Global Warming Potential Research Articles

Study on the Environmental Impact and Benefits of Incorporating Humus Composites in Anaerobic Co-Digestion Treatment.

This study evaluated the environmental impact and overall benefits of incorporating humus composites in the anaerobic co-digestion of kitchen waste and residual sludge. The life cycle assessment method was used to quantitatively analyze the environmental impact of the entire anaerobic co-digestion treatment process of waste, including garbage collection, transportation, and final product utilization. Moreover, the comprehensive assessment of the environmental impact, energy-saving and emission-reduction abilities, and economic cost of using humus composites in the anaerobic co-digestion treatment process was conducted using a benefit analysis method. The results showed that the anaerobic co-digestion of kitchen waste and residual sludge significantly contributed to the mitigation of global warming potential (GWP), reaching -19.76 kgCO2-eq, but had the least impact on the mitigation of acidification potential (AP), reaching -0.10 kgSO2-eq. In addition, the addition of humus composites significantly increased the production of biogas. At a concentration of 5 g/L, the biogas yield of the anaerobic co-digestion process was 70.76 m3, which increased by 50.62% compared with the blank group. This amount of biogas replaces ~50.52 kg of standard coal, reducing CO2 emissions by 13.74 kg compared with burning the same amount of standard coal. Therefore, the anaerobic co-digestion treatment of kitchen waste and residual sludge brings considerable environmental benefits.

Life cycle assessment of electric kick scooters: consolidating environmental impact quantification and concluding climate-friendly use options

BackgroundThe environmental impact of electric scooters has been the subject of critical debate in the scientific community for the past 5 years. The data published so far are very inhomogeneous and partly methodologically incomplete. Most of the data available in the literature suffer from an average bias of 34%, because end-of-life (EOL) impacts have not been modelled, reported or specified. In addition, the average lifetime mileage of shared fleets of e-scooters, as they are operated in cities around the world, has recently turned out to be much lower than expected. This casts the scooters in an unfavourable light for the necessary mobility transition. Data on impact categories other than the global warming potential (GWP) are scarce. This paper aims to quantify the strengths and weaknesses of e-scooters in terms of their contribution to sustainable transport by more specifically defining and extending the life cycle assessment (LCA) modelling conditions: the modelling is based on two genuine material inventories obtained by dismantling two different e-scooters, one based on a traditional aluminium frame and another, for the first time, based on plastic material.ResultsThis study provides complete inventory data to facilitate further LCA modelling of electric kick scooters. The plastic scooter had a 26% lower lifetime GWP than the aluminium vehicle. A favourable choice of electric motor promises a further reduction in GWP. In addition to GWP, the scooter's life cycles were assessed across seven other impact categories and showed no critical environmental or health impacts compared to a passenger car. On the other hand, only the resource extraction impact revealed clear advantages for electric scooters compared to passenger cars.ConclusionsUnder certain conditions, scooters can still be an important element of the desired mobility transition. To assure a lifetime long enough is the crucial factor to make the electric scooter a favourable or even competitive vehicle in a future sustainable mobility system. A scooter mileage of more than 5400 km is required to achieve lower CO2eq/pkm emissions compared to passenger cars, which seems unlikely in today's standard use case of shared scooter fleets. In contrast, a widespread use of e-scooters as a commuting tool is modelled to be able to save 4% of greenhouse gas (GHG) emissions across the German mobility sector.

Residue Management and Nutrient Stoichiometry Control Greenhouse Gas and Global Warming Potential Responses in Alfisols

Although crop residue returns are extensively practiced in agriculture, large uncertainties remain about greenhouse gas (GHG) emissions and global warming potential (GWP) responses to residue return (RR) rates under different residue placements and nutrient supplements. We conducted a laboratory mesocosm experiment in Alfisol in central India to investigate the responses of soil GHG emissions (CO2, N2O, and CH4) and the global warming potential to four wheat RR rates (R0: no residue; R5: 5 Mg/ha; R10: 10 Mg/ha; R15: 15 Mg/ha) and two placements (surface [Rsur] and incorporated [Rinc]) under three nutrient supplement levels (NSLs) (NS0: no nutrients, NS1: nutrients (N and P) added to balance the stoichiometry of C:N:P to achieve 30% humification in RR at 5 t/ha, NS2: 3 × NS1). The results demonstrated a significant (p < 0.05) interaction effect of RR × NSL × residue placement on N2O emission. However, CH4 and GWP responses to the RR rate were independent of NSL. N2O fluxes ranged from −2.3 µg N2O-N kg−1 soil (R5 NS0 Rsur) to 43.8 µg N2O-N kg−1 soil (R10 NS2 Rinc). A non-linear quadratic model yielded the best fit for N2O emissions with RR rate (R2 ranging from 0.55 to 0.99) in all NSLs and residue placements. Co-applying wheat residue at 10 and 15 Mg/ha at NS1 reduced CH4 and N2O emissions (cf. R0 at NS1). However, increasing NSLs in NS2 reduced the nutrient stoichiometry to < 12:1 (C:N) and < 50:1 (C:P), which increased N2O emissions in all RR rates (cf. R0) across all residue placements. Averaged across nutrient levels and residue placements, the order of the effects of RR rates on CH4 emissions (µg C kg−1 soil) was R10 (5.5) > R5 (3.8) > R15 (2.6) > R0 (1.6). Our results demonstrated a significant linear response of total GWP to RR rates R15 > R10 > R5 > R0, ranging from 201.4 to 1563.6 mg CO2 eq kg−1 soil. In conclusion, quadratic/linear responses of GHGs to RR rates underscore the need to optimize RR rates with nutrient supplements and residue placement to reduce GHG emissions and GWP while ensuring optimal soil health and crop productivity.

Life Cycle Assessment of Wheat Straw Pyrolysis with Volatile Fractions Chemical Looping Combustion

Among the approaches to facilitating negative CO2 emissions is biochar production. Biochar is generated in the pyrolysis of certain biomasses. In the pyrolysis process, carbon in the biomass is turned into a solid, porous, carbon-rich, and stable material that can be captured from the soil after a period of from a few decades to several centuries. In addition to this long-term carbon sequestration role, biochar is also beneficial for soil performance as it helps to restore soil fertility and improves the retention and diffusion of water and nutrients. This work presents a Life Cycle Assessment of different pyrolysis approaches for biochar production. Biomass pyrolysis is performed in a fixed-bed reactor, which operates at a mild temperature (550 °C). Biochar is obtained as solid product of the pyrolysis, but there are also liquid (bio-oil) and gaseous products (syngas). The pyrolysis gas is partly used to fulfil the energy demand of the pyrolysis process, which is highly endothermic. In the conventional approach, CO2 is produced during the combustion of syngas and emitted to the atmosphere. Another approach to facilitate CO2 capture and thus obtain more negative CO2 emissions in the pyrolysis process is burning syngas and bio-oil in a Chemical Looping Combustion unit. Life Cycle Assessment was performed of these approaches toward biomass pyrolysis to evaluate their environmental impact. The Chemical Looping Combustion approach significantly reduced the values of 7 of the 16 environmental impact indicators studied, along with the Global Warming Potential among them, it slightly increased the value of one indicator related to the use of fossil resources, and it maintained the values of the remaining 8 indicators. Environmental impact reduction occurs due to the avoidance of CO2 and NOx emissions with Chemical Looping Combustion. The CO2 balances of the different pyrolysis approaches with Chemical Looping Combustion configurations were compared with a base case, which constituted the direct combustion of wheat straw to obtain thermal energy. Direct biomass combustion for the production of 17.1 MJ of thermal energy had CO2 positive emissions of 0.165 kg. If the gaseous fraction was burned by Chemical Looping Combustion, CO2 was captured and the emissions became increasingly negative, until a value of −3.30 kg/17.1 MJ was generated. If bio-oil was also burned by this technology, the negative trend of CO2 emissions continued, until they reached a value of −3.66 kg.

Alternative climate metrics to the Global Warming Potential are more suitable for assessing aviation non-CO2 effects

A growing body of research has highlighted the major contribution of aviation non-CO2 emissions and effects to anthropogenic climate change. Regulation of these emissions, for example in the EU Emissions Trading System, requires the use of a climate metric. However, choosing a suitable climate metric is challenging due to the high uncertainties of aviation non-CO2 climate impacts, their variability in atmospheric lifetimes and their dependence on emission location and altitude. Here we use AirClim to explore alternatives to the conventional Global Warming Potential (GWP) by analysing the neutrality, temporal stability, compatibility and simplicity of existing climate metrics and perform a trade-off. We find that using the temperature-based Average Temperature Response (ATR) or using an Efficacy-weighted GWP (EGWP) would enable a more accurate assessment of existing as well as future aircraft powered by novel aviation fuels.

From Scraps to Solutions: Harnessing the Potential of Vegetable and Fruit Waste in Pharmaceutical Formulations

Background:: Food waste is a major worldwide problem due to the increasing population and imbalances in supply chains. Waste from fruits and vegetables are a substantial proportion of the overall food waste generated, accounting for approximately 42% of the waste produced. Methane, a strong greenhouse gas with a significant potential for global warming, is produced when these waste products are typically dumped in landfills. Objectives:: The study's goal is to present a thorough overview of the most recent findings and developments in the use of vegetable and fruit waste for creating therapeutic formulations. Recognizing the opportunities and challenges in this developing area of study, as well as the promise that vegetable and fruit waste contains for the creation of environmentally friendly and economically advantageous pharmaceutical formulations. Methods:: A comprehensive review of existing literature on the utilization of vegetable and fruit waste in pharmaceutical formulations was conducted. The review included studies on the chemical composition and bioactive compounds present in various types of vegetable and fruit waste, their extraction methods, and their potential applications in pharmaceutical formulations. Additionally, current waste management practices and challenges associated with waste disposal were also analyzed. Conclusion:: The review highlights the significant potential of vegetable and fruit waste in the development of pharmaceutical formulations. Fruit and vegetable waste offer a wide range of bioactive compounds, such as antioxidants, antimicrobials, and antiinflammatory agents, which could be utilized in drug formulation. Moreover, this approach can promote environmental sustainability by reducing waste generation and enhancing waste utilization. Further research and development efforts should focus on optimizing extraction methods, evaluating the efficacy and safety of wastederived compounds, and addressing regulatory requirements for integrating vegetable and fruit waste into pharmaceutical products. Harnessing the potential of vegetable and fruit waste in pharmaceutical formulations can lead to sustainable advancements in the pharmaceutical industry while addressing environmental concerns.

Creating Atomically Iridium-Doped PdOx Nanoparticles for Efficient and Durable Methane Abatement.

The urgent environmental concern of methane abatement, attributed to its high global warming potential, necessitates the development of methane oxidation catalysts (MOC) with enhanced low-temperature activity and durability. Herein, an iridium-doped PdOx nanoparticle supported on silicalite-1 zeolite (PdIr/S-1) catalyst was synthesized and applied for methane catalytic combustion. Comprehensive characterizations confirmed the atomically dispersed nature of iridium on the surface of PdOx nanoparticles, creating an Ir4f-O-Pdcus microstructure. The atomically doped Ir transferred more electrons to adjacent oxygen atoms, modifying the electronic structure of PdOx and thus enhancing the redox ability of the PdIr/S-1 catalysts. This electronic modulation facilitated methane adsorption on the Pd site of Ir4f-O-Pdcus, reducing the energy barrier for C-H bond cleavage and thereby increasing the reaction rate for methane oxidation. Consequently, the optimized PdIr0.1/S-1 showed outstanding low-temperature activity for methane combustion (T50 = 276 °C) after aging and maintained long-term stability over 100 h under simulated exhaust conditions. Remarkably, the novel PdIr0.1/S-1 catalyst demonstrated significantly enhanced activity even after undergoing harsh hydrothermal aging at 750 °C for 16 h, significantly outperforming the conventional Pd/Al2O3 catalyst. This work provides valuable insights for designing efficient and durable MOC catalysts, addressing the critical issue of methane abatement.

Environmental Sustainability and Physicochemical Property Screening of Chitin and Chitin-Glucan from 22 Fungal Species.

Thanks to its biobased character with embedded biogenic carbon, chitin can aid in the transition to a sustainable circular economy by replacing fossil carbon from the geosphere. However, meeting current demands for material availability and environmental sustainability requires alternative methods limiting conventional chemical and energy-consuming chitin extraction from crustaceans. To assist future chitinous bioproduct development, this work analyzes the physicochemical properties and potential environmental sustainability of fungal chitin-glucan complexes. A conventional isolation procedure using sodium hydroxide, a weak acid, and short reaction times are applied to the fruiting body of 22 fungal species. Besides, the valorization of underutilized waste streams including Agaricus bisporus and Agaricus brunnescens stipes is investigated. The carbohydrate analysis renders chitin fractions in the range of 9.5-63.5 wt %, while yields vary from 4.2 to 29.9%, and the N-acetylation degree in found in between 53.0 and 98.7%. The sustainability of the process is analyzed using life cycle assessment (LCA), providing impact quantification for global warming potential, terrestrial acidification, freshwater eutrophication, and water use. With 87.5-589.3 kg·CO2-equiv per kilo, potentially lower global warming potential values in comparison to crustacean chitin are achieved. The crystallinity degree ranged from 28 to 78%, while the apparent chitin crystalline size (L020) is between 2.3 and 5.4 nm. Ten of the species yield α-chitin coexisting with semicrystalline glucans. Zwitterionic properties are observed in aqueous solutions, shifting from cationic to anionic at pH 4.5. With its renewable carbon content, fungal chitin is an environmentally sustainable alternative for high-value applications due to its balance of minimal treatment, low carbon footprint, material renewability, ease of isolation, thermal stability, zwitterionic behavior, biodegradability, and noncytotoxicity.

Carbon footprint analysis of fossil power plants in Bangladesh: measuring the impact of CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${CO}_{2}$$\\end{document} and greenhouse gas emissions

Greenhouse gas (GHG) emissions have increased substantially due to industrialization and the rapid growth in energy demand in Bangladesh. The aim of this study is to conduct a comprehensive carbon footprint analysis of fossil power plants in Bangladesh, focusing on the impact of GHG emissions. We evaluate the carbon footprint of fossil power plants based on their power generation capacity, fuel type, specific emission rates, and global warming potential (GWp) for various GHGs. The emission factor approach has been used in conjunction with the International Panel on Climate Change (IPCC) methodology. Findings of the study indicate that fossil power plants in Bangladesh contribute significantly to the country's overall carbon footprint, with CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${CO}_{2}$$\\end{document} and other GHG emissions being the primary drivers. Furthermore, we evaluate Bangladesh's GHG emissions in comparison with neighbouring countries to determine its position. In terms of greenhouse gas emissions from fossil-based power plants, we find that Bangladesh has relatively low emissions compared to its neighbours and developing countries in Asia. Nevertheless, Bangladesh has witnessed a significant increase in coal-fired power generation in recent years, which has emerged as a significant contributor to emissions. Following an analysis of GHG emissions from fossil fuel power plants, we recommend adopting advanced technologies such as carbon capture and storage (CCS) with improved energy efficiency systems and integrating renewable energy sources into the power generation mix. We conclude our analysis by highlighting the importance of transitioning to cleaner, sustainable energy sources to reduce future carbon emissions.

Condensation heat transfer of zeotropic refrigerant mixtures R407C and R448A in a horizontal smooth tube

Zeotropic refrigerant blends have attracted wide interest due to their promises to reduce global warming potential as well as their potential ability to improve the performance of heat pumps and air conditioners. The complex phenomenon of non-isothermal phase change complicates condensation of zeotropic refrigerant mixtures and merits extensive investigation to better understand their performance profiles. The present work experimentally studied condensation heat transfer of R407C and R448A – two R134a-based zeotropic refrigerant mixtures – in a horizontal smooth tube, condensed by counter-current water cooling. Measurements for mass flux were in the range of 120 to 320 kg m−2s−1 and saturation temperature in the range of 42 to 64 °C. Variation in refrigerant temperature and composition shift during condensation were quantitatively presented. The experimental data showed the effects of mass flux and saturation temperature on the heat transfer coefficients of R407C and R448A in different vapor quality regions. The analysis of heat and mass transfer resistances related to the flow regimes and refrigerant thermophysical properties provides a deep understanding of the condensation heat transfer of zeotropic refrigerant mixtures. The experimental data presented in this work are of value for the design of condensers.

Effects of Controlled-release Blended Fertilizer on Crop Yield and Greenhouse Gas Emissions in Wheat-maize Rotation System

The increasing use of nitrogen fertilizers exerts extreme pressure on the environment (e.g., greenhouse gas emissions, GHGs) for winter wheat-summer maize rotation systems in the North China Plain. The application of controlled-release fertilizers is considered as an effective measure to improve crop yield and nitrogen fertilizer utilization efficiency. To explore the impact of one-time fertilization of controlled-release blended fertilizer on crop yield and GHGs of a wheat-maize rotation system, field experiments were carried out in Dezhou Modern Agricultural Science and Technology Park from 2020 to 2022. Five treatments were established for both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 5:5 and 3:7, respectively), and CRU2 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 7:3 and 5:5, respectively). The differences in yield, nitrogen fertilizer utilization efficiency, fertilization economic benefits, and GHGs among different treatments were compared and analyzed. The results showed that nitrogen application significantly increased the single season and annual crop yields of the wheat-maize rotation system (P < 0.05). Compared with those of FFP, the CRU1 and CRU2 treatments increased the yields of summer maize by 0.4% to 5.6%, winter wheat by -5.4% to 4.1%, and annual yields by -1.1% to 3.9% (P > 0.05). N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (NPFP) were increased by -8.6%-43.4%, 2.05-6.24 kg·kg-1, and 4.24-10.13 kg·kg-1, respectively. Annual net income increased by 0.2% to 6.3%. Nitrogen application significantly increased the annual emissions of soil N2O and CO2 in the rotation system (P < 0.05) but had no effect on the annual emissions of CH4 (except for in the FFP treatment in the first year). The annual total N2O emissions under the CRU1 and CRU2 treatments were significantly reduced by 23.4% to 30.2% compared to those under the FFP treatment (P < 0.05). Additionally, nitrogen application significantly increased the annual global warming potential (GWP) of the rotation system (P < 0.05), but the intensity of greenhouse gas emissions was reduced due to the increase in crop yields. Compared with that under FFP, the annual GWP under the CRU1 and CRU2 treatments decreased by 9.6% to 11.5% (P < 0.05), and the annual GHGs decreased by 11.2% to 13.8% (P > 0.05). In summary, the one-time application of controlled-release blended fertilizer had a positive role in improving crop yield and economic benefits, reducing nitrogen fertilizer input and labor costs, and GHGs, which is an effective nitrogen fertilizer management measure to promote cleaner production of food crops in the North China Plain.

Efficient Mineralization of Lithium Bis(pentafluoroethanesulfonyl)imide and Related Electrolyte Fluorochemicals Using Superheated Water.

Lithium bis(pentafluoroethanesulfonyl)imide, Li[N(SO2C2F5)2], a typical fluorochemical aimed at better electrochemical performance of battery electrolytes, in superheated water was studied for its waste treatment. When Li[N(SO2C2F5)2] was reacted in pure superheated water at 300 °C, little F- ions were produced. In contrast, complete mineralization of the fluorine, sulfur, and nitrogen atoms in Li[N(SO2C2F5)2] was achieved when the reaction was performed in the presence of KMnO4. Specifically, when Li[N(SO2C2F5)2] was treated for 18 h with 158 mM of KMnO4, the F- and SO42- yields were 101 and 99%, respectively, and the sum of the NO3- and NO2- yields was 101%. In the gas phase, trace CO2 was detected and no CHF3, which has high global warming potential, was formed. Furthermore, the fluorine, sulfur, and nitrogen atoms in the analogues K[N(SO2C4F9)2] and K[N(SO2CF2)2CF2] also underwent complete mineralization using the same approach.

A comparative exergoenvironmental assessment of thermochemical copper-chlorine cycles for sustainable hydrogen production

Hydrogen is one of the highly promising clean solutions to address the concerns of energy security in the future given the rapid rate of depletion of naturally occurring hydrocarbon sources. However, it is of immense importance that hydrogen is obtained through sources that ensure sustainability. Thermochemical water-splitting processes are among such routes of hydrogen production that are both sustainable and environmentally benign. Thus, this study focuses on assessing the copper-chlorine thermochemical cycles that are among the more promising cycles of the chlorine family in terms of efficiency and cost-effectiveness. Moreover, this study considers a comparative exergoenvironmental evaluation of the four variants of the copper-chlorine cycle that vary in the number and the nature of steps. A comparison in this regard is carried out between the various steps of each cycle in terms of the component-associated environmental impact rates and environmental impact rates of energy transfer as well as the overall environmental impacts of all cycles. In addition, a comparison of the global warming potential of hydrogen synthesized through utilizing various electricity sources is also performed. Based on our evaluations, hydrolysis and electrolysis are the common steps in the five-step cycle, the four-step cycle, and the three-step cycle configuration 1 yielding the highest component-associated environmental impact rates and environmental impact rates of energy transfer, respectively. Conversely, in the three-step cycle configuration 2, the electrolysis and thermal decomposition steps yield the highest corresponding values, respectively. In addition, the three-step cycle configuration 2 (4,869 mPts/h) and the five-step cycle (3,194 mPts/h) have the highest and the lowest component-associated environmental impact rates, respectively while the five-step (530,694 mPts/h) and the four-step (248,050 mPts/h) cycles result in the highest and the lowest environmental impact rates of energy transfer, respectively.

Multi-objective (Carbon-Exergy) optimization study of CO2 cascade systems using multiple refrigerant pairs

In order to guide the operation of the actual cascade system, this paper takes the cascade system as the research object and compares the use of six refrigerant pairs. Unlike the previous single-objective optimization of refrigeration system carbon emissions and other indicators, this research uses a multi-objective optimization algorithm, that is, we consider the cascade system's exergy efficiency and carbon emissions at the same time. We reduce carbon emissions while improving the system's exergy efficiency, and finally find out the specific operating conditions under which the system can realize low-carbon and high-efficiency operation, which further promotes the process of achieving energy saving and emission reduction in factories. The optimization results show that among the six refrigerant pairs, the use of R744-R134a and R744-R290 refrigerant pairs can make the system operate better, but considering the high global warming potential (GWP) of R134a refrigerant, the use of R744-R290 combination is more recommended.

Properties and environmental sustainability of fungal chitin nanofibril reinforced cellulose acetate films and nanofiber mats by solution blow spinning

Materials from biological origin composed by renewable carbon facilitate the transition from linear carbon-intensive economy to a sustainable circular economy. Accordingly, we use solution blow spinning to develop fully biobased cellulose acetate films and nanofiber mats reinforced with fungal chitin nanofibrils (ChNFs), an emerging bio-colloid with lower carbon footprint compared to crustacean-derived nanochitin. This study incorporates fungal ChNFs into spinning processes for the first time. ChNF addition reduces film surface roughness, modifies film water affinity, and tailors the nanofiber diameter of the mats. The covalently bonded β-D-glucans of ChNFs act as a binder to improve the interfacial properties and consequently load transference to enhance the mechanical properties. Accordingly, the Young's modulus of the films increases from 200 ± 18 MPa to 359 ± 99 MPa with 1.5 wt% ChNFs, while the elongation at break increases by ~45 %. Life cycle assessment (LCA) is applied to quantify the environmental impacts of solution blow spinning for the first time, providing global warming potential values of 69.7–347.4 kg·CO2-equiv.·kg−1. Additionally, this work highlights the suitability of ChNFs as reinforcing fillers during spinning and proves the reinforcing effect of mushroom-derived chitin in bio-based films, opening alternatives for sustainable materials development beyond nanocelluloses in the near future.

Thermodynamic and environmental analysis of integrated supercritical water gasification of sewage sludge for power and hydrogen production

Supercritical water gasification is a promising process for treating sewage sludge (SS) to obtain hydrogen and electrical energy. Here, a novel thermodynamic equilibrium model for supercritical water gasification of sewage sludge was developed and the thermodynamic and environmental effects of operating parameters on the system were investigated. The sensitivity analysis revealed that the optimum reaction condition for the system was: reaction temperature of 750 °C, preheated water to SS ratio of 1, and SS concentration of 25 %. Under this condition, the system energy efficiency and exergy efficiency were 44.74 % and 46.51 %, respectively, with H2 production of 103.19 kg/h and power generation of 2526.2 kW. The energy and exergy efficiencies could be improved by reducing the preheated water to SS ratio and increasing the reaction temperature and SS concentration. The heat exchangers and the heater were the key units causing exergy losses, accounting for 40.3 % and 19.5 % of the total exergy losses, respectively. When utilizing carbon capture and storage (CCS), the global warming potential (GWP) value was only 0.31 kg CO2-eq under the optimal operating parameters, which was 61.44 % less than without CCS.

Microwave-assisted pyrolysis in biomass and waste valorisation: Insights into the life-cycle assessment (LCA) and techno-economic analysis (TEA)

Microwave-assisted pyrolysis (MAP) has been perceived as a promising technology for biomass and waste conversion due to its distinctive features, including fast, even, and precise heating. This results in higher energy efficiency when compared to conventional pyrolysis via thermal heating. However, the scaling up of MAP of biomass and waste poses challenges, with investigations ongoing to uncover not only the technological aspect, but also both the environmental impacts and economic feasibility associated with this process/technology. The possible environmental impacts associated with MAP processes can be analyzed through systematic life-cycle assessment (LCA), while the economic feasibility can be evaluated via techno-economic analysis (TEA). This paper presents an overview of the current research trend in MAP and the products produced, as well as the LCA and TEA of the pyrolysis technologies. The LCA study reported a 2.5 folds reduction in energy consumption and up to 62% reduction in global warming potential. TEA study revealed that conventional pyrolysis has a greater profit for long-term assessment due to a higher maturity and less complexity technology; however, MAP may be more economically feasible in the future owing to the increased maturity and more established technology. Finally, the challenges and future perspectives for LCA and TEA in MAP are elucidated.

Conversion of biodigestate into activated carbon for electrochemical application: Process performance and life cycle assessment

Carbons derived from pyrolysis and activation of waste biomass are attracting much attention as components of energy technologies, such as batteries, supercapacitors and fuel cells. This experimental study focuses on the production of a high-surface-area biochar (LAC) obtained from the treatment of lignin-rich waste of a biodigester plant, by applying KHCO3 as an activating agent. The pyrolysis-activation conditions were set by following the process by thermogravimetric analysis and by checking the purity and porosity of the resulting carbon by several analytical techniques. The best pyrolysis condition provided a microporous carbon featuring up to 1840 m2 g−1, which was demonstrated at a 25 g biodigestate batch-scale. Moreover, the production process was critically analyzed by means of life cycle assessment to identify environmental hotspots and thus derive recommendations for process optimization. The impact of substance- and energy-recovery and the use of renewable energy sources on the sustainability of the product was demonstrated in several scenarios, complemented by benchmarking and an outlook regarding further optimization needs. In the best case scenario, the global warming potential of the proposed biochar could be reduced to 15.9 kg CO2-eq per kg of LAC. The activating agent KHCO3 was dominant in almost all environmental impact categories, hence, a theoretical recovery process for this substance was suggested and evaluated via life cycle assessment.

Residential long-span timber floor typologies: a comprehensive performance assessment and opportunities for value adding to plantation hardwood

ABSTRACT High-performance engineered wood products (EWPs) and composite mass timber products (CMTPs) are being employed more frequently in residential projects with increasing interest in more sustainable systems that achieve long-spans. The relative performance of these systems is not readily apparent, with individual manufacturers offering proprietary products assembled from specific timber resources. In addition, the suitability of producing these long-span systems using plantation hardwoods is currently unknown. This research investigated the comparative performance of four typical EWPs and CMTPs; 1. solid slab, 2. thin-walled cassette, 3. T-sections, and 4. slab on beam. Key performance metrics of depth, mass, stiffness, vibration response, fire performance and global warming potential were assessed. The mechanical performance of two high-strength plantation hardwood varieties (Eucalyptus nitens and Eucalyptus globulus) were determined experimentally and subsequently used to re-calculate performance criteria for the previously assessed typologies. Substantial improvements over the typical softwood varieties were identified, particularly in structural efficiency, global warming potential and fire performance. This highlights the potential for value adding to plantation hardwoods by using them in high-performance long-span engineered floor products.

Synergistic reduction of pollution and carbon mitigation in constructed wetlands-microbial fuel cell using sludge-derived biochar

Integrating microbial fuel cells (MFC) into constructed wetland systems (CW) has been an efficient wastewater treatment to improve the pollutants removal and regenerate power energy. This study fabricated a sludge biochar material (SBM) to sequestrate the carbon of residual sludge. Thereafter used SBM and modified SBM as the substrate materials to construct three groups of CW-MFC for decreasing the greenhouse gas (GHG) emission. The water quality improvement in removal efficiency achieved (2.59 %, 3.10 %, 5.21 % for COD; 3.31 %, 3.60 %, 6.71 % for TN; 1.80 %, 7.38 %, 4.93 % for TP) by the application of MFC, SBM, and modified SBM in wastewater treatment, respectively. Additionally, the reduction in global warming potential (GWP) realized 17.2 %, 42.2 %, and 64.4 % resulting from these applications. The carbon flow and fate diagrams showed MFC shifted the gas phase‑carbon flow from CH4 to CO2, and SBM promoted this shift trends. Microbial diversity indicated enrichment of electrochemically active bacteria (EAB), denitrifying bacteria, and phosphate accumulating organisms (PAOs) by SBM. Metabolic pathways analysis showed that introduction of MFC and SBM exhibited significant increases of key functional genes in metabolic pathway of anaerobic oxidation of methane (AOM). This study highlights the benefit of CW-MFC in and provides a new strategy for removing pollutants and abating GHG emissions in wastewater treatment.