for gasification simulations. To demonstrate the model capability, CD-MELT is used to assess the need for slag recycling for the non-isothermal melting of municipal solid wastes (MSW) in a prototype waste-to-energy research facility. The simulation encompasses the full fixed-bed slagging gasification process, including chemical reactions and melting of MSW and slag. In order to assess the need for slag recycling, comparisons are made for the two cases of with and without, in terms of the slag mass, liquid slag volume fraction, exit gas composition, and temperature distribution in the gasifier. The prediction results enable the tracking of liquid molten slag as it permeates through the solids-packed bed for the first time in the literature as far as we are aware, which is crucial to address design considerations such as distribution of bed temperature and optimal location for slag-tap holes at the bottom, as well as potential slag clogging within the porous media. The model also predicts an uneven and intermittent slag permeation through the packed bed without the recycling, and provides a plausible explanation for the operators’ experience of why slag recycling is important for process stability. Finally, the predicted slag outlet temperature using the proposed CFD approach also agrees well with the measurement data published in an earlier case study for the same facility. Full article

Research focusing on waste management and CO₂ mineralization simultaneously has been a popular topic in the mining community, and a common approach is to mineralize CO₂ with coal-based solid waste (CSW, e.g., gangue (CG), fly ash (FA), coal gasification slag (CGS)) produced by mining activities. Despite the understanding of CO₂ mineralization by cementitious materials, the mineralization capacity of alkali-activated CSWs remains unknown. Therefore, the mineral composition evolution and mineralization capacity of different alkali-activated materials (prepared with CG, FA, CGS, and sodium hydroxide (which works as the alkali-activator), respectively) are investigated with the adoption of Gibbs Energy Minimization Software (GEMS). The results indicate that the abovementioned three alkali-activated CSWs are majorly composed of calcium silicate hydrate, magnesium silicate hydrate, kaolinite, sodium zeolite, and liquid. Due to the difference in the chemical composition of different CSWs, the amount of hydration products varies. Specifically, the alkali-activated CSWs made with CGS have the maximum calcium silicate hydrate (C-S-H), while those prepared with FA enjoy the lowest porosity. In addition, the CO₂ mineralization process will result in the formulation of carbonate and, theoretically, the maximum quantity of mineralized CO₂ is less than 20% of the binder used. Furthermore, compared with CG and CGS, FA is characterized with the highest mineralization capacity. The findings in this study contribute to the understanding of CO₂ mineralization with alkali-activated CSWs. Full article

Global fossil fuel consumption has induced emissions of anthropogenic carbon dioxide (CO₂), which has emanated global warming. Significant levels of CO₂ are released continually into the atmosphere from the extraction of fossil fuels to their processing and combustion for heat and power generation including the fugitive emissions from industries and unmanaged waste management practices such as open burning of solid wastes. With an increase in the global population and the subsequent rise in energy demands and waste generation, the rate of CO₂ release is at a much faster rate than its recycling through photosynthesis or fixation, which increases its net accumulation in the atmosphere. A large amount of CO₂ is emitted into the atmosphere from various sources such as the combustion of fossil fuels in power plants, vehicles and manufacturing industries. Thus, carbon capture plays a key role in the race to achieve net zero emissions, paving a path for a decarbonized economy. To reduce the carbon footprints from industrial practices and vehicular emissions and attempt to mitigate the effects of global warming, several CO₂ capturing and valorization technologies have become increasingly important. Hence, this article gives a statistical and geographical overview of CO₂ and other greenhouse gas emissions based on source and sector. The review also describes different mechanisms involved in the capture and utilization of CO₂ such as pre-combustion, post-combustion, oxy-fuels technologies, direct air capture, chemical looping combustion and gasification, ionic liquids, biological CO₂ fixation and geological CO₂ capture. The article also discusses the utilization of captured CO₂ for value-added products such as clean energy, chemicals and materials (carbonates and polycarbonates and supercritical fluids). This article also highlights certain global industries involved in progressing some promising CO₂ capture and utilization techniques. Full article

Plastic waste poses a serious threat to the environment and it has been increasing at an alarming rate. In 2022, global plastic waste generation was reported to be around 380 million tonnes as compared to 353 million tonnes in 2019. Production of liquid fuel from plastic waste is regarded as a viable method for disposing of the plastic and utilizing its energy. Currently, a wide range of technologies have been explored for turning plastic waste into fuel, including the conventional pyrolysis, incineration, gasification and advanced oxidation. However, a systematic summary and comparative analysis of various technologies has still not reported. Traditional non-biodegradable plastic waste (NPW) treatment methods include landfilling and incineration, but these methods encounter bottlenecks and are unable to adequately address NPW issues. This review attempts to present a thorough summary of treatment methods for plastic waste (both conventional and novel treatment technologies that have recently been reported), examine their mechanism and their current state of development. Furthermore, the superiority and drawbacks of each technology are analysed and the prospects of technology application are proposed. By tackling the problems of white pollution and energy scarcity, this review intends to inspire the use of solid waste as a source of energy. Full article

The perspective of the emerging environmentally friendly and economically efficient detonation gun technology for the high-temperature gasification of organic wastes with ultra-superheated mixture of steam and carbon dioxide is discussed. The technology is readily scalable and allows the establishment of a highly reactive atmospheric-pressure environment in a compact water-cooled gasifier due to very high local temperature (above 2000 °C), intense in situ shock-induced fragmentation of feedstock, and high-speed vortical convective flows enhancing interphase exchange processes. These unique and distinctive features of the technology can potentially provide the complete conversion of solid and liquid wastes into syngas, consisting exclusively of hydrogen and carbon monoxide; microparticles, consisting of environmentally safe simple oxides and salts of mineral residues, as well as aqueous solutions of oxygen-free acids such as HCl, HF, H₂S, etc., and ammonia NH₃. A small part of the syngas product (ideally approximately 10%) can be used for replacing a starting fuel (e.g., natural gas) for the production of a detonation-born gasifying agent, while the rest can be utilized for the production of electricity, heat, and/or chemicals. Full article

The pulsed detonation (PD) gun technology was applied for the autothermal high-temperature conversion of natural gas and atmospheric-pressure oxygen-free allothermal gasification of liquid/solid organic wastes by detonation-born ultra-superheated steam (USS) using two flow reactors of essentially different volume: 100 and 40 dm³. Liquid and solid wastes were waste machine oil and wood sawdust, with moisture ranging from 10 to 30%wt. It was expected that decrease in the reactor volume from 100 to 40 dm³, other conditions being equal, on the one hand, should not affect natural gas conversion but, on the other hand, could lead to an increase in the gasification temperature in the flow reactor and, correspondingly, to an increase in the product syngas (H₂ + CO) quality. The PD gun was fed by natural gas–oxygen mixture and operated at a frequency of 1 Hz. As was expected, complete conversion of natural gas to product syngas in the PD gun was obtained with H₂/CO and CO₂/CO ratios equal to 1.25 and 0.25, irrespective of the reactor volume. Liquid and solid wastes were gasified to H₂, CO, and CH₄ in the flow reactors. The steady-state H₂/CO and CO₂/CO ratios in the syngas produced from waste machine oil were 0.8 and 0.5 for the 100-dm³ reactor and 0.9 and 0.2 for the 40-dm³ reactor, respectively, thus indicating the expected improvement in syngas quality. Moreover, the maximum mass flow rate of feedstock in the 40-dm³ reactor was increased by a factor of over 4 as compared to the 100-dm³ reactor. The steady-state H₂/CO and CO₂/CO ratios in the syngas produced from the fixed weight (2 kg) batch of wood sawdust were 0.5 and 0.8 for both reactors, and the gasification time in both reactors was about 5–7 min. The measured H₂ vs. CO₂ and CO vs. CO₂ dependences for the syngas produced by the autothermal high-temperature conversion of natural gas and atmospheric-pressure allothermal gasification of liquid/solid organic wastes by USS at f = 1 Hz were shown to be almost independent of the feedstock and reactor volume due to high values of local instantaneous gasification temperature. Full article

The technology of a pulsed detonation gun for gasification of organic waste with ultra-superheated steam has been experimentally demonstrated for the first time. Experiments were performed on natural gas conversion as well as on the gasification of liquid (waste machine oil) and solid (wood sawdust) waste by hot detonation products of natural gas–oxygen mixture at a frequency of detonation pulses f = 1 Hz. Periodic release of detonation products to a 100 L flow reactor provided a time-averaged mean temperature and pressure in the reactor at about 1200 K and 0.1 MPa. It is shown that the technology of a pulsed detonation gun can provide complete (100%) natural gas conversion to syngas containing H₂ and CO with a H₂/CO ratio of 1.25. During the gasification of liquid and solid wastes, the total volume fraction of combustible gases (H₂, CO, and CH₄) in the product syngas was 80 and 65% with H₂/CO ratios of 0.8 and 0.5, respectively. Comparison of the experiments on natural gas conversion and liquid/solid organic waste gasification under the same conditions at f = 1 Hz showed that the composition of the product syngas in terms of H₂ and CO content almost did not depend on the type of used feedstock. The estimated ideal energy gain defined as the ratio of the total energy of product syngas to the energy spent in its production from dry wood sawdust is about 4.6, i.e., the pulsed detonation technology of biomass gasification is economically very attractive. Full article

The importance of medical waste management has grown during the COVID-19 pandemic because of the increase in medical waste quantity and the significant dangers of these highly infected wastes for human health and the environment. This innovative review focuses on the possibility of materials, gas/liquid/solid fuels, thermal energy, and electric power production from medical waste fractions. Appropriate and promising treatment/disposal technologies, such as (i) acid hydrolysis, (ii) acid/enzymatic hydrolysis, (iii) anaerobic digestion, (vi) autoclaving, (v) enzymatic oxidation, (vi) hydrothermal carbonization/treatment, (vii) incineration/steam heat recovery system, (viii) pyrolysis/Rankine cycle, (ix) rotary kiln treatment, (x) microwave/steam sterilization, (xi) plasma gasification/melting, (xii) sulfonation, (xiii) batch reactor thermal cracking, and (xiv) torrefaction, were investigated. The medical waste generation data were collected according to numerous researchers from various countries, and divided into gross medical waste and hazardous medical waste. Moreover, the medical wastes were separated into categories and types according to the international literature and the medical waste fractions’ percentages were estimated. The capability of the examined medical waste treatment technologies to produce energy, fuels, and materials, and eliminate the medical waste management problem, was very promising with regard to the near future. Full article

Thermochemical processes use heat and series of endothermic chemical reactions that achieve thermal cracking and convert a wide range of solid waste deposits via four thermochemical processes to hydrocarbon gaseous and liquid products such as syngas, gasoline, and diesel. The four thermochemical reactions investigated in this research article are: incineration, pyrolysis, gasification, and integrated gasification combined cycle (IGCC). The mentioned thermochemical processes are evaluated for energy recovery pathways and environmental footprint based on conceptual design and Aspen HYSYS energy simulation. This paper also provides conceptual process design for four thermochemical processes as well as process evaluation and techno-economic analysis (TEA) including energy consumption, process optimization, product yield calculations, electricity generation and expected net revenue per tonne of feedstock. The techno-economic analysis provides results for large scale thermochemical process technologies at an industrial level and key performance indicators (KPIs) including greenhouse gaseous emissions, capital and operational costs per tonne, electrical generation per tonne for the four mentioned thermochemical processes. Full article

The global net emissions of the Kyoto Protocol greenhouse gases (GHG), such as carbon dioxide (CO₂), fluorinated gases, methane (CH₄), and nitrous oxide (N₂O), remain substantially high, despite concerted efforts to reduce them. Thermal treatment of solid waste contributes at least 2.8–4% of the GHG in part due to increased generation of municipal solid waste (MSW) and inefficient treatment processes, such as incineration and landfill. Thermal treatment processes, such as gasification and pyrolysis, are valuable ways to convert solid materials, such as wastes into syngas, liquids, and chars, for power generation, fuels, or for the bioremediation of soils. Subcoal™ is a commercial product based on paper and plastics from the source segregated waste that is not readily recyclable and that would otherwise potentially find its way in to landfills. This paper looks at the kinetic parameters associated with this product in pyrolysis, gasification, and combustion conditions for consideration as a fuel for power generation or as a reductant in the blast furnace ironmaking process. Thermogravimetric Analysis (TGA) in Nitrogen (N₂), CO₂, and in air, was used to measure and compare the reaction kinetics. The activation energy $(E_a)$ and pre-exponential factor $A$ were measured at different heating rates using non-isothermal Ozawa Flynn Wall and (OFW) and Kissinger-Akahira-Sonuse (KAS) model-free techniques. The TGA curves showed that the thermal degradation of Subcoal™ comprises three main processes: dehydration, devolatilization, and char and ash formation. In addition, the heating rate drifts the devolatilization temperature to a higher value. Likewise, the derivative thermogravimetry (DTG) results stated that T_m degradation increased as the heating rate increased. Substantial variance in $E_a$ was noted between the four stages of thermal decomposition of Subcoal™ on both methods. The $E_a$ for gasification reached 200.2 ± 33.6 kJ/mol by OFW and 179.0 ± 31.9 kJ/mol by KAS. Pyrolysis registered $E_a$ values of 161.7 ± 24.7 kJ/mol by OFW and 142.6 ± 23.5 kJ/mol by KAS. Combustion returned the lowest $E_a$ values for both OFW (76.74 ± 15.4 kJ/mol) and KAS (71.0 ± 4.4 kJ/mol). The low $E_a$ values in combustion indicate shorter reaction time for Subcoal™ degradation compared to gasification and pyrolysis. Generally, TGA kinetics analysis using KAS and OFW methods show good consistency in evaluating Arrhenius constants. Full article