Total Global Warming Potential Research Articles

Salt freezing-thawing damage evolution model based on the time-dependent hydration reaction incorporating rice husk ash and recycled coarse aggregate

Rice husk ash (RHA), an abundant agricultural by-product, has led to significant environmental pollution due to current treatment methods. To achieve resource utilization, the feasibility of RHA recycled concrete subjected to the salt freezing-thawing resistance was assessed, including the macroscopic properties, microstructure and sustainability, and an evolutionary model of salt freeze-thaw damage was established based on the time-dependent hydration reaction of the cement paste. The results indicate that RHA particles effectively retard damage by limiting chloride ion diffusion and preventing salt crystallization, while deteriorating the concrete performance due to reduced hydration products at high RHA replacement ratios. The established salt freeze-thaw damage evolution model has an R2 as high as 0.9817, which indicates that the model fits with high accuracy and can capture the performance variations of different types of RHA recycled concrete under extreme environmental conditions. Additionally, the synergistic preparation of concrete using RHA with a 20 % replacement ratio and recycled coarse aggregate (RCA) with a 50 % replacement ratio reduces the total global warming potential (GWP) by 16.65 %, which means that it has the potential to advance low-carbon sustainable development in the construction industry while meeting the engineering requirements. This research is expected to provide a theoretical reference for applying and promoting biobased low-carbon concrete with RHA in saline-alkali cold areas.

Changes in the environmental impacts of the waste management system after implementing the waste‐sorting policy: A Beijing case study

AbstractQuantifying the environmental impacts of a household waste‐sorting policy on the household waste management system, including collection, transportation, and treatment, is the basis for evaluating the policy's effectiveness. Beijing, the capital of China, began to implement the mandatory domestic waste‐sorting policy in May 2020. In this study, we aimed to evaluate the environmental impacts of the household waste management system in Beijing before and after implementing the sorting policy using the life cycle assessment method. Implementing the policy at the waste collection stage reduced the environmental impacts by minimizing the number of garbage bins consumed through their removal and consolidation. At the transportation stage, implementing the policy increased the environmental impacts per unit of waste via transportation structure changes. However, the overall impact was reduced because more recyclable materials were separated after waste sorting. The environmental impacts were reduced after implementing the policy at the treatment stage mainly because of the change in waste composition and the decrease in the total volume of treatment. Global warming potential (GWP) was the main contributor to the environmental impacts. After waste sorting, the GWP of the collection, transportation, and treatment stages decreased by −19.96%, −24.36%, and −38.08%, respectively, resulting in a total GWP reduction of −37.90%. However, incineration and biochemical treatments may offer environmental benefits.

Life-cycle-based considerations in design of driven piles in sand

This study conducts a life-cycle assessment to evaluate the environmental impacts of driven shafts across 12 different siliceous sand sites, selected from a database of static load pile tests. Through parametric studies, this paper investigates the influence of soil properties, pile geometry and on-site activities on environmental impacts. For a single pile, the findings demonstrate that material production is the most impactful phase, contributing 88.4% of global warming potential (GWP) per unit capacity, while on-site operations contribute minimally at 1%. Sensitivity analyses show that variations in fuel consumption by ±25% and linear interpolations of blow counts result in negligible difference in GWP (less than 0.1 and 1%, respectively). On average, the total GWPs for steel and concrete piles are approximately 4.3 and 0.92 kg carbon dioxide (CO2) equivalent per kilonewton capacity, respectively. Although various factors influence pile design and installation, the results presented herein provide a foundational framework for geotechnical engineers to integrate environmental impacts into project planning, design and construction considerations.

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.

Towards a low-emission resource circulation of valuable metals from municipal solid waste incineration fly ash

The incineration fly ash (IFA) resulting from municipal solid waste combustion is laden with heavy metals, necessitating proper treatment not only for environmental management but also to reclaim the metal values. The surge in non-traditional metals like cobalt as emerging contaminant within IFA samples further attracts to address this issue. In response, the hydrometallurgical recycling of a cobalt-bearing IFA has been studied. Thereby, approximately 98 % zinc and 96 % cobalt were leached using a 1.0 mol/L H2SO4 solution at 90 °C and 1 h of leaching time. In-depth analysis of the leaching process unveiled metals' dissolution primarily via the ion-exclusion mechanism, as evidenced by lower diffusion coefficients (between 10−9 and 10−11 m2/s) and activation energies (9.6–14.9 kJ/mol). Above 99 % separation of zinc from the cobalt-bearing leach liquor was achieved by extraction with 1.0 mol/L D2EHPA at an equilibrium pH below 3.0, followed by stripping with a 2.0 mol/L H2SO4 solution. Cobalt, remained in the raffinate was efficiently precipitated by adding a 20 % excess dosage of oxalic acid to the stoichiometric ratio of C2O42−:Co2+, resulting in only 5 mg/L cobalt left in the solution when precipitation occurred at a pH of 2.8. Additionally, the conversion of CoC2O4 to high-purity Co3O4 was conducted through heat-treatment at 600 °C. The resulting Co3O4 was mixed with Li2CO3 at a Li/Co molar ratio of 1.1, yielding a LiCoO2 precursor that exhibited good electrochemical properties with a capacity of 128 mAh/g, thus affirming the high quality of the recycled cobalt. A comprehensive life-cycle assessment of the recycling process revealed that cobalt precipitation alone contributes approximately 50 % of the total global warming potential (GWP = 4.2624 kg CO2-eq). Notably, this value is remarkably lower than the GWP reported for primary cobalt production, highlighting the environmentally-friendly approach of this recycling endeavor.

An evaluation of the environmental impact and energy efficiency of producing geopolymer mortar with plastic aggregates

The imperative to mitigate carbon emissions and seek sustainable alternatives to cementitious materials has driven the advancement of geopolymer binders, which are inorganic binders of aluminosilicate industrial-waste materials activated by alkaline agents. The use of geopolymers carries the potential for significant reductions in greenhouse gas emission. Furthermore, the incorporation of plastic waste as aggregates addresses not only resource conservation but also environmental sustainability. This study conducted a comprehensive life-cycle assessment of the use of geopolymers from fly ash as a precursor with polyethylene terephthalate (PET) waste as a substitute for natural aggregates. It was observed that when replacing natural aggregates with PET waste to the maximum extent, the global warming potential (GWP) in the category of emissions related to aggregate preparation increased by 16.7 %. This increase was attributed to significant emissions generated during PET processing, including activities such as washing and grinding. The total GWP to produce one cubic meter of geopolymer mixture was 643.55 kgCO2-e without PET aggregates and 667.86 kgCO2-e with maximum use of PET aggregates. The optimization of energy-intensive PET preparation processes led to a remarkable reduction of 19.63 % for production of geopolymer mixture with maximum use of PET aggregates. These findings show the potential for improved sustainability in the production of geopolymer mixtures and emphasize the critical role of optimizing the production processes in mitigating their environmental impact.

Mature compost promotes biodegradable plastic degradation and reduces greenhouse gas emission during food waste composting

Mature compost can promote the transformation of organic matter (OM) and reduce the emission of polluting gases during composting, which provides a viable approach to reduce the environmental impacts of biodegradable plastics (BPs). This study investigated the impact of mature compost on polybutylene adipate terephthalate (PBAT) degradation, greenhouse gas (GHG) emission, and microbial community structure during composting under two treatments with mature compost (MC) and without (CK). Under MC, visible plastic rupture was advanced from day 14 to day 10, and a more pronounced rupture was observed at the end of composting. Compared with CK, the degradation rate of PBAT in MC was increased by 4.44 % during 21 days of composting. Thermobifida, Ureibacillus, and Bacillus, as indicator species under MC treatment, played an important role in PBAT decomposition. Mature compost reduced the total global warming potential (GWP) by 25.91 % via inhibiting the activity of bacteria related to the production of CH4 and N2O. Functional Annotation of Prokaryotic Taxa (FAPROTAX) further revealed that mature compost addition increased relative abundance of bacteria related to multiple carbon (C) cycle functions such as methylotrophy, hydrocarbon degradation and cellulolysis, inhibited nitrite denitrification and denitrification, thus alleviating the emission of GHGs. Overall, mature compost, as an effective additive, exhibits great potential to simultaneously mitigate BP and GHG secondary pollution in co-composting of food waste and PBAT.

Energy budgeting and global warming potential of traditional rice production system in Eastern Ghats region of Odisha

Aim: This study aims to focus on traditional agricultural practices which are gaining momentum around the globe as an energy efficient and sustainable approach in the changing climate condition. In this study, an attempt was under taken to quantify the energy use, green house gas emission and global warming potential of rice cultivated by traditional method in terraced low land. Methodology: The data were collected through Focused Group Discussion (FGD) from farmers of the study area using the questionnaire. The sample size was calculated by Neyman method. Results: Total input and output energy required for traditional rice production were 8513.0 MJ ha-1 and 77356.88 MJ ha-1, respectively. Energy use efficiency was calculated as 9.01. Total global warming potential (GWP) was 610.19 CO2 eq ha-1. In this study, the output and input carbon were found to be 2580.48 and 164.75 kg C ha-1, respectively and the carbon efficiency ratio was 15.66. Energy productivity of this traditional method of rice production system was approximately 1.21 to 3.64 times higher than that of other rice production system. Interpretation: Rice is the staple food of tribal's habited in the highland region of Eastern Ghats Odisha, India, and these tribal people mostly cultivate rice by traditional method. This traditional rice production system can be considered as an environmental friendly and sustainable agricultural system in this changing climatic condition, and this system is also economical than the conventional rice cultivation practices. Key words: Budgeting, Energy, Eastern Ghats, Green house gases, Global warming, Rice

Life cycle analysis in hazardous waste logistics in Türkiye: a case study

ABSTRACT The collection and transportation activities engaged in waste management (WM) are known to have significant environmental impacts. This study assessed the current environmental situation regarding the use of diesel fuel in hazardous waste (HW) collection and transportation using a LCA methodology. The study utilized the actual transportation data of the HW collection and transportation activities of a WM company, IZAYDAS, for the year 2021. The functional unit (FU) chosen for analysis was the “environmental impact per annual total fuel consumption.” In addition, the study aimed to understand potential changes in environmental impact if electricity were used as a fuel alternative. The findings revealed that in the current scenario with diesel fuel, the Abiotic Depletion Potential (Fossil Fuel) (ADP Fossil) effect category had a dominant effect (3.92E + 06 MJ). The total Global Warming Potential (GWP100a) effect for HW transportation was determined to be 5.28E + 05 kg CO2 eq in 2021. When electricity was considered a fuel alternative, a decrease was observed in the GWP100a and ADP impact categories. At the same time, Human Toxicity (HTP), Acidification (AP), and Eutrophication (EP) showed an increase due to fossil fuel-based energy production. Sensitivity analysis indicated that all effects are lower in countries that depend on clean energy sources for electricity production.

Life cycle assessment of hemp-lime concrete wall constructions: The impact of wall finish type and renewal regimes

Using sustainable building materials is one of the key methods for minimising the negative environmental impacts of the global construction industry. Bio-based buildings building materials, such as hemp-lime concrete, are considered more sustainable, as they make use of a renewable raw material and can sequester CO2 from the atmosphere. Studies have shown that hemp-lime concrete can have a favourable global warming potential, though the life cycle of building materials affects a wide variety of negative environmental phenomena that should also be considered. Studies examining the life cycle of hemp-lime concrete have so far primarily focused on the material itself. Though the exterior surface of a hemp-lime concrete wall needs to be protected and have a finish applied to it, few studies have considered the environmental impacts of coated hemp-lime concrete wall constructions. Using life cycle assessment methodology, through a wide range of environmental impact categories, the study analysed the environmental impacts of applying lime putty and sand coatings to a hemp-lime concrete wall in pessimistic, average and optimistic scenarios, It also compared the environmental impacts of four types of appropriate wall finishes and the impacts of applying varying finish renewal regimes in the use phase. It was found that applying lime putty and sand finishes to the exterior and interior surface of a hemp lime concrete wall increased the total global warming potential by 19.054–30.793 kgCO2eq and had a noticeable effect on all other impact categories. It was found that while no one finish type could be considered globally superior to the others, in a majority of circumstances applying lime-based coatings resulted in lower embodied environmental impacts, than applying a ventilated façade with timber cladding.

Sustainability Assessment Of Carbon Dioxide Emission Reduction From Energy Use In Cement Production Via Life Cycle Assessment And Ahp

The cement industry in supporting sustainable development is faced with the challenge of reducing energy consumption, natural resources and emissions generated from its production activities. PT X is one of the cement industries in Indonesia that has a production design capacity of 2.6 million tons/year. PT X's cement production activities use several fossil fuel energy sources and alternative fuels that can produce carbon dioxide emissions that are wasted into the environment. This study aims to identify process units that produce significant impacts to determine alternative environmental improvement scenarios. The method used is Life Cycle Assessment (LCA) as a tool for calculating potential environmental impacts, and AHP as an alternative selection of environmental improvement program scenarios. The scope of the LCA study carried out with the scope of "Cradle to Gate" includes the stages of the raw material extraction process, the production process to the distribution of cement. The resulting potential environmental impact is a total Global Warming Potential (GWP) of 0.20543 tons CO2 eq/ton. The largest potential impact comes from the kiln unit of 0.20221 tons CO2 eq/ton or an impact contribution of 98.43%. Based on the environmental impacts generated, there are 4 alternative programs that can be used to reduce the environmental impacts generated. The selection of alternative program scenarios is based on 3 criteria based on 3 types of respondents. Alternatif program yang memiliki nilai prioritas tertinggi yaitu alternatif program 1 dengan sebesar 35,5%, 38,1%, dan 23,4%.

Biochar mitigates the mineralization of allochthonous organic matter and global warming potential of saltmarshes by influencing functional bacteria

Saltmarshes are suffering from severe degradation due to anthropogenic activities, leading to the loss of blue carbon and greenhouse gas (GHG) emissions. Given the significant potential of biochar in mitigating climate change, adding biochar to saltmarshes would alleviate this situation. This study investigated the effects of different biochar (made from Spartina alterniflora, corn straw, and Laminaria japonica) and their aged biochar on the carbon fraction contents, GHG emissions, and microbial community structure of saltmarsh soils with allochthonous organic matter (Enteromorpha prolifera) addition. After 60 days of incubation, total organic carbon (TOC) loss and global warming potential (GWP) of biochar-amended soils were reduced by 67.29–124.33% and 4.91–123.24%, respectively (p < 0.05). Biochar reduced the proportion of labile carbon (dissolved organic carbon (DOC) and microbial biomass carbon (MBC)) in organic carbon by 61.92–86.15% (p < 0.05). In addition, biochar reduced the relative abundance of specific functional bacteria (inc. cellulolysis, aromatic compound degradation, and xylanolysis) involved in organic carbon decomposition by 20.02–37.82% (p < 0.05). These results suggest that even in the presence of high levels of liable organic matter, the application of biochar to saltmarshes has a sustained effect in promoting carbon accumulation and reducing GHG emissions, and this effect is regulated by a decrease of functional bacteria associated with carbon metabolism. Therefore, the in situ study of biochar on restoring carbon sink function of saltmarshes is proposed for practical engineering in future.Graphical

A comparative life cycle assessment of recycling waste concrete powder into CO2-Capture products

Waste concrete powder (WCP), a byproduct of construction and demolition (C&D), currently has a low degree of recycling despite its potential for environmentally friendly applications. WCP can serve as a valuable substitute for cement, offering advantages for resource conservation and carbon sequestration. However, there are very few studies that quantitatively assess the environmental impact of incorporating WCP into the circular economy as a secondary material instead of disposing of it. The energy-intensive processing of WCP raises questions about the optimal carbonation time using available equipment. This study aims to fill this knowledge gap by employing carbon footprint and life cycle assessments (LCA) to optimize WCP recycling. Three recycling WCP scenarios are analyzed. The first scenario involved the conversion of WCP into compacts that absorb CO2 during the carbonation process. The results of the first scenario revealed that the optimal carbonation time for WCP compacts was 8 h, during which 42.7 kg CO2-e per tonne of WCP compacts was sequestered. The total global warming potential (GWP) was −4.22 kgCO2-e, indicating a carbon-negative recycling process. In the second and third scenarios, LCA was conducted to compare the use of carbonated and uncarbonated WCP as a partial replacement for cement in concrete. In these scenarios, it was found that uncarbonated WCP is a more effective solution for reducing the carbon footprint of traditional concrete mixes, achieving a significant 16% reduction of GWP when 20% of cement is replaced. Conversely, using carbonated WCP as a partial cement replacement in concrete mixtures shows limited potential for CO2 uptake. The sensitivity analysis reveals that the carbon footprint of the WCP compacts production process is strongly influenced by the electricity supplier used.

The external/internal sources and sinks of greenhouse gases (CO2, CH4, N2O) in the Pearl River Estuary and adjacent coastal waters in summer

Estuary acts as a hotspot of greenhouse gases (GHGs, including CO2, CH4 and N2O) to the atmosphere. However, the GHGs budgets, including input/output fluxes through interfaces and biogeochemical source/sink processes in water columns, of the estuarine systems are still not well constrained due to the lacking of comprehensive observational data. Here, we presented the spatial distributions of GHGs of surface/bottom water and sediment porewater along the Pearl River Estuary (PRE) and adjacent region during summertime. The incorporation of the monitoring for the sediment-water interface (SWI) with these of the water-air interface (WAI) allows us to close the budget revealing additional information of internal consumption/production processes of the three GHGs. The oversaturated CO2 (481–7573 μatm), CH4 (289–16,990 %) and N2O (108–649 %) in surface water suggested PRE is a significant GHGs source to the atmosphere, in which CO2 is the major contributor accounting for 90 % of total global warming potential (GWP), leaving 2.8 % from CH4, and 7.2 % from N2O. Addition to the river input, the SWI releases GHGs to the overlying water with fluxes of 3.5 × 107, 10.8 × 104 and 0.7 × 104 mol d−1 for CO2, CH4 and N2O, respectively. Although all three GHGs exhibited emission to the atmosphere, our mass balance calculation showed that 16.9× 107 mol d−1 of CO2 and 1.0 × 104 mol d−1 of N2O were consumed, respectively, inside the estuary water body, while extra-production (13.8 × 104 mol d−1) of CH4 was demanded in the water body to support its output flux. This is the first experiment quantitatively assessing the importance of internal carbon and nitrogen biogeochemical processes in the PRE. Our finding is of guiding significance to constrain the GHGs budget and draw up realistic pathways for modeling works of GHGs prediction.

On a new environment-friendly gas mixture for Resistive Plate Chambers

The standard gas mixture for the Resistive Plate Chambers (RPC), composed of C2H2F4/i-C4H10/SF6, allows the detector operation in avalanche mode, as required by the high-luminosity collider experiments. The gas density, the low total charge delivered inside the gas and the comfortable avalanche-streamer separation guarantee high detection efficiency, rate capability and slow detector aging. The standard RPC gas mixture is mostly based on Hydrofluorocarbons, HFCs, extensively used in the refrigeration industry. The Hydrofluorocarbons are now considered to be non-eco-friendly gases for their high Global Warming Potential (GWP). The SF6 has the largest GWP, 22900, but, due to its low concentration, it contributes only with few tens of units to the total value. The major contribution comes from the main standard gas mixture component, the C2H2F4 (GWP ≈ 1300). These gases are not recommended for industrial uses anymore, thus their availability will be increasingly difficult over time and the search for an alternative gas mixture with low-GWP is then of absolute priority within the RPC community. We report the performance of the RPC working with new environment-friendly gases which could replace the standard mixture. In this work the standard mixture main component, the C2H2F4, is replaced by a proper mixture of CO2 (GWP = 1) and Tetrafluoropropene (C3H2F4, GWP≈6). The other high-GWP component, the SF6, is replaced by a molecule, the Chloro-Trifluoropropene (C3H2ClF3, GWP ≈ 5) never tested in RPC detectors. The mixtures studied have a total GWP ≈ 10. We report, for several eco-gas mixtures, the detection efficiency, streamer probability, electronic and ionic charge as a function of the high voltage. Moreover, the timing properties are studied and the detector time resolution is measured. We also focus the attention on a new category of signals having intermediate properties between avalanche and streamer, called ”transition events”. This category is negligible for the standard gas mixture but relevant for HFO/CO2-based gas mixtures. We show a direct comparison between SF6 and C3H2ClF3 to study in depth the possibility to replace the SF6.

Costs, carbon footprint, and environmental impacts of lithium-ion batteries – From cathode active material synthesis to cell manufacturing and recycling

Strong growth in lithium-ion battery (LIB) demand requires a robust understanding of both costs and environmental impacts across the value-chain. Recent announcements of LIB manufacturers to venture into cathode active material (CAM) synthesis and recycling expands the process segments under their influence. However, little research has yet provided combined costs and environmental impact assessments across several segments of the LIB value-chain. To address this gap, we provide a combined cost assessment and life cycle assessment (LCA), covering CAM synthesis, cell manufacturing and hydrometallurgy recycling. 1 kWh cell capacity (NMC811-C) is chosen as functional unit. Results for cell manufacturing in the United States show total cell costs of $94.5 kWh−1, a global warming potential (GWP) of 64.5 kgCO2eq kWh−1, and combined environmental impacts (normalizing and weighing 16 impact categories) of 4.0 × 10−12 kWh−1. Material use contributes 69% to costs and 93% to combined environmental impacts. Energy demand, meanwhile, accounts for 35% of GWP. Initially, hydrometallurgy recycling adds 5 to 10% to total costs, GWP, and environmental impacts. Including recycling credits, as recycled material substitutes new virgin material, shows benefits for recycling. Combined environmental impacts benefit most from recycling (−75%), followed by costs (−44%) and GWP (−37%). Further, we present a comprehensive dashboard which reveals how different scenarios, such as, using wind power instead of grid electricity, influence costs, GWP, and environmental impacts across process segments. Switching to low-carbon energy, for example, reduces GWP more than recycling would. Also, our dashboard shows that recycling or low scrap are more suitable options if reduction of costs or combined environmental impacts is the objective.

High-efficiency utilization of biomass and seawater resources based on a distributed system with SOFC-assisted CO2 capture: Feasibility analysis and optimization

This paper develops a distributed system with SOFC-assisted carbon capture (SACC) by integrating the Rankine cycle, double-effect absorption chiller and multi-effect distillation unit to produce electricity, cooling and freshwater. To study the feasibility of the developed system, thermodynamic, economic and carbon footprint analyses and optimization are conducted on six different cases for the system. The results reveal that regardless of the biomass sources used as fuel, the developed SACC system requires 5%-9% less power consumption for CO2 capture compared to traditional methods. Moreover, the system fueled by switch grass exhibits superior efficiencies, and the system thermal efficiency (ηth) with SACC achieves 56.35% with corresponding levelized cost of products (cp) and total global warming potential (GWPt) of 54.94 $/GJ and −0.129 kg/kWh. Exergy analysis demonstrates that the prime mover unit (PMU) deserves the greatest irreversibility for all cases with a relative exergy destruction rate (y*k) of over 65% of the whole system. Within the PMU, the gasifier and SOFC are responsible for the highest irreversibility, and the y*k of the gasifier is over 50% and the SOFC’s is close to 9%. The parameter study indicates that an increase in the gasification temperature is unfavorable to ηth, however, it is conducive to the improvement of net power output (Wnet) when the temperature exceeds a certain value (e.g., 914.3℃ and 885.7℃ for Case-5 and Case-6). An appropriate increase in current density improves ηth and Wnet, and reduces cp, albeit slightly detrimental to environment. The optimization results demonstrate that Case-2 and Case-6 have superior thermodynamics and economics but are detrimental to the environment. In contrast, Case-1 and Case-5 are the most environmentally friendly, but their economics and thermodynamics are degraded to some extent.

The combined effects of nitrogen fertilizer and biochar on soil aggregation, N2O emission, and yield from a vegetable field in southeastern China.

Biochar amendment is a recently promoted agricultural management strategy that can exert distinct impacts on reducing greenhouse gas (GHG) emissions and improving soil fertility and crop productivity. This study aims to evaluate the combined effects of biochar and nitrogen (N) fertilizer on soil aggregation, nitrous oxide (N2O) emission, global warming potential (GWP), vegetable yield, and greenhouse gas intensity (GHGI). The experiments were conducted in a vegetable field with two consecutive vegetable crops in 2019 and 2020 in southeastern China. There were four treatments: control (CK), conventional N fertilizer (U), biochar applied at 15 t ha-1 with N fertilizer (UB1), and biochar applied at 30 t ha-1 with N fertilizer (UB2). The results indicate that while N application significantly increased N2O emission of the vegetable field, both UB1 and UB2 led to significant reductions of the total N2O emission, GWP, and yield-scaled GHGI as well as significant growth of the total vegetable crop yield compared with U. However, no significant differences have been found in N2O emission, GWP, crop yield, and yield-scaled GHGI between UB1 and UB2. Meanwhile, biochar application in addition to N fertilizer did not result in any significant change in the soil water-stable aggregate size distribution and stability compared with U. Soil water-stable aggregates smaller than 0.25 mm and those larger than 5 mm have been found to significantly impact N2O emission and vegetable yield.

A comparative environmental Life Cycle Assessment study of hydrogen fuel, electricity and diesel fuel for public buses

Hydrogen fuel and electricity are energy carriers viewed as promising alternatives for the modernization and decarbonization of public bus transportation fleets. In order to choose development pathways that will lead transportation systems toward a sustainable future, the authors developed an environmental model based on the Life Cycle Assessment approach. The model tested the impact of energy carrier consumption during driving as well as the electricity origin employed to power electric buses and produce hydrogen. Energy sources such as wind, solar, waste and grid electricity were investigated. The scope of the study included the life cycles of the energy carrier and the necessary infrastructure. The results were presented from two perspectives: the total environmental impact and global warming potential. In order to create a roadmap, an original method for choosing sustainable development pathways was prepared. It was shown that the modernization of conventional bus fleets using hydrogen and electrical pathways can provide significant environmental benefits from both perspectives, but especially in terms of global warming potential. It was emphasized that attention should be paid to the use of low- and zero-emission energy sources, because their impact often strongly influenced the final environmental judgment. The energy carrier consumption also had a strong impact on the results obtained, and that is why efforts should be made to reduce it. In addition, it was confirmed that hydrogen and electricity production systems based on electricity generated by a waste-to-energy plant could be an environmentally reasonable dual solution for both sustainable waste management and meeting transport needs.

Evaluating carbon payback time by optimizing insulation materials for different orientations: A cradle-to-gate life cycle assessment

The European Union aims to reduce greenhouse gases emissions by 80–95% compared to 1990 levels by 2050. Therefore the life cycle concept has gained widespread acceptance as a model for evaluating the environmental impact of goods and services. In this study, the optimal thickness of various insulation materials for external walls, roofs, and floors using a Mediterranean climate zone's hot summers and mild winters for a hypothetical residential building for four cardinal orientations was determined. The criteria for determining the optimum thickness represent a turning point in terms of cooling energy consumption (electricity). The optimum thickness of nine different types of insulation materials was defined using the aforementioned approach. These materials included aerogel, polyisocyanurate, polyurethane, extruded polystyrene, expanded polystyrene, phenolic foam, cellulose fiber (cellulose), mineral wool, and glass wool (GW). The purpose of this paper is to calculate the carbon payback time (CPBT) using the cradle-to-gate life cycle assessment method by considering the global warming potential (GWP) of insulation materials at their optimum thickness. The CPBT is calculated as the ratio of the total building's GWP to the GWP of savings from cooling and heating (electricity and natural gas). The results indicated that when evaluating the average CPBT for four cardinal orientations (FCO), aerogel has the longest CPBT of 2.34 years, and GW has the shortest CPBT of just 0.09 years. Aside from cost payback time, the findings of this study provide a new perspective on selecting appropriate thermal insulation.