Used baby diaper consists of a combination of decomposable cellulose, non-biodegradable plastic materials (e.g. polyolefins) and super-absorbent polymer materials, thus making it difficult to be sorted and separated for recycling. Microwave pyrolysis was examined for its potential as an approach to transform used baby diapers into value-added products. Influence of the key operating parameters comprising process temperature and microwave power were investigated. The pyrolysis showed a rapid heating process (up to 43 °C/min of heating rate) and quick reaction time (20-40 min) in valorizing the used diapers to generate pyrolysis products comprising up to 43 wt% production of liquid oil, 29 wt% gases and 28 wt% char product. Microwave power and operating temperature were observed to have impacts on the heating rate, process time, production and characteristics of the liquid oil and solid char. The liquid oil contained alkanes, alkenes and esters that can potentially be used as chemical additives, cosmetic products and fuel. The solid char contained high carbon, low nitrogen and free of sulphur, thus showing potential for use as adsorbents and soil additives. These observations demonstrate that microwave pyrolysis has great prospect in transforming used baby diaper into liquid oil and char products that can be utilised in several applications.
The valorization and conversion of biomass into various value-added products and bioenergy play an important role in the realization of sustainable circular bioeconomy and net zero carbon emission goals. To that end, microwave technology has been perceived as a promising solution to process and manage oil palm waste due to its unique and efficient heating mechanism. This review presents an in-depth analysis focusing on microwave-assisted torrefaction, gasification, pyrolysis and advanced pyrolysis of various oil palm wastes. In particular, the products from these thermochemical conversion processes are energy-dense biochar (that could be used as solid fuel, adsorbents for contaminants removal and bio-fertilizer), phenolic-rich bio-oil, and H2-rich syngas. However, several challenges, including (1) the lack of detailed study on life cycle assessment and techno-economic analysis, (2) limited insights on the specific foreknowledge of microwave interaction with the oil palm wastes for continuous operation, and (3) effects of tunable parameters and catalyst's behavior/influence on the products' selectivity and overall process's efficiency, remain to be addressed in the context of large-scale biomass valorization via microwave technology.
Microwave co-pyrolysis was examined as an approach for simultaneous reduction and treatment of environmentally hazardous hospital plastic waste (HPW), lignocellulosic (palm kernel shell, PKS) and triglycerides (waste vegetable oil, WVO) biowaste as co-feedstock. The co-pyrolysis demonstrated faster heating rate (16-43 °C/min) compared to microwave pyrolysis of single feedstock (9-17 °C/min). Microwave co-pyrolysis of HPW/WVO performed at 1:1 ratio produced a higher yield (80.5 wt%) of hydrocarbon liquid fuel compared to HPW/PKS (78.2 wt%). The liquid oil possessed a low nitrogen content (< 4 wt%) and free of sulfur that could reduce the release of hazardous pollutants during its use as fuel in combustion. In particular, the liquid oil obtained from co-pyrolysis of HPW/WVO has low oxygenated compounds (< 16%) leading to reduction in generation of potentially hazardous sludge or problematic acidic tar during oil storage. Insignificant amount of benzene derivatives (< 1%) was also found in the liquid oil, indicating the desirable feature of this pyrolysis approach to suppress the formation of toxic polycyclic aromatic hydrocarbons (PAHs). Microwave co-pyrolysis of HPW/WVO improved the yield and properties of liquid oil for potential use as a cleaner fuel, whereas the liquid oil from co-pyrolysis of HPW/PKS is applicable in the synthesis of phenolic resin.
•Microplastic pollution threats environmental and human health.•The resolution of End Plastic Pollution promotes the global strategy against plastic pollution.•The governments should launch relevant policies to implement this resolution.
Nowadays, a growing number of microplastics are released into the environment due to the extensive use and inappropriate management of plastic products. With the increasing body of evidence about the pollution and hazards of microplastics, microplastics have drawn major attention from governments and the scientific community. As a kind of emerging and persistent environmental pollutants, microplastics have recently been detected on a variety of substrates in the world. Therefore, this paper reviews the recent progress in identifying the sources of microplastics in soil, water, and atmosphere and describing the transport and fate of microplastics in the terrestrial, aquatic and atmospheric ecosystems for revealing the circulation of microplastics in the ecosystem. In addition, considering the persistence of microplastics, this study elucidates the interactions of microplastics with other pollutants in the environment (i.e., organic pollutants, heavy metals) with emphasis on toxicity and accumulation, providing a novel insight into the ecological risks of microplastics in the environment. The negative impacts of microplastics on organisms and environmental health are also reviewed to reveal the environmental hazards of microplastics. The knowledge gaps and key research priorities of microplastics are identified to better understand and mitigate the environmental risks of microplastics.
Metals are micropollutants that cannot be degraded by microorganisms and are infiltrated into various environmental media, including both freshwater and marine water. Metals from polluted water are absorbed by many aquatic species, especially fish. Fish is a staple food in the diets of many regions in the world; hence, both the type and concentration of metals accumulated and transferred from contaminated water sources to fish must be determined and assessed. In this study, the heavy metal concentration was determined and assessed in fish collected from freshwater sources via published literature and Estimated Daily Intake (EDI), Target hazard quotient (THQ), and Carcinogenic Risk (CR) analyses, aiming to examine the metal pollution in freshwater fish. The fish was used as a bioindicator, and Geographic information system (GIS) was sued to map the polluted regions. The results confirmed that Pb was detected in fish sampled at 28 locations, Cr at 24 locations, Cu and Zn at 30 locations, with values Pb detected ranging from 0.0016 mg kg-1 to 44.3 mg kg-1, Cr detected ranging from 0.07 mg kg-1 to 27 mg kg-1, Cu detected ranging from 0.031 mg kg-1 to 35.54 mg kg-1, and Zn detected ranging from 0.242 mg kg-1 to 103.2 mg kg-1. The strongest positive associations were discovered between Cu-Zn (r = 0.74, p
Nitrate is required to maintain the growth and metabolism of plant and animals. Nevertheless, in excess amount such as polluted water, its concentration can be harmful to living organisms such as microalgae. Recently, studies on microalgae response towards nutrient fluctuation are usually limited to lipid accumulation for the production of biofuels, disregarding the other potential of microalgae to be used in wastewater treatments and as source of important metabolites. Our study therefore captures the need to investigate overall metabolite changes via NMR spectroscopy approach coupled with multivariate data to understand the complex molecular process under high (4X) and low (1/4X) concentrations of nitrate ([Formula: see text]). NMR spectra with the aid of chemometric analysis revealed contrasting metabolites makeup under abundance and limited nitrate treatment. By using NMR technique, 43 types of metabolites and 8 types of fatty acid chains were detected. Nevertheless, only 20 key changes were observed and 16 were down regulated in limited nitrate condition. This paper has demonstrated the feasibility of NMR-based metabolomics approach to study the physiological impact of changing environment such as pollution to the implications for growth and productivity of microalgae population.
Waste cooking oil (WCO) is a hazardous waste generated at staggering values globally. WCO disposal into various ecosystems, including soil and water, could result in severe environmental consequences. On the other hand, mismanagement of this hazardous waste could also be translated into the loss of resources given its energy content. Hence, finding cost-effective and eco-friendly alternative pathways for simultaneous management and valorization of WCO, such as conversion into biodiesel, has been widely sought. Due to its low toxicity, high biodegradability, renewability, and the possibility of direct use in diesel engines, biodiesel is a promising alternative to mineral diesel. However, the conventional homogeneous or heterogeneous catalysts used in the biodiesel production process, i.e., transesterification, are generally toxic and derived from non-renewable resources. Therefore, to boost the sustainability features of the process, the development of catalysts derived from renewable waste-oriented resources is of significant importance. In light of the above, the present work aims to review and critically discuss the hazardous WCO application for bioenergy production. Moreover, various waste-oriented catalysts used to valorize this waste are presented and discussed.
Here we investigate if lead may be a contributing factor to the observed population decline in a Baltic colony of incubating eiders (Somateria mollissima). Body mass and blood samples were obtained from 50 incubating female eiders at the Baltic breeding colony on Christiansø during spring 2017 (n = 27) and 2018 (n = 23). All the females were sampled twice during early (day 4) and late (day 24) incubation. The full blood was analysed for lead to investigate if the concentrations exceeded toxic thresholds or changed over the incubation period due to remobilisation from bones and liver tissue. Body mass, hatch date and number of chicks were also analysed with respect to lead concentrations. The body mass (mean ± SD g) increased significantly in the order: day 24 in 2018 (1561 ± 154 g)
This study proposes an integrated cattle breeding and cultivation system that provides zero emission and sustainable livelihood for the community in rural areas. The proposed integrated farming system improves agricultural productivity and environmental and sanitation conditions, minimizes the amount of waste, and increases the family income up to 41.55%. Several waste types can be recycled and transformed into valuable products, such as energy for cooking, organic fertilizer for crops, and cattle feed for breeding. Wastewater effluent from the biogas tank can be treated by biochar and results show that it then meets the standards for irrigation purposes. Also, the waste flow from cattle breeding supplies enough nutrients to cultivate plants, and the plants grown supply are adequate food for the 30 cows living on the farm. This research shows that the use of an integrated farming system could achieve zero-emission goal. Thereby, it provides a sustainable livelihood for cattle breeding family farms. The proposed integrated cattle breeding and cultivation system improves agricultural productivity, environmental and increases the farmer income up to 41.55%.
A continuous increase in the amount of greenhouse gases (GHGs) is causing serious threats to the environment and life on the earth, and CO2 is one of the major candidates. Reducing the excess CO2 by converting into industrial products could be beneficial for the environment and also boost up industrial growth. In particular, the conversion of CO2 into methanol is very beneficial as it is cheaper to produce from biomass, less inflammable, and advantageous to many industries. Application of various plants, algae, and microbial enzymes to recycle the CO2 and using these enzymes separately along with CO2-phillic materials and chemicals can be a sustainable solution to reduce the global carbon footprint. Materials such as MOFs, porphyrins, and nanomaterials are also used widely for CO2 absorption and conversion into methanol. Thus, a combination of enzymes and materials which convert the CO2 into methanol could energize the CO2 utilization. The CO2 to methanol conversion utilizes carbon better than the conventional syngas and the reaction yields fewer by-products. The methanol produced can further be utilized as a clean-burning fuel, in pharmaceuticals, automobiles and as a general solvent in various industries etc. This makes methanol an ideal fuel in comparison to the conventional petroleum-based ones and it is advantageous for a safer and cleaner environment. In this review article, various aspects of the circular economy with the present scenario of environmental crisis will also be considered for large-scale sustainable biorefinery of methanol production from atmospheric CO2.
Soil contamination by emerging pollutants tetrabromobisphenol A (TBBPA) and microplastics has become a global environmental issue in recent years. However, little is known about the effect of microplastics on degradation of TBBPA in soil, especially aged microplastics. In this study, the effect of aged polystyrene (PS) microplastics on the degradation of TBBPA in soil and the mechanisms were investigated. The results suggested that the aged microplastics exhibited a stronger inhibitory effect on the degradation of TBBPA in soil than the pristine microplastics, and the degradation efficiency of TBBPA decreased by 21.57% at the aged microplastic content of 1%. This might be related to the higher TBBPA adsorption capacity of aged microplastics compared to pristine microplastics. Aged microplastics strongly altered TBBPA-contaminated soil properties, reduced oxidoreductase activity and affected microbial community composition. The decrease in soil oxidoreductase activity and relative abundance of functional microorganisms (e.g., Bacillus, Pseudarthrobacter and Sphingomonas) caused by aged microplastics interfered with metabolic pathways of TBBPA. This study indicated the importance the risk assessment and soil remediation for TBBPA-contaminated soil with aged microplastics.
With rapid growing world population and increasing demand for natural resources, the production of sufficient food, feed for protein and fat sources and sustainable energy presents a food insecurity challenge globally. Insect biorefinery is a concept of using insect as a tool to convert biomass waste into energy and other beneficial products with concomitant remediation of the organic components. The exploitation of insects and its bioproducts have becoming more popular in recent years. This review article presents a summary of the current trend of insect-based industry and the potential organic wastes for insect bioconversion and biorefinery. Numerous biotechnological products obtained from insect biorefinery such as biofertilizer, animal feeds, edible foods, biopolymer, bioenzymes and biodiesel are discussed in the subsequent sections. Insect biorefinery serves as a promising sustainable approach for waste management while producing valuable bioproducts feasible to achieve circular bioeconomy.
The removal of antibiotics and resistance genes in wastewater treatment plants has attracted widespread attention, but the potential role of residual antibiotics in the disposal of waste activated sludge (WAS) has not been clearly understood. In this study, the effect of roxithromycin (ROX) on volatile fatty acid (VFA) recovery from WAS anaerobic fermentation was investigated. The experimental results showed that ROX made a positive contribution to the production of VFAs. With the increase of ROX dosages from 0 to 100 mg/kg TSS, the maximum accumulation of VFAs increased from 295 to 610 mg COD/L. Mechanism studies revealed that ROX promoted the solubilization of WAS by facilitating the disruption of extracellular polymeric substances. In addition, ROX enhanced the activity of acetate kinase and inhibited the activities of α-glucosidase and coenzyme F420, and showed a stronger inhibitory effect on methane production than the hydrolysis process, thus resulting in an increase in VFA accumulation. These findings provide a new insight for the role of antibiotics in anaerobic fermentation of WAS.
The use of agro-biowaste compost fertilizers in agriculture is beneficial from technical, financial, and environmental perspectives. Nevertheless, the physical, mechanical, and agronomical attributes of agro-biowaste compost fertilizers should be engineered to reduce their storage, handling, and utilization costs and environmental impacts. Pelletizing and drying are promising techniques to achieve these goals. In the present work, the effects of process parameters, including compost particle size/moisture content, pelletizing compression ratio, and drying air temperature/velocity, were investigated on the density, specific crushing energy, and moisture diffusion of agro-biowaste compost pellet. The Taguchi technique was applied to understand the effects of independent parameters on the output responses, while the optimal pellet properties were found using the iterative thresholding method. The soil and plant (sweet basil) response to the optimal biocompost pellet was experimentally evaluated. The farm application of the optimal pellet was also compared with the untreated agro-biowaste compost using the life cycle assessment approach to investigate the potential environmental impact mitigation of the pelletizing and drying processes. Generally, the compost moisture content was the most influential factor on the density and specific crushing energy of the dried pellet, while the moisture diffusion of the wet pellet during the drying process was significantly influenced by the pelletizing compression ratio. The density, specific crushing energy, and moisture diffusion of agro-biowaste compost pellet at the optimal conditions were 1242.49 kg/m3, 0.5054 MJ/t, and 8.2 × 10-8 m2/s, respectively. The optimal biocompost pellet could release 80% of its nitrogen content evenly over 98 days, while this value was 28 days for the chemical urea fertilizer. Besides, the optimal pellet could significantly improve the agronomical attributes of the sweet basil plant compared with the untreated biocompost. The applied strategy could collectively mitigate the weighted environmental impact of farm application of the agro-biowaste compost by more than 63%. This reduction could be attributed to the fact that the pelletizing-drying processes could avoid methane emissions from the untreated agro-biowaste compost during the farm application. Overall, pelletizing-drying of the agro-biowaste compost could be regarded as a promising strategy to improve the environmental and agronomical performance of farm application of organic biofertilizers.
The dispersion of hyperaccumulators used in the phytoremediation process has caused environmental concerns because of their heavy metal (HM) richness. It is important to reduce the environmental risks and prevent the HM to reenter the ecological cycle and thereby the human food web. In this work, supercritical water gasification (SCWG) technology was used to convert Sedum plumbizincicola into hydrogen (H2) gas and to immobilize HMs into biochar. The H2 production correlated with temperature ranging from 380 to 440 ℃ with the highest H2 yield of 2.74 mol/kg at 440 ℃. The free-radical reaction and steam reforming reaction at high temperatures were likely to be the mechanism behind the H2 production. The analyses of bio-oil by the Gas Chromatography-Mass Spectrometer (GC-MS) and Nuclear magnetic resonance spectroscopy (NMR) illustrated that the aromatic compounds, oxygenated compounds, and phenols were degraded into H2-rich gases. The increase of temperature enhanced the HM immobilization efficiency (>99.2 % immobilization), which was probably due to the quickly formed biochar that helped adsorb HMs. Then those HMs were chemically converted into stable forms through complexation with inorganic components on biochar, e.g., silicates, SiO2, and Al2O3. Consequently, the SCWG process was demonstrated as a promising approach for dispersing hyperaccumulators by immobilizing the hazardous HMs into biochar and simultaneously producing value-added H2-rich gases.
Biochar has been considered as a potential tool to mitigate soil ammonia (NH3) volatilization and greenhouse gases (GHGs) emissions in recent years. However, the aging effect of biochar on soils remains elusive, which introduces uncertainty on the effectiveness of biochar to mitigate global warming in a long term. Here, a meta-analysis of 22 published works of literature with 217 observations was conducted to systematically explore the aging effect of biochar on soil NH3 and GHGs emissions. The results show that, in comparison with the fresh biochar, the aging makes biochar more effective to decrease soil NH3 volatilization by 7% and less risk to contribute CH4 emissions by 11%. However, the mitigation effect of biochar on soil N2O emissions is decreased by 15% due to aging. Additionally, aging leads to a promotion effect on soil CO2 emissions by 25% than fresh biochar. Our findings suggest that along with aging, particularly the effect of artificial aging, biochar could further benefit the alleviation of soil NH3 volatilization, whereas its potential role to mitigate global warming may decrease. This study provides a systematic assessment of the aging effect of biochar to mitigate soil NH3 and GHGs, which can provide a scientific basis for the sustainable green development of biochar application.
Household food waste (FW) was converted into biohydrogen-rich gas via steam gasification over Ni and bimetallic Ni (Cu-Ni and Co-Ni) catalysts supported on mesoporous SBA-15. The effect of catalyst method on steam gasification efficiency of each catalyst was investigated using incipient wetness impregnation, deposition precipitation, and ethylenediaminetetraacetic acid metal complex impregnation methods. H2-TPR confirmed the synergistic interaction of the dopants (Co and Cu) and Ni. Furthermore, XRD and HR-TEM revealed that the size of the Ni particle varied depending on the method of catalyst synthesis, confirming the formation of solid solutions in Co- or Cu-doped Ni/SBA-15 catalysts due to dopant insertion into the Ni. Notably, the exceptional activity of the Cu-Ni/SBA-15-EMC catalyst in FW steam gasification was attributed to the fine distribution of the concise Ni nanoparticles (9 nm), which resulted in the highest hydrogen selectivity (62 vol%), gas yield (73.6 wt%). Likewise, Cu-Ni solid solution decreased coke to 0.08 wt%.
CO2 sequestration into coalbed seams is one of the practical routes for mitigating CO2 emissions. The adsorption mechanisms of CO2 onto Malaysian coals, however, are not yet investigated. In this research CO2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO2 adsorption capacity of 1.3 mmol g-1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below -13 kJ mol-1, indicating that adsorption of CO2 onto coals occurred through physisorption. The results demonstrate that CO2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO2 injection into Malaysian coalbed seams.