Publications by authors named "Wei-Hsin Chen"

113 Publications

COVID-19 and industrial waste mitigation via thermochemical technologies towards a circular economy: A state-of-the-art review.

J Hazard Mater 2022 02 16;423(Pt B):127215. Epub 2021 Sep 16.

Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand.

The increasing awareness of waste circular economy has motivated valorization strategies for minimizing resource consumption and waste production in the private sector. With the rise of various industrial wastes and with the emergence of COVID-19 wastes, a sustainable approach is needed to mitigate the growing concern about wastes. Thermochemical treatment technologies in the form of direct combustion, torrefaction, pyrolysis, and gasification have been identified to have vital roles in the value-creation of various waste streams. Moreover, the alignment of thermochemical processes for waste mitigation concerning the circular economy framework needs to be established. Accordingly, a comprehensive review of the different thermochemical treatment options for industrial and the novel COVID-19 medical wastes streams is conducted in this study. This review focuses on highlighting the instrumental role of thermochemical conversion platforms in achieving a circular economy in the industrial sector. Various strategies in waste mitigation through various thermochemical processes such as management, recovery, reduction, and treatment are discussed. The results show that thermochemical technologies are beneficial in addressing the sustainability concerns on mitigating wastes from the industrial sector and wastes brought by the COVID-19 pandemic. This also includes the current issues faced as well as future perspectives of the thermochemical conversion technologies.
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http://dx.doi.org/10.1016/j.jhazmat.2021.127215DOI Listing
February 2022

Mesoporous and adsorption behavior of algal biochar prepared via sequential hydrothermal carbonization and ZnCl activation.

Bioresour Technol 2021 Nov 17:126351. Epub 2021 Nov 17.

Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City 81157, Taiwan. Electronic address:

In this study, biochar derived from brown algal Ascophyllum nodosum was synthesized through hydrothermal carbonization (HTC) coupling with ZnCl chemical activation and applied as a sustainable adsorbent for antibiotic removal from water exemplified by ciprofloxacin (CIP). Various surface analysis techniques such as Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and zeta potential were used to clarify the surface properties of prepared biochars. The adsorption performance of biochars was investigated using batch adsorption experiments with a variety of parameters (initial pH, ionic types, temperature and water matrixes). The application of prepared biochar in CIP removal showed a good result of adsorption capacity (150-400 mg g) in different conditions. Overall, algal biochars, as a product recycled from biowaste, demonstrated a novel and promising adsorbent for effective and sustainable method for removal of antibiotics from water.
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http://dx.doi.org/10.1016/j.biortech.2021.126351DOI Listing
November 2021

Synthesis of 5-hydroxymethylfurfural from glucose, fructose, cellulose and agricultural wastes over sulfur-doped peanut shell catalysts in ionic liquid.

Chemosphere 2021 Nov 9:132829. Epub 2021 Nov 9.

Environmental Engineering Program, National Graduate School of Engineering, University of the Philippines Diliman, Quezon City, 1101, Philippines; Energy Engineering Program, National Graduate School of Engineering, University of the Philippines Diliman, Quezon City, 1101, Philippines; Department of Chemical Engineering, University of the Philippines Diliman, Quezon City, 1101, Philippines. Electronic address:

In this study, waste peanut shells were sulfur-impregnated and used as acid catalysts in the presence of an ionic liquid for the conversion of fructose, glucose, and cellulose into 5-hydroxymethylfurfural, a useful chemical intermediate for biofuel production. Effects of sulfur-doping duration (1 h and 5 h), solvent type and proportion, reaction temperature (130 °C, 140 °C, and 150 °C), time (30-240 min), catalyst-to-substrate ratio (1-2.5 m/m), and agricultural residue (peanut shell, Canada wheat straw, water hyacinth, stalk, and reed) on HMF yields were investigated. Monophasic and biphasic ionic liquids such as [amim]Cl, [bmim]HSO, and [emim]Cl were employed in combination with choline chloride and dimethyl sulfoxide to improve HMF yields. Results show that peanut shells subjected to prolonged sulfur impregnation produced higher HMF yields. At 130 °C and 2 h, HMF yields from fructose and glucose reached 94.6% and 55.1%, respectively. Higher reaction temperatures improved HMF yields and accelerated conversion rates for the sugar substrates. Moreover, HMF production from waste biomass namely, peanut shells, peanut stalk, Canadian wheat straw, reed, and water hyacinth were examined in separate one-pot catalytic reactions. Overall, the study showed the effectiveness of sulfur-doped peanut shells as solid acid catalysts for the synthesis of HMF from various sources and the results may be used in designing large-scale production of furanic biofuel precursors from agricultural wastes.
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http://dx.doi.org/10.1016/j.chemosphere.2021.132829DOI Listing
November 2021

Smart sustainable biorefineries for lignocellulosic biomass.

Bioresour Technol 2021 Oct 30:126215. Epub 2021 Oct 30.

Department of Chemical and Materials Engineering, Tunghai University, Taichung 407, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan.

Lignocellulosic biomass (LCB) is considered as a sustainable feedstock for a biorefinery to generate biofuels and other bio-chemicals. However, commercialization is one of the challenges that limits cost-effective operation of conventional LCB biorefinery. This article highlights some studies on the sustainability of LCB in terms of cost-competitiveness and environmental impact reduction. In addition, the development of computational intelligence methods such as Artificial Intelligence (AI) as a tool to aid the improvement of LCB biorefinery in terms of optimization, prediction, classification, and decision support systems. Lastly, this review examines the possible research gaps on the production and valorization in a smart sustainable biorefinery towards circular economy.
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http://dx.doi.org/10.1016/j.biortech.2021.126215DOI Listing
October 2021

Liquid hot water as sustainable biomass pretreatment technique for bioenergy production: A review.

Bioresour Technol 2021 Oct 26;344(Pt A):126207. Epub 2021 Oct 26.

Institute of Engineering, Ho Chi Minh city University of Technology (HUTECH), Ho Chi Minh city, Vietnam. Electronic address:

In recent years, lignocellulosic biomass has emerged as one of the most versatile energy sources among the research community for the production of biofuels and value-added chemicals. However, biomass pretreatment plays an important role in reducing the recalcitrant properties of lignocellulose, leading to superior quality of target products in bioenergy production. Among existing pretreatment techniques, liquid hot water (LHW) pretreatment has several outstanding advantages compared to others including minimum formation of monomeric sugars, significant removal of hemicellulose, and positive environmental impacts; however, several constraints of LHW pretreatment should be clarified. This contribution aims to provide a comprehensive analysis of reaction mechanism, reactor characteristics, influencing factors, techno-economic aspects, challenges, and prospects for LHW-based biomass pretreatment. Generally, LHW pretreatment could be widely employed in bioenergy processing from biomass, but circular economy-based advanced pretreatment techniques should be further studied in the future to achieve maximum efficiency, and minimum cost and drawbacks.
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http://dx.doi.org/10.1016/j.biortech.2021.126207DOI Listing
October 2021

Progress in thermochemical conversion of aquatic weeds in shellfish aquaculture for biofuel generation: Technical and economic perspectives.

Bioresour Technol 2021 Oct 25;344(Pt A):126202. Epub 2021 Oct 25.

Henan Province Engineering Research Center for Biomass Value-Added Products, School of Forestry, Henan Agricultural University, Zhengzhou, Henan 450002, China; Higher Institution Centre of Excellence (HICoE), Institute of Tropical Aquaculture and Fisheries (Akuatrop), Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia. Electronic address:

Rapid growth of aquatic weeds in treatment pond poses undesirable challenge to shellfish aquaculture, requiring the farmers to dispose these weeds on a regular basis. This article reviews the potential and application of various aquatic weeds for generation of biofuels using recent thermochemical technologies (torrefaction, hydrothermal carbonization/liquefaction, pyrolysis, gasification). The influence of key operational parameters for optimising the aquatic weed conversion efficiency was discussed, including the advantages, drawbacks and techno-economic aspects of the thermochemical technologies, and their viability for large-scale application. Via extensive study in small and large scale operation, and the economic benefits derived, pyrolysis is identified as a promising thermochemical technology for aquatic weed conversion. The perspectives, challenges and future directions in thermochemical conversion of aquatic weeds to biofuels were also reviewed. This review provides useful information to promote circular economy by integrating shellfish aquaculture with thermochemical biorefinery of aquatic weeds rather than disposing them in landfills.
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http://dx.doi.org/10.1016/j.biortech.2021.126202DOI Listing
October 2021

Recent advances in lignocellulosic biomass for biofuels and value-added bioproducts - A critical review.

Bioresour Technol 2021 Oct 25:126195. Epub 2021 Oct 25.

Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science, Chulalongkorn University, Pathum Wan, Bangkok 10330, Thailand; Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand.

Lignocellulosic biomass is a highly renewable, economical, and carbon-neutral feedstock containing sugar-rich moieties that can be processed to produce second-generation biofuels and bio-sourced compounds. However, due to their heterogeneous multi-scale structure, the lignocellulosic materials have major limitations to valorization and exhibit recalcitrance to saccharification or hydrolysis by enzymes. In this context, this review focuses on the latest methods available and state-of-the-art technologies in the pretreatment of lignocellulosic biomass, which aids the disintegration of the complex materials into monomeric units. In addition, this review deals with the genetic engineering techniques to develop advanced strategies for fermentation processes or microbial cell factories to generate desired products in native or modified hosts. Further, it also intends to bridge the gap in developing various economically feasible lignocellulosic products and chemicals using biorefining technologies.
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http://dx.doi.org/10.1016/j.biortech.2021.126195DOI Listing
October 2021

Integrating Taguchi method and artificial neural network for predicting and maximizing biofuel production via torrefaction and pyrolysis.

Bioresour Technol 2022 Jan 15;343:126140. Epub 2021 Oct 15.

Department of Mechanical Engineering, Graphic Era Deemed to be University, Dehradun, Uttarakhand, India.

Artificial neural network (ANN) is one kind of artificial intelligence in the computing system that aims to process information as the way neurons in the human brain. In this study, the combination of the Taguchi method and ANN are used to maximize and predict biofuel yield from spent mushroom substrate torrefaction and pyrolysis via microwave irradiation. The Taguchi method is utilized to design the multiple factors (particle size, catalyst, power, and magnetic agent) and levels of experiment parameters. The highest total biofuel yield (biochar + bio-oil) is 99.42%, accomplished by a combination of 355 µm particle size, 300 mg·g-SMS catalyst, 900 W power, and 300 mg·g-SMS magnetic agent. ANN with one hidden layer shows the outstanding linear regression predictions for the highest biofuel yields (biochar 0.9999 and bio-oil 0.9998). This high linear regression indicates that ANN with a quick propagation algorithm is an appropriate approach for predicting biofuel conversion.
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http://dx.doi.org/10.1016/j.biortech.2021.126140DOI Listing
January 2022

Co-pyrolysis of microalgae and other biomass wastes for the production of high-quality bio-oil: Progress and prospective.

Bioresour Technol 2021 Oct 6:126096. Epub 2021 Oct 6.

Korea Biochar Research Center, APRU Sustainable Waste Management Program & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea.

Microalgae are the most prospective raw materials for the production of biofuels, pyrolysis is an effective method to convert biomass into bioenergy. However, biofuels derived from the pyrolysis of microalgae exhibit poor fuel properties due to high content of moisture and protein. Co-pyrolysis is a simple and efficient method to produce high-quality bio-oil from two or more materials. Tires, plastics, and bamboo waste are the optimal co-feedstocks based on the improvement of yield and quality of bio-oil. Moreover, adding catalysts, especially CaO and Cu/HZSM-5, can enhance the quality of bio-oil by increasing aromatics content and decreasing oxygenated and nitrogenous compounds. Consequently, this paper provides a critical review of the production of bio-oil from co-pyrolysis of microalgae with other biomass wastes. Meanwhile, the underlying mechanism of synergistic effects and the catalytic effect on co-pyrolysis are discussed. Finally, the economic viability and prospects of microalgae co-pyrolysis are summarized.
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http://dx.doi.org/10.1016/j.biortech.2021.126096DOI Listing
October 2021

Fast hydropyrolysis of biomass Conversion: A comparative review.

Bioresour Technol 2021 Dec 1;342:126067. Epub 2021 Oct 1.

School of Environmental Engineering, University of Seoul, Seoul 02504, Republic of Korea. Electronic address:

Recent studies show that fast hydropyrolysis (i.e., pyrolysis under hydrogen atmosphere operating at a rapid heating rate) is a promising technology for the conversion of biomass into liquid fuels (e.g., bio-oil and C hydrocarbons). This pyrolysis approach is reported to be more effective than conventional fast pyrolysis in producing aromatic hydrocarbons and also lowering the oxygen content of the bio-oil obtained compared to hydrodeoxygenation (a common bio-oil upgrading method). Based on current literature, various non-catalytic and catalytic fast hydropyrolysis processes are reviewed and discussed. Efforts to combine fast hydropyrolysis and hydrotreatment process are also highlighted. Points to be considered for future research into fast hydropyrolysis and pending challenges are also discussed.
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http://dx.doi.org/10.1016/j.biortech.2021.126067DOI Listing
December 2021

Emerging technologies for sustainable production of biohydrogen production from microalgae: A state-of-the-art review of upstream and downstream processes.

Bioresour Technol 2021 Dec 28;342:126057. Epub 2021 Sep 28.

Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan. Electronic address:

Biohydrogen (BioH) is considered as one of the most environmentally friendly fuels and a strong candidate to meet the future demand for a sustainable source of energy. Presently, the production of BioH from photosynthetic organisms has raised a lot of hopes in the fuel industry. Moreover, microalgal-based BioH synthesis not only helps to combat current global warming by capturing greenhouse gases but also plays a key role in wastewater treatment. Hence, this manuscript provides a state-of-the-art review of the upstream and downstream BioH production processes. Different metabolic routes such as direct and indirect photolysis, dark fermentation, photofermentation, and microbial electrolysis are covered in detail. Upstream processes (e.g. growth techniques, growth media) also have a great impact on BioH productivity and economics, which is also explored. Technical and scientific obstacles of microalgae BioH systems are finally addressed, allowing the technology to become more innovative and commercial.
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http://dx.doi.org/10.1016/j.biortech.2021.126057DOI Listing
December 2021

Impacts of COVID-19 pandemic on the global energy system and the shift progress to renewable energy: Opportunities, challenges, and policy implications.

Energy Policy 2021 Jul 28;154:112322. Epub 2021 Apr 28.

Institute of Maritime, Ho Chi Minh City University of Transport, Viet Nam.

Being declared a global emergency, the COVID-19 pandemic has taken many lives, threatened livelihoods and businesses around the world. The energy industry, in particular, has experienced tremendous pressure resulting from the pandemic. In response to such a challenge, the development of sustainable resources and renewable energy infrastructure has demonstrated its potential as a promising and effective strategy. To sufficiently address the effect of COVID-19 on renewable energy development strategies, short-term policy priorities should be identified, while mid-term and long-term action plans should be formulated in achieving the well-defined renewable energy targets and progress towards a more sustainable energy future. In this review, opportunities, challenges, and significant impacts of the COVID-19 pandemic on current and future sustainable energy strategies were analyzed in detail; while drawing from experiences in identifying reasonable behaviors, orientating appropriate actions, and policy implications on the sustainable energy trajectory were also mentioned. Indeed, the question is that whether the COVID-19 pandemic will kill us or provide us with a precious lesson on future sustainable energy development.
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http://dx.doi.org/10.1016/j.enpol.2021.112322DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8455103PMC
July 2021

Engineered macroalgal and microalgal adsorbents: Synthesis routes and adsorptive performance on hazardous water contaminants.

J Hazard Mater 2022 Feb 16;423(Pt A):126921. Epub 2021 Aug 16.

Korea Biochar Research Center, APRU Sustainable Waste Management Program & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.

Colourants, micropollutants and heavy metals are regarded as the most notorious hazardous contaminants found in rivers, oceans and sewage treatment plants, with detrimental impacts on human health and environment. In recent development, algal biomass showed great potential for the synthesis of engineered algal adsorbents suitable for the adsorptive management of various pollutants. This review presents comprehensive investigations on the engineered synthesis routes focusing mainly on mechanical, thermochemical and activation processes to produce algal adsorbents. The adsorptive performances of engineered algal adsorbents are assessed in accordance with different categories of hazardous pollutants as well as in terms of their experimental and modelled adsorption capacities. Due to the unique physicochemical properties of macroalgae and microalgae in their adsorbent forms, the adsorption of hazardous pollutants was found to be highly effective, which involved different mechanisms such as physisorption, chemisorption, ion-exchange, complexation and others depending on the types of pollutants. Overall, both macroalgae and microalgae not only can be tailored into different forms of adsorbents based on the applications, their adsorption capacities are also far more superior compared to the conventional adsorbents.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126921DOI Listing
February 2022

Microwave-assisted gasification of biomass for sustainable and energy-efficient biohydrogen and biosyngas production: A state-of-the-art review.

Chemosphere 2022 Jan 25;287(Pt 1):132014. Epub 2021 Aug 25.

Korea Biochar Research Center, APRU Sustainable Waste Management & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.

Biohydrogen and biosyngas are among the sustainable bioenergy products from biomass resources through gasification. Microwave-assisted gasification (MAG) is still a novel technology, but it is definitely a promising conversion technology to achieve a sustainable bioeconomy. Although this technology shows a massive potential to be fully implemented in the near future, the selectivity and efficiency of biohydrogen and syngas production still need enhancements and further research to secure a cost-effective and energy-efficient industrialization. This article comprehensively reviews the regular, microwave-induced plasma, and catalytic MAG systems in relation to their biohydrogen and biosyngas production, carbon conversion efficiency, and tar removal while discussing the significance of optimal operating conditions and considerations in the gasification system design. Several perspectives such as benefits, challenges, numerical simulations, and scalable opportunities are also explored to provide factual insights for further research and industrial application.
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http://dx.doi.org/10.1016/j.chemosphere.2021.132014DOI Listing
January 2022

Aerosol deposition and airflow dynamics in healthy and asthmatic human airways during inhalation.

J Hazard Mater 2021 08 20;416:125856. Epub 2021 Apr 20.

Department of Environmental Engineering, National Cheng Kung University, Tainan 701, Taiwan.

Inhalation of aerosols such as pharmaceutical aerosols or virus aerosol uptake is of great concern to the human population. To elucidate the underlying aerosol dynamics, the deposition fractions (DFs) of aerosols in healthy and asthmatic human airways of generations 13-15 are predicted. The Navier-stokes equations governing the gaseous phase and the discrete phase model for particles' motion are solved using numerical methods. The main forces responsible for deposition are inertial impaction forces and complex secondary flow velocities. The curvatures and sinusoidal folds in the asthmatic geometry lead to the formation of complex secondary flows and hence higher DFs. The intensities of complex secondary flows are strongest at the generations affected by asthma. The DF in the healthy airways is 0%, and it ranges from 1.69% to 52.93% in the asthmatic ones. From this study, the effects of the pharmaceutical aerosol particle diameters in the treatment of asthma patients can be established, which is conducive to inhibiting the inflammation of asthma airways. Furthermore, with the recent development of COVID-19 which causes pneumonia, the predicted physics and effective simulation methods of bioaerosols delivery to asthma patients are vital to prevent the exacerbation of the chronic ailment and the epidemic.
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http://dx.doi.org/10.1016/j.jhazmat.2021.125856DOI Listing
August 2021

Ultra-low PCDD/F emissions and their particle size and mass distribution in a hazardous waste treatment system.

J Hazard Mater 2022 Feb 26;423(Pt A):127032. Epub 2021 Aug 26.

School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.

An integrated gasification-flameless combustion-melting process was approached by a twin-cyclonic flow in a hazardous waste thermal treatment plant. A series of advanced scrubber, cyclonic demister, activated carbon adsorption, and baghouse processes were equipped for the end-of-pipe treatment. The untreated filterable particulate matter, CO, and NOx levels were only 283, 47.1, and 15.9 mg/Nm, indicating the flameless combustion inhibited their formation by narrowing the post-combustion zone. The filterable particle mass-size distribution was equally contributed by nucleation, accumulation, and coarse formations, while their number concentration was predominated by nucleation (99.6%). That could enhance the adsorption of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) on ultrafine particles. Both total mass and toxic equivalent concentrations of PCDD/Fs were reduced 99.9% by the new air pollution control system when a slight reformation occurred during scrubbing. However, the escaped PCDD/Fs were mainly distributed on the ultrafine particles, which should be further inhibited by either increasing their sizes or equipping backup filtrations. Finally, the new process concentrates the PCDD/Fs into the scrubbing sludge, which could be recirculated back into the thermal process. This study not only reveals the emission risk of the ultrafine particle-bound PCDD/Fs, but also provides an effective process to remove them for industrial application.
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http://dx.doi.org/10.1016/j.jhazmat.2021.127032DOI Listing
February 2022

Assessment of the emission factors for potentially toxic elements from coal-fired boilers and sintering furnaces in a steel production plant.

Sci Total Environ 2021 Oct 7;792:148329. Epub 2021 Jun 7.

Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan.

The emission factor (EF), the weight of potentially toxic elements (PTEs) per unit energy or weight of sinter produced were evaluated for coal-fired boilers and sintering furnaces integrated in a steel plant. From three coal-fired boilers, 15 samples were taken while 22 samples were taken from four sintering furnaces. Investigations were performed on the EF of lead, cadmium, mercury, arsenic and chromium (VI). The coefficient of variance for the first 3 samples from each PTE was used to decide whether 2 more samples were necessary for the investigation. Three samples were sufficient for Cr (VI), however, 5 samples were required for Pb, Cd, Hg, and As, since the variances in concentrations of the first three samples exceeded 20%. The ranges for the ratio of the laboratory-based EF to the default EF applied by the Environment Protection Administration (EPA Taiwan) for Pb, Cd, Hg, and As for the coal-fired boiler were 0.08-0.013, 0.014-0.017, 0.019-0.033, 0.047-0.066 and for the sintering furnaces were 0.059-0.232, 0.05-0.151, 0.05-0.364, and 0.067-0.824. The ratio for Cr (VI)- was constant at 0.005 for all the coal fired boilers while it ranged from 0.057-0.709 for the sintering furnaces. Whilst source identification, enrichment factors, and spatial distributions for PTEs are often studied, laboratory-based investigations on the EFs for PTEs from industrial plants are rarely performed. This study filled the information gap and compared the obtained EFs with the EPA default values. To avoid overcharging industrial plants equipped with the best available technology for emission control, the EPA should apply field investigations and laboratory-based EFs instead of the default EPA EFs to calculate air pollution fees. Insights from this investigation can be applied to promote the adoption of appropriate air pollution control devices to cut down the emission of PTEs.
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http://dx.doi.org/10.1016/j.scitotenv.2021.148329DOI Listing
October 2021

Waste furniture gasification using rice husk based char catalysts for enhanced hydrogen generation.

Bioresour Technol 2021 Dec 21;341:125813. Epub 2021 Aug 21.

School of Environmental Engineering, University of Seoul, Seoul 02504, Republic of Korea. Electronic address:

Present study provides biohydrogen production methods from waste furniture via catalytic steam gasification with bio-char catalysts (raw char, KOH-activated char and steam-activated char). Total gas yield for the prepared chars was in the order of KOH-activated char > steam-activated char > raw char, whereas, H selectivity was in the sequence of raw char > steam-activated char > KOH-activated char. Though KOH-activated char showed the highest gas yield, highest H selectivity was obtained at the gasification experiment with raw char due to the large amount of Ca and K and its reasonable surface area (146.89 m/g). Although the activation of raw biochar results in the increase of gas yield, it has the negative effect on H generation due to the removal of alkali and alkaline earth metals for the KOH activated char and steam-activated char. This study shows that raw bio-char could be a potential solution for eco-friendly hydrogen production.
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http://dx.doi.org/10.1016/j.biortech.2021.125813DOI Listing
December 2021

Pretreatment, modification and applications of sewage sludge-derived biochar for resource recovery- A review.

Chemosphere 2022 Jan 21;287(Pt 1):131969. Epub 2021 Aug 21.

School of Mechanical Engineering, Beijing Institute of Technology, Beijing, 100081, China.

With the quick increase in industrialization and urbanization, a mass of sludge has been produced on the account of increased wastewater treatment facilities. Sewage sludge (SS) management has become one of the most crucial environmental problems because of the existence of various pollutants. However, SS is a carbon-rich material, which has favored novel technologies for biochar production, which can be utilized for dissimilar applications. This review systematically analyzes and summarizes the pretreatment, modification, and especially application of sewage sludge-derived biochar (SSBC), based on published literature. The comparative assessment of pretreatment technology such as pyrolysis, hydrothermal carbonization, combustion, deashing, and co-feeding is presented to appraise their appropriateness for SS resource availability and the production of SSBC. In addition, the authors summarize and analyze the current modification methods and divide them into two categories: physical properties and surface chemical modifications. The applications of SSBC as absorbent, catalyst and catalyst support, electrode materials, gas storage, soil amendment, and sold biofuel are reviewed in detail. Furthermore, the discussion about the existing problems and the direction of future efforts are presented at the end of each section to envisage SS as a promising opportunity for resources rather than a nuisance.
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http://dx.doi.org/10.1016/j.chemosphere.2021.131969DOI Listing
January 2022

Pyrolysis of sewage sludge for sustainable biofuels and value-added biochar production.

J Environ Manage 2021 Nov 11;298:113450. Epub 2021 Aug 11.

Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Energy and Environmental Engineering, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, 600077, India.

The study deals with the pyrolysis of sewage sludge to produce eco-friendly and sustainable fuels along with value-added biochar products. The experiments were conducted in a fixed-bed cylindrical glass reactor in the temperature range of 250-700 °C and achieved the product yield of 22.4 wt% bio-oil, 18.9 wt % pyrolysis gases, and 58.7 wt% biochar at 500 °C optimum temperature. The chemical composition of bio-oil was investigated by gas chromatograph-mass spectroscopy and fourier transformation infrared techniques. The ASTM standard procedures were used to assess the fuel qualities of bio-oil, and they were found to be satisfactory. Bio-oil has a greater H/C ratio (3.49) and a lower O/C ratio (1.10), indicating that it is suitable for engine use. The gas chromatographic analysis of pyrolysis gases confirmed the presence of 41.16 wt % combustible gases, making it suitable for use in spark-ignition engines. X-ray fluorescence analysis of biochar showed that it had a good amount of carbon, nitrogen, phosphorus, and potassium along with some micro-and macro-nutrient which proves its potential to utilize as organic manure in the agriculture sector. In addition, the data obtained from the TGA analysis during the pyrolysis of sewage sludge was applied to calculate kinetic parameters via the Coats-Redfern method.
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http://dx.doi.org/10.1016/j.jenvman.2021.113450DOI Listing
November 2021

Removal of methylene blue from wastewater using ternary nanocomposite aerogel systems: Carboxymethyl cellulose grafted by polyacrylic acid and decorated with graphene oxide.

J Hazard Mater 2022 01 31;421:126752. Epub 2021 Jul 31.

Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan.

In this study, environmentally-friendly nanocomposite hydrogels were fabricated. These hydrogels consisted of semi-interpenetrating networks of carboxymethyl cellulose (CMC) molecules grafted to polyacrylic acid (PAA), as an eco-friendly and non-toxic polymer with numerous carboxyl and hydroxyl functional groups, which were reinforced with different levels of graphene oxide particles (0.5, 1.5 or 3% wt). Field-emission electron scanning microscopy (FESEM) images indicated that the pore size of the nanocomposites decreased with increasing graphic oxide concentration. The presence of the graphic oxide increased the storage modulus and thermal stability of the nanocomposite hydrogels. The hydrogels had an adsorption capacity of 138 mg/g of a model cationic dye pollutant (methylene blue) after 250 min. Moreover, a reusability test showed that the adsorption capacity remained at around 90% after 9 cycles. Density functional theory (DFT) simulations suggested that the adsorption of methylene blue was mainly a result of π-π bonds, hydrogen bonds, and electrostatic interactions with graphene oxide. Our results indicated that the nanocomposite hydrogels fabricated in this study may be eco-friendly, stable, efficient, and reusable adsorbents for ionic pollutants in wastewater treatment.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126752DOI Listing
January 2022

Microplastic degradation as a sustainable concurrent approach for producing biofuel and obliterating hazardous environmental effects: A state-of-the-art review.

J Hazard Mater 2021 09 11;418:126381. Epub 2021 Jun 11.

Mechanical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922 Manila, Philippines.

As plastics have been omnipresent in society ever since their introduction in 1907, global plastic production has ballooned in the 20th century or the Plasticene Era (Plastic Age). After their useful life span, they deliberately or accidentally, are disposed of in the environment. Influenced by different factors, plastics undergo fragmentation into microplastics (MPs) and present hazardous risks in all life forms including humans. Obliterating MPs from the environment has been a global challenge for the attainment of sustainable development goals (SDGs). This review aims to present MP degradation routes with a great focus on the thermodegradation and biodegradation routes as sustainable routes of MP degradation. These routes can achieve the reduction and obliteration of MPs in the environment, thus reducing their hazardous effects. Moreover, the thermodegradation of MPs can produce fuels that help solve the dilemma of energy security. Overall, continued research and development are still needed, however, these novel approaches and the increased awareness of the microplastics' hazards give us hope that we can achieve sustainable development in the near future.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126381DOI Listing
September 2021

Oxidative torrefaction performance of microalga Nannochloropsis Oceanica towards an upgraded microalgal solid biofuel.

J Biotechnol 2021 Sep 21;338:81-90. Epub 2021 Jul 21.

School of Information, Systems and Modelling, Faculty of Engineering and Information Technology, University of Technology Sydney, NSW, 2007, Australia.

Microalgae are a promising feedstock for carbon-neutral biofuel production due to their superior cellular composition. Alternatively, oxidative torrefaction has been recognized as a potential thermochemical technique for microalgal solid biofuel upgrading. Herein, by using microalga N. oceanica as a feedstock, several characterizations are adopted for evaluating the potential of oxidative torrefaction towards microalgal solid biofuel production. The oxidatively torrefied microalgae can be upgraded as lignite. After in-depth analysis, significant change in the surface microstructure of oxidatively torrefied microalgae is largely changed (via wrinkle and fragmentation) The hydrophobicity, thermal decomposition, thermal stability, and aromatization of oxidatively torrefied microalgae can be largely enhanced as the oxidative torrefaction severity increase. With the increasing torrefaction temperature, the hydrophobicity of oxidative torrefied microalgae gradually improved. The decomposition of C-2/3/5, and -OCH, the CO bonds of CHCO-, and the aromatization occurs via oxidative torrefaction according to the NMR analysis. For XPS analysis, torrefaction operation significantly decreases the carbide carbon and enhances the graphitization. As a result, the thermal stability of oxidatively torrefied microalgae is improved. Conclusively, the information obtained in this study can provide insights into the evaluation of oxidative torrefaction performance and fuel properties of microalgal solid biofuel, which may help accelerate the advancement of oxidative torrefaction industrialization.
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http://dx.doi.org/10.1016/j.jbiotec.2021.07.009DOI Listing
September 2021

Neuronal basis for pain-like and anxiety-like behaviors in the central nucleus of the amygdala.

Pain 2021 Jun 25. Epub 2021 Jun 25.

Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan Brain Research Center, National Yang-Ming University, Taipei, Taiwan.

Abstract: Chronic pain is often accompanied by anxiety and depression disorders. Amygdala nuclei play important roles in emotional responses, fear, depression, anxiety, and pain modulation. The exact mechanism of how amygdala neurons are involved in pain and anxiety is not completely understood. The central nucleus of the amygdala contains 2 major subpopulations of GABAergic neurons that express somatostatin (SOM+) or protein kinase Cδ (PKCδ+). In this study, we found about 70% of phosphorylated ERK-positive neurons colocalized with PKCδ+ neurons in the formalin-induced pain model in mice. Optogenetic activation of PKCδ+ neurons was sufficient to induce mechanical hyperalgesia without changing anxiety-like behavior in naïve mice. Conversely, chemogenetic inhibition of PKCδ+ neurons significantly reduced the mechanical hyperalgesia in the pain model. By contrast, optogenetic inhibition of SOM+ neurons induced mechanical hyperalgesia in naïve mice and increased phosphorylated ERK-positive neurons mainly in PKCδ+ neurons. Optogenetic activation of SOM+ neurons slightly reduced the mechanical hyperalgesia in the pain model but did not change the mechanical sensitivity in naïve mice. Instead, it induced anxiety-like behavior. Our results suggest that the PKCδ+ and SOM+ neurons in the central amygdala exert different functions in regulating pain-like and anxiety-like behaviors in mice.
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http://dx.doi.org/10.1097/j.pain.0000000000002389DOI Listing
June 2021

Energy balance of torrefied microalgal biomass with production upscale approached by life cycle assessment.

J Environ Manage 2021 Sep 8;294:112992. Epub 2021 Jun 8.

Mechanical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922, Manila, Philippines; Center for Engineering and Sustainable Development Research, De La Salle University, Manila, 0922, Philippines.

Torrefaction is a thermochemical process used to convert the biomass into solid fuel. In this study, torrefaction increased the raw microalgal biomass' energy content from 20.22 MJ⋅kg to 27.93 MJ⋅kg. To determine if more energy is produced than energy consumption from torrefaction, this study identified the energy balance of torrefied microalgal biomass production based on a life cycle approach. The energy analysis showed that, among all processes, torrefaction had the least amount of energy demand. The experimental setup, defined as scenario A, revealed that the principal source of energy demand, about 85%, was consumed on the microalgal growth using a photobioreactor system. A sensitivity analysis was also performed to determine the varying energy demand for torrefied microalgal biomass production. The different types of cultivation methods and various production scales were considered in scenarios B to D. Scenario D, which represented the commercial production-scale, the energy demand drastically decreased by 59.46% as compared to the experimental setup (scenario A). The open-pond cultivation system resulted in the least energy requirement, regardless of the production scale (scenarios B and C) among all the given scenarios. Unlike scenarios A and D, scenarios B and C identified the drying process to consume a high amount of energy. All the scenarios have shown an energy demand deficit. Therefore, efforts to decrease the energy demand on the upstream processes are needed to make the torrefied microalgal biomass a viable alternative energy source.
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http://dx.doi.org/10.1016/j.jenvman.2021.112992DOI Listing
September 2021

Supercritical water gasification (SCWG) as a potential tool for the valorization of phycoremediation-derived waste algal biomass for biofuel generation.

J Hazard Mater 2021 09 2;418:126278. Epub 2021 Jun 2.

Department of Chemical and Materials Engineering, College of Engineering, Tunghai University, Taichung, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, Taiwan; Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan. Electronic address:

Phycoremediation is an emerging technology, where algae-based processes were used to effectively remove nutrients, organic wastes, and toxic heavy metals from the polluted environment. The waste algal biomass obtained after phycoremediation, which may contain residual hazardous materials, could still be used as feedstock to produce biofuels/bioenergy preferably through thermochemical conversion technology. This review proposes a synergistic approach by utilizing the phycoremediation-derived algal biomass (PCDA) as feedstock for efficient hazardous waste treatment and clean energy generation via supercritical water gasification (SCWG). The review provides an in-depth study of catalytic, non-catalytic, and continuous SCWG of algal biomass, aiming to lay out the foundations for future study. In addition, the concepts of heat integration as well as water, nutrient, and CO recycling were introduced for a sustainable algae-to-biofuel process, which significantly enhances the overall energy and material efficiency of SCWG. The production of biofuel from algal biomass via other advanced gasification technologies, such as integration with other thermochemical conversion techniques, co-gasification, chemical looping gasification (CLG), and integrated gasification and combined cycle (IGCC) were also discussed. Furthermore, the discussion of kinetics and thermodynamics models, as well as life cycle and techno-economic assessments, appear to provide insights for future commercial applications.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126278DOI Listing
September 2021

Pyrolysis: An effective technique for degradation of COVID-19 medical wastes.

Chemosphere 2021 Jul 23;275:130092. Epub 2021 Feb 23.

Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Pathumwan, Bangkok, 10330, Thailand. Electronic address:

COVID-19 has led to the enormous rise of medical wastes throughout the world, and these have mainly been generated from hospitals, clinics, and other healthcare establishments. This creates an additional challenge in medical waste management, particularly in developing countries. Improper managing of medical waste may have serious public health issues and a significant impact on the environment. There are currently three disinfection technologies, namely incineration, chemical and physical processes, that are available to treat COVID-19 medical waste (CMW). This study focuses on thermochemical process, particularly pyrolysis process to treat the medical waste. Pyrolysis is a process that utilizes the thermal instability of organic components in medical waste to convert them into valuable products. Besides, the technique is environmentally friendly, more efficient and cost-effective, requires less landfill capacity, and causes lower pollution. The current pandemic situation generates a large amount of plastic medical wastes, which mainly consists of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and nylon. These plastic wastes can be converted into valuable energy products like oil, gas and char through pyrolysis process. This review provides detailed information about CMW handling, treatment, valuable product generation, and proper discharge into the open environment.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7901847PMC
July 2021

Green additive to upgrade biochar from spent coffee grounds by torrefaction for pollution mitigation.

Environ Pollut 2021 Sep 28;285:117244. Epub 2021 Apr 28.

School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, Nibong Tebal, 14300, Pulau Pinang, Malaysia.

A green approach using hydrogen peroxide (HO) to intensify the fuel properties of spent coffee grounds (SCGs) through torrefaction is developed in this study to minimize environmental pollution. Meanwhile, a neural network (NN) is used to minimize bulk density at different combinations of operating conditions to show the accurate and reliable model of NN (R = 0.9994). The biochar produced from SCGs torrefied at temperatures of 200-300 °C, duration of 30-60 min, and HO concentrations of 0-100 wt% is examined. The results reveal that the higher heating value (HHV) of biochar increases with rising temperature, duration, or HO concentration, whereas the bulk density has an opposite trend. The HHV, ignition temperature, and bulk density of biochar from torrefaction at 230 °C for 30 min with a 100 wt% HO solution (230-100%-TSCG) are 27.00 MJ∙kg, 292 °C, and 120 kg∙m, respectively. This HHV accounts for a 29% improvement compared to that of untorrefied SCG. The contact angle (126°), water activity (0.51 a), and moisture content (7.69%) of the optimized biochar indicate that it has higher resistance against biodegradation, and thereby can be stored longer. Overall, HO is a green treatment additive for SCGs solid fuel. This study has successfully produced biochar with greater HHV and low bulk density at low temperatures. The green additive development can effectively reduce environmental pollutants and upgrade wastes into resources, and achieve "3E", namely, environmental (non-polluting green additives), energy (biofuel), and circular economy (waste upgrade). In addition, the produced biochar has great potential in the fields of bioadsorbents and soil amendments.
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http://dx.doi.org/10.1016/j.envpol.2021.117244DOI Listing
September 2021

Valorization of sorghum distillery residue to produce bioethanol for pollution mitigation and circular economy.

Environ Pollut 2021 Sep 26;285:117196. Epub 2021 Apr 26.

Sugar Business Division, Taiwan Sugar Corporation, Tainan, 701, Taiwan.

This research aims to study the wet torrefaction (WT) and saccharification of sorghum distillery residue (SDR) towards hydrochar and bioethanol production. The experiments are designed by Box-Behnken design from response surface methodology where the operating conditions include sulfuric acid concentration (0, 0.01, and 0.02 M), amyloglucosidase concentration (36, 51, and 66 IU), and saccharification time (120, 180, and 240 min). Compared to conventional dry torrefaction, the hydrochar yield is between 13.24 and 14.73%, which is much lower than dry torrefaction biochar (yield >50%). The calorific value of the raw SDR is 17.15 MJ/kg, which is significantly enhanced to 22.36-23.37 MJ/kg after WT. When the sulfuric acid concentration increases from 0 to 0.02 M, the glucose concentration in the product increases from 5.59 g/L to 13.05 g/L. The prediction of analysis of variance suggests that the best combination to maximum glucose production is 0.02 M HSO, 66 IU enzyme concentration, and 120 min saccharification time, and the glucose concentration is 30.85 g/L. The maximum bioethanol concentration of 19.21 g/L is obtained, which is higher than those from wheat straw (18.1 g/L) and sweet sorghum residue (16.2 g/L). A large amount of SDR is generated in the kaoliang liquor production process, which may cause environmental problems if it is not appropriately treated. This study fulfills SDR valorization for hydrochar and bioenergy to lower environmental pollution and even achieve a circular economy.
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http://dx.doi.org/10.1016/j.envpol.2021.117196DOI Listing
September 2021

Renewable hydrogen production from biomass and wastes (ReBioH-2020).

Bioresour Technol 2021 Jul 17;331:125024. Epub 2021 Mar 17.

Department of Molecular Biosciences and Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.

Growing consumption of fossil reserves to meet the rising demand of energy has led to climate deterioration and simultaneous waste generation, urging modern society to find sustainable energy resource that can meet the growing energy demands and reduce greenhouse gas emissions and carbon footprints. In this aspect, hydrogen (H) is one of the most promising sustainable clean fuels that has gained significant interest in recent years. This article highlights the major research progress on biohydrogen production from renewable bioresources such as organic wastes, lignocellulosic biomass, algal biomass, and industrial wastewaters. It summarizes the research highlights of manuscripts published in the special issue (VSI: ReBioH2-2020), which contains twenty-two articles, including seven critical reviews and fifteen research articles, focusing on biotechnological and thermochemical routes for biohydrogen production from renewable feedstocks. The major findings of the research works in this special issue can be used as a road-map for sustainable renewable hydrogen production from bioresources.
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http://dx.doi.org/10.1016/j.biortech.2021.125024DOI Listing
July 2021
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