Thermochemical Conversion Research Articles

Promoting Circular Economy of the Building Industry by the Use of Straw Bales: A Review

Over the past decade, the concept of a circular economy has increasingly gained attention as a framework for guiding businesses and policymakers. Given its significant environmental impact, the building industry plays a pivotal role in the transition toward a circular economy. To address this, our review proposes a bio-based building material, specifically straw bale, which elaborates on the circularity of bio-based buildings based on the 3R principles of a circular economy: reduce, reuse, and recycle. In terms of the “reduce” principle, straw-bale buildings can reduce construction waste, the environmental impact, energy requirements, and carbon emissions. Regarding the “reuse” principle, straw-bale buildings utilize agricultural waste resources and are easily disassembled due to their prefabrication. As for the “recycle” principle, straw-bale buildings can undergo physical, biological, and biochemical conversion processes (thermochemical conversion), yielding both wooden composite boards and potential biogas and biomass fuels for electricity and heating. This study evaluates the contribution of straw packaging construction and the use of straw as a raw material, using the 3R principles to determine future research opportunities for the construction industry to achieve a circular economy. The results of this study offer circular economy solutions and interdisciplinary research insights for researchers and practitioners interested in the building environment.

Effectiveness of Soil-amended Biochar in Improving Crop Production, Soil Health and Environmental Aspects

Sustainable agriculture has assumed greater importance in today’s world. Biochar has the potential to increase crop yield and soil fertility in agriculture while reducing greenhouse gas emissions at the same time. Biochar production technology and biomass type has great influence on its quality and yield which in turn is responsible for altering soil fertility status and enhancing other soil properties. Biochar is produced via thermochemical conversion of biomasses by the process of pyrolysis with different pyrolysis conditions which include heating rate, temperature or residence time that affect the product distribution and yield for biochar produced from same biomass. Biochar is produced sustainably from eco-friendly sources under manageable conditions such as agricultural woody and non-woody wastes or crop residues or animal wastes. Biochar’s acknowledgement in removing heavy toxic metals, organic solvents and pesticide residues from soil as well as in waste water management aids in environmental protection. Yield response of biochar produced from various feedstock sources on vegetable crop production is discussed to compare their relative effectiveness. Biochar is a carbonaceous substance produced that sequester carbon and remain in soil for thousands of years and thus offers stability in soil. Biochar as Negative Emissions Technology (NET) in removing CO2 from atmosphere and other greenhouse gases such as N2O and CH4 is a prominent methodology in mitigating serious concern of climate change. The objective of this review paper is to extensively justify the role and importance of biochar in agriculture and sustainable growth.

Thermochemical conversion of guaiacol with supercritical CO2: Experimental insights

The excessive CO2 in the environment resulting from the combustion of fossil fuels has posed a significant challenge in terms of its conversion and utilization. In this work, the thermochemical conversion of guaiacol under supercritical CO2 (scCO2) was proposed, which not only enabled the consumption of CO2 but also facilitated the conversion of biomass into valuable products. It was concluded that the carbon gasification efficiency (CE) and hydrogen gasification efficiency (HE) were 37.10 % and 51.77 %, respectively, when the CO reached the maximum of 8.72 ± 0.28 mol/kg at 700 °C for 20 min. The addition of catalyst promoted the production of H2 and increased CE, the H2 yield of guaiacol gasification under different catalysts was ordered as Al2O3 > KOH > without catalyst > KCl. As the reaction temperature increased, the unreacted guaiacol and phenol decreased and were gradually converted to liquid products such as pyrene and benzo[c]phenanthrene. With the increase in reaction temperature, the more fully guaiacol was reacted, the easier it was to carbonize and form more carbon microspheres. In addition, reaction pathways for free radicals were proposed, including cleavage of free radicals, isomerization of free radicals, secondary cleavage of free radicals and recombination of free radicals. In short, degrading guaiacol using scCO2 is a feasible approach, which provides a new direction for the disposal and energy recovery of biomass in the future.

Thermodynamic and economic analysis of a deployable and scalable process to recover Monomer-Grade styrene from waste polystyrene

Less than 5 % of polystyrene is recycled, motivating a search for energy efficient and economical methods for polystyrene recycling that can be deployed at scale. One option is chemical recycling, consisting of thermal depolymerization and purification to produce monomer-grade styrene (>99 %) and other co-products. Thermal depolymerization and distillation are readily scalable, well-established technologies; however, to be considered practical, they must be thermodynamically efficient, economically feasible, and environmentally responsible. Accordingly, mass and energy balances of a pyrolysis reactor for thermal depolymerization and two distillation columns to separate styrene from α-methyl styrene, styrene dimer, toluene, and ethyl benzene co-products, were simulated using ASPEN to evaluate thermodynamic and economic feasibility. These simulations indicate that monomer-grade styrene can be recovered with energy inputs < 10 MJ/kg, comparable to the energy content of pyrolysis co-products. Thermodynamic sensitivity analysis indicates the scope to reduce these values and enhance the robustness of the predictions. A probabilistic economic analysis of multiple scenarios combined with detailed sensitivity analysis indicates that the cost for recycled styrene is approximately twice the historical market value of fossil-derived styrene when styrene costs are fixed at 15 % of the total product cost or less than the historical value when feedstock costs are assumed to be zero. A Monte Carlo and Net Present Value-based economic performance analysis indicates that chemical recycling is economically viable for scenarios assuming realistic feedstock costs. Furthermore, the CO2 abatement cost is roughly $1.5 per ton of averted CO2, relative to a pyrolysis process system to produce fuels. As much as 60 % of all polystyrene used today could be replaced by chemically recycled styrene, thus quantifying the potential benefits of this readily scalable approach.

MXene/biochar composites for enhanced wastewater reclamation and bioenergy production: A kinetics and thermodynamics study

The study explores the synthesis and utilization of biochar (BC) and multi-layer MXene to MXene/biochar (MB) composites for wastewater treatment. Simultaneously, it also investigates their energy generation potential through biomass and soil property assessments. The integrated column and batch treatments have shown significant results, elevating total dissolved solids from 63.7 to 125.5 mg L-1 with column treatment, while reducing them to 6.37 % and 1.35 % with BC and MB treatment, respectively. BC with high carbon content, demonstrated increased hydrophobicity, which was amplified by the integration of MXene, thereby enhancing its potential for advanced wastewater treatment. Treated wastewater exhibited elevated nutrient concentrations (Ca, Cu, Fe, K, Na, and NH4+), promoting the growth of Pennisetum purpureum. WW_B shows promising energy potential, with a higher heating value of 25.03 MJ kg-1 and a lower heating value of 23.57 MJ kg-1. They demonstrated high volatile matter exceeding 70.9 wt. %, and a fixed carbon from 10.02-27.53 wt. %, signifying their potential for efficient conversion and bio-oil yield during pyrolysis. The ultimate analysis emphasized significant carbon, with oxygen content ranging from 43.42-47.78 wt. %., influencing combustion characteristics. MT_B exhibited its suitability for energy production through thermochemical conversion, underlined by its high flammability and low volatile ignition values. In the absence of BC, the Ea ranged from 24.77-77.88 kJ mol-1 in wastewater and from 21.67-69.6 kJ mol-1 in MB treated wastewater. Meanwhile, when soil contained BC and was irrigated with wastewater, the Ea varied from 24.66-80.91 kJ mol-1. In the case of MB treated wastewater, it ranged from 25.01-75.79 kJ mol-1. The research thereby affirms the potential of MB composites to advance water and energy sustainability setting us for broader nexus-based applications.

CO2 conversion to CO by fluidized bed biomass gasification: Measuring CO2 utilization via stable carbon isotope ratios

Thermochemical conversion of CO2 in biomass gasification is a promising technology for utilizing CO2 as a feedstock to produce a CO-rich gas. Simultaneous decomposition reactions of biomass and various gas-solid and gas-gas reactions form the product gas in this process. The overlap in sub-processes makes it challenging to assess the conversion of feedstock CO2 with common methods like mass balancing. This work introduces stable carbon isotope ratio analysis (δ13C) to identify the sourcing of carbonaceous product gas components and determine the conversion of CO2. This methodology is applied to evaluate experiments conducted for one hour of continuous operation in a lab-scale fluidized bed gasifier. Softwood pellets and wood char are used as fuel, with Olivine as a bed material, a target heating temperature of 1000 °C and atmospheric pressure. Product gas with more than 80vol% CO was generated when wood char was used as fuel. Stable carbon isotope measurements show that CO2 is converted at 48 to 93% in this process, underpinning the position of biomass CO2 gasification as carbon capture and utilization technology. These results were up to 25% higher than suggested by mass balancing, with higher discrepancies at lower CO2 conversions when using softwood as fuel. Therefore, stable carbon isotope ratio measurement can be a valuable tool for improving the process understanding of biomass CO2 gasification. The results can be used for carbon accounting and the technical development of gasifiers with high CO2 utilization efficiency.

Determining the influence of synthesis gas additives on the environmental performance of internal combustion engine

The object of research is the environmental parameters of a reciprocating engine when using a synthesis gas additive to the main fuel. The research is aimed at solving the problem of reducing the concentration of harmful components in the exhaust gases of an internal combustion engine by adding synthesis gas to the main fuel. Experimentally, the dependences of the effect of the addition of synthesis gas to ethanol on the change in the environmental performance of a piston engine with spark ignition were obtained. The positive effect of the addition of synthesis gas obtained by thermochemical conversion to ethanol in an amount of up to 5 % by weight on the environmental performance of a spark-ignition piston engine was established. Provided that the engine achieves the same effective power, the use of a synthesis gas additive to the main fuel made it possible to reduce the concentration of CO by 61.5 % and CH by 51.3 % in the exhaust gases. no more than 25–30 words The addition of synthesis gas contributed to the formation of radicals that activate oxidation chain reactions, and also made it possible to increase the normal combustion rate of the fuel-air mixture by 6.25 %. This ensures normal engine operation on a leaner fuel-air mixture (α=1.21) without deterioration of environmental, energy and economic performance. no more than 25-30 words The simultaneous reduction of the concentration of harmful components in the exhaust gases and engine efficiency can be achieved by using fuels with a wide concentration limit of ignition and high combustion rate in a lean mixture. The experimental data obtained can be used in the design or modernization of transport and stationary power plants with internal combustion engines as an approach to meet ever-increasing environmental standards

Comparative Evaluation on Enhancing Fuel Properties of Biocoal from Bagasse Using Hydrothermal Carbonization and Torrefaction Processes

This research investigates the thermochemical conversion of sugarcane bagasse into biocoal using a subcritical aqueous medium (water, 200–250°C) and a limited oxygen atmosphere (nitrogen, 250–300°C). The aim is to discover alternative renewable energy sources to replace fossil fuels. The effects of those different methods on the physiochemical properties of the solid product were determined. The best results of fixed carbon (37.13%), carbon content (62.17%), fuel ratio (0.61), and higher heating value (HHV) (25.75 MJ/kg) were obtained under hydrothermal carbonization (HTC) at 250°C. Additionally, the HTC process effectively reduced the ash and sulphur content of the solid products. Moreover, HTC was found to be a promising method for depolymerizing hemicellulose. Hydrochar produced at 250°C is located within the range of lignite, which is typically obtained at lower reaction temperatures compared to biochar samples. Consequently, the conversion of sugarcane bagasse into solid biofuel through HTC shows great potential from a thermochemical perspective.

Agricultural Waste Valorization: Exploring Environmentally Friendly Approaches to Bioenergy Conversion

The pursuit of sustainable energy production through the conversion of agricultural waste into different bioenergy resources is of paramount importance given its potential to mitigate environmental impact while meeting energy demands. In this review, a comprehensive overview of the technologies for the biochemical and thermochemical conversion of agricultural waste into bioenergy is provided. A summary of the process of its conversion into different bioenergy products such as biogas, bio-oil, and biofuel is provided, in addition to the potential advantages and challenges faced using different biomass conversion technologies. The review highlights the potential of agricultural waste valorization to address the current energy demand while at the same time contributing to environmental benefits and greenhouse gas emission reductions. Moreover, this review highlights some significant gaps for improvement. These include the challenges in the pretreatment of agricultural waste biomass in optimizing the conversion rates and lowering the required energy consumption throughout the process while enhancing both the quantity and quality of the output. Some recommendations are proposed to address the identified challenges. These include the need for further studies for a thorough assessment to evaluate the efficacity and sustainability of agricultural waste valorization technologies. Assessment methods such as life cycle assessment (LCA), life cycle analysis (LCA), net energy ratio (NER) calculations, life cycle costing (LCC), as well as techno-economic assessment (TEA), are recommended, together with collaboration among governments, farmers, and researchers, as well as the integration of cutting-edge technologies to enhance various aspects of agricultural waste, optimizing the conversion process, cost efficiency, time management, and labor requirements, consequently boosting the conversion efficiency and product quality.

Different effects of mesophilic and thermophilic anaerobic digestion on subsequent pyrolysis: Characteristics, kinetics and thermodynamic analysis

Anaerobic digestion (AD) combined with pyrolysis has been used as an innovative sludge-to-energy process that enhances energy recovery. This study investigated the different impacts of mesophilic and thermophilic AD on subsequent pyrolysis. The pyrolysis characteristics, kinetics, and thermodynamics of raw sludge (RS) and digested sludge (DS) after both mesophilic and thermophilic AD were investigated using thermogravimetric analysis (TGA) and three kinetic models (Starink, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose). TGA results indicated that thermophilic AD reduced the weight loss from 71.2-75.6 % for RS to 55.0–59.1 % for DS, more considerably than mesophilic AD (reducing from 70.6-75.2 % to 61.3–69.5 %), indicating higher organic matter removal. Kinetic analysis showed that the activation energy (E) of RS and DS pyrolysis ranged from 128.9 to 399.9 kJ/mol and 117.3 to 470.4 kJ/mol, respectively. Mesophilic AD generally increased the E, while thermophilic AD did not markedly alter E at low conversion rates (0.2–0.5) but increased it at high conversion rates (0.6–0.8), changing from 203.7–399.9 kJ/mol for RS to 248.9–470.4 kJ/mol for DS. Thermodynamic analysis showed that mesophilic AD generally enhanced pyrolysis favorability and reactivity but impeded activated complex formation. Thermophilic AD enhanced favorability and favored complex formation at low conversion rates but hindered it at high conversion rates. Reactivity varied with thermophilic AD extent, with excessive AD reducing reactivity. Pyrolysis–gas chromatography/mass spectrometry analysis confirmed that AD, on the one hand, decomposed biodegradable organics into low-molecular-weight organics, retained them in the DS, and facilitated subsequent pyrolysis. On the other hand, AD could accumulate large bio-refractory molecules, rendering DS less prone to pyrolytic decomposition. This effect of thermophilic AD was more significant than that of mesophilic AD. Given more favorable change was observed in kinetics and thermodynamics at lower conversion rates, low-temperature pyrolysis to produce biochar might be a promising strategy for DS treatment. The insights gained in this study may guide the optimization of AD conditions to maximize the efficiency of subsequent pyrolysis, providing more insight into the thermochemical conversion of DS and pyrolysis design.

Sustainability assessment of orange peel waste valorization pathways from juice industries

AbstractA wide variety of products such as high value-added bioactive materials, biofuels, biochemicals and bioplastics can be obtained by the valorization of waste streams in a comprehensive and holistic biorefinery concept. In this study a meta-analysis of the available technologies utilizing organic waste derived from the juice industry is conducted. Initially, a mass flow analysis is performed to quantitatively illustrate the available orange peel waste volumes in the EU followed by a geographic distribution. The overall sustainability of the available valorization scenarios is then analyzed by considering critical environmental, economic and energy indicators and comparing innovative and conventional valorization technologies. Innovative technologies are better in terms of energy requirements and extraction time and also, in product yield and environmental performance than the conventional ones (85.1%, 9.5% and 47.9% lower CO2 eq values for the extraction of essential oils, pectin and phenolic compounds respectively). In terms of orange peel waste valorization scenarios, landfilling shares the largest environmental impact, followed by thermochemical and biological conversion alternatives. Complex biorefinery schemes are proportionate to environmental performance and energy consumption, but inversely proportionate to production cost. Finally, a trade-off analysis illustrates a positive correlation between environmental indicators of the most under study valorization scenarios.

Synergistic effects on properties of biofuel and biochar produced through co-feed pyrolysis of Erythrina indica and Azadirachta indica biomass

Co-feed pyrolysis is a thermochemical conversion process that entails the simultaneous or sequential decomposition of various feedstock in an oxygen-free environment, concurrently improving the quality of the end products. The technique is widely used to produce a range of valuable products, including biofuels, chemicals and biochar, capitalizing on the synergies between various feedstock. The current study focuses on the synergistic effects of co-feed pyrolysis of Erythrina indica (EI) and Azadirachta indica (AI) biomass at different co-feed ratios (EI:AI) of 1:4, 1:3, 1:2, 1:1, 2:1, 3:1 and 4:1 on weight basis. The reactions were carried out at a temperature of 600 °C under a pressure of 1 bar using nitrogen as inert atmosphere. The bio-oil yield produced through the co-feed pyrolysis reactions ranged from 29.51 to 32.40 % by weight, while the biochar and non-condensable gases yields ranged from 38.25 to 42.48 % and 26.90 to 30.73 % by weight, respectively. Positive synergistic effects of co-feed pyrolysis led to a notable enhancement in physicochemical properties of the fuel phase, especially by virtue of calorific value, density and presence of low mol. wt. components when compared to their individual counterparts. Specifically, the fuel phase obtained at 1:1 co-feed ratio exhibited the peak calorific value of 36.80 MJ/kg along with lowest density of 0.82 g/ml and pH of 3.58 which is the pinnacle accomplishment of this work; and comparable with commercial gasoline. Gas chromatography and mass spectroscopy of biofuels revealed alkanes, alkenes, alcohols, aromatics, esters, nitro compounds and organosilicons as their main compounds. Specific compounds, including cyclopentane, methyl-, 1-cyclohexyl-2-propen-1-ol and 1-pentene, 3-methyl, are the most significant compounds at co-feed ratio of 1:1. Biochar produced at co-feed ratio of 1:1 also depicted excellent physiochemical properties with the highest elemental carbon of 79.23 wt % and lowest oxygen and hydrogen contents of 18.49 wt % and 2.28 wt %, respectively with a maximum calorific value of 29.23 MJ/kg; which can be utilized as solid fuels. The biochar produced from the co-feed pyrolysis reactions also possesses highly porous structure which can be useful as a soil conditioner, carbon sequestration water filtration or wastewater treatment. Additionally, non-condensable gases composed of 7.45 vol % hydrogen, 34.26 vol % carbon monoxide, 21.32 vol % methane and 36.97 vol % carbon dioxide when co-feed ratio is 1:1.

Factors influencing synergistic pyrolysis of biomass and polypropylene for alcohols and hydrocarbon production

Results are presented on the co-pyrolysis of different blends of rapeseed stalk and plastic polypropylene (100:0, 75:25, 50:50, 25:75 and 0:100) using thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS), independently. The effect of temperature (450, 550 and 650 °C) on the synergistic effect between rapeseed stalk and polypropylene at different blend ratios as well as on the yield and amounts of alcohols and hydrocarbons produced are presented. The thermogravimetric analysis results showed that at the same temperature, increase of polypropylene in the mixture, gradually increased the intensity and rate of pyrolysis reaction. The weight loss data revealed improved pyrolysis during the process. The Fourier transform infrared spectroscopy results showed that the transmittance of ketones, esters and acids increased while the content of ketones, esters and acids decreased with increased polypropylene in the mixture. The pyrolyzer-gas chromatography/mass spectrometry results showed that temperature and feedstock mixture ratio had an impact on the yield and amounts of alcohols and hydrocarbons. The pyrolysis effect was most favorable at 550 °C temperature and rapeseed stalk/polypropylene mixture ratio of 1:3. These results provide some practical insights on clean energy recovery from mixtures of agricultural residues and waste plastics using thermochemical conversion.

Co-pyrolysis of waste tire with agricultural and forestry residues: Pyrolysis behavior, products distribution and synergistic effects

Co-utilization of waste tires (WT) and agricultural and forestry residues (AFR) provides an effective means to produce energy while simultaneously providing solution for waste treatment and environment protection. In this paper, co-pyrolysis of WT and AFR (cotton stalk, CS, peanut shell, PS, and poplar branch, PB) was performed using thermogravimetric analysis (TGA), Fourier transform infrared spectrometer (FTIR), and pyrolyzer coupled with gas chromatograph/mass spectrometer (Py-GC/MS). The synergistic effects of mass loss rate and hydrocarbon content were quantified from the results of co-pyrolysis of WT with CS, PS, or PB with the weighted average of individual pyrolysis of the feedstocks. The results showed that the mass loss rate of WT with CS, PS, or PB in co-pyrolysis increased by 3.06 %, 3.84 %, and 0.61 %, respectively, compared to the weighted average of individual pyrolysis, while the hydrocarbon content increased by 19.20 %, 18.26 % and 2.97 %, respectively. The addition of AFR to WT made the pyrolysis easier. In co-pyrolysis, the amount of O-compounds decreased while that of hydrocarbons (aromatic hydrocarbons and aliphatic hydrocarbons) increased. Co-pyrolysis of AFR and WT had an effect on reducing aromatic and nitrogen content. These results provide insights into the synergistic effects, from the products distribution and offer potential waste treatment method for these wastes via thermochemical conversion.

Tailoring microwave frequencies for high-efficiency hydrogen production from biomass

Generating green hydrogen through biomass thermochemical conversion is pivotal for contributing to carbon neutrality. However, the efficiency of hydrogen production is hindered by the byproduct of tar formed during biomass depolymerization. This study employed a variable-frequency microwave ranging from 2430 to 6000 MHz to investigate the influence of microwave frequency on tar removal and hydrogen recovery over activated charcoal (AC). Experimental results indicated that microwave frequencies significantly impact the temperature distribution and heating rates of AC. Notably, at 4640 MHz the AC rapidly reached 1145 °C within seconds, with an instantaneous heating rate of 2022 °C/min. The ultra-fast heating rate crucially contributes to achieving 100 % efficiency in tar cracking, resulting in a hydrogen yield of 32.8 mmol/g. With a hydrogen recovery rate surpassing 94 %, the 4640 MHz frequency represents a 15.4-fold increase compared to the conventional 2450 MHz. This innovative approach holds significant promise for enhancing energy efficiency in the pursuit of carbon-neutral energy production.

Comparative assessment on thermo-chemical conversion of different waste plastics to value added syngas: thermodynamic investigation

Comparative assessment on thermo-chemical conversion of different waste plastics to value added syngas: thermodynamic investigation

Catalytic aquathermolysis of contaminated polyolefin plastic waste over an in situ iron hydroxide/oxide nanocatalyst derived from an oil-soluble iron precursor

With the substantial increase in global plastic consumption over the past 50 y, society faces the challenges of managing and recovering resources from considerable amounts of plastic waste. A promising strategy for use in addressing this problem is to upcycle plastic waste into valuable materials via thermochemical conversion, and hydrothermal liquefaction, which uses low-cost and green H2O, has attracted attention as a sustainable technology. In this study, we introduced an aquathermolysis system using oil-soluble Fe-2-ethylhexanoate (Fe-2EH) as a catalyst precursor under superheated steam conditions to convert highly contaminated polyolefin plastic waste to liquid fuel. The excellent dispersibility and decomposition behavior of Fe-2EH facilitated the formation of highly dispersed in situ Fe-based catalysts, enabling their involvement in the early stages of aquathermolysis. The presence of H2O and the in situ catalyst significantly promoted the decomposition of C–X bonds (X = Cl, S, N, or O) rather than C–C bonds, and C–C cleavage was driven by thermal energy. Moreover, the presence of H2O with the catalysts reduced the proportion of non-paraffinic products, including olefins and aromatics that cause char/coke formation. During the reaction, the in situ catalyst particles comprised nanosized Fe oxide cores with Fe hydroxide-rich surfaces, preventing the accumulation of metal contaminants. Based on deuterium tracing studies, the H transfer index of the catalyst was closely related to the catalytic performance. These results indicated that catalytic aquathermolysis using Fe-2EH is an efficient system for use in improving product quality by effectively removing contaminants and suppressing char/coke formation.

Absorbing oxygen carriers promotes phosphorus recovery from sludge via the microwave thermal conversion process

This study aims to apply the Absorbing oxygen carriers (AOCs) to induce the migration and transformation of phosphorus compounds during the microwave thermal conversion of sludge so the hard-to-extract organic phosphorus (OP) can be converted to easy-to-extract inorganic phosphorus (IP) and be enriched onto the sludge char. The AOCs were recycled by screen separation from the IP-rich sludge char, with the latter being a renewable phosphorus source from sludge. The AOCs in this novel process enhanced the conversion efficiency of OP into non-apatite inorganic phosphorus (NAlP), which was further converted to apatite inorganic phosphorus (AP). Most phosphorus in the sludge char is presented in the form of orthophosphate.

A Data-driven Framework to Inform Sustainable Management of Animal Manure in Rural Agricultural Regions using Emerging Resource Recovery Technologies

Thermochemical conversion technologies are emerging as preferred resource recovery practices for managing animal manure in agricultural regions. Although the implementation of such technologies has been previously studied, difficulties exist in maintaining balance between high rate of resource recovery and low environmental, economic, and social impacts, particularly in rural regions with limited resources. We developed a data-driven framework by integrating machine learning with life cycle thinking that can be used as an open-source tool to help overcome these barriers. The framework was applied to compare two emerging technologies: pyrolysis versus hydrothermal carbonization for managing the excess poultry litter in a rural agricultural region. Among different machine learning models, random forest regression was the most successful to predict resource recovery of both technologies. Next, sustainability analysis indicated that the environmental (global warming), economic (annual worth), and social (system intrusiveness) impacts of pyrolysis was lower than hydrothermal carbonization. Finally, the framework revealed that implementation of pyrolysis at 600 °C for one hour with the heating rate of 20 °C/min would result in the highest rate of resource recovery that corresponded to the lowest impacts. These results can be helpful in providing operational conditions for implementing emerging resource recovery technologies in rural agricultural regions.

Study on CO2 co-gasification of cellulose and high-density polyethylene via TG-FTIR and ReaxFF MD

CO2 co-gasification of solid waste and biomass presents an approach for the comprehensive utilization of waste materials, biomass and carbon dioxide. In this study, the CO2 co-gasification of cellulose and high-density polyethylene was explored utilizing TG-FTIR method and ReaxFF MD simulation. The thermal behavior, synergistic effect, volatile release characteristics, activation energy and reaction mechanism were thoroughly analyzed. The experimental findings indicated that CO2 co-gasification involved four stages: drying, cellulose pyrolysis, polyethylene pyrolysis and semi-coke gasification. Co-gasification inhibited cellulose pyrolysis but promoted polyethylene pyrolysis, with the most pronounced promoting effect occurring at 40% polyethylene content. The absorbance curve suggested that CO release was associated with cellulose pyrolysis and the reaction between cellulose coke and CO2, and C-H release was related to the pyrolysis of cellulose and polyethylene. Co-gasification alleviated the energy barrier, with the greatest effect occurring at 40% polyethylene content. The simulated results confirmed that the promotion of polyethylene pyrolysis was attributed to the connection of radicals from cellulose with polyethylene. Additionally, the combination of hydrocarbon radicals and hydrogen from polyethylene and cellulose contributed to gas production. This investigation provides insights into the thermochemical conversion characteristics for CO2 co-gasification of biomass and high-density polyethylene.