A techno-economic comparison of Fischer–Tropsch and fast pyrolysis as ways of utilizing sugar cane bagasse in transportation fuels production

Significance Statement

In recent years, critical issues such as energy security, petrol price upsurge and increasing consciousness of global warming, have all garnered attention from all walks of life to focus on the prospects of a bioenergy sector. The concept of biorefinery has recently emerged where biomass has already been identified as the sole source of renewable energy which has properties similar to fossil fuels. Sugarcane is currently the most cost-effective feedstock for the biofuel production and could become even cheaper and more advantageous if the waste bagasse would also be converted to biofuels. From various technoeconomic analysis, two techniques: the fast pyrolysis-hydro processing route and gasification coupled with Fischer–Tropsch synthesis, have been considered to be feasible for application in the large-scale production of bio fuels from the sugarcane bagasse.

In a recent paper published in Chemical Engineering Research and Design Stavros Michailos and Colin Webb from the School of Chemical Engineering and Analytical Science at University of Manchester in collaboration with David Parker at University of Exeter compared the economic and technological feasibility of the fast pyrolysis-hydro processing route (repurposed to enhance hydrogen production) and gasification coupled with Fischer–Tropsch synthesis processes. They aimed at resolving which between the two processes would deliver final products of fuels that can be directly used within the inherent technological infrastructure cheaply.

The adaptability of gasification followed by Fischer–Tropsch synthesis and fast pyrolysis coupled with hydro processing were examined against economic and thermodynamic criteria. Sugarcane bagasse was adopted as the feedstock at a flow rate of 100 metric tonnes per hour. The research team then utilized the Aspen plus process simulation software to build robust and thermodynamically rigorous simulations of the constituent processes of these biofuel conversion options processes. Mass, energy balance of the constituent processes, the overall thermochemical energy and economic efficiencies were calculated for each option based on the quantification and assessment of the yield.

From the comparative analysis of two near term biomass-to-liquid fuels conversion options, the researchers observed that the higher fuels productivity associated with the Fischer–Tropsch process resulted in in higher thermodynamic efficiencies than fast pyrolysis process. During fast pyrolysis, lignin is exploited in a steam cycle to generate electricity while in Fischer–Tropsch process, lignin is gasified and thereby it contributes to liquid fuels production. Moreover, almost forty percent of electricity generated by fast pyrolysis CHP unit is utilized to compress hydrogen. According to economic assessment Fischer–Tropsch process outplays fast pyrolysis process achieving higher values for all economic indicators. In addition, it is more lenient to variations of the elementary financial specifications. Conversely, the fast pyrolysis process delivers higher product diversity.

In light of the aforementioned remarks and outcomes, the choice of the best alternative conversion route depends on many aspects including factors aside from those enumerated in this study, such as market demand and location of the plant. However, at the moment and solely based on thermo-economic criteria Fischer–Tropsch process is more efficient than fast pyrolysis process mainly due to higher thermodynamic performance, minimal risk and substantial economic returns.

A techno-economic comparison of Fischer–Tropsch and fast pyrolysis as ways of utilizing sugar cane bagasse in transportation fuels production - renewable energy global innovations

Reference

Stavros Michailos1, David Parker2, Colin Webb1. A techno-economic comparison of Fischer–Tropsch and fast pyrolysis as ways of utilizing sugar cane bagasse in transportation fuels production. Chemical Engineering Research and Design. Volume 118 (2017) pages 206–214.

Show Affiliations
  1. School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
  2. School of Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK

 

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