About Us

Our research interests are in biorefinery and biological systems for wastes and wastewater treatment and production of new generation energy and chemicals. Our research tools include physicochemical analysis of plant-based polymer structure, bioconversion to hydrolysis, fermentation, process design and mathematical modelling to enhance biological processes. We are also efficiently working on functionalization and utilization of the key building-block chemicals from lignocellulosic biomass, underscoring the utility of both classical and newly developed methods in lignocellulosic biorefinery.

project 1

Lignocellulosic Biorefinery

Temperature Profiling to Maximize Energy Yield with Reduced Water Input in A Lignocellulosic Ethanol Biorefinery

Cellulosic bioethanol is a green alternative of fossil fuels, of which aim to mitigate global climate change and facilitate rural economics. Production of this biofuel from municipal wastes requires the following processes: (1) pretreatment of lignocellulosic biomass; (2) saccharification/fermentation; and (3) separation by distillation. Among these unit operations, distillation of ethanol from fermentation broth is an energy intensive step which accounts up to 80% total energy demand in the whole biorefinery process. The energy ratio (in/out) of distillation process can reduce by 25% when ethanol titer from saccharification/fermentation processes can be increased from 60 g/L to 80 g/L, but literature values for cellulosic ethanol concentrations have rarely exceeded 60 g/L. In this work, whole slurry SSF of sulfite pretreated Monterey pine wood chips were conducted without detoxification (Dong et al., 2018b). The final ethanol concentration of SSF was successfully increased to 80 g/L by reducing the fermentation temperature to 28°C (Fig. 1). Based on the mass balance of the whole slurry and washed substrate for ethanol production, ethanol yield was increased from 157 kg/ton wood to 205 kg/ton wood through the established biorefinery. Following this finding, the net energy consumption and water consumption of a few selected bioconversion processes was calculated and compared in Fig. 2 (Dong et al., 2018a). Significant amount of energy can be saved in the distillation process by increasing the ethanol concertation through the new process. The energy yield of the new process is 2,410 MJ, which is approximately 43.5-234.7% higher than other published processes for treating 1 ton softwood. By eliminate the washing step of pretreatment, the new process has an extremely low water demand of 3.65 tons/ton-od wood, which is approximately 25.8-51.2% lower than the other processes (except for steam explosion process).

Fig.2. Energy (a) and water footprint (b) of different wood-to-bioethanol techniques. Process I – pretreatment; Process II – milling/concentration/dilution; Process III – distillation; and Process VI shows the heating values of the final products (ethanol).


Reference

Dong, C.Y., Wang, Y., Chan, K.L., Bhatia, A., Leu, S.Y. 2018a. Temperature profiling to maximize energy yield with reduced water input in a lignocellulosic ethanol biorefinery. Applied Energy, 214, 63-72.

Dong, C.Y., Wang, Y., Zhang, H., Leu, S.Y. 2018b. Feasibility of high-concentration cellulosic bioethanol production from undetoxified whole Monterey pine slurry. Bioresource Technology, 250, 102-109.

project 2

Biofuel and Biorefinery

Converting Biomass to Biofuels April 2007

Developing biorefinery techniques to convert lignocellulosic biomass into biofuels and value-added chemicals is an environmentally progressive way in mitigating global climate changes. This approach has been recently shown to be applicable in converting forestry residues into bioethanol. In the United States, lignocellulosic biomass such as forest residues derived from timber harvesting activities (figure at right) are being collected and used as a feedstock in a biomass-to-bioethanol biorefinery. A typical biorefinery process includes four main steps, i.e., pretreatment, hydrolysis, fermentation, and separation. Wood and other similar wastes can be converted into easily hydrolysable substrates after different types of pretreatment, a process simliar to pulping processes but with less requirment on energy and chemicals inputs.

The substrates are then hydrolyzed by using enzyme complex (for example cellulase) or catalysts to form different types of mono-saccharides, such as glucose, xylose, and mannose. The monosaccharides can be fermented by yeast or engineered bacteria to produce bioethanol and/or other products. An example of the products at different stages of the biorefinery processes are shown in the following figure: Douglas-Fir wood chips (left) was processed to produce substrates (middle), and bioethanol (right). In addition, lignocellulosic wastes and the pretreatment liquid also contains various amounts of valuable products, such as hemicelluloses and lignin. With proper treatment, many components such as nano-fibers, chemicals (i.e. organic acids, HMF, and furfural), lignosulfonate and lignin-based compounds can be recovered to produce bio-based materials, composites, and/or other useful products. In Hong Kong, biorefinery techniques could be useful in reducing solid wastes and may create new outlets of the waste-derived products for sustainable urban development. More details of the research see Leu et al. (2014) and Leu and Zhu (2013)

project 3

Biological Processes

Gas phase real-time monitoring is a unique technique understanding biological activities in a complex system. Combining the theories of gas transfer, aquatic chemistry, and dynamic modeling into practices, our research group has successfully applied this expertise in many areas for improving the microbial metabolisms in engineered environments, i.e., wastewater aeration, nutrient removal, bioaugmentation, and simultaneous saccharification and fermentation (SSF) processes. Bioaugmentation is a technique that uses specially acclimated biomass cultures to increase the degradation of the "target component(s)" in otherwise conventional activated sludge processes; and SSF is the most commonly applied approach to convert pretreated substrates into functional by-products in a biorefinery.

eration in liquid is a fundamental science of which investigating the mechanisms and kinetics of gases passing through the air-liquid interface and dissolving in the liquid. We are interested in many different gases in nature and/or engineered systems, such as O2, H2S, CO2, VOCs, and NOx. Oxygen is vital to aquatic lives but is only partially soluble in water as dissolved oxygen. In wastewater treatment plants, the choices of aeration greatly depend on the desired oxygen transfer efficiency (OTE), which is directly related to the operational costs of wastewater treatment. Maximizing OTE has become the major task in WWTPs to reduce operational costs;but this parameter cannot be easily accessed by conventional tools (e.g., COD and DO reading) without sophisticated biological model. Refer to our publication for more details.

Real-time gas monitoring technique(Fig. 2&3) is implemented to find out the change in gas phase oxygen fraction over time. In our study, mathematical modeling coupled with field studies and laboratory observations has been used to develop the theoretical basis to enhance several process improvements, i.e., using bioaugmentation to improve removals of a hazardous waste (1-NA) (Leu et al., 2009) bioaugmentation to improve nitrification (Leu et al., 2010) real-time monitoring to save energy on aeration and reduce peak energy consumption (Leu et al., 2009) and using CO2/O2 fraction to quantify nitrification efficiency (Leu et al., 2010).


On-going projects

Grant Type Title Role Period
General Research Fund, Hong Kong Research Grant Council (RGC/GRF, PolyU 152123/17E) Study of Natural Deep Eutectic Solvents Induced Pretreatment Process for Bioconversion of Refuse-Derived Lignocellulosic Biomass in Hong Kong PI 2018/01-2020/12
Innovation and Technology Fund – University-Industry Collaboration Programme (ITF-UICP, UIM/333) New Solvent-Based Biorefinery Techniques to Extract Lignin from Timber Wastes for High Titer Biofuel Production PI 2018/05-2020/05
Environment and Conservation Fund (ECF 85/2017) Incorporating metabolites based organosolv pretreatment in reducing the recalcitrant of lignocellulosic biomass to saccharification in food/yard/timber waste treatment processes PI 2018/01-2020/01
Block Grant except CRG, Project of Research Institute of Sustainable Urban Development (RISUD), PolyU New Paradigm of Integrated Urbanwater Management Co-PI 2017/03-2020/02
Environment and Conservation Fund (ECF 85/2017) Smart noise barriers/enclosures for dual active and passive control of construction noise Co-PI 2018/04-2020/03
Block Grant except CRG, Project of Research Institute of Sustainable Urban Development (RISUD), PolyU New Paradigm of Integrated Urbanwater Management Co-PI 2017/03-2020/02
Block Grant except CRG, Project of Research Institute of Sustainable Urban Development (RISUD), PolyU New Technologies for Smart Management of Urban Trees Co-PI 2018/04-2021/03
Hong Kong Jockey Club (HKJC) Charities Trust Jockey Club Smart City Tree Management Project Co-PI 2018/02-2021/02

courses

CSE29371 – Environmental Chemisrty

This course will teach you the basic chemical processes that can affect the quality of air, water and soil. You will study the basic chemistry concepts in both the natural and human perturbed systems. After the course, you should be able to identify the chemistries behind some environmental issues. Through the tutorials and experiments you will obtain the basic skills and the “engineering sense” to quantitatively evaluate certain environmental phenomena. The fundamental developed in this course will be also useful to help you study more advanced subjects and to conduct environmental researches in the future.

CSE520 – Solid and Hazardous Waste Management

This course is designed to provide student the fundamental concepts for management and treatment of the municipal and hazardous solid wastes. The courses will begin with an introduction of the generation of the solid wastes due to human activities. The students will study both the state-of-the-art strategies and the innovative techniques with great potential for solid wastes treatment. The details of the courses will cover the scientific background and the real-world examples to better understand the problems of solid waste treatment policies and alternatives in Hong Kong.

Members

Publications

Please follow: Google Scholar

Selected (latest) Publications:

  1. Ho-Yin, T.†, Cheng, S.-C., Yeung, C. S.^*, Lau, C.-Y.^, Wong, W.-H.^, Dong, C.†, Leu, S.-Y.* (2019) Development of a waste-derived lignin-porphyrin bio-polymer with enhanced photoluminescence at high water fraction with wide pH range and heavy metal sensitivity investigations. Green Chemistry.
  2. Chi, X., Li, J., Leu, S.-Y., Wang, X., Zhang, Y., Wang, Y.^* (2019) Features of a Staged Acidogenic/Solventogenic Fermentation Process to Improve Butanol Production from Rice Straw. Energy & Fuels, 33 (2), 1123-1132.
  3. Shi, L., Li, Y., Zeng, F., Ran, S., Dong, C.†, Leu, S.-Y., Boles, S.T., and Lam, K.H. (2019) In situ growth of amorphous Fe2O3 on 3D interconnected nitrogen-doped carbon nanofibers as high-performance anode materials for sodium-ion batteries, Chemical Engineering Journal, 356, 107-116.
  4. Wang, W.; Fu, S.; Leu, S.-Y.; Dong, C.†, A Nano-Ink for gel pens based on scalable CNC preparation. Cellulose, 2018, 25 (11), 6465-6478.
  5. 1Yang, P.; Leng, L.; Tan, G.-Y. A.; Dong, C.†; Leu, S.-Y.*; Chen, W.-H.; Lee, P.-H., Upgrading lignocellulosic ethanol for caproate production via chain elongation fermentation. International Biodeterioration & Biodegradation, 2018, 135, 103-109.
  6. Chan, K.-L.†, Dong, C.†, Wong, M.S., Kim, L.-H., Leu, S.-Y.* (2018) Plant Chemistry Associated Dynamic Modelling to Enhance Urban Vegetation Carbon Sequestration Potential via Bioenergy Harvesting, Journal of Cleaner Production, 197, 1084-1094.
  7. Dong, C.†, Wang, Y.^, Bhatia, A.^, Leu, S.-Y.* (2018) Temperature Profiling to Maximize Energy Yield with Reduced Water Input in a Lignocellulosic Ethanol Biorefinery, Applied Energy, 214, 63-72.
  8. Chi, X., Li, J., Wang, X., Zhang, Y., Leu, S.-Y.*, Wang, Y.^ (2018) Bioaugmentation with Clostridium tyrobutyricum to improve butyric acid production through direct rice straw bioconversion, Bioresource Technology, 263, 562-568.
  9. Li, Y., Ji, L., Liu, R., Zhang, C., Mak, C.H., Zou, X., Shen, H.H., Leu, S.-Y., Hsu, H.Y. (2018) A Review on Morphology Engineering for Highly Efficient and Stable Hybrid Perovskite Solar Cells, Journal of Materials Chemistry A.
  10. Zheng, S., Alvarado, V., Xu, P., Leu, S.-Y., Hsu, S.-C. (2018) Exploring spatial patterns of carbon dioxide emission abatement via energy service companies in China, Resources, Conservation and Recycling, 137, 145-155.
  11. Dong, C.†, Wang, Y.^, Zhang, H.^, Leu, S.-Y.* (2018) Feasibility of high-concentration cellulosic bioethanol production from undetoxified whole Monterey pine slurry, Bioresource Technology, 250, 102-109.
  12. Hu, Y., Du, C., Leu, S.-Y., Jing, H.†, Li, X., Lin, CSK. (2018) Valorisation of textile waste by fungal solid state fermentation: An example of circular waste-based biorefinery, Resources, Conservation and Recycling, 129, 27-35.
  13. Zhang, C.; Liu, R.; Mak, C. H.; Zou, X.; Shen, H.-H.; Leu, S.-Y.; Ji, L.; Hsu, H.-Y. (2018) Photophysics of organic photovoltaic devices: a review. Journal of Photonics for Energy, 8 (2), 021001.
  14. Hsu, H.-Y.; Ji, L.; Zhang, C.; Mak, C. H.; Liu, R.; Wang, T.; Zou, X.; Leu, S.-Y.; Edward, T. Y. (2018) Ultra-stable 2D layered methylammonium cadmium trihalide perovskite photoelectrodes. Journal of Materials Chemistry C, 6(43), 11552-11560.

Vacancy

Job description

We are currently seeking for new Postdoctoral Fellows and Research Assistant to support our recent project “New Solvent-Based Biorefinery Techniques to Extract Lignin from Timber Wastes for High Titer Biofuel Production”. The related research topics include, but not limiting to, designing/constructing biological processes and bioreactor for biofuels; “decoding” lignocellulosic cell wall structure with advanced technique (NMR, GC/MS) for efficient pretreatment; and/or synthesizing valuable chemicals from biomass extractives. Interested candidates should apply for the position by sending your Curriculum Vitae to Dr. Ben Leu via syleu@polyu.edu.hk. More details of the positions are as follow:

POSTDOCTORAL FELLOW

Ph.D. graduate in Bio-techniques, Plant Science, or are welcome to submit your application. Our positions are highly competitive. PolyU CEE Department ranked #1 in Hong Kong and #10 in the world (2017/18 QS). PolyU has recently obtained a few sophisticated analytical tools for the related research, including a 3rd Generation DNA Sequencer and a 500 MHz solid-/liquid-state NMR.

RESEARCH ASSISTANT

Current B.S. Student or Graduate in Environmental, Chemistry, and Biology programs are both welcome to apply for the position. The main duty includes supporting the experimental and field works, data analysis, and other related works upon the supervision of the research staff. The position can be either full-time or part-time, and priority will be provided to whom are interested in seeking for career in academia.