Iris KM Yu

• PhD
• Assistant Professor at National University of Singapore

Microwaves offer volumetric heating with a higher energy efficiency than conductive–convective heat transfer in conventional approaches. The emerging application of microwave heating in biorefineries is a low-emission strategy to produce bio-based chemicals and materials. In this Review, we discuss the use of microwaves in biorefinery applications,...

Catalytic oxidation through the transfer of lattice oxygen from metal oxides to reactants, namely the Mars–van Krevelen mechanism, has been widely reported. In this study, we evidence the overlooked oxidation route that features the in situ formation of surface OH species on Cu catalysts and its selective addition to the reactant carbonyl group. We...

In aqueous mediums, the chemical environment for catalytic reactions is not only comprised of water molecules but also of corresponding ionized species, i.e., hydronium ions, which can impact the mechanism and kinetics of a reaction. Here we show that in aqueous-phase hydrogenation of furfural on Pd/C, increasing the hydronium ion activities by fiv...

Biorefinery, the transformation of biomass to renewable energy and materials, is a prominent player in the sustainability agenda to achieve carbon neutrality in 30-40 years. In the reductive upgrading of bio-based aromatic compounds (e.g., furfural), disparity in the reported product profiles leads to a scientific question-what general principles g...

A considerable amount of food waste generated globally could be upcycled to synthesise platform chemicals to enhance environmental sustainability and help realise a circular economy. This study investigates the catalytic production of the vital platform molecule levulinic acid (LA) from bread waste, a typical stream of starch-rich food waste genera...

Gluconic acid (GOA) and glucaric acid (GAA) are valuable chemicals for a wide range of applications, yet conventional technologies for their production suffer from low efficiency, high cost, and especially environmental concerns. It is imperative to develop sustainable heterogeneous catalytic systems exhibiting promising catalytic activity and good...

Development of non-noble metal cluster catalysts, aiming at concurrently high activity and stability, for emission control systems has been challenging because of sintering and overcoating of clusters on the support. In this work, we reported the role of well-dispersed copper nanoclusters supported on TiO2 in CO oxidation under industrially relevan...

To close the carbon loop of biomass waste valorization, it is imperative to utilize the unavoidable by-products such as humins, a carbonaceous residue with complex and heterogeneous composition. In this study, starch-rich rice waste was effectively converted into value-added chemicals (e.g., 5-hydroxymethylfurfural) under microwave heating at 160 o...

To tackle the crisis associated with the rising commercial food waste generation, it is imperative to comprehend how corporates’ recycling behaviour is influenced by different industry structures and economies. This study aims to fill in the information gap that various factors might be affecting corporates’ recycling behaviour in two different eco...

Sustainable utilisation of food waste in biorefineries is imperative to actualising a circular economy and alleviating the massive environmental burden. An efficient biorefinery system design necessitates comprehensive understanding of the...

Microwaves (MWs) are promising technologies for energy-efficient biorefineries which reduce our dependence on petroleum. Here we present evidence for the first time of important interactions between MW and starch, a major biomass from massive global food wastes, which can be observed under both hydrolytic and pyrolytic conditions. Starch is transfo...

In article number 1900149, Daniel C. W. Tsang and co‐workers review the advanced tailoring of the physicochemical properties of biochar, a next‐generation material that creates opportunities in a wide range of industrial applications, including catalytic production of biofuels and high‐value chemicals, tar removal, syngas reforming, energy storage,...

Efficient depolymerization of lignocellulosic biomass is a prerequisite for sugar production and its subsequent up-gradation to fuels and chemicals. Organic carbonate solvents, i.e., propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC), which are low in toxicity and biodegradable, were investigated as ‘green’ co-solvents...

PurposeThis communication aims to foster the integration of biorefinery and soil management for achieving Sustainable Development Goals (SDGs).Methods The latest advances in biomass waste utilization and soil quality improvement are reviewed, based on which we identify the opportunity of bridging the two research areas and suggest strategic approac...

Driven by the worldwide demand for sustainable resources and renewable energy, the synthesis of bio-based platform chemicals has attracted broad interest. The isomerisation of glucose to fructose acts as a critical intermediate step among many chemical synthesis routes. In this study, biochar (BC), graphitic oxide (GIO), and graphene oxide (GO) wer...

The past decades have seen an increasing interest in developing pathways to produce bio-based chemicals from lignocellulosic biomass and organic waste as renewable resources. Using biomass as a source of chemical building blocks is critical to a future sustainable chemical industry. The successful development of bio-chemicals will also have a profo...

Energy-saving, chemical-free, and high-efficiency microwave (MW)-assisted water treatment can be greatly facilitated via tailored design of an economical, sustainable, and ‘green’ carbonaceous catalyst. In this study, various biochars (BC) were pyrolyzed from two lignocellulosic waste biomasses, oak (O) and apple tree (A), at high temperature (900...

The use of biomass wastes for biochar production is a promising waste management option, and biochars can be potentially applied in the food waste recycling industry to produce value-added chemicals. In this study, an advanced Sn-functionalised biochar catalyst was synthesised via a novel solvent-free ball milling protocol to facilitate the isomeri...

Hydrogen is recognized as one of the cleanest energy carriers, which can be produced from renewable biomass as a promising feedstock to achieve sustainable bioeconomy. Thermochemical technologies (e.g., gasification and pyrolysis) are the main routes for hydrogen production from biomass. Although biomass gasification, including steam gasification a...

Biochar (BC) is a material synthesized from biomass by thermochemical conversion. Physicochemical and functional properties of BCs can be enhanced by several methods of activation or functionalization. The activated and functionalized BCs with a large surface area and abundant surface functional groups can serve as effective catalysts or catalyst s...

Proper food waste management measures are crucial to environmentally-friendly and sustainable development. To opt for the most environmentally beneficial food waste management strategies, a comprehensive decision-guiding tool is important to evaluate and compare the performance of the handling techniques. Previous studies have demonstrated LCA as a...

This chapter introduces a psychological model, which is commonly known as the theory of planned behavior (TPB), provides theoretical framework to assist in our understanding of the factors influencing behavioral choices. Three key constructs are proposed in TPB that directly affect individuals' intention and thus their behavior, namely attitude, su...

Ever-increasing global demand for energy and resources has been drawing more and more attention to sustainable and cost-effective materials and technologies. Turning renewable resources and energy to sustainable materials applied in the construction and building industry is of great significance. Carbohydrate-derived biomass, including fiber, bioch...

Lignocellulosic wastes constitute a significant portion of the municipal solid waste, which should be valorised for the synthesis of value-added chemicals to achieve circular bioeconomy. This study evaluates the use of γ-valerolactone (GVL) and acetone as green co-solvents to produce levulinic acid (LA) from lignocellulosic paper towel waste at dif...

Efficient conversion of food waste to value-added products necessitates the development of high-performance heterogeneous catalysts. This study evaluated the use of Al2O3 as a low-cost and abundant support material for fabricating Lewis acid catalysts, i.e., through the in-situ doping of Cu, Ni, Co, and Zr into Al2O3 followed by calcination. The ch...

Research attention is increasingly drawn on constructing a circular bioeconomy and enhancing the value of material flows. Circular bioeconomy aims to achieve sustainable consumption and production with reduction of greenhouse gas emission. This study identifies research gaps on how circular bioeconomy can be achieved through sustainable food waste...

Layered double hydroxides (LDHs) with varying crystallite sizes (2.6–43 nm), layer numbers (3–70), specific surface area (18–455 m² g⁻¹), pore volume (0.025–1.6 mL g⁻¹), and functional groups were synthesised via conventional urea hydrolysis and co-precipitation methods and aqueous miscible organic solvent (AMOST) treatment. They were evaluated as...

We have developed a sustainable graphitic biochar for environmental remediation from wood waste through catalytic pyrolysis under the synergistic effects between CO2 and Cu heteroatoms, which for the first time are found to significantly enhance the oxygen functionalities, defective sites, and highly ordered sp2-hybridized carbon matrix. The copper...

Solid wastes containing potentially toxic elements (PTEs) are widely generated around the globe. Critical concerns have been raised over their impacts on human health and the environment, especially for the exposure to PTEs during the transfer and disposal of the wastes. It is important to devise highly-efficient and cost-effective treatment techno...

Food wastes are generated massively across global food supply chains. Conventional treatments of food waste (e.g., landfilling and incineration) cause environmental, economic, and social problems. There is a more sustainable and profitable management option by valorization of food waste into value-added chemicals. Consumer chemicals, including acid...

Graphite (G), graphite oxide (GIO), and graphene oxide (GO) were evaluated for the first time as carbonaceous supports to synthesise heterogeneous Lewis acid catalysts, via simple AlCl3 pretreatment followed by one-step thermal modification. The GIO- and GO-supported Al catalysts were active towards catalytic isomerisation of glucose in water as th...

This study investigates the structure-performance relationships in different zeolite-solvent systems that are suitable for microwave-assisted dehydration of food waste-derived fructose to 5-hydroxymethylfurfural (HMF). Different types of zeolites (MFI, BEA, and Y) were examined as acid catalysts. Water was first tested as the greenest solvent (base...

CO 2 capture is projected as one of the pragmatic approaches to deal with the global warming phenomenon. Adsorption-based CO 2 capture is considered an economically attractive option to reduce CO 2 emission. The success of the adsorption-based capture primarily relies on adsorbents and thus a variety of adsorbents have been investigated in the lite...

The distinct physicochemical properties and renewable origin of gamma-valerolactone (GVL) have provided opportunities for diversifying its applications, particularly as a green solvent, excellent fuel additive, and precursor to valuable chemicals. Among the related publications found in the SCOPUS database (≈172 in the last 10 years), we focused ou...

A novel biochar-based heterogeneous catalyst has been devised to facilitate isomerisation of glucose to fructose for achieving sustainable biorefineries. A series of aluminium-biochar composites (Al biochars) with wide-ranging properties were synthesised from waste wood biomass. These properties including surface area, porosity, crystalline/amorpho...

Layered double hydroxides (LDHs) have been intensively studied in recent years owing to their great potential in CO 2 capture. However, the severe aggregation between platelets and low surface area restricted it from exhibiting very high CO 2 adsorption capacity and CO 2 /N 2 selectivity. In this research, we for the first time synthesized Ni-Al-CO...

This study tailored a novel engineered biochar as a solid catalyst for glucose isomerization by pyrolyzing Sn-functionalized wood waste under varying hypothesis-driven selected conditions (i.e., 650, 750, and 850 °C in N2 and CO2 atmosphere). The results showed that properties of biochar support (e.g., porosity and acid/base property) and chemical...

This paper evaluates a novel sorbent for the removal of potentially toxic elements, inherent cations, and hetero-chloride from hydraulic fracturing wastewater (FWW). A series of iron-biochar (Fe-BC) composites with different Fe/BC impregnation mass ratios (0.5:1, 1:1, and 2:1) were prepared by mixing forestry wood waste-derived BC powder with an aq...

Immense global generation of food waste calls for advanced technologies to maximise the use of such renewable carbon-based resources. In this study, corn, taro, lettuce, and bean sprout, were valorised for the production of value-added chemicals via sequential supercritical CO2 (scCO2) extraction and thermochemical conversion. The scCO2 extraction...

A series of organic acids, including maleic acid (maleicA), malic acid (malicA), succinic acid (SA), and oxalic acid (OA)/oxalate, was evaluated as green additives, to promote the selective Al(III)-catalyzed production of hydroxymethylfurfural (HMF) from food waste. The roles of Al(III)–organic acid interactions in altering the catalytic functions...

Changing individual's recycling attitude and behaviour is of utmost importance in achieving sustainable construction and demolition (C&D) waste management, yet it has often been underachieved. To understand the motivations for recycling, this study identifies and prioritizes the key factors that affect C&D waste recycling behaviour of various stake...

In this study, red seaweed (Gracilaria lemaneiformis) food waste with high carbohydrate content was valorized into levulinic acid (LA) and algae hydrochar through microwave-assisted low-temperature hydrothermal treatment in dilute acid solution. Various parameters including treatment temperature (160–200 °C), reaction time (1–40 min), acid concentr...

In this work, glucose isomerization to fructose was conducted via a solid base biochar catalyst derived from spent coffee grounds and melamine. The X-ray photoelectron spectroscopy (XPS) spectra identified the majority of pyridinic nitrogen on the biochar surface, which imparted the strong base character of the catalyst. Activity of the catalyst wa...

In recent years, the government and community have focused extensive attention on food waste recycling to achieve sustainable waste management. However, the motivation of stakeholders from the commercial and industrial sector to change recycling behaviour has not received enough attention. This study aimed to identify, prioritise, and quantify the...

Platform chemicals such as hydroxymethylfurfural (HMF) can be obtained through the conversion of biomass with the aid of metal catalyst (i.e., Cr(III) or Sn(IV)) systems. In this study, we examined the use of an environmentally compatible co-catalyst, namely maleic acid (MA), to regulate the reaction kinetics and product selectivity in the metal-ca...

A novel alternative bioconversion and chemical transformation method for valorisation of food and beverage (F&B) waste to hydroxymethylfurfural (HMF) is reported. Solid-to-liquid ratio of 70% was applied to hydrolyse F&B waste by glucoamylase and sucrase to yield a hydrolysate consisted of glucose and fructose. After impurity removal using chromato...

Food waste can serve as a potential substitute for fossil-derived feedstocks for producing value-added chemicals, such as hydroxymethylfurfural (HMF), yet their environmental performance has not yet been evaluated, thus impeding informed decision-making. This study aims to develop a life-cycle assessment (LCA) framework to guide decisions on select...

Lignin is an abundant biomass resource in aromatic structure with a low price in market, which can serve as renewable precursors of value-added products. However, valorization rate of annually produced lignin is less than 2%, suggesting the need for technological advancement to capitalize lignin as a versatile feedstock. In recent years, efficient...

A new and environmentally benign photocatalyst is introduced in this study, which was synthesized via incipient wetness impregnation onto MIL-47(V) using an ethanolic Fe(III) chloride solution. The resultant materials were characterized by XRD, FE-SEM, and HR-TEM analyses. The photocatalytic capability of Fe/MIL-47 towards removal of methylene blue...

The catalytic activity of engineered biochar was scrutinized for generation of glucose and hydroxymethylfurfural (HMF) from starch-rich food waste (bread, rice, and spaghetti). The biochar catalysts were synthesized by chemical activation of pinewood sawdust with phosphoric acid at 400-600 °C. Higher activation temperatures enhanced the development...

Two green solvents, namely propylene carbonate (PC) and γ-valerolactone (GVL), were examined as co-solvents in the conversion of bread waste to hydroxymethylfurfural (HMF) over SnCl4 as the catalyst under microwave heating at 120 oC, and their performances were compared with water and acetone as a common solvent. The results showed that a HMF yield...

Food waste is responsible for a significant portion of solid waste generation in the international airports, where efficient on-site or off-site sorting and recycling may be feasible. The aim of this study is to develop a Life-Cycle Cost-Benefit Analysis (LC-CBA) framework, through the integration of the life-cycle assessment (LCA) and cost-benefit...

The scarceness of virgin resources and sustainable management of waste materials in high-density city arouse heightened focus on new technology development for waste recycling and local utilization. Wood waste recovery from construction activities and upcycling into secondary products allow the substitution of virgin resources and minimize the envi...

This study investigated the use of 30 w/v% H2SO4 sulfonated wood waste-derived biochar as catalysts for production of value-added chemicals from carbohydrates in water as an environmentally benign solvent. Physicochemical characteristics of the sulfonated biochar were revealed by Fourier transform infrared spectroscopy (FTIR), acid-base neutralizat...

Sulfonated biochar derived from forestry wood waste was employed for the catalytic conversion of starch-rich food waste (e.g., bread) into 5-hydroxymethylfurfural (HMF). Chemical and physical properties of catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (S...

Valorisation of bread waste for hydroxymethylfurfural (HMF) synthesis was examined in dimethyl sulfoxide (DMSO)-, tetrahydrofuran (THF)-, acetonitrile (ACN)-, and acetone-water (1:1v/v), under heating at 140°C with SnCl4 as the catalyst. The overall rate of the process was the fastest in ACN/H2O and acetone/H2O, followed by DMSO/H2O and THF/H2O due...

To transform construction wood waste by magnesia-phosphate cement (MPC) into cement-bonded particleboards, instability of MPC in water that compromises durability of particleboards in moist environment needs to be addressed. This study proposed a novel use of alumina and red mud to improve water resistance of MPC particleboards. Cement hydration ch...

This study aims to produce levulinic acid (LA) from paper towel waste in environment-friendly and economically feasible conditions, and evaluate the difference using solid and aqueous Brønsted acids. Direct dehydration of glucose to LA required sufficiently strong Brønsted acidity, where Amberlyst 36 demonstrated rapid production of approximately 3...

This review addresses the use of biochar as a green and versatile catalyst support for emerging high-end applications beyond soil remediation, including chemical synthesis and biodiesel production from biomass, and pollutant degradation in the environment. Their catalytic performances are comparable or even superior to the conventional resin-, sili...

This study presents the catalytic valorization of vegetable waste into levulinic acid (LA) over a solid Brønsted acid, Amberlyst 36, in aqueous solution with/without polar aprotic solvent (dimethyl sulfoxide, DMSO). With the aid of microwave heating, the cellulosic structure in the vegetable started hydrolysis at 120 °C. Increasing temperature to 1...

This study aimed to produce a high-value platform chemical, hydroxymethylfurfural (HMF), from food waste and evaluate the catalytic performance of trivalent and tetravalent metals such as AlCl3, CrCl3, FeCl3, Zr(O)Cl2, and SnCl4 for one-pot conversion. Starchy food waste, e.g., cooked rice and penne produced 4.0–8.1 wt% HMF and 46.0–64.8 wt% glucos...

This study elucidated the roles of hydration chemistry and reaction sequence of magnesia-phosphate cement (MPC) for upcycling construction wood waste into rapid-shaping cement-bonded particleboards. The mineralogy and microstructure was evaluated using thermogravimetry, quantitative X-ray diffraction, scanning electron microscope, and mercury intru...

Conversion of biomass waste to hydroxymethylfurfural (HMF), a value-added platform chemical, has captured great research interests driven by the economic and environmental incentives. This review evaluates the recent development of biomass conversion systems for high HMF yield and selectivity, with a focus on the performance of emerging catalysts a...

This study aimed to transform food waste into a value-added chemical, hydroxymethylfurfural (HMF), and unravel the tangled effects induced by the metal catalysts on each single step of the successive conversion pathway. The results showed that using cooked rice and bread crust as surrogates of starch-rich food waste, yields of 8.1-9.5% HMF and 44.2...