• Study location Mälardalen University, room Beta (Västerås campus) and via Zoom
  • 2020-10-23 09:00–11:00

The public defense of Chaudhary Awais Salman’s doctoral thesis in Energy and Environmental Engineering

The public defense of Chaudhary Awais Salman’s doctoral thesis in Energy and Environmental Engineering will take place at Mälardalen University, room Beta (Västerås campus) and via Zoom at 09.00 on October 23.

Title: Waste integrated biorefineries: A path towards efficient utilization of waste

Serialnumber: 322

The faculty examiner is Associate Professor Mika Järvinen, Aalto University and the examining committee consists of Professor Jukka Konttinen, Tampere University, Associate Professor Elisabeth Wetterlund, Luleå University of Technology, Associate Professor Cecilia Sundberg, Swedish University of Agricultural Sciences.

Reserve: Associate Professor Xingxing Zhang, Dalarna University



If you want to participate as an audience in the dissertation, register with Madeléne Westerberg at madelene.westerberg@mdh.se no later than 19 October 2020. Indicate if you want to participate on site in the hall (hall Beta at Campus Västerås) or via a link. Also enter the first and last name you want to use if you participate via link.



Waste management systems have progressed from landfilling and dumping to its prevention, recycling, and resource recovery. In state-of-the-art waste management industries, waste is separated among various fractions and treated via suitable processes. The non-recyclable organic fraction of waste can be incinerated for combined heat and power (CHP) production while biodegradable waste can convert to biomethane through anaerobic digestion (AD) process.

Thermochemical processes e.g. gasification and pyrolysis are alternative processes to treat various fractions of waste. Even though gasification and pyrolysis of waste are not yet commercially mature technologies, greater benefits regarding energy and economics can be achieved by integrating them with existing waste management technologies. This thesis aims to design energy-efficient and cost-effective waste integrated biorefineries by integrating the thermochemical processing of waste in existing WtE technologies.

A system analysis of five process integration case studies has been studied through modelling and simulation. The first case assesses the limitations and operational limits of thermochemical processes retrofitted in existing waste-based CHP plants. Second and third case studies evaluate the feasibility of current CHP plants to shift from cogeneration to polygeneration of biofuels, heat, and power. In the fourth case study, a new process configuration is presented that couples the AD with pyrolysis. The last case deals with the handling of digested sludge from WWTPs through the integration of thermochemical processes.

The findings suggest that waste utilization in the integrated biorefineries enhances the flexibility of waste management in terms of products and operation. The waste biorefineries can also utilize infrastructure and products from existing waste industries through process integration and improve the overall process efficiencies and economics. Existing waste-based CHP plants can provide the excess heat for integrated thermochemical processes, however, modifications required are different for different gasifiers and pyrolzer. Similarly, waste can be utilized for various biofuels production along with heat and power without disturbing the operation of the CHP operation, but biomethane and DME showed higher process feasibility than methanol and drop-in biofuels.

The integration of pyrolysis with the AD process can almost double biomethane production. Drying of sludge digestate from WWTPs is the bottleneck step for its post-processing through thermochemical processes. However, waste heat from the existing CHP plant can be utilized for the drying of sludge that can also replace some of the boiler feed through coincineration with waste biomass.

The economic performance of waste integrated biorefineries will depend on the volatility of market conditions.

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