Environmental Engineering Reference
In-Depth Information
Table 4.4
Comparison of the four main processing technologies used for the production of
platform molecules from biomass.
Thermal
Chemical-catalytic
Biological
Extraction
Advantages
Widely applicable to
various biomass types
Widely applicable
to various biomass
types
Mild conditions
Higher-value
products
Can be decentralised
(liquefaction at site of
biomass production)
Good selectivity
Good
selectivity
Natural
products
Very fast
Fast
Natural
products
Disadvantages
Complex mixtures
produced
Toxic/corrosive
reagents may be
needed
Slow
Low quantity
of products
Harsh conditions
May require
specialised
heterogeneous
catalysts
Expensive
pretreatment,
recovery and
purification
Scalability
Unstable product
Mass transfer
issues when using
heterogeneous
catalysis
Specific
feedstock
(sugars)
required
Limited to a
small range
of products
Extraction can also form a useful pretreatment and can be a means by which to
obtain higher-value components such as waxes, sterols, pigments, flavours and
fragrances. For extraction of platform molecules, the focus should generally be on
those compounds that are available in large quantities such as triglycerides and
terpenes (pinenes and d-limonene).
Clearly apparent when considering all the processing techniques above is the
variety of molecules obtainable from the various biomass types by applying these
different technologies. Different biomasses and different desired platform mole-
cules require different processing technologies. Shown in Table 4.4 are some
general advantages and disadvantages for each of the four main technologies. No
one technology is inherently superior to another, and all are required for the
biorefinery to allow diversity in the platform molecules produced.
A biorefinery dealing with varied biomass feedstocks will most likely require
an approach to platform molecule production that integrates all four of the
processing technologies described above. This integrated approach is needed as
the constituent variability in biomass and the desire to access a range of platform
molecules warrants all four technologies to be available. Some platform molecules
require more than one processing technology for their production such as, for
example, FAMEs, which require extraction followed by chemical-catalytic
transesterification, or hydroxyl acids that involve first biological routes to PHAs,
followed by extraction and finally chemical-catalytic hydrolysis.
