Novel pathway from hazardous waste to hydrogen

Significance 

Recently, the use of fossil fuels has experienced stringent mitigation measures in an effort to minimize carbon emissions. This has favored the development of sustainable alternative renewable energy sources. In particular, hydrogen gas has attracted significant attention of researchers as a clean energy carrier owing to its zero emissions. However, the production of hydrogen gas has been hindered by several challenges.

Presently, considering the increasing population growth especially in town and city centers, production of manifold wastes has been on the rise with sewage sludge being at the forefront. Considering the high pollutant nature of sewage sludge, effective methods for proper treatment, use, and disposal of these wastes are highly desirable. In the recently published literature, thermochemical conversion of sludge to energy has been identified as an alternative and effective way of using the sewage sludge.

Among the available methods for converting sludge waste into energy, pyrolysis is widely preferred due to high production value and minimal emissions. It is generally used to convert sludge into hydrogen that can be used for the production of electric power. Even though present highly scale hydrogen production is done through coal gasification and natural gas steam reforming, current climatic changes and unpredictable fuel prices have shifted the focus to the development of non-fuel technologies for large scale hydrogen production. Currently, sludge pyrolysis has been identified as a promising solution despite its low efficiency. As such, various improvements are needed to unleash the full potential of sludge pyrolysis in production of hydrogen.

To this note, researchers from School of Environment, Tsinghua University (China): Dr. Ming Zhao, Fan Wang (Ph.D. candidate), Dr. Yiran Fan, Abdul Raheem (Ph.D. candidate), and researcher from Department of Mechanical and Process Engineering, ETH Zürich (Switzerland) Dr. Hui Zhou proposed the enhancing hydrogen gas production through sludge pyrolysis with carbon capture. It is the first time that alkaline pyrolysis of sewage sludge is investigated. This technology has the advantages of high carbon conversion, high H2 production, low COx production, and low tar formation, which has great potential in hazardous sludge management industry.

Additionally, based on the alkaline thermal treatment of sewage sludge, they investigate the effects of the following parameters: temperature, heating rate, and sodium hydroxide ratio on hydrogen production. Their main aim was to improve solid waste management through waste reduction, recycling, treatment and recovery, the work is currently published in the journal, International Journal of Hydrogen Energy.

The authors observed that sodium hydroxide significantly enhanced hydrogen production by suppressing carbon dioxide and carbon monoxide production. On the other hand, the high temperature was responsible for breaking down the bonds. For instance, the maximum hydrogen yield, that is, 10.3 mmol g-1 was achieved at a temperature of 500 °C. Furthermore, an optimum heating rate of 100 °C min-1 was noted to favor high hydrogen yield. To actualize their study, they performed solid residue analysis using the X-ray diffraction method and confirmed the existence of sodium carbonate in the solid.

In summary, the team proposed alkaline pyrolysis of sewage sludge in enhancing hydrogen production and verified the feasibility . According to their study, alkaline pyrolysis of sludge proved a promising solution for enhancing sludge management and beneficial use in producing hydrogen that will advance sustainable and carbon-free fuel development.

Novel pathway from hazardous waste to hydrogen - Advances in Engineering

About the author

Dr Ming Zhao is the founder of the Lab for Biomass Energy and CCU Technologies (LBC). He obtained his PhD in chemical engineering from the University of Sydney in 2010. The LBC’s research is focused on biomass conversion into value-added fuels and chemicals, and advanced materials and processes for CO2 capture and utilization.

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About the author

Fan Wang is a PhD candidate in the School of Environment, Tsinghua University Beijing, China. She received her bachelor degrees from School of Environmental Science and Engineering, Beijing Forestry University Beijing, China. She is working on high purity hydrogen production by catalytic pyrolysis of municipal sludge.

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About the author

Yiran Fan is a post-doctor in Tsinghua University. She has own the first class oversea outstanding post-doctor fellowship in 2018. She received her doctoral and master degrees from Department of Civil and Environmental Engineering, Imperial College London. Her research interests are biomass pyrolysis, utilization of biomass and municipal solid waste and soil remediation.

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About the author

Abdul Raheem is a PhD student with a China Government Scholarship in the School of Environment, Tsinghua University Beijing, China. Currently, he is working on parametric modeling of algal biomass gasification under the supervision of Dr Ming Zhao. He obtained his MSc from the Universiti Putra Malaysia in 2015.

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About the author

Hui Zhou is a Marie Skłodowska-Curie Individual Fellow in Department of Mechanical and Process Engineering, ETH Zurich. He received his doctoral and bachelor degrees from Department of Energy and Power Engineering, Tsinghua University, China, with a minor degree in Computer Science. He has won Outstanding Doctoral Graduate Award and Outstanding Doctoral Thesis Award in 2015. His doctoral thesis entitled Combustible Solid Waste Thermochemical Conversion has been published by Springer in 2017.

His research interests are catalysis in thermochemical energy conversion processes, utilization of biomass and municipal solid waste, renewable hydrogen production, and in-situ carbon capture.

Reference

Zhao, M., Wang, F., Fan, Y., Raheem, A., & Zhou, H. (2019). Low-temperature alkaline pyrolysis of sewage sludge for enhanced H2 production with in-situ carbon capture. International Journal of Hydrogen Energy, 44(16), 8020-8027.

Go To International Journal of Hydrogen Energy

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