There is a high need for alternative cleaner solid fuels, as emissions from fossil fuel utilization directly contribute to global warming and environmental pollution. Biomass, such as agricultural and forest residues, are produced in high amounts (millions of tonnes) worldwide, which have the potential to contribute to cleaner energy and electricity production. For that reason, countries like Finland, Sweden, Norway, Canada, Austria, Germany, USA, UK, and China are now actively increasing the share of bioenergy in their energy mix.
However, the ash composition of these biomass residues is a big challenge, severely limiting their utilization in large-scale thermochemical applications for bioenergy and biofuel production, such as combustion, pyrolysis, and gasification.
In this dissertation work, Singhal tried to tackle this challenge by improving the composition of different types of biomasses using water-washing pretreatment. Water washing is a low-cost, effective, and simple pretreatment option compared to other pretreatment options such as torrefaction, steam explosion and acid washing. However, it’s been limitedly explored so far and has not been adapted for large-scale applications.
A more advanced pretreatment method – Step washing
In this dissertation, Singhal studied the effect of water washing on the inorganic composition of five different biomasses (wheat straw, rice straw, groundnut shell, empty fruit bunches of oil palm and spruce bark) and improved overall scientific understanding of the pretreatment. Singhal conducted this dissertation in close collaboration with Valmet Technologies Oy and partly with the Department of Chemical Engineering, Lund University, Sweden.
In this dissertation, Singhal studied the effect of water washing on the inorganic composition of five different biomasses which are wheat straw, rice straw, groundnut shell, empty fruit bunches of oil palm and spruce bar, and improved overall scientific understanding of the pretreatment.
“One of the major highlights of the dissertation work is the “step washing method” which is a novel washing method developed during the dissertation work. It is much more effective than conventional single-step washing process with 90-100% removal efficiency and takes much less time, only 4-15 min instead of 6-24 hrs”, Singhal says.
Another major highlight of the work is the extensive laboratory-, bench-, and pilot-scale testing conducted with the help of Valmet. It testifies that water washing is an effective method for improving biomass fuel quality, and it can be upscaled successfully for large-scale practical applications.
The dissertation was conducted as a part of the Doctoral School of Industrial Innovation (DSII).
Besides six open access journal publications, data from this dissertation is published openly in Phyllis 2 database (organized by TNO, The Netherlands) for the scientific community and public use.
Singhal is from Rajasthan, India. He will continue working at the Faculty of Engineering and Natural Sciences, Tampere University, as a postdoctoral researcher focusing on combined leaching and steam explosion pretreatment of biomass, and life-cycle analysis of different waste streams.
Public Defence on Friday 28 April
The doctoral dissertation of M. Tech. Abhishek Singhal in the field of Energy and Environmental Engineering titled Improving inorganic composition of lignocellulosic biomass by water leaching pretreatment for thermochemical applications will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University auditorium Pieni Sali 1 in the Festia building, Hervanta Campus (address: Korkeakoulunkatu 8, Tampere, Finland) at 12 o’clock on Friday, 28 April 2023. The Opponent will be Assistant Professor Nikolai De Martini, University of Toronto Canada. The Custos will be Professor Jukka Konttinen Tampere University from the Faculty of Engineering and Natural Sciences at Tampere University.
The doctoral dissertation is available online.
The public defence can be followed via remote connection.
Photo: Sheba Nair