Environmental Engineering Reference
In-Depth Information
Within this chapter the status of the current fossil-based chemical industry is
briefly described with regards to the use of building-block chemicals, and an
analogy to a bio-based equivalent discussed. Current rationale around the concept
of platform molecules is discussed, leading to a working definition for these bio-
derived chemicals. The constituent parts of the biomass feedstock are reviewed,
and some possible chemicals derivable from each constituent are highlighted,
showing the importance of the composition of the biomass with regards to the
molecules obtainable from it. The processing technologies used to produce
platform molecules from biomass are described and a list of current platform
molecules given, with four examined in further detail (one from each of the
identified processing technologies).
The concept of bio-based platform molecules stems from the late twentieth
century where it was envisaged that simple, small molecules derivable from
biomass could be utilised as building blocks for higher-value chemicals and
materials [1, 2]. However, it was not until the US Department of Energy's (US
DOE) report on Top Value Added Chemicals from Biomass in 2004 that such
focus and intensive research was directed towards this type of biomass-derived
product [3]. It has been widely purported that the utilisation of biomass as a
replacement feedstock to fossil fuels requires the successful implementation of
integrated biorefineries, and that these biorefineries will need to simultaneously
produce fuels, energy and chemical/material products to operate competitively
against petroleum refineries. To assist in the progression towards a bio-based
economy and to accelerate the technical development of biorefineries, the US
DOE set out to critically assess the large range of biomass-derivable chemicals to
generate a succinct list of the most promising candidates, thus focusing global
research efforts. It was anticipated that the chemicals and materials produced
from a biorefinery would be the major source of profit in such operations, much
in the same way that petrochemicals, although representing less than 10% of
annually extracted fossil resources, enjoy a much higher profit margin than fossil
fuels and energy.
Interestingly, the US DOE 2004 report does not make reference to the term
'platform molecule', though it does discuss the analogy to fossil-derived base
chemicals. The 2004 report also focused on molecules derivable from sugars,
syngas and triglycerides, omitting chemicals derivable from lignin which were
addressed in a later report [4]. The building-block chemicals identified by the US
DOE were not all fully analogous to base chemicals; some (such as 2,5-furandi-
carboxylic acid, FDCA) are themselves produced from a building-block molecule
(i.e. 5-hydroxymethylfurfural, HMF). The US DOE report was instead aiming to
list molecules that could, with further development, be produced on a significant
scale and have a range of options for conversion to higher-value chemicals and
materials. In addition, some biomass-derivable chemicals were omitted as they
were already established on a commodity scale, such as bioethanol, and did not
require extensive research and development. Since publication of the US DOE
