Gasification Technology

BACKGROUND
Interest in using “Biomass” and “Solid Wastes” for energy production has been increasing dramatically, as biomass is a renewable resource for energy and environmentally friendly material. Additionally, there are many other solid waste materials which can be utilized to generate energy efficiently and more economically. For example, Sewage sludge, unavoidable product from wastewater treatment, and Municipal Solid Wastes which mostly contain carbon and other organic matters as well as inorganic matters such as heavy metals. The improper disposal of sewage sludge wastes can cause all types of pollution: air, soil, and water. Indiscriminate dumping of sewage sludge wastes can contaminate surface and ground water supplies. These negative environmental impacts are only a result of solid waste disposal; they do not include the substantial environmental degradation resulting from the extraction and processing of materials at the beginning of the product life cycle. Therefore, it has become a matter of urgency to unearth alternative options to solve this problem. Incineration is the main technology in Singapore, which is used for converting those solid waste materials into heat via complete combustion process. The heat produced is used to generate super-heated steam which is subsequently used to drive turbo-generators to produce electricity. However, burning of solid wastes in incinerators leads to the seriously negative environmental and public health effects which caused by the release of toxic gases such as NOx, furans and dioxins. Moreover, there is less and less space for land fill of ashes, arising from the incineration process, in a comparatively small country.

Figure 1 Gasification for conversion biomass and/or solid wastes into clean energy

GASIFICATION, whereby biomass and/or wastes is converted to synthesis gas (a mixture of H2 and CO) and other gases, provides an attractive alternative process to incineration as the reducing (or oxygen-deficient) atmosphere in gasifier does not provide environment required for those toxic gases to be formed, and hence preventing the aforesaid problems of incineration.

IMPORTANCE OF THIS GASIFICATION AND WASTE-TO-ENERGY RESEARCH
As Singapore is an energy import society, energy security is one of the most important issues. By this energy recovery from solid waste materials such as “waste” woody biomass and other solid wastes which need to be disposed in every single day, it would reduce the dependence on imported fuel and raise the level of energy self-sufficiency.
Moreover, the disposal of solid residues such as char and ashes – the unavoidable solid by-products from gasification facilities – is also one of the concerns as ashes may contain concentrations of mineral compounds, heavy metals and also organic compounds (i.e. PAHs) arising from incomplete combustion of solid wastes. As a result, disposal of the ashes is creating grave risks to the environment as well as human health. Majority of ashes is dumped or used in low-valued methods such as using as a land-fill material. However, the cost of landfilling is now dramatically increasing due to the presence of toxic compounds, strict environmental regulations and limited availability of landfill space, especially in land-limited countries likes Singapore. From those points of view, it is important to develop beneficial applications of ashes as well as char to solve the concerns associated with their disposal. This will not only provides a cost-effective and environmental friendly way of recycling the solid residue wastes from gasification, significantly reducing its environmental effects, but also produces the highly-valued products.

SCOPE OF WORK
Figure 2 shows the overview of our GASIFICATION AND WASTE-TO-ENERGY researches which includes three main parts: (i) biomass and solid wastes gasification for syngas and/or electricity generation, focusing on both experimental and numerical simulation works; (ii) evaluation of human health and environmental effects of all emissions from the gasification system, mainly focusing on establishing a standard protocol for rapid screening of gasification ashes on the basis of in vitro and in vivo testing; and (iii) utilization of solid residual wastes generated from gasification process, mainly focusing on the conversion of fly/bottom ashes, char and other residues into high value materials.

Figure 2 Summary of our GASIFICATION AND WASTE-TO-ENERGY researches

Figure 2A Hybrid Energy System Combined Gasifier and Solar Energy (Green Building)

 

PARTNERSHIPS AND COLLABORATION
We have cooperated with industrial partner, i.e. Bioplas Energy (Asia Pacific) Pte Ltd., on developing of gasification systems (medium and industrial scales) for biomass and solid waste. Moreover, we have also cooperated with Sembcorp on developing of high value products from ash wastes arising from gasification and/or incineration facilities. 

OUR ACHIEVEMENTS
We have successfully conducted gasification of biomass and some solid wastes such as sewage sludge, chicken and horse manures and food waste by using downdraft fixed bed gasifier (lab scale) in order to produce syngas (as a fuel for electricity generation). We are now moving forward to the next step by collaborating with industrial partner in developing of gasification systems (including medium and industrial scales). Moreover, we are now also cooperating with another industrial partner in developing of high value products from ash wastes arising from gasification and/or incineration facilities.

MEDIA EXPOSURE

1. Eco-friendly way to dispose of waste(published at Apr 8, 2016, THE STRAITSTIMES):http://www.straitstimes.com/singapore/eco-friendly-way-to-dispose-of-waste

2. Found: Powerful ways of reusing waste(published at Nov 3, 2017, THE STRAITSTIMES):http://www.straitstimes.com/singapore/found-powerful-ways-of-reusing-waste

So far, our works have results in the significant amount of scientific publications and conference papers, as shown bellows:

Publications

1. Y. Shen, X. Li, Z. Yao, X. Cui, C.H. Wang, “CO2 gasification of woody biomass: Experimental study from a lab-scale reactor to a small-scale autothermal gasifier”, Energy, 170, 497-506 (2019).

2. X. Yang, A. Tsibart, H. Nam, J. Hur, A. El-Naggar, Fi. M.G. Tack, C.H. Wang, Y..H. Lee, D. C.W. Tsang, Y.S. Ok, “Effect of gasification biochar application on soil quality: trace metal behavior, microbial community, and soil dissolved organic matter”, Journal of Hazardous Material, 365, 684-694 (2019).

3. Y. Shen, C. He, X. Chen, A.A. Lapkin, W. Xiao, C.H. Wang, “Nitrogen removal and energy recovery from sewage sludge by combined hydrothermal pretreatment and CO2 gasification”, ACS Sustainable Chemistry & Engineering, in press (2018).

4. S. You, Y.S. Ok, D. C.W. Tsang, E.E. Kwon, C.H. Wang, “Towards Practical Application of Gasification: A Critical Review from Syngas and Biochar Perspectives”, Critical Reviews in Environmental Science and Technology, in press (2018).

5. X. Yang, W.C. Ng, B.S. Ee Wong, G. H. Baeg, C.H. Wang, Y. S. Ok, “Characterization and ecotoxicological investigation of biochar produced via slow pyrolysis: effect of feedstock composition and pyrolysis conditions”, Journal of Hazardous Materials, in press (2018).

6. A.Uzi,Y. Shen, K. Sibudjing, A. Levy, C.H. Wang, “Permittivity and chemical characterization of woody biomass during pyrolysis and gasification”, Chem. Eng. J. 355, 255-268 (2019).

7. K. Kima, C.H. Wang, Y. S. Ok, S.E. Lee, “Heart developmental toxicity by carbon black waste generated from oil refinery on zebrafish embryos (Danio rerio): Combined toxicity on heart function by nickel and vanadium”, Journal of Hazardous Materials, 363, 127-137 (2019).

8. S. You, Y.S. Ok, D. C.W. Tsang, E.E. Kwon, C.H. Wang, “Towards Practical Application of Gasification: A Critical Review from Syngas and Biochar Perspectives”, Critical Reviews in Environmental Science and Technology, in press (2018).

9. X. Cui, H. Li, Z. Yao, Y. Shen , Z. He, X. Yang, H. Y. Ng, C.H. Wang, “Removal of nitrate and phosphate by chitosan composited beads derived from crude oil refinery waste: sorption and cost-benefit analysis”, Journal of Cleaner Production, in press (2018).

10. H. Tong, Z. Yao, J. W. Lim, L. Mao, J. Zhang, T. Ge, Y.H. Peng, C.H. Wang, Y.W. Tong Harvest green energy through energy recovery from waste: A technology review and an assessment of Singapore Renewable & Sustainable Energy Reviews, in press (2018).

11. S. You, S.W. Ho, T. Maneerung, C.H. Wang, “Techno-economic analysis of geopolymer production from the coal fly ash with high iron oxide and calcium oxide contents”, J. Hazardous Materials, in press (2018).

12. X. Cui, Y. Shen, Q. Yang, S. Kawi, Z. He, X. Yang, C.H. Wang, “Simultaneous syngas and biochar production during heavy metal separation from Cd/Zn hyperaccumulator (Sedum alfredii) by gasification”, Chem. Eng. Journal 347, 543-551 (2018).

13. H. Tong, Y. Shen, J. Zhang, C.H. Wang, T.S. Ge, Y.W. Tong, “A comparative life cycle assessment on four waste-to-energy scenarios for food waste generated in eateries”, Applied Energy, 225, 1143-1157 (2018)

14. W. Y. Lin, W.C. Ng, B.S.E. Wong, S. L.M. Teo, G. d/o Sivananthan, G. H. Baeg, Y. S. Ok, C.H. Wang, “Evaluation of sewage sludge incineration ash as a potential land reclamation material”, J. Hazardous Materials, 357, 63-72 (2018).

15. X. Yang, A.D. Igalavithana, S.E. Oh, H. Nam, M. Zhang, C.H. Wang, E.E. Kwon, D.C.W. Tsang, Y.S. Ok, “Characterization of bioenergy biochar and its utilization for metal/metalloid immobilization in contaminated soil”, Science of the Total Environment, 640, 704-713 (2018).

16. S. You, Y.J. Lim, Y. Dai, C.H. Wang, “On the temporal modelling of solar photovoltaic soiling: Energy and economic impacts in seven cities”, Applied Energy, 228, 1136-1146 (2018).

17. Z. Yao, S. You, Y. Dai, C.H. Wang, “Particulate Emission from the Gasification and Pyrolysis of Biomass: Concentration, Size Distributions, Respiratory Deposition-based Control Measure Evaluation”, Environmental Pollution, 242, 1108-1118 (2018).

18. C.Y. Li, J.Y. Wu, Y. Shen, X. Kan, Y.J. Dai, C.H. Wang, “Evaluation of a combined cooling, heating, and power system based on biomass gasification in different climate zones in the U.S.”, Energy, 144, 326-340 (2018).

19. J.X. Zhang, X. Kan, Y. Shen, K.C. Loh, Y.J. Dai, C.H. Wang, Y.W. Tong. “A Hybrid Biological and Thermal Waste-To-Energy System with Heat Energy Recovery and Utilization for Solid Organic Waste Treatment.” Energy, 152, 214-222 (2018).

20. T. Maneerung, X. Li, C. Li , Y. Dai, C.H. Wang, “Integrated downdraft gasification with power generation system and gasification bottom ash reutilization for clean waste-to-energy and resource recovery system”, J. Cleaner Production, 188, 69-79 (2018).

21. W.C. Yan, Y. Shen, S. You, S.H. Sim, Z.H. Luo, Y.W. Tong, C.H. Wang, “Model-Based Downdraft Biomass Gasifier Operation and Design for Synthetic Gas Production”, J. Cleaner Production, 178, 476-493 (2018).

22. X. Kan, J. Zhang, Y.W. Tong, C.H. Wang, “Overall evaluation of microwave-assisted alkali pretreatment for enhancement of biomethane production from brewers’ spent grain”, Energy Management and Conversion, 158, 315-326 (2018).

23. X Kan, D. Zhou, W. Yang, X. Zhai, C.H. Wang, “An investigation on utilization of biogas and syngas produced from biomass waste in premixed spark ignition engine, Applied Energy, 212, 201-222 (2018).

24. G. Zhan, W.C. Ng, S.N. Koh, C.H. Wang, “Template-Free Synthesis of Alkaline Earth Vanadates Nanomaterials from Leaching Solutions of Oil Refinery Waste”, ACS Sustainable Chemistry & Engineering, 6(2), 2292-2301 (2018).

25. G. Zhan, W.C. Ng,W.Y. Lin, S N. Koh, C.H. Wang, “Effective Recovery of Vanadium from Oil Refinery Waste into Vanadium-Based Metal–Organic Frameworks”, Environmental Science & Technology, 52(5), 3008-3015 (2018).

26. J.L.X Hong, T. Maneerung, S.N. Koh, S. Kawi,and C.H. Wang, “Conversion of Coal Fly Ash into Zeolite Materials: Synthesis and Characterizations, Process Design, and Its Cost-Benefit Analysis”, I & EC Research, 56(40), 11565-11574 (2017).

27. Z. Yao, S. You, T. Ge, C.H. Wang, “Biomass Gasification for Syngas and Biochar Co-production: Energy Application and Economic Evaluation”, Applied Energy, 209, 43-55 (2018).

28. S. You, H. Tong, J. Armin-Hoiland, Y. W. Tong, C.H. Wang, “Techno-economic and Greenhouse Gas Savings Assessment of Decentralized Biomass Gasification for Electrifying the Rural Areas of Indonesia”, Applied Energy, 208, 495-510 (2017).

29. X. Li , Y. Shen, X. Kan, T. K. Hardiman, Y. Dai, C.H. Wang, “Thermodynamic assessment of a solar/autothermal hybrid gasification CCHP system with an indirectly radiative reactor”, Energy, 142, 201-214 (2017).

30. W.C. Ng, S. You, R. Ling, K.Y.H. Gin, Y. Dai, C.H. Wang, “Co-gasification of woody biomass and chicken manure: syngas production, biochar reutilization, and cost-benefit analysis”, Energy, 139, 732-742 (2017).

31. X. Li, M. Lin, Y. Dai, C.H. Wang, “Comparison-based optical assessment of hyperboloid and ellipsoid reflectors in a beam-down solar tower system with linear Fresnel heliostats”, Journal of Solar Energy Engineering, 139(6) (2017).

32. Y. Shen, M.T.T. Tan, C. Chong, W. Xiao, C.H. Wang, “An environmental friendly animal waste disposal process with ammonia recovery and energy production: Experimental study and economic analysis”, Waste Management, 68, 636-645 (2017).

33. S. You, Z. Yao, Y. Dai, C.H. Wang, “A comparison of PM exposure related to emission hotspots in a hot and humid urban environment: Concentrations, compositions, respiratory deposition, and potential health risks”, Science of the Total Environment, 599-600, 464-473 (2017).

34. C.H. Wang, D. Zhao, A. Tsutsumi, S. You, “Sustainable energy technologies for energy saving and carbon emission reduction”, Aplied Energy, 194, 223-224 (2017).

35. C.H. Wang, Y.W. Tong, K.C. Loh, R. Wang, X. Li, “Advanced technologies on sustainable energy and environment: SET2016 virtual special issue”, Energy, 137, 350-352 (2017).

36. S. You, Y.S. Ok, S. S. Chen, D.C.W. Tsang, E.E. Kwon, J. Lee, C.H. Wang, “A Critical Review on Sustainable Biochar System through Gasification: Energy and Environmental Applications”, Bioresource Technology, 246, 242-253 (2017).

37. S.S. Chen, T. Maneerung, D.C.W. Tsang, Y.S. Ok, C.H. Wang, “Valorization of Biomass to Hydroxymethylfurfural, Levulinic Acid, and Fatty Acid Methyl Ester by Heterogeneous Catalysts”, Chem. Eng. J. 328, 246-273 (2017).

38. S. Ramachandrana, Z. Yao, S. You, T. Massier, U. Stimming, C.H. Wang, “Life Cycle Assessment of a Sewage Sludge and Woody Biomass Co-gasification System”, Energy, 137, 369-376 (2017).

39. J. Zhang, K.C. Loh, J. Lee, C.H. Wang, Y. Dai, Y.W. Tong, “Three-stage anaerobic co-digestion of food waste and horse manure”, Scientific Report, 7, 1269 (2017).

40. Z. Yao, W. Li, X. Kan, Y. Dai, Y. W.Tong, C.H. Wang, “Anaerobic Digestion and Gasification Hybrid System for Potential Energy Recovery from Yard Waste and Woody Biomass”, Energy, 124, 133-145 (2017).

41. P. Dong, T. Maneerung, W.C. Ng, X. Zhen, Y. Dai, Y.W. Tong, Y.P. Ting, S.N. Koh, C.H. Wang, K.G. Neoh, “Chemically treated carbon black waste and its potential applications”, J. Hazardous Material, 321, 62-72 (2017).

42. X. Zhen, W.C. Ng, Fendy, Y. W. Tong, Y. Dai, K.G. Neoh, C.H. Wang, “Toxicity assessment of carbon black waste: a by-product from oil refineries”, J. Hazardous Material, 321, 600-610 (2017).

43. S. You, K.G. Neoh, Y.W. Tong, Y. Dai, C.H. Wang, “Variation of household electricity consumption and potential impact of outdoor PM2.5 concentration: A comparison between Singapore and Shanghai”, Applied Energy, 188, 475-484 (2017).

44. X. Kan, Z. Yao, J. Zhang, Y.W. Tong, W. Yang, Y. Dai, C.H. Wang “Energy performance of an integrated bio-and-thermal hybrid system for lignocellulosic biomass waste treatment”, Bioresource Technology, 228, 77-88 (2017).

45. T. Maneerung, S. Kawi, Y. Dai, C.H. Wang, “Sustainable Biodiesel Production via Transesterification of Waste Cooking Oil by using CaO Catalysts Derived from Chicken Manure”, Energy Management and Conversion, Energy Management and Conversion, 123, 487-497 (2016).

46. S. You, W. Wang, Y. Dai, Y. W. Tong, C.H. Wang, “Comparison of the co-gasification of sewage sludge and food wastes and cost-benefit analysis of gasification- and incineration-based waste treatment schemes”, Bioresource Technology, 218, 595-605 (2016).

47. T. Maneerung, J. Liew, Y. Dai, S. Kawi, C. Chong, C.H. Wang, “Activated carbon derived from carbon residue from biomass gasification and its application for dye adsorption: kinetics, isotherms and thermodynamic studies”,  Bioresource Technology, 200, 350–359 (2016).

48. Z. Yang, S.K. Koh, N.W. Cheng, C.J.R. Lim , Y. Shen, C. Chong, T.W. Tan, Y.W. Tong, Y. Dai, C.H. Wang, “Potential Application of Gasification to Recycle Food Waste and Rehabilitate Acidic Soil from Secondary Forests on Degraded Land in Southeast Asia”; Journal of Environmental Management, 172, 40-48 (2016).

49. X. Zhen, L. Rong, W.C. Ng, C. Ong, G. H. Baeg, W. Zhang, S.N. Lee, S.F.Y. Li, Y. Dai, Y.W. Tong, K.G. Neoh, C.H. Wang, “Rapid toxicity screening of gasification ashes”, Waste Management, 50, 93-104 (2016).

50. S. You, YW Tong, K.G. Neoh, Y. Dai, C.H. Wang, “On the Association between Outdoor PM2.5 Concentration and the Seasonality of Tuberculosis for Beijing and Hong Kong”, Environmental Pollution, 218, 1170-1179 (2016).

51. Y.P Cheng, Z. Thow, C.H. Wang, “Biomass Gasification with CO2 in a Fluidized Bed”, Powder Technology, vol. 296, pp. 87-101 (2016).

52. T. Maneerung, S. Kawi , C.H. Wang, “Biomass gasification bottom ash as a source of CaO catalyst for biodiesel production via transesterification of palm oil”, Energy Conversion and Management, 92, 234–243. (2015)

53. L. Rong, T. Maneerung, J. C. Ng, K. G. Neoh, B. H. Bay, Y. W. Tong, Y. Dai, C.H. Wang, “Co-gasification of sewage sludge and woody biomass in a fixed bed downdraft gasifier: Toxicity assessment of solid residues”, Waste Management, 36, 241-255 (2015).

54. Z. Ong, Y. Cheng, T. Maneerung, Z. Yao, Y. Dai, Y.W. Tong, C.H. Wang, “Co-gasification of woody biomass and sewage sludge in a fixed bed downdraft gasifier”, AIChE Journal, 61, 2508-2521 (2015)

55. Y. Cheng, W. Zhang, G. Guan, C. Fushimi, A. Tsutsumi, C.H. Wang, Numerical studies of solid–solid mixing behaviors in a downer reactor for coal pyrolysis, Powder Technology, 253, 722–732 (2014).

56. Y. Cheng, L. Lee, W. Zhang, C.H. Wang, “Investigation on Electrostatic Charging and Its Effect on Mixing of Binary Particles in a Vibrating bed”, Industrial and Engineering Chemistry Research, 53, 14166-14174 (2014).

57. Y. Cheng, C.H. Wang, “Numerical study on coal gasification in the downer reactor of a triple bed combined circulating fluidized bed”, Industrial and Engineering Chemistry Research, 53 (16), 6624–6635 (2014).

 

Conferences

1. C.H. Wang, “Investigation on electrostatics in the downer and its applications in coal gasification”, Collaborative Research Center for Energy Engineering (CEE) International Symposium 2012, Sanjo Conference Hall, The University of Tokyo, November 19-20, 2012 (Keynote Lecture).
http://www.energy.iis.u-tokyo.ac.jp/html_seminar/20121119/20121119_program.pdf

2. W. Zhang, Y. Cheng, C.H. Wang, C. Wang, W. Yang “Investigation on Hydrodynamics of Triple-Bed Combined Circulating Fluidized Bed using Electrostatic Sensor and Electrical Capacitance Tomography”, 9th European Congress of Chemical Engineering, World Forum, The Hagen, Netherlands, April 21-25, 2013.

3. Y. Cheng, C.H. Wang, “Numerical simulation of coal/biomass gasification for clean energy applications”, 9th European Congress of Chemical Engineering, World Forum, The Hagen, Netherlands, April 21-25, 2013.

4. Y. Cheng, C.H. Wang, “Numerical Study On Coal/Biomass Gasification in the Downer of a Triple-Bed Combined Circulating Fluidized Bed”, AIChE Annual Meeting, San Francisco, 3-8 November 2013.

5.  X. Jiang, W. Gao, Y. Cheng, K.G. Neoh and C.H. Wang, “Co-Gasification of Sewage Sludge and Biomass in a Fixed Bed Downdraft Gasifier”, AIChE Annual Meeting, San Francisco, 3-8 November 2013.

6.  C.H. Wang, “Numerical and experimental studies on biomass/sewage sludge co-gasification in downdraft gasifier”, 7th World Congress on Particle Technology, Beijing, 19-22 May, 2014. (Keynote Lecture)

7. Z. Ong, Y. Cheng, C.H. Wang, “Numerical study of biomass and sludge gasification in downdraft gasifiers”, The Sixth Global Chinese Symposium of Chemical Engineering: Education, Research and Development, Hong Kong, 16-19 July 2014. (Invited Lecture)

8.  C.H. Wang, K.G. Neoh, T. Maneerung, “WASTE-TO-ENERGY: Biomass/Solid Waste to Clean Energy through Gasification”, 13th International Conference on Sustainable Energy Technologies, HES-SO – Geneva – Switzerland, 25th – 28th August 2014.

9.  C.H. Wang, “Gasification of Wastewater Sludge”, The International Workshop on Biomass Energy, Faculty of Agricultural Technology UGM, Yogyakarta, Indonesia, 5-6 September, 2014. (Keynote Lecture)

10.  R Le, K.G. Neoh, YW Tong, TW Tan, Z Yang, C.H. Wang, “Toxicity Assessment of Bottom Ash from Biomass and Sewage Sludge Co-Gasification”, AIChE Annual Meeting, Atlanta, USA, 16-21 November, 2014.

11T. Maneerung, J. Liew, S. Kawi, C.H. Wang, “Development of Catalysts and Absorbents from Waste Materials”, AIChE Annual Meeting, Atlanta, USA, 16-21 November, 2014.

12Z. Ong, Y. Cheng, T. Maneerung, W.C. Yan, S.H. Sim, Z. Yao, Y. Dai, Y.W. Tong, C.H. Wang, “Biomass and Solid Waste Gasification for Clean Energy Production: Experimental and Simulation Studies”, AIChE Annual Meeting, Atlanta, USA, 16-21 November, 2014.

13. C.H. Wang, “Biomass and Solid Waste Gasification for Syngas Production and Utilization of Solid Residue”, 7th Global Chinese Chemical Engineering Symposium, Saixiang Hotel, Tianjin, China, 12-15 July 2015. (Plenary Lecture)

14. Z. Yang, S.K. Koh, W.C. Ng, R.C.J. Lim, H.T.W. Tan, Y.W. Tong, Y. Dai C. Chong, C.H. Wang, “Application of Biochar Arising from Gasification to Rehabilitate Soil of Tropical Secondary Forest on Degraded Land”, 14th International Conference on Sustainable Energy Technologies, Nottingham, UK, 25-27 August 2015.

15. P Dong, T. Maneerung, Z. Yang, Y Shen, X Kan, K.G. Neoh, C.H. Wang,, Y.W. Tong, Y. Dai C. Chong, “Co-gasification of Woody Biomass and Solid Waste for Clean Energy Production”, 14th International Conference on Sustainable Energy Technologies, Nottingham, UK, 25-27 August 2015.

16.  C.H. Wang, Y.W. Tong, “Challenges on the Co-gasification of Woody Biomass and Solid Waste: A Singapore Story on Waste Minimization and Energy Production”, 14th International Conference on Sustainable Energy Technologies, Nottingham, UK, 25-27 August 2015. (Keynote Lecture)

17.T. Maneerung, J. Liew, K.Sibudjing, Y. Dai, C.H. Wang, “Preparation and characterizations of activated carbon from char produced from woody biomass gasification and its application for dye removal”, AIChE Annual Meeting, Salt Lake City, Utah, USA, 7-13 November 2015.

18. X. Zhen, Fendy, W.C. Ng, P. Dong, Y. Dai, K.G. Neoh, C.H. Wang, “Oxidative stress and apoptosis induced by carbon soot in human cell line”, AIChE Annual Meeting, Salt Lake City, Utah, USA, 7-13 November 2015.

19. X. Zhen, L. Rong, C. Ong, G.H. Baeg, W. Zhang, S.N. Lee, S.F.Y. Li, Y. Dai, Y.W. Tong, K.G. Neoh, C.H. Wang “Rapid Toxicity Screening of Gasification Ashes”, AIChE Annual Meeting, Salt Lake City, Utah, USA, 7-13 November 2015.

20. Z. Yao, Y. Shen, W.C. Yan, Y. Dai, Y.W. Tong, C.H. Wang, “Numerical simulation and experimental study of fixed bed downdraft gasifier”, AIChE Annual meeting (November 2015), AIChE Annual Meeting, Salt Lake City, Utah, USA, 7-13 November 2015.

21. Z. Yao, W. Li, X. Kan, Y. Dai, Y.W. Tong, C.H. Wang, “Investigation of woody biomass and solid residue generated from anaerobic digestion and their allocation to potential energy generation”, AIChE Annual Meeting, Salt Lake City, Utah, USA, 7-13 November 2015.

22. X. Kan, Z. Yao, J. Zhang, Y.W. Tong, C.H. Wang, “Energy performance of a two-stage treatment for waste lignocellulosic biomass: Effects of organic loading rate, hydraulic residence time and carrier gas”, 15th International Conference on Sustainable Energy Technologies (SET2016), Singapore, 20-22 July 2016.

23. Z. Yao, W. Li, X. Kan, Y. Dai, Y.W. Tong and C.H. Wang, “Experimental and numerical study on combining anaerobic digestion and gasification for potential energy recovery from biomass and sewage sludge”, 15th International Conference on Sustainable Energy Technologies (SET2016), Singapore, 20-22 July 2016.

24. Y. Shen, C. Chong, W.D. Xiao, C.H. Wang, “Struvite precipitation for ammonia removal for gasification”, 15th International Conference on Sustainable Energy Technologies (SET2016), Singapore, 20-22 July 2016.

25. W.C. Ng, R. Ling, Y. Shen, Y. Dai, C.H. Wang, ‘Co-gasification of woody biomass and chicken manure for syngas production and reutilization of gasification derived biochar for water pollutant removal’, 15th International Conference on Sustainable Energy Technologies (SET2016), Singapore, 20-22 July 2016.

X. Kan, Y. Shen, Z. Yao, Y. Dai and C.H. Wang, “Numerical Study on Utilization of Biogas and Syngas Produced from Municipal Solid Waste in Internal Combustion Engine”, AIChE Annual Meeting, San Francisco, 12-18 November 2016. 26. W.C. Ng, W.L. Teo, P. Dong, Y.P. Ting, K.G. Neoh, C.H. Wang, “Leaching and recovery of vanadium from carbon soot”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

27. Y. Shen, W.C. Yan, W. Zhan, Y.W. Ng, Z.H. Luo, C.H. Wang, “Numerical Simulation of Downdraft Biomass Gasifier: Influence of Structure Designs Using CFD Simulation”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

28. Y. Shen, C. Chong, W. Xiao, C.H. Wang, “Struvite Precipitation for Nitrogen Removal in Horse Manure for Gasification: Experimental Study and Economic Analysis”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

29. Z. Yao, W. Li, X. Kan, Y. Dai, Y.W. Tong, C.H.Wang, “Experimental and Numerical Study on Combining Anaerobic Digestion and Gasification for Potential Energy Recovery from Biomass and Sewage Sludge”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

30. Z.Yao, S. You, W.C. Yan, Y. Dai, Y.W. Tong, C.H. Wang, “Experimental and Numerical Study on Combining Anaerobic Digestion and Gasification for Potential Energy Recovery from Biomass and Sewage Sludge”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

31. S. You, Z.Yao, Y. Dai, Y.W. Tong, C.H. Wang, “Size-Dependent Chemical Compositions in Particulate Matters from Major Outdoor Sources in a Megacity and Corresponding Inhalation Exposure Assessment”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

32. S. You, Z.Yao, Y. Dai, Y.W. Tong, C.H. Wang, “Particulate Pollutants Emission from Gasification and Corresponding Inhalation Exposure Assessment”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

33. W. Zhan, C.H. Wang, “Numerical Study on the Hydrodynamics Behaviour in Bubbling Fluidized Bed for Sewage Sludge Gasification”, AIChE Annual Meeting, San Francisco, 12-18 November 2016.

34. T. Maneerung, W.C. Ng, C.H. Wang, “Turning Biomass/Solid Waste into Energy and Valuable Materials”, 2nd International Conference on Biological Waste as Resource 2017 (BWR2017), Hong Kong, 25-27 May 2017 (Keynote Lecture)

35. S. You, Z. Yao, Y. Dai, Y.W. Tong, C.H. Wang, “Particulate emission from the gasication o solid wastes: Feedstock-dependant particle size distributions and chemical compositions”, 5th International Conference on Sustainable Solid Waste Management, Athens, Greece, 21–24 June 2017.

36. T. Maneerung, X. Li, S. Ye, K. Xiang, Y. Dai, C.H. Wang, “Conversion of Biomass and Waste Materials into Biofuel, Bioenergy and and Valuable Resources” 1st International Symposium on Bioenergy and Environment (BEE2017), Tianjin, China, 9-12 July, 2017.

37. X. Kan, D. Zhou, W. Yang, C.H. Wang, “A waste-to-energy study on utilization of biogas and syngas produced from biomass waste in internal combustion engine”, 16th International Conference on Sustainable Energy Technologies 17-20 July 2017, Bologna, Italy.

38. T. Maneerung, X. Li, C. Li, Y. Dai, C.H.Wang, “Combined fixed-bed gasification with power generation as a hybrid waste-to energy system”, Asian Particle Technology Symposium (APT2017) , Taoyuan, Taiwan, 30 August – 3 September 2017. 2017 (Keynote Lecture)

39. C.H. Wang, Y. Shen, W. Xiao, M.T.T. Tan, C. Chong, “Ammonia removal by struvite precipitation for horse manure waste gasification: Experimental study and economic analysis”, 10th World Congress of Chemical Engineering, Barcelona, Spain, 1-5 October, 2017