Aqueous amine enables sustainable monosaccharide, monophenol, and pyridine base coproduction in lignocellulosic biorefineries.

Thought-out utilization of entire lignocellulose is of great importance to achieving sustainable and cost-effective biorefineries. However, there is a trade-off between efficient carbohydrate utilization and lignin-to-chemical conversion yield. Here, we fractionate corn stover into a carbohydrate fraction with high enzymatic digestibility and reactive lignin with satisfactory catalytic depolymerization activity using a mild high-solid process with aqueous diethylamine (DEA). During the fractionation, in situ amination of lignin achieves extensive delignification, effective lignin stabilization, and dramatically reduced nonproductive adsorption of cellulase on the substrate. Furthermore, by designing a tandem fractionation-hydrogenolysis strategy, the dissolved lignin is depolymerized and aminated simultaneously to co-produce monophenolics and pyridine bases. The process represents the viable scheme of transforming real lignin into pyridine bases in high yield, resulting from the reactions between cleaved lignin side chains and amines. This work opens a promising approach to the efficient valorization of lignocellulose.

Monolignol Potential and Insights into Direct Depolymerization of Fruit and Nutshell Remains for High Value Sustainable Aromatics.

The inedible parts of nuts and stone fruits are low-cost and lignin-rich feedstock for more sustainable production of aromatic chemicals in comparison with the agricultural and forestry residues. However, the depolymerization performances on food-related biomass remains unclear, owing to the broad physicochemical variations from the edible parts of the fruits and plant species. In this study, the monomer production potentials of ten major fruit and nutshell biomass were investigated with comprehensive numerical information derived from instrumental analysis, such as plant cell wall chemical compositions, syringyl/guaiacyl (S/G ratios, and contents of lignin substructure linkages (ß-O-4, ß-ß, ß-5). A standardized one-pot reductive catalytic fractionation (RCF) process was applied to benchmark the monomer yields, and the results were statistically analyzed. Among all the tested biomass, mango endocarp provided the highest monolignol yields of 37.1 % per dry substrates. Positive S-lignin (70-84 %) resulted in higher monomer yield mainly due to more cleavable ß-O-4 linkages and less condensed C-C linkages. Strong positive relationships were identified between ß-O-4 and S-lignin and between ß-5 and G-lignin. The analytical, numerical, and experimental results of this study shed lights to process design of lignin-first biorefinery in food-processing industries and waste management works.

Bio-Inspired Microreactors Continuously Synthesize Glucose Precursor from CO2 with an Energy Conversion Efficiency 3.3 Times of Rice.

Excessive CO2 and food shortage are two grand challenges of human society. Directly converting CO2 into food materials can simultaneously alleviate both, like what green crops do in nature. Nevertheless, natural photosynthesis has a limited energy efficiency due to low activity and specificity of key enzyme D-ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). To enhance the efficiency, many prior studies focused on engineering the enzymes, but this study chooses to learn from the nature to design more efficient reactors. This work is original in mimicking the stacked structure of thylakoids in chloroplasts to immobilize RuBisCO in a microreactor using the layer-by-layer strategy, obtaining the continuous conversion of CO2 into glucose precursor at 1.9 nmol min-1 with enhanced activity (1.5 times), stability (≈8 times), and reusability (96% after 10 reuses) relative to the free RuBisCO. The microreactors are further scaled out from one to six in parallel and achieve the production at 15.8 nmol min-1 with an energy conversion efficiency of 3.3 times of rice, showing better performance of this artificial synthesis than NPS in terms of energy conversion efficiency. The exploration of the potential of mass production would benefit both food supply and carbon neutralization.

Application of roadside air purifiers in urban street canyons: A pilot-scale study in Hong Kong.

The implementation of roadside air purifiers has emerged as an effective active control measure to alleviate air pollution in urban street canyons. However, technical questions raised under real conditions remain challenging. In this study, we conducted a pilot-scale investigation involving seven units of self-designed roadside air purifiers in an urban street canyon in Hong Kong. The air cleaning effects were quantified with an air quality sensor network after rigorous quality control. The removal efficiencies of Nitrogen dioxide (NO2), Fine suspended particulates (PM2.5), Carbon monoxide (CO), and Nitric oxide (NO) were determined by comparing with simultaneously measured ambient concentrations, with hourly average efficiencies of 14.0 %-16.9 %, 3.5-10.0 %, 11.9 %-18.7 %, and 19.2 %-44.9 %, respectively. Generally, the purification effects presented variations depending on the ambient pollutants' levels. Higher ambient concentrations of NO2, PM2.5, CO correlated with increased purification effects, while NO presented the opposite trend. The influence of interval distance combined with spatial distribution indicated the operation of purifiers will induce local NO2 attenuation even at an interval distance of four meters. Statistical analysis delivered evidence the air cleaning ability exhibited optimal performance when relative humidity level is ranged from 70 % to 90 %, aligning with the prevailing conditions in Hong Kong. Additionally, improved purification effects were observed at the downwind direction, and their performance was enhanced when the wind speed exceeded 2.5 m/s. Moreover, we estimated the operational lifetime of the air purifiers to be approximately 130 days, offering crucial information regarding the filter replacement cycle. This work serves as a pioneering case study, showcasing the feasibility and deployment considerations of roadside air purifiers in effectively controlling air pollution in urban environments.

Anthraquinone-Based Silicate Covalent Organic Frameworks as Solid Electrolyte Interphase for High-Performance Lithium-Metal Batteries.

Lithium (Li)-metal batteries (LMBs) possess the highest theoretical energy density among current battery designs and thus have enormous potential for use in energy storage. However, the development of LMBs has been severely hindered by safety concerns arising from dendrite growth and unstable interphases on the Li anode. Covalent organic frameworks (COFs) incorporating either redox-active or anionic moieties on their backbones have high Li-ion (Li+) conductivities and mechanical/chemical stabilities, so are promising for solid electrolyte interphases (SEIs) in LMBs. Here, we synthesized anthraquinone-based silicate COFs (AQ-Si-COFs) that contained both redox-active and anionic sites via condensation of tetrahydroxyanthraquinone with silicon dioxide. The nine Li+-mediated charge/discharge processes enabled the AQ-Si-COF to demonstrate an ionic conductivity of 9.8 mS cm-1 at room temperature and a single-ion-conductive transference number of 0.92. Computational studies also supported the nine Li+ mechanism. We used AQ-Si-COF as the solid electrolyte interphase on the Li anode. The LMB cells with a LiCoO2 cathode attained a maximum reversible capacity of 188 mAh g-1 at 0.25 C during high-voltage operation. Moreover, this LMB cell demonstrated suppressed dendrite growth and stable cyclability, with its capacity decreasing by less than 3% up to 100 cycles. These findings demonstrate the effectiveness of our redox-active and anionic COFs and their practical utility as SEI in LMB.

Substrate-related factors and kinetic studies of Carbohydrate-Rich food wastes on enzymatic saccharification.

Food waste biorefinery is a sustainable approach to producing green chemicals, however the essential substrate-related factors hindering the efficacy of enzymatic hydrolysis have never been clarified. This study explored the key rate-limiting parameters and mechanisms of carbohydrate-rich food after different cooking and storing methods, i.e., impacts of compositions, structural diversities, and hornification. Shake-flask enzymatic kinetics determined the optimal dosages (0.5 wt% glucoamylase, 3 wt% cellulase) for food waste hydrolysis. First order kinetics and simulation results determined that reaction coefficient (K) of cooked starchy food was âˆ¼ 3.63 h-1 (92 % amylum digestibility) within 2 h, while those for cooked cellulosic vegetables were 0.25-0.5 h-1 after 12 h of hydrolysis. Drying and frying reduced âˆ¼ 71-89 % hydrolysis rates for rice, while hydrothermal pretreatment increased the hydrolysis rate by 82 % on vegetable wastes. This study provided insights into advanced control strategy and reduced the operational costs by optimized enzyme doses for food waste valorization.

Combination of deep eutectic solvent and functionalized metal-organic frameworks as a green process for the production of 5-hydroxymethylfurfural and furfural from sugars.

Biomass is an abundant and sustainable resource that can be converted into energy and chemicals. Therefore, the development of efficient methods for the conversion of biomass into platform intermediates is crucial. In this study, the one-pot conversion of sugars into 5-hydroxymethylfurfural (HMF) and furfural was achieved using the metal-organic framework combined with metal ions [MIL-101(Cr)] as a high-activity catalyst, and a deep eutectic solvent (choline chloride and lactic acid) as a green solvent. The optimal temperature, time, amount of catalyst used, and amount of deep eutectic solvent used were all determined. The highest HMF yield of 49.74% and furfural yield of 55.90% were obtained. The recyclability of the catalysts and deep eutectic solvent was also investigated. After three reaction runs, the HMF yield was still nearly 30.00%. Finally, the MIL-101(Cr) catalytic system was selected to study the kinetic mechanism underlying the conversion of glucose into HMF.

Insights into the Occurrence, Fate, Impacts, and Control of Food Additives in Food Waste Anaerobic Digestion: A Review.

The recovery of biomass energy from food waste through anaerobic digestion as an alternative to fossil energy is of great significance for the development of environmental sustainability and the circular economy. However, a substantial number of food additives (e.g., salt, allicin, capsaicin, allyl isothiocyanate, monosodium glutamate, and nonnutritive sweeteners) are present in food waste, and their interactions with anaerobic digestion might affect energy recovery, which is typically overlooked. This work describes the current understanding of the occurrence and fate of food additives in anaerobic digestion of food waste. The biotransformation pathways of food additives during anaerobic digestion are well discussed. In addition, important discoveries in the effects and underlying mechanisms of food additives on anaerobic digestion are reviewed. The results showed that most of the food additives had negative effects on anaerobic digestion by deactivating functional enzymes, thus inhibiting methane production. By reviewing the response of microbial communities to food additives, we can further improve our understanding of the impact of food additives on anaerobic digestion. Intriguingly, the possibility that food additives may promote the spread of antibiotic resistance genes, and thus threaten ecology and public health, is highlighted. Furthermore, strategies for mitigating the effects of food additives on anaerobic digestion are outlined in terms of optimal operation conditions, effectiveness, and reaction mechanisms, among which chemical methods have been widely used and are effective in promoting the degradation of food additives and increasing methane production. This review aims to advance our understanding of the fate and impact of food additives in anaerobic digestion and to spark novel research ideas for optimizing anaerobic digestion of organic solid waste.

Bio-oil and biochar from the pyrolytic conversion of biomass: A current and future perspective on the trade-off between economic, environmental, and technical indicators.

Over the years, the transformation of biomass into a plethora of renewable value-added products has been identified as a promising strategy to fulfil high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Techno-economic analysis (TEA) and life-cycle assessment (LCA) are essential to scale up this process while lowering the conversion cost. In this study, trade-offs are made between economic, environmental, and technical indicators produced from these methodologies to better evaluate the commercialization potential of biomass pyrolysis. This research emphasizes the necessity of combining LCA and TEA variables to assess the performance of the early-stage technology and associated constraints. The important findings based on the LCA analysis imply that most of the studies reported in literature focussed on the global warming potentials (GWP) under environmental category by considering greenhouse gases (GHGs) as evaluation parameter, neglecting many other important environmental indices. In addition, the upstream and downstream processes play an important role in understanding the life cycle impacts of a biomass based biorefinery. Under upstream conditions, the use of a specific type of feedstock may influence the LCA conclusions and technical priority. Under downstream conditions, the product utilization as fuels in different energy backgrounds is crucial to the overall impact potentials of the pyrolysis systems. In view of the TEA analysis, investigations towards maximizing the yield of valuable co-products would play an important role in the commercialization of pyrolysis process. However, comprehensive research to compare the conventional, advanced, and emerging approaches of biomass pyrolysis from the economic perspective is currently not available in the literature.

Biomass pyrolysis: A review on recent advancements and green hydrogen production.

Biomass pyrolysis has recently gained increasing attention as a thermochemical conversion process for obtaining value-added products, thanks to the development of cutting-edge, innovative and cost-effective pyrolysis processes. Over time, new and novel pyrolysis techniques have emerged, and these processes can be tuned to maximize the production of high-quality hydrogen. This review examines recent advancements in biomass pyrolysis by classifying them into conventional, advanced and emerging approaches. A comprehensive overview on the recent advancements in biomass pyrolysis, highlighting the current status for industrial applications is presented. Further, the impact of each technique under different approaches on conversion of biomass for hydrogen production is evaluated. Techniques, such as inline catalytic pyrolysis, microwave pyrolysis, etc., can be employed for the sustainable production of hydrogen. Finally, the techno-economic analysis is presented to understand the viability of pyrolysis at large scale. The outlook highlights discernments into future directions, aimed to overcome the current shortcomings.

Bioconversion of food and lignocellulosic wastes employing sugar platform: A review of enzymatic hydrolysis and kinetics.

Bioenergy and biochemicals can be sustainably produced through fermentation and anaerobic digestion (AD). However, this bioconversion processes could be more economical if the hydrolysis rates of substrates in bioreactors can be accelerated. In this review, the feasibilities of including enzymatic hydrolysis (EH) in various bioconversion systems were studied to facilitate the biological synergy. The reaction kinetics of EH in bioconversion systems comparing pretreated lignocellulosic biomass (LCB) and food waste (FW) substrates were reviewed. Possible strategies to improve the hydrolysis efficiency were explored, including co-cultivation during enzyme production and replacement of pure enzyme with on-site produced fungal mash during EH. Key insights into improvement of current AD and fermentation technologies were summarized and further formed into suggestions of future directions in techno-economic feasibility of biorefinery using mixture of the first-generation food crop feedstock with FW; and/or co-digestion of FW with LCB.

Pyrolysis of anaerobic digested residues in the presence of catalyst-sorbent bifunctional material: Pyrolysis characteristics, kinetics and evolved gas analysis.

We investigated the potential application of anaerobically digested residues for generating bioenergy in the presence of alkali bifunctional material, sodium zirconate (Na2ZrO3, NZ) using a thermogravimetric analyzer connected to a mass spectrometer. Isoconversional kinetic models, compensation effect and master-plots method were used on data obtained under multiple heating rates (10, 15 and 20 °C min-1) to calculate the activation energy (Eα) and pre-exponential value (A) and reaction mechanism. The average Eα for blend samples C-DSW (NZ mixed with digested municipal solid waste (DSW)), and C-DSM (NZ mixed with digested swine manure (DSM)) were 172.24 and 171.63 kJ mol-1, which were much lower when compared to plain samples, DSW (202.51 kJ mol-1) and DSM (215.22 kJ mol-1). The total gas yields increased by 19.5 and 17.1% for NZ blended samples C-DSW and C-DSM, respectively. In addition, the hydrogen yields also increased by 79 and 44% for C-DSW and C-DSM, respectively.

Progress in the development and use of refrigerants and unintended environmental consequences.

The world has entered into the "fourth-generation" of refrigerants, and it is an undeniable fact that we will continue to encounter several issues in identifying a suitable refrigerant that suits the purpose and poses no harm to the environment. The ever-changing regulations on the use of refrigerants have often posed great challenges to the refrigeration industry and there is a pressing need to develop new refrigerants and develop better equipment to use them. Theoretically, an ideal refrigerant should possess characteristics such as low-global warming potential (GWP), non-toxic, non-flammable, and zero-ozone depletion potential (ODP). In addition, the refrigerants are also expected to have excellent thermodynamic and thermophysical properties. Many new synthetic refrigerants have been reported as alternative refrigerants and have very low atmospheric life as well as low GWP and zero-ODP. However, it is irrefutable that most of the studies that reported the so-called new refrigerants are actually not new. From the invention of R-12 (Dichlorodifluoromethane) in 1930s to the invention of R-1234yf in 2000s, these substances are available for decades even before being recognized as refrigerants. This review attempts to provide chronicles on different aspects of refrigerants such as their progress since their invention in the early 1800s, classification and properties. In addition, concepts such as issues associated with the long-term use of refrigerants, barriers for the inclusion of low-GWP refrigerants, various protocols and accords that have occurred since the inception of refrigerants are also critically discussed.

Efficient saccharification of wheat straw pretreated by solid particle-assisted ball milling with waste washing liquor recycling.

Wheat straw was pretreated using ball milling (BM) promoted by solid particles (NaOH, NaCl, citric acid). NaOH showed the best synergistic interaction effect, due to the breakage of ß-1,4-glycosidic bonds among cellulose molecules by the alkali solid particles induced by BM. NaOH-BM pretreatment decreased the straw crystallinity from 46% to 21.4% and its average particle size from 398.3 to 50.6 µm in 1 h. After 4 h milling, the reducing-end concentration of cellulose increased by 3.8 times from 12.5 to 60.2 µM, with glucose yield increased by 2.1 times from 26.6% to 82.4% for 72 h enzymatic hydrolysis at cellulase loading of 15 FPU/g dry substrate. The pretreatment washing liquor was recycled for the re-treatment of partially pretreated biomass at 121 °C for 30 min, resulting in 99.4% glucose yield by enzymatic hydrolysis. BM assisted with alkali particles was an effective approach for improving biomass enzymatic saccharification.

Recent advances of lignin valorization techniques toward sustainable aromatics and potential benchmarks to fossil refinery products.

Aromatic compounds are important fuels and key chemical precursors for organic synthesis, however the current aromatics market are mainly relying on fossil resources which will eventually contribute to carbon emissions. Lignin has been recognized as a drop-in substitution to conventional aromatics, with its values gradually realized after tremendous research efforts in the recent five years. To facilitate the development of a possible lignin economics, this study overviewed the recent advances of various biorefinery techniques and the remaining challenging for lignin valorization. Starting with recent discovery of unexplored lignin structures, the potential functions of lignin related chemical structures were emphasized. The important breakthrough of lignin-first pretreatment, catalytic lignin depolymerization, and the high value products with possible benchmark with modern aromatics were reviewed with possible future targets. Possible retrofit of conventional petroleum refinery for lignin products were also introduced and hopefully paving a way to progressively migrate the industry towards carbon neutrality.

Biotechnology of Plastic Waste Degradation, Recycling, and Valorization: Current Advances and Future Perspectives.

Invited for this month's cover is the collaborative group of Dr. Carol Sze Ki Lin and Dr. Xiang Wang. The image illustrates the biodegradation of plastics and the potential for plastic waste recycling and valorization to address the plastic waste dilemma. The Minireview itself is available at 10.1002/cssc.202100752.

Construction of a structural enzyme adsorption/kinetics model to elucidate additives associated lignin-cellulase interactions in complex bioconversion system.

Enzymatic hydrolysis is a rate-limiting process in lignocellulose biorefinery. The reaction involves complex enzyme-substrate and enzyme-lignin interactions in both liquid and solid phases, and has not been well characterized numerically. In this study, a kinetic model was developed to incorporate dynamic enzyme adsorption and product inhibition parameters into hydrolysis simulation. The enzyme adsorption coefficients obtained from Langmuir isotherm were fed dynamically into first-order kinetics for simulating the equilibrium enzyme adsorption in hydrolysis. A fractal and product inhibition kinetics was introduced and successfully applied to improve the simulation accuracy on adsorbed enzyme and glucose concentrations at different enzyme loadings, lignin contents, and in the presence of bovine serum albumin (BSA) and lysozyme. The model provided numerical proof quantifying the beneficial effects of both additives, which improved the hydrolysis rate by reducing the nonproductive adsorption of enzyme on lignin. The hydrolysis rate coefficient and fractal exponent both increased with increasing enzyme loadings, and lignin inhibition exhibited with increasing fractal exponent. Compared with BSA, the addition of lysozyme exhibited higher hydrolysis rates, which was reflected in the larger hydrolysis rate coefficients and smaller fractal exponents in the simulation. The model provides new insights to support process development, control, and optimization.

Biorefinery potential of chemically enhanced primary treatment sewage sludge to representative value-added chemicals - A de novo angle for wastewater treatment.

Chemically enhanced primary treatment (CEPT) is an emerging sewage treatment strategy due to its high efficiency and small land requirement. CEPT sludge can be easily dewatered and used for energy recovery through incineration. However, with large amount of reusable nutrients (40% organic carbon, 23% lipids, and 17% protein), the value of CEPT sludge may have been underestimated. In this study, the biorefinery potential of CEPT sludge has been proven via production of 28.9 g/L ethanol or 50.3 g/L lactic acid (LA) or 1.43 filter paper unit (FPU)/mL cellulase from 10 g of CEPT sludge experiment. Inhibition on cell growth and potential inhibitors from plasticizers, pharmaceuticals, and surfactants were determined. Nevertheless, production titer was not affected or performed even better than the non-inhibitors controls. CEPT sludge showed significant potential in biochemical conversion, and the related products may offer an opportunity to support wastewater treatment toward sustainability and carbon neutrality.

Biotechnology of Plastic Waste Degradation, Recycling, and Valorization: Current Advances and Future Perspectives.

Although fossil-based plastic products have many attractive characteristics, their production has led to severe environmental burdens that require immediate solutions. Despite these plastics being non-natural chemical compounds, they can be degraded and metabolized by some microorganisms, which suggests the potential application of biotechnologies based on the mechanism of plastic biodegradation. In this context, microbe-based strategies for the degradation, recycling, and valorization of plastic waste offer a feasible approach for alleviating environmental challenges created by the accumulation of plastic waste. This Minireview highlights recent advances in the biotechnology-based biodegradation of both traditional polymers and bio-based plastics, focusing on the mechanisms of biodegradation. From an application perspective, this Minireview also summarizes recent progress in the recycling and valorization of plastic waste, which are feasible solutions for tackling the plastic waste dilemma.

Insights into unexpected photoisomerization from photooxidation of tribromoacetic acid in aqueous environment using ultrafast spectroscopy.

Haloacetic acids are carcinogenic disinfection by-products (DPBs) and their photo-decomposition pathways, especially for those containing bromine and iodine, are not fully understood. In this study, femtosecond transient absorption (fs-TA) spectroscopy experiments were introduced for the first time to investigate the photochemistry of tribromoacetic acid. The fs-TA experiments showed that a photoisomerization intermediate species HOOCCBr2-Br (iso-TBAA) was formed within several picoseconds after the excitation of TBAA. The absorption wavelength of the iso-TBAA was supported by time-dependent density calculations. With the Second-order Møller-Plesset perturbation theory, the structures and thermodynamics of the OH-insertion reactions of iso-TBAA were elucidated when water molecules were involved in the reaction complex. The calculations also revealed that the isomer species were able to react with water with its reaction dynamics dramatically catalyzed by the hydrogen bonding network. The proposed water catalyzed OH-insertion/HBr elimination mechanism predicted three major photoproducts, namely, HBr, CO and CO2, which was consistent with the photolysis experiments with firstly reported CO formation rate and mass conversion yield as 0.096 min-1 and 0.75 ± 0.1 respectively. The spectroscopic technique, numerical tool and disclosed mechanisms provided insights on photodecomposition and subsequent reactions of polyhalo-DPBs contain heavy atom(s) (e.g., Br, I) with water, aliphatic alcohols or other nucleophiles.