Superheated Steam Torrefaction of Biomass Residues with Valorisation of Platform Chemicals—Part 1: Ecological Assessment

Abstract

Within the last decade, research on torrefaction has gained increasing attention due to its ability to improve the physical properties and chemical composition of biomass residues for further energetic utilisation. While most of the research works focused on improving the energy density of the solid fraction to offer an ecological alternative to coal for energy applications, little attention was paid to the valorisation of the condensable gases as platform chemicals and its ecological relevance when compared to conventional production processes. Therefore, the present study focuses on the ecological evaluation of an innovative biorefinery concept that includes superheated steam drying and the torrefaction of biomass residues at ambient pressure, the recovery of volatiles and the valorisation/separation of several valuable platform chemicals. For a reference case and an alternative system design scenario, the ecological footprint was assessed, considering the use of different biomass residues. The results show that the newly developed process can compete with established bio-based and conventional production processes for furfural, 5-HMF and acetic acid in terms of the assessed environmental performance indicators. The requirements for further research on the synthesis of other promising platform chemicals and the necessary economic evaluation of the process were elaborated.

Superheated Steam Torrefaction of Biomass Residues with Valorisation of Platform Chemicals Part—2: Economic Assessment and Commercialisation Opportunities

“…Table 1 lists the assumptions and parameters for the economic analysis. The determination of the investment costs is based on a list of equipment that is developed from the process flow diagram [37] and Part 1 of our publication series in the Materials and Methods section [41], and thus on the mass and energy balance of the biorefinery. For this purpose, the process equipment was dimensioned for an input flow of 1000 kg/h of chipped beech wood residue within the scope of this project.…”

“…The biorefinery investigated in this publication series fulfills both the ecological [41] and the economic sustainability criteria, provided that product revenues do not fall by more than 15% compared to the current market price level.…”

Exploring the Properties of the Torrefaction Process and Its Prospective in Treating Lignocellulosic Material

“…Here, we distinguish between different types of torrefaction. In general, we differ the types into primary media phase or carrying gas or dry torrefaction, then wet torrefaction [39], then steam torrefaction [40]. The comparison of different torrefactions, their advantages and disadvantages, and a review of some recent papers is presented in Table 3.…”