In this study, hydrothermal carbonization (HTC) of a biomass was used as a means to improve the physicochemical properties of rubber seed shell (RSS) and enhance its reactivity in the char-CO2 gasification reaction, known as the Boudouard reaction (C + CO2 ↔ 2CO). Hydrochar samples were developed by hydrothermal treatment of RSS, without separating the solid residue from the liquid product, at 433, 473, 513, and 553 K under autogenous pressure. The CO2 gasification reactivity of the developed hydrochars was then investigated at different heating rates (5, 10, 20, and 30 K/min) by the non-isothermal thermogravimetric method. The hydrochars revealed higher reactivity and improved gasification characteristics compared to the untreated biomass, while the hydrochar which was filtered from the liquid slurry showed lower reactivity compared to the untreated biomass. This was due to the chemical and structural evolutions of the biomass during hydrothermal treatment as indicated by various analyses. The gasification reactivity of the hydrochar was substantially enhanced by introduction of a catalyst (NaNO3) during HTC. Kinetic analysis of the char-CO2 gasification reaction was carried out by applying Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink isoconversional methods, and thermodynamic parameters were also determined. The activation energy of the Na-loaded RSS hydrochar in CO2 gasification (120-154 kJ/mol) was considerably lower than that of the untreated biomass (153-172 kJ/mol). Thermodynamic studies also confirmed the promoting effect of hydrothermal treatment and catalyst impregnation on enhancement of reactivity of the virgin biomass and reduction of gasification temperature.
A rapid growth in the development of power generation and transportation sectors would result in an increase in the carbon dioxide (CO2) concentration in the atmosphere. As it will continue to play a vital role in meeting current and future needs, significant efforts have been made to address this problem. Over the past few years, extensive studies on the development of heterogeneous catalysts for CO2 methanation have been investigated and reported in the literatures. In this paper, a comprehensive overview of methanation research studies over lanthanide oxide catalysts has been reviewed. The utilisation of lanthanide oxides as CO2 methanation catalysts performed an outstanding result of CO2 conversion and improvised the conversion of acidity from CO2 gas to CH4 gas. The innovations of catalysts towards the reaction were discussed in details including the influence of preparation methods, the structure-activity relationships as well as the mechanism with the purpose of outlining the pathways for future development of the methanation process.
This research article aims to investigate the moderating role of financial development in Environmental Kuznets Curve (EKC) in the context of Malaysia for the period 1970-2016. As the time series variables are integrated of different order therefore, Auto-Regressive Distributed Lag (ARDL) model has been employed to estimate the long-run equilibrium relationship among the variables. The results indicate that EKC does exist for Malaysia and financial development has negative impact on carbon emission. Moreover, financial development is found to have significant moderating impact on income environment relation. More financial development brings early turning point of the EKC. The results recommend that financial development can be used as one of the policy measures to reduce the environmental cost of economic growth in Malaysia.
There are many advantages of geothermal energy, as an environmental friend resource. This heat radiation emanating from beneath the earth's surface presents man with good opportunities to harness it and makes a good level of agricultural food production and its processing in the EU region. The primary objective of this research is to examine the impact of geothermal energy on agri-food supply among the 27 European countries (EU27), within the time frame 1990 to 2021. The study adopted the autoregressive distributed lag (ARDL), and the findings from this study revealed that agri-food supply can increase significantly among the 13 European countries (EU13 emerging economies), leveraging on geothermal energy and economic growth variables than in the EU14 emerged economies. Furthermore, the outcome of this study showed that there could be a significant decrease in the food products coming from agricultural practices among the 13 European countries (EU13 emerging economies), due to an ineffective population density than in EU14 emerged economies. Furthermore, fossil fuel and institutional quality contribute more positively to the agri-food supply in the EU14 emerged economies than in the EU13 emerging economies. This results in an outcome that means that the agri-food supply among the EU13 emerging economies could be greatly boosted by replacing fossil fuel consumption with geothermal energy, and this facilitates the attainment of the European energy goals by the year 2030. Substituting fossil fuels with geothermal will also assist in minimizing the risks of environmental pollution and climate change. All projected calculations were seen as valid in this study, and this was confirmed by the three estimators adopted which are the pooled mean group, the mean group, and the dynamic fixed effect. This study, therefore, recommends that the 27 European countries should lay more emphasis on geothermal energy production as this will help in ensuring food security in the region. Policymakers and other government authorities as well as local and foreign investors should make more investments in geothermal energy resources as this study has proven that this will lead to agri-food security and sustainability. Not only this, it will as well curb the incidence of climate change and environmental pollution.
Agricultural production is sensitive to climate variability, so climate change-agriculture sector nexus is topical in developing countries. To this end, this study examines the impact of climate change variables-rainfall and temperature-and non-climatic factors on maize production in Somalia for the period between 1980 and 2018 using the autoregressive distributed lag (ARDL) bound test, dynamic ordinary least square (DOLS), variance decomposition(VD), and impulse response function (IRF). The empirical results of the ARDL bound test confirmed the presence of long-run cointegration between the dependent variable and the explanatory variables. Furthermore, the long-run results revealed that average temperature, average rainfall, and political instability significantly inhibit maize production in the long and short runs, but rainfall has a favorable effect on maize production in the short run. Furthermore, rural population and land area under maize cultivation have negative and positive effects on maize production in the long run, respectively-albeit they are statistically insignificant. The empirical results of the study are robust to different econometric methods. Based on these findings, the study emphasizes the importance of the de-escalation of conflicts and the implementation of irrigation facilities which will enhance the productivity of maize crop production.
According to the United Nations Agenda, the 2023 sustainable environment is necessary to secure this planet's future; public-private partnerships investment in energy is crucial to sustainable development. The research examines the quantile association between public-private partnership ventures in energy and environmental degradation in ten developing nations, and data is used from January 1998-December 2016. The advanced econometrics quantile-on-quantile regression approach is used to control the issues of heterogeneity and asymmetric relationship. According to the quantile-on-quantile approach, there is a strong positive association between public-private partnerships in energy and environmental degradation in Argentina, Brazil, Bangladesh, and India. But the negative relationship is observed on different quantiles of China, Malaysia, Mexico, Peru, Thailand, and the Philippines. The findings suggest that the world needs to act as a single community and divert its resources toward renewable energy sources to control climate change; also, to accomplish the UN 15-year road map of Agenda 2023 with 17-SDGs; out of these 17 sustainable goals, SDG-7 is related to affordable and clean energy, SDG-11 is about sustainable cities and communities, and SDG-13 focuses on climate action for sustainable development.
Hydrocarbon-degrading bacteria, which can be found living with eukaryotic phytoplankton, play a pivotal role in the fate of oil spillage to the marine environment. Considering the susceptibility of calcium carbonate-bearing phytoplankton under future ocean acidification conditions and their oil-degrading communities to oil exposure under such conditions, we investigated the response of non-axenic E. huxleyi to crude oil under ambient versus elevated CO2 concentrations. Under elevated CO2 conditions, exposure to crude oil resulted in the immediate decline of E. huxleyi, with concomitant shifts in the relative abundance of Alphaproteobacteria and Gammaproteobacteria. Survival of E. huxleyi under ambient conditions following oil enrichment was likely facilitated by enrichment of oil-degraders Methylobacterium and Sphingomonas, while the increase in relative abundance of Marinobacter and unclassified Gammaproteobacteria may have increased competitive pressure with E. huxleyi for micronutrient acquisition. Biodegradation of the oil was not affected by elevated CO2 despite a shift in relative abundance of known and putative hydrocarbon degraders. While ocean acidification does not appear to affect microbial degradation of crude oil, elevated mortality responses of E. huxleyi and shifts in the bacterial community illustrates the complexity of microalgal-bacterial interactions and highlights the need to factor these into future ecosystem recovery projections.
As the negative repercussions of environmental devastation, such as global warming and climate change, become more apparent, environmental consciousness is growing across the world, forcing nations to take steps to mitigate the damage. Thus, the current study assesses the effect of green investments, institutional quality, and political stability on air quality in the G-20 countries for the period 2004-2020. The stationarity of the variables was examined with the Pesaran (J Appl Econ 22:265-312, 2007) CADF, the long-term relationship between the variables by Westerlund (Oxf Bull Econ Stat 69(6):709-748, 2007), the long-run relationship coefficients with the MMQR method proposed by Machado and Silva (Econ 213(1):145-173, 2019), and the causality relationship between the variables by Dumitrescu and Hurlin (Econ Model 29(4):1450-1460, 2012) panel causality. The study findings revealed that green finance investments, institutional quality and political stability increased the air quality, while total output and energy consumption decreased air quality. The panel causality reveals a unidirectional causality from green finance investments, total output, energy consumption and political stability to air quality, and a bidirectional causality between institutional quality and air quality. According to these findings, it has been found that in the long term, green finance investments, total output, energy consumption, political stability, and institutional quality affect air quality. Based on these results, policies implications were proposed.
This study empirically investigates the effect of meat consumption on greenhouse gas emissions (carbon dioxide, methane, and nitrous oxide) in the USA. The impact of meat consumption on greenhouse gas emissions is examined by controlling for economic growth and energy consumption. The empirical analysis finds that all these variables are cointegrated for the long run. Moreover, meat consumption aggravates greenhouse gas emissions. Specifically, meat consumption (except for beef) has a U-shaped relationship with carbon emissions and an inverted U-shaped relationship with methane and nitrous oxide emissions. The causality analysis indicates a unidirectional causality running from meat consumption to greenhouse gas emissions. These empirical findings indicate that the US livestock sector has the potential to become more environmentally friendly with careful policy formulation and implementation.
This comprehensive paper conducts an in-depth review of personal exposure and air pollutant levels within the microenvironments of Asian city transportation. Our methodology involved a systematic analysis of an extensive body of literature from diverse sources, encompassing a substantial quantity of studies conducted across multiple Asian cities. The investigation scrutinizes exposure to various pollutants, including particulate matters (PM10, PM2.5, and PM1), carbon dioxide (CO2), formaldehyde (CH2O), and total volatile organic compounds (TVOC), during transportation modes such as car travel, bus commuting, walking, and train rides. Notably, our review reveals a predominant focus on PM2.5, followed by PM10, PM1, CO2, and TVOC, with limited attention given to CH2O exposure. Across the spectrum of Asian cities and transportation modes, exposure concentrations exhibited considerable variability, a phenomenon attributed to a multitude of factors. Primary sources of exposure encompass motor vehicle emissions, traffic dynamics, road dust, and open bus doors. Furthermore, our findings illuminate the influence of external environments, particularly in proximity to train stations, on pollutant levels inside trains. Crucial factors affecting exposure encompass ventilation conditions, travel-specific variables, seat locations, vehicle types, and meteorological influences. The culmination of this rigorous review underscores the need for standardized measurements, enhanced ventilation systems, air filtration mechanisms, the adoption of clean energy sources, and comprehensive public education initiatives aimed at reducing pollutant exposure within city transportation microenvironments. Importantly, our study contributes to the growing body of knowledge surrounding this subject, offering valuable insights for policymakers and researchers dedicated to advancing air quality standards and safeguarding public health.
In an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2 as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2 during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2 in reference to N2 revealed no occurrence of the heterogeneous reaction between CO2 and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2 and CO2 were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2 in reference to N2 were different. In sum, the homogeneous reactions between CO2 and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2 suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2 in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3 and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.
Limited knowledge about vertical variation in wood CO2 efflux (Rwood) is still a cause of uncertainty in Rwood estimates at individual and ecosystem scales. Although previous studies found higher Rwood in the canopy, they examined several tree species of similar size. In contrast, in the present study, we measured vertical variation in Rwood for 18 trees including 13 species, using a canopy crane for a more precise determination of the vertical variation in Rwood, for various species and sizes of trees in order to examine the factors affecting vertical variation in Rwood and thus, to better understand the effect of taking into account the vertical and inter-individual variation on estimates of Rwood at the individual scale. We did not find any clear pattern of vertical variation; Rwood increased significantly with measurement height for only one tree, while it decreased for two more trees, and was not significantly related with measurement height in 15 other trees. Canopy to breast height Rwood ratio was not related to diameter at breast height or crown ratio, which supposedly are factors affecting vertical variation in Rwood. On average, Rwood estimates at individual scale, considering inter-individual variation but ignoring vertical variation, were only 6% higher than estimates considering both forms of variation. However, estimates considering vertical variation, while ignoring inter-individual variation, were 13% higher than estimates considering both forms of variation. These results suggest that individual measurements at breast height are more important for estimating Rwood at the individual scale, and that any error in Rwood estimation at this scale, due to the absence of any more measurements along tree height, is really quite negligible. This study measured various species and sizes of trees, which may be attributed to no clear vertical variation because factors causing vertical variation can differ among species and sizes.
Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 efflux, even though significant variations in wood CO2 efflux are an important source of errors when estimating whole-tree total wood CO2 efflux. This study aimed to clarify vertical variations in wood CO2 efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 efflux. First, we measured wood CO2 efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ∼ 40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 efflux estimates regardless of the patterns of vertical variations in CO2 efflux because the surface area in the canopy, where wood CO2 efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in little effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 efflux estimates using measured wood CO2 efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 efflux in the canopy did not cause any bias in stem CO2 efflux scaling, but affected branch CO2 efflux.
Understory plants in tropical forests often experience a low-light environment combined with high CO2 concentration. We hypothesized that the high CO2 concentration may compensate for leaf carbon loss caused by the low light, through increasing light-use efficiency of both steady-state and dynamic photosynthetic properties. To test the hypothesis, we examined CO2 gas exchange in response to an artificial lightfleck in Dipterocarpus sublamellatus Foxw. seedlings under contrasting CO2 conditions: 350 and 700 μmol CO2 mol(-1) air in a tropical rain forest, Pasoh, Malaysia. Total photosynthetic carbon gain from the lightfleck was about double when subjected to the high CO2 when compared with the low CO2 concentration. The increase of light-use efficiency in dynamic photosynthesis contributed 7% of the increased carbon gain, most of which was due to reduction of photosynthetic induction to light increase under the high CO2. The light compensation point of photosynthesis decreased by 58% and the apparent quantum yield increased by 26% at the high CO2 compared with those at the low CO2. The study suggests that high CO2 increases photosynthetic light-use efficiency under both steady-state and fluctuating light conditions, which should be considered in assessing the leaf carbon gain of understory plants in low-light environments.
The review focuses on the application of supercritical fluids as antisolvents in the pharmaceutical field and demonstrates the supercritical antisolvent method in the use of drug encapsulation. The main factors for choosing the solvent and biodegradable polymer to produce fine particles to ensure effective drug delivery are emphasized and the effect of polymer structure on drug encapsulation is illustrated. The review also demonstrates the drug release mechanism and polymeric controlled release system, and discusses the effects of the various conditions in the process, such as pressure, temperature, concentration, chemical compositions (organic solvents, drug, and biodegradable polymer), nozzle geometry, CO(2) flow rate, and the liquid phase flow rate on particle size and its distribution.
Cyanobacteria are widely distributed Gram-negative bacteria with a long evolutionary history and the only prokaryotes that perform plant-like oxygenic photosynthesis. Cyanobacteria possess several advantages as hosts for biotechnological applications, including simple growth requirements, ease of genetic manipulation, and attractive platforms for carbon neutral production process. The use of photosynthetic cyanobacteria to directly convert carbon dioxide to biofuels is an emerging area of interest. Equipped with the ability to degrade environmental pollutants and remove heavy metals, cyanobacteria are promising tools for bioremediation and wastewater treatment. Cyanobacteria are characterized by the ability to produce a spectrum of bioactive compounds with antibacterial, antifungal, antiviral, and antialgal properties that are of pharmaceutical and agricultural significance. Several strains of cyanobacteria are also sources of high-value chemicals, for example, pigments, vitamins, and enzymes. Recent advances in biotechnological approaches have facilitated researches directed towards maximizing the production of desired products in cyanobacteria and realizing the potential of these bacteria for various industrial applications. In this review, the potential of cyanobacteria as sources of energy, bioactive compounds, high-value chemicals, and tools for aquatic bioremediation and recent progress in engineering cyanobacteria for these bioindustrial applications are discussed.
Forest carbon sequestration is a promising negative emissions technology as it is relatively simple and inexpensive. Its potential for climate mitigation could be particularly high in tropical rainforests as they can store more carbon at a faster rate. However, the understanding of its sustainability is limited due to the scarcity of studies. Focusing on reforestation, this work is the first to present an extensive environmental and economic assessment of forest CO2 sequestration in a tropical rainforest country such as Malaysia. Life cycle assessment (LCA) and life cycle costing (LCC) are combined to evaluate the sustainability of reforestation with four tropical tree species: keruing (Dipterocarpus spp.), meranti (Shorea leprosula), rubber (Hevea brasiliensis) and kapok (Ceiba Pentandra). Considering the horizon of 60 years, the system boundaries comprise site infrastructure, land clearing, tree planting and growing, and forest management. The dynamics of greenhouse gas (GHG) and other air emissions are also considered over the period, including carbon sequestration and land use change, nitrous oxide and ethylene emissions. All tree species lead to a net-negative GHG emissions, ranging from -558 to -808 kg CO2 eq./t CO2 removed, with kapok having the highest and rubber the lowest sequestration potential. The latter has the highest values in 13 other impact categories considered, while keruing is the best option for 12 impacts. The main environmental hotspot for all species is the forest management stage. The LCC range from -US$17 to US$12/t CO2 removed. Reforestation on lands available in Malaysia could remove 105.9-473.3 Mt CO2 over 60 years, or 1.8-7.9 Mt CO2/yr, equivalent to 7.4-33 % of the agricultural emissions. Rubber and kapok could generate US$640 M and US$8.06 bn in profits over 60 years from latex and fibre, respectively. Therefore, reforestation has a significant potential to help tropical countries, such as Malaysia, achieve net-negative emissions, while at the same time boosting the economy.
We report a case of a 59 year old man who developed venous air embolism (VAE) during an elective craniotomy for parasagittal meningioma resection. The surgery was done in the supine position with slightly elevated head position. VAE was provisionally diagnosed by sudden decreased in the end tidal carbon dioxide pressure from 34 to 18 mmHg, followed by marked hypotension and atrial fibrillation. Prompt central venous blood aspiration, aggressive resuscitation and inotropic support managed to stabilize the patient. Post operatively, he was admitted in neuro intensive care unit and made a good recovery without serious complications.
A highly active and stable nano structured Pt/Mg1-xNixO catalysts was developed by a simple co-precipitation method. The obtained Pt/Mg1-xNixO catalyst exhibited cubic structure nanocatalyst with a size of 50-80 nm and realized CH4 and CO2 conversions as high as 98% at 900°C with excellent stability in the dry reforming of methane. The characterization of catalyst was performed using various kinds of analytical techniques including XRD, BET, XRF, TPR-H2, TGA, TEM, FESEM, FT-IR, and XPS analyses. Characterization of spent catalyst further confirms that Pt/Mg1-xNixO catalyst has high coke-resistance for dry reforming. Thus, the catalyst demonstrated in this study, offers a promising catalyst for resolving the dilemma between dispersion and reducibility of supported metal, as well as activity and stability during high temperature reactions.
The treatment of high-strength organic brewery wastewater with added acetaminophen (AAP) by an anaerobic digester was investigated. An anaerobic packed-bed reactor (APBR) was operated as a continuous process with an organic loading rate of 1.5-g COD per litre per day and a hydraulic retention time of three days. The results of steady-state analysis showed that the greatest APBR performances for removing COD and TOC were as high as 98 and 93%, respectively, even though the anaerobic digestibility after adding the different AAP concentrations of 5, 10 and 15 mg L(-1) into brewery wastewater can affect the efficiency of organic matter removal. The average CH4 production decreased from 81 to 72% is counterbalanced by the increased CO2 production from 11 to 20% before and after the injection of AAP, respectively. The empirical kinetic models for substrate utilisation and CH4 production were used to predict that, under unfavourable conditions, the performance of the APBR treatment process is able to remove COD with an efficiency of only 6.8%.