Conversion Of Solid Waste Research Articles

Life cycle analysis of gasification and Fischer-Tropsch conversion of municipal solid waste for transportation fuel production

Non-recyclable municipal solid waste (MSW) can be used as feedstock for liquid fuel production via gasification followed by Fischer-Tropsch (FT) processes. Given the heterogeneity of MSW material composition and variation in material properties, its convertibility to liquid hydrocarbon fuels could vary widely, affecting the sustainability of utilizing non-recyclable MSW for fuel production. This study evaluates the life cycle greenhouse gas (GHG) emissions (carbon intensities [CIs]) of FT fuels from non-recyclable MSW. Key issues that could greatly affect the CIs were examined, including fossil carbon content of the MSW, emission implications of diverting non-recyclable MSW from landfills to fuel production, and conversion efficiency. Results show that the CIs of fuels produced from various waste streams range 80–105 gCO2e/MJ, which may exceed the CI of petroleum fuels. Higher fossil carbon content in the MSW feedstock tends to incur higher GHG emissions as biogenic carbon emissions are considered carbon neutral. Meanwhile, diverting different fractions of non-recyclable MSW, such as food waste and low-quality paper, from landfills may result in GHG emissions that may include the potential avoidance of methane emissions and potential sequestration of biogenic carbon that is foregone. To reduce GHG emissions, a carbon capture and sequestration option in the fuel production stage is considered, which could reduce the CI by 53–64 gCO2e/MJ. Carbon fates of different non-recyclable MSW in landfills are further evaluated to determine how they vary and impact the CIs of MSW-derived fuels.

(Invited) Electrochemical Valorization of Waste Activated Sludge to Chemicals

Population growth have led to producing more solid waste from wastewater treatment plants (WWTPs), increasing both energy and cost for treatment and disposal of waste-activated sludge (WAS). If not treated properly, WAS poses serious threats to human health and the environment. The annual production of WAS reached 2 billion tons in 2011 worldwide and it is expected that this number will grow to 9.5 billion tons per year by 2050 [1]. Conversion of solid waste to value added chemicals and fuels could address environmental concerns imposed by the growing of WAS.To confront these challenges, Botte’s research group is working in the electrochemical valorization of WAS to chemicals [2]. In this talk, we will describe recent findings in the electrocatalysis of sludge using transition metals for the synthesis of ammonia and short-chain fatty acids production. Short-chain fatty acids (e.g., acetic acid, propionic acid, butyric acid, etc.) are the intermediate chemicals in anaerobic digestion. The global market demand for short-chain fatty acids in 2020 was 18,500 kt and it is expected to increase annually by 3% per year over the next three years [3].[1] Lemar, M.; De Fontaine, A., Energy Data Management Manual for the Wastewater Treatment Sector. Technical Report ORNL/SPR-2018/14 2017, United States. https://doi.org/10.2172/1432164[2] Jafari, M.; Botte, G. G., Electrochemical treatment of sewage sludge and pathogen inactivation. Journal of Applied Electrochemistry 2021, 51 (1), 119-130.[3] Ramos-Suarez, M.; Zhang, Y.; Outram, V., Current perspectives on acidogenic fermentation to produce volatile fatty acids from waste. Reviews in Environmental Science and Bio/Technology 2021, 20 (2), 439-478.

Performance analysis and biofuels conversion yield correlations for solar-thermal wood chips pyrolysis reactor using response surface methodology

The development of innovative sustainable methods and strategies for the conversion of biomass and waste materials to clean and alternative fuels using renewable power systems are needed to foster the clean energy transition. The main objective of this study is to optimize the performance of the pyrolysis reactor powered with solar parabolic trough collector (PTC) to maximize the quantity and quality of the biofuels production. The goal is to develop sustainable thermal conversion processes for the conversion of biomass and solid waste to renewable fuels. An integrated Modeling and simulation analysis based on the mass and energy balance of the thermal conversion process of the biomass (wood waste) and response surface methodology (RMS) for the optimization of the biofuel (bio-oil) yields was used in the present study. The effects of three main input factors: biomass volumetric flow rate, solar irradiance and biomass particle diameter on the performance of the PTC pyrolysis reactor were determined. The results show an average monthly bio-oil production of 44.58% by weight. The maximum bio-oil yield through the year occurs in May and June and it is around 58% by weight. Three new correlations for biofuel yields based on the three input factors were developed. The coefficients of determination R 2 for the three correlations were between 0.8951 and 0.9986 (0.14–10.49% errors). The perturbation graph of bio-oil conversion yield shows that the most significant input factor is the solar irradiance followed by biomass volumetric flow rate and then the particle diameter. The optimum conditions for bio-oil production (volume flow rate = 0.0058 m 3 /h; solar irradiance = 918 W/m 2 , and biomass particle diameter of 8 mm) for the selected pyrolysis reactor are also determined. The results obtained in the course of this study show the benefits of using solar thermal energy for the conversion of biomass and solid waste to renewable and alternative fuels.

A Bibliometric Analysis of Research Progress and Trends on Fly Ash-Based Geopolymer.

The objective of this work is to present the research progress and applications of fly ash-based geopolymer, and summarize the future research hotpots. Since 1998, scholars have made important contributions to the study of fly ash-based geopolymer, and a large number of research studies have been published. Therefore, a bibliometric analysis for the determination of the research status, trend, and history of fly ash-based geopolymer was conducted in the present study. A total of 4352 publications on fly ash-based geopolymer were collected between 1998 and 2022, with an increasing trend year by year. China and Australia are the largest contributors to the field, and the research institutions in each country cooperate closely. In addition, the most contributing research areas are MATERIALS SCIENCE, ENGINEERING, and CONSTRUCTION & BUILDING TECHNOLOGY. The keywords including fly ash, compressive strength, and mechanical property are the most frequently appearing words. On the whole, the development of fly ash-based geopolymer could be divided into three stages including the replacement of ordinary Portland cement, the development of multifunctional materials, and the reduction of environmental impact by the conversion of solid waste. This overview could provide an important guidance for the development of fly ash-based geopolymer.

Exploration of solid waste materials for sustainable manufacturing of cementitious composites.

The problem of disposing and managing solid waste materials has become one of the major environmental, economic, and social issues. Utilization of solid wastes in the production of building materials not only solves the problem of their disposal but also helps in the conversion of wastes into useful and cost-effective products. In the present study, solid waste materials of organic and inorganic nature were applied in the production of sustainable cementitious composites (CC) and studied the effect of incorporated wastes on physical and mechanical properties of the resultant CC. The selected solid waste materials were cotton, polyester, PET, carpet, glass, and granulated blast furnace slag (GBFS). These wastes were incorporated in CC in different proportions and form the tuff tiles using moulds (12.5″ × 6″ × 2.5″). The various physical (fineness, setting time, bulk density, and water absorption capacity) and mechanical (flexural strength) properties of all the specimens were determined after curing period of 3, 7, and 28days. The results show that the incorporation of solid wastes in CC did not much affect their physical characteristics. However, the CC incorporated with the selected solid waste materials have a pronounced effect of their flexural strength and found to be higher (12-875%) compared to the plain CC. Similarly, the incorporation of the selected inorganic wastes (302-715 psi) in CC exhibit much higher flexural strength compared to the organic wastes (136-235 psi). The maximum flexural strength was observed when GBFS was utilized as a solid waste. The present work will provide a reliable step for the solid waste management and conversion of such wastes into useful commercial products for concrete manufacturing.

A comparative techno-economic assessment of fast pyrolysis, hydrothermal liquefaction, and intermediate pyrolysis of municipal solid waste for liquid transportation fuels production

The conversion of municipal solid waste (MSW) to transportation fuels can be an attractive route to reduce greenhouse gas emissions from the transportation and municipal sectors. Thermochemical conversion routes like hydrothermal liquefaction (HTL), fast pyrolysis (FP), and intermediate pyrolysis (IP) have been shown to be adept at converting organic dominant MSW into bio-crude or bio-oil. However, to produce compatible transportation grade fuels, it is necessary to upgrade the intermediate product (bio-crude or bio-oil) from all the processes, the extent of which differs depending on the process. Moreover, depending on the conversion technique, the production configuration can be either centralized or decentralized. In a centralized system, feed is transported to a facility to produce the intermediate and upgrade it (on-site upgrading), while in a decentralized system, the intermediate is produced elsewhere and transported to an upgrading facility (off-site upgrading).. Four scenarios were developed and modeled to compare the cost of production of gasoline, diesel and jet fuel from bio-crudes produced from HTL, FP, and IP.. The scenarios are: 1) a centralized HTL plant (C-HTL); 2000 dry t per day; on-site upgrading, 2) a centralized FP plant (C-FP); 2000 dry t per day; on-site upgrading, 3) a decentralized FP plant (D-FP); 50 dry t per day; off-site upgrading, and 4) a decentralized IP plant; 12 dry t per day; off-site upgrading.. Jet fuel was the primary fuel for comparison and the production costs were calculated to be $ 0.72, $ 0.85, $ 1.04, and $ 0.81 per liter for the C-HTL, the C-FP, the D-FP, and the D-IP plants, respectively. Secondary products (gasoline and diesel) can be produced alongside in cost ranges of $ 0.97 - $ 1.40 per liter and $ 1.02 - $ 1.47 per liter, respectively. The information conveyed in this study helps to identify the potential of thermochemical conversion processes to produce transportation fuels at competitive prices. The critical barriers to adopt such large-scale production processes and the opportunities of small-scale decentralized production are also mentioned. The outcomes of this study can be used to direct research and investment to address the major roadblocks that are slowing the extensive development of these technologies.

Development of a MSW-fueled sustainable co-generation of hydrogen and electricity plant for a better environment comparing PEM and alkaline electrolyzers

Efficient conversion of Municipal Solid Waste (MSW) into useful energy by anaerobic digestion is a sustainable method which received growing interest, particularly for small-scale decentralized energy systems. This paper aims at development of an efficient combined cogeneration cycle for production of electricity and hydrogen from biogas generated using anaerobic digestion of MSW. When it comes to the topping cycle, the proposed system makes use of a micro gas turbine, whose waste heat is converted to electricity by an absorption power cycle. This additional electricity is provided to a water electrolyzer, which uses it to generate hydrogen. Two types of electrolyzers, including the Proton Exchange Membrane Electrolyzer (PEME) and the Alkaline Electrolyzer (AE) are considered, and their performances (as a component of the overall suggested combined systems) are compared from economic and thermodynamic viewpoints. The CO2 emission index is also addressed, and tri-objective optimization based on exergy, cost, and emission indices is carried out to compare the two systems. Obtained results indicated important outcomes, including that the system integrated with PEME is superior in terms of exergetic performance and emissions, whereas the system with AE is superior in terms of economics. The former has a 3.0% greater efficiency and a 3.3% lower emissions at optimal point established by tri-objective optimization, while it has a 9.3% higher levelized product cost.

Thermochemical conversion of municipal solid waste into energy and hydrogen: a review.

The rising global population is inducing a fast increase in the amount of municipal waste and, in turn, issues of rising cost and environmental pollution. Therefore, alternative treatments such as waste-to-energy should be developed in the context of the circular economy. Here, we review the conversion of municipal solid waste into energy using thermochemical methods such as gasification, combustion, pyrolysis and torrefaction. Energy yield depends on operating conditions and feedstock composition. For instance, torrefaction of municipal waste at 200 °C generates a heating value of 33.01 MJ/kg, while the co-pyrolysis of cereals and peanut waste yields a heating value of 31.44 MJ/kg at 540 °C. Gasification at 800 °C shows higher carbon conversion for plastics, of 94.48%, than for waste wood and grass pellets, of 70–75%. Integrating two or more thermochemical treatments is actually gaining high momentum due to higher energy yield. We also review reforming catalysts to enhance dihydrogen production, such as nickel on support materials such as CaTiO3, SrTiO3, BaTiO3, Al2O3, TiO3, MgO, ZrO2. Techno-economic analysis, sensitivity analysis and life cycle assessment are discussed.

Performance analysis of a pilot-scale municipal solid waste gasification and dehumidification system for the production of energy and resource

Energy consumption and waste management are two significant challenges for human societies. To realize zero waste management, a pilot-scale demonstration of the conversion of municipal solid waste to energy/resource, which is comprised of a gasification system and a dehumidification air-conditioning to produce heat, cooling, and construction-used char, is investigated and analyzed. The waste heat (60 °C hot water) from a gasification system is applied to drive a dehumidification system for cooling, while the char from the gasification is added to the construction material. The effect of cycle time and air flow rate on the performance of the dehumidification system is also analyzed. The waste to energy efficiency of 57.2%, the maximum average moisture removal of 11.6 g/kgDA, and thermal coefficient of performance of 0.76 are obtained under the climate conditions of 34 °C, 67.5% relative humidity in Singapore. Through comparison between the brand new and used desiccant coated heat exchanger, it is noted that there is a 29.37% decrease of average moisture removal corresponding with a 17.1% loss of thermal coefficient of performance. A 14.6% compressive strength increment after seven days of curing age and 10.3% of compressive strength increment after 28 days are investigated by studying the mechanical behavior of a mortar containing char.

Thermogravimetric and kinetic study of thermal degradation of various types of municipal solid waste (MSW) under N2, CO2 and oxy-fuel conditions

Oxy-fuel combustion is one carbon capture and sequestration (CCS) technique that uses both O2 and recirculated flue gas as an oxidiser. As a result, the produced gas is composed mainly of CO2 and H2O, which makes its sequestration more cost-effective. Changing the atmosphere from N2 to CO2 affects combustion behaviour. To study the impact of the atmosphere on the combustion process, the thermal degradation of representative types of municipal solid waste (MSW) under N2, CO2, and O2/CO2 atmospheres was analysed using a thermogravimetric (TG) instrument. Nonisothermal degradation experiments were conducted, and three heating rates were examined. Isoconversional methods were employed to determine kinetic data. Comparing N2 and CO2 atmospheres, it was found that below 600 °C, the shape of TG curves was not affected significantly. However, above 600 °C under CO2 atmosphere, a second peak appeared, which indicated gasification reactions of the char with carbon dioxide. In the presence of oxygen, the second peak was shifted to lower temperatures, indicating that thermal decomposition with O2 was more rapid. The reported kinetic parameters provide fundamental information on the conversion of solid waste. Thus, they are essential for designing chambers dedicated to the oxy-combustion of waste.

Trash to Energy: A Measure for the Energy Potential of Combustible content of Domestic solid waste generated from an industrialized city of Pakistan

BackgroundThe current study was designed to calculate the approximate energy potential of combustible fraction shared in the overall domestic solid waste stream generated from Faisalabad, the 3rd largest city and an industrial hub of Pakistan through ASTM standards. MethodsCharacterization of samples were collected during the rainy season from June-August 2020 and January-March 2021 from three discrete socio-economic classes (lower income class [Rs. 15,000 (US $100)], middle-income class [Rs. 50,000 (US $350)] and high-income class [Rs. ≥1,00,000 (US $1,000)]) and segregated into 13 different physical components consisting of organic waste, yard waste, wood, cardboard, textile, plastic, paper, metal, rubber, glass, ceramic, diapers, dust, stone and miscellaneous. Significant FindingsMore than 70% of the overall generated solid waste was shared by organic waste in the study area, comprising 64.75% moisture content on average. Among all the physical elements of solid waste, combustible content was estimated at 37% in dry mass with 19.23% of ash content and 80.77% of the volatile organic compound. The results of the study approximate about 27.18 MW of energy generation from the available combustible fraction of 1,155 t of domestic solid waste generated from the city daily which can fulfil the need of almost 5,00,000 houses having an average usage of 500 W electricity on monthly basis. The study concludes the conversion of solid waste into energy is the suitable practice for solid waste generated but needed to make this solution practicable with the help of government officials with the involvement of appropriate private sector which will definitely generate new jobs for unemployed persons. The summary demands appropriate adaptation in current waste disposal practice to convert the combustible fraction of generated waste into energy to combat the shortfall of energy/electricity in the city of industries.

Conversion of municipal solid waste to hydrogen and its storage to methanol

Municipal solid waste (MSW) has become a challenging issue for many decades, especially in developing countries, leading to several social and environmental problems. Appropriate treatment and conversion of this MSW are urgently demanded. In this study, an efficient conversion of MSW to methanol is proposed and analyzed. The developed system consists of simultaneous processes, integrating hydrothermal treatment (HTT), direct chemical looping, methanol synthesis, and combined cycle for power generation. HTT is conducted to increase the carbon content and caloric value of the MSW, as well as to physically uniform the material. The treated MSW flows to direct chemical looping for conversion to hydrogen while separating CO2. The produced hydrogen and CO2 are then used as feeds for methanol synthesis. Finally, the heat involved in the system is recovered by gas and steam turbines for power generation. Several operating parameters are analyzed in terms of total energy efficiency and methanol production, including chemical looping pressure, methanol synthesis temperature, and pressure. As general result, the proposed system shows high energy efficiency and methanol production. The highest total energy efficiency which can be obtained is 45.4%, under the conditions of chemical looping pressure of 4.0 MPa, and methanol synthesis temperature and pressure of 200 °C and 5.0 MPa, respectively. The integrated system can produce 41 kg/h methanol from 100 kg/h MSW, and it can independently cover the electricity required throughout the whole system.

Production of aromatic hydrocarbons from microwave-assisted pyrolysis of municipal solid waste (MSW)

The microwave-assisted conversion of municipal solid waste (MSW) into value-added products would be a promising option to tackle MSW piles. The present work was intended to understand the effect of microwave power (300, 450, and 600 W) and graphite susceptor loading (10, 30, and 50 g) on MSW valorization. Response surface methodology was used to analyze the impact of input variables on product yields and energy consumption. The heating rate increased, and microwave energy consumption decreased with the increase in microwave power. An increase in susceptor quantity resulted in a reduction in heating rates and also energy consumption. Nearly 84–88 wt% of MSW was converted into gases (42–60%), oil (26–42%), and char (12–16%) products. The carbon number distribution of oil fraction is in the range of C5 to C20 with a high yield of carbon content (74–91%). A high yield of aromatic hydrocarbons (84.5%) was obtained at 600 W microwave power and 30 g of the susceptor. The char fraction is rich in carbon content (80–90%) with a reasonable pore area (111–152 m2/g). This work demonstrated the feasibility of MSW upgradation into value-added chemicals, materials, and energy-rich fuel products.

Comparisons of Incineration and Gasification Thermal Conversion of Municipal Solid Waste in Trinidad and Tobago

The emissive, economic, and technical, aspects of gasification and incineration for Trinidad and Tobago municipal solid waste were investigated in this study. To collect data for this study, a questionnaire was designed. Sima-Pro software was utilised for the Life Cycle analysis of the emissive aspect. Incineration had a 66.5 percent efficiency, gasification had an 83.1 percent efficiency, and CHP gasification had an 87.53 percent efficiency. The overall Green House Gas (GHG) emissions from the incineration process were 472.36 Gg CO2 eq/yr. The economic analysis proves that gasification would be a loss if the maximum-tipping fee of USD-6.512 million was used. The incineration process is profitable, with a net profit of USD 9.850 million one year before the expected plant life. A risk analysis was performed using Monte Carlo simulation to evaluate the values uncertainty. Based on the parameters, the incineration process was considered satisfactory than the gasification method.

Tailoring ZSM-5 zeolite porosity and acidity for efficient conversion of municipal solid waste to fuel

Municipal solid waste contains essential building blocks of transportation fuel but is often deposited into landfills. Available conversion processes are still in their infancy; thus, requiring foundational knowledge to control reaction pathways and transform waste macromolecules into desired products. Active, robust, and low-cost catalysts with highly accessible active sites are needed for selective cleavage of certain bonds. The rapid deactivation and diffusion limitations are the major challenges to date which can be controlled by the catalyst pore structure and acidity. In this paper, we developed novel mesoporous ZSM-5 catalysts to maximise levoglucosan conversion, the dominant product of cellulose pyrolysis, into furfural. The concentration of levoglucosan dropped from 12.1% to 3.8% over the mesoporous ZSM-5. Furthermore, the pyrolysis of plastic materials that existed in the waste provided supplementary hydrogen, which synergistically contributed to the hydrodeoxygenation of some compounds like 5-hydroxymethylfurfural and 4-methyl-1,2-Benzenediol. The total amount of non-oxygenated compounds over the mesoporous catalyst reached 77% compared to 59.7% in non-catalytic pyrolysis based on 13 C NMR results. The integration of 13 C NMR and GC-MS results provided an effective tool in identifying key reaction pathways and linking that to the catalyst's textural and acidic properties. • Co-pyrolysis of biomass and polyethylene was catalysed by core-shell hierarchical ZSM-5. • The conversion of levoglucosan, the dominant product from cellulose, reached 68.3% over meso-ZSM-5. • Desired compounds including aliphatic C–C and hydrodeoxygenated products were obtained. • Accessible zeolite active sites were produced due to mesoporous networks enabling conversion of bulky sugar compounds.

Conversion of crop residual waste in to fuel for thermal plants and fertilizer for farmers

The conversion of solid waste (dry leafs and dry seeds) into fuel and fertilizer is an idea for educating and mobilizing the farmers to stop the burning of crop residue seasonally. In India it is a common practise for the farmers to fire the crop residue after the cultivation is completed by which air and soil pollution is increasing. The idea here is to convert that crop residue (waste) into a useful form by pulverising and blending in a ratio. In this work the emphasis is made on rice stubble, wheat stubble, cotton stubble, neem leafs and Moringa oleifera leafs. In addition to them rice husk, dry neem seeds, tamarind seeds, Indian date seeds and agro waste seeds are used. The produced fuel (in powder form) has found a calorific value of 4180 Kcal/Kg and the fertilizer has shown the typical value of nitrogen in nitrate form is 24.94%, phosphorous in phosphate form of 12.35% and potassium of 61.75%. This work makes an arena to the farmers to stop burning the crop residue (agro waste) and substantially converting it into the fuel and fertilizer.

Waste tire derived char supported Ni‐Fe catalyst for catalytic thermochemical conversion of wet municipal solid waste

Thermochemical conversion technology (pyrolysis/gasification) has been extensively employed for biomass, fossil fuels, and MSW feedstock to transform them into valuable products (gas, oil, and char). Since the practical application of waste tire derived char (WTC) faces uncertainty, the exploitation of WTC's high-value application would significantly impact the overall economy of the waste tire pyrolysis process. Therefore, in this study, WTC was utilized as a support material for developing Ni-Fe-based catalysts (Ni-WTC, Fe-WTC, and Ni-Fe-WTC). The catalyst performance for wet MSW catalytic conversion was studied in a fixed-bed reactor. The results affirmed that the application of catalysts considerably boosted the H2 concentration (29.26% to 38.24%-42.15%), dry gas yield (0.73 to 1.04-1.16 Nm3/kg MSW), and H2 yield (212 to 396-487 mL/g MSW). Meanwhile, the tar content reduced significantly from 9.11% (without catalyst) to 2.15%, (Ni-WTC), 2.83% (Fe-WTC), and 2.47% (Ni-Fe-WTC). The tar analysis indicated that the chemical composition significantly transformed with the application of catalysts. This work successfully suggested that WTCs can be used as an effective and inexpensive support material for developing Ni-based catalysts that can offer greater opportunity toward tar and hydrocarbons catalytic cracking and reforming during MSW conversion.

In situ evolution of functional groups in char during cellulose pyrolysis under the catalysis of KCl and CaCl2

A combination of in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, perturbation-correlation moving-window two-dimensional correlation spectroscopy (PCMW2D) and two-dimensional correlation spectroscopy (2D-COS) was used to reveal the catalytic mechanism of KCl and CaCl2 on cellulose char evolution during slow pyrolysis. Pretreatments of the one-dimensional spectra ensure the semi-quantitative analysis of the evolution of functional groups in pyrolysis char, which invoked principal component analysis followed by a Butterworth filter for denoising and extended multiplicative scatter correction. Through the differential processing of the absolute changes, the char evolution product was divided into ‘char rearrangement’ and ‘char devolatilization’ processes containing a high contribution from chemical reactions and physical migration, respectively. The ‘char rearrangement’ of cellulose pyrolysis consists of four stages, i.e. the budding, development, climax and decline stages, which were dominated by H-bond network reconfiguration, the consumption of C–O–C and OH, homogeneous devolatilization and aromatization, respectively. The uppermost influence of the two salts on the pyrolysis is the relationship alteration of C–O–C cleavage, dehydration reactions and ‘char devolatilization’. For neat, KCl-loaded and CaCl2-loaded cellulose, the unsaturated bonds were formed in the light reaction intermediate, heavy reaction intermediates and cellulose chain, respectively. Especially, the cleavage of most C–O–C following dehydration reactions conduced a shoulder peak in the differential thermogravimetry curve before the maximum weight loss rate of CaCl2-loaded sample. Due to the alteration, the pyrolysis was advanced but slowed down by the high content of unsaturated bonds in char. This study provides a powerful tool for the in situ semi-quantitative analysis of char evolution during the non-catalytic and catalytic thermo-chemical conversion of solid fuels and waste, and the results benefit to both biomass pyrolysis mechanism revelation and industrial production of biochar.

Evaluation of the Thermal Behavior, Synergistic Catalysis, and Pollutant Emissions during the Co-Combustion of Sewage Sludge and Coal Gasification Fine Slag Residual Carbon

The conversion of solid waste into energy through combustion is sustainable and economical. This study aims to comprehensively evaluate and quantify the co-combustion characteristics, synergistic catalysis, and gaseous pollutant emission patterns of sewage sludge (SS) and coal gasification fine slag residual carbon (RC) as well as their blends through thermogravimetry coupled with mass spectrometry (TG-MS). The results showed that the co-combustion of SS and RC can not only improve the ignition and burnout property but also maintain the combustion stability and comprehensive combustion performance at a better level. The kinetic analysis results showed that a first-order chemical reaction and three-dimensional diffusion are the reaction mechanisms during the co-combustion of SS and RC. The synergistic catalysis between SS and RC can well explain the changes in activation energy and reaction mechanism. Furthermore, the blending ratio of SS is recommended to be maintained at 40% because of the lowest activation energy (Ea = 81.6 kJ/mol) and the strongest synergistic effect (Xi = 0.36). The emission of gaseous pollutants is corresponding to the primary combustion stages of SS, RC, and their blends. In co-combustion, the NH3, HCN, NOx, and SO2 emissions gradually rise with the increase of SS proportion in the blends due to the high content of organic compounds in SS.

Exploring the feasibility of thermal digestion process: A novel technique, for the rapid treatment and reuse of solid organic waste as organic fertilizer

The study developed a holistic approach based on the thermal digestion (TD) technique for the rapid conversion of solid organic waste (SOW) into nutrient-rich organic fertilizer. The effect of digestion temperatures (110oC–170 °C) on the weight reduction from the SOW and the availability of the nutrients were thoroughly investigated. The potential weight reduction of 75.2% was achieved at a temperature of 150 °C for 135 min, as illustrated by response surface methodology (RSM). Scanning electron microscope (SEM) study was carried out to analyze the changes into surface morphology of the sample before and after the digestion. Fourier transform infrared (FTIR) analysis was conducted to study the mineralization process. Thermogravimetric-Differential thermal analysis (TG-DTA) was conducted to study the thermal decomposition behavior of the untreated and digested SOW. The digested SOW resulted high nutrient-rich end product (N-2.08 ± 0.01%, P-0.42 ± 0.00%, & K-1.65 ± 0.06%), which have potential to be used as organic fertilizer. Fertilizing potential of the digested SOW complied with the delineated norms of the organic fertilizer given by the Fertilizer Association of India (2019). Maturity and phytotoxicity of the digested SOW were explored on the basis of C:N ratio (18.07 ± 0.17), humification index (3.43 ± 0.02), heavy metals content, as well as through seed germination index (>90%). The proposed technology may lead to the paradigm shift in waste management and provides an efficient alternative for the recycling of nutrients.