Page 167 - Refining Biomass Residues for Sustainable Energy and Bioproducts

A Biorefinery approach towards development of renewable platform chemicals 139

products. The evolution of microorganism and anaerobic network system paved a
way for the efficient and large diversity of quality molecules (Henrich et al., 2009).
The bio-based chemicals are produced based on bowtie principles involving nat-
ural chemical and ecological route. The base carbon bowtie is converted to redox
bowtie by electron donors. The following molecules are further converted to energy
molecules and polymeric storage compounds. The introduction of bowtie principle
faced various difficulties in terms of composition and quality. The issues were
solved by the biorefinery approach with limited set of platform chemicals of low
molecular weight. The realistic approach of biorefinery is expected to show reason-
able yield when the biomass has high mass fraction. The optimization of bowtie
principle was reported to be based on the selection of microorganism and crops.
This principle is associated with major challenge known as trade-off biomass. Also,
they require high separation and purification process, which simultaneously
increase the cost of production. Fermentation technology acts as core technology in
this industry. The capital cost was reported to be minimized with certain change in
the infrastructure and development of genomics techniques (Csete and Doyle,
2004).

6.3.3 Strategies involved in the conversion of biomass
The production of target chemicals obtained from renewable resources depends
mainly on two different strategies, namely, drop-in and emerging strategies. These
strategies differ in compatibility, processing technologies, utilization of feedstock,
and infrastructure. Drop-in strategy includes utilization of existing process chain
with the formation of intermediates. The platform molecules enter a mature market
as determined at larger size. An example of this strategy is the conversion of sugar
cane or corn (biomass resources) to ethanol (platform chemical) by fermentation
followed by dehydration into ethylene. In emerging strategies the desired final pro-
ducts are produced by new process chains. The infrastructure for the production of
platform chemicals is extensively modified. The market size of the product is
expected to face many challenges at its initial stage due to new implementation
technologies and a new market size. The investment is really high when compared
to the products produced by drop-in method, as there is no established method and
market. The production of 2,5-furandicarboxylic acid or levulinic acid ketals is the
best example of this approach utilizing hexose dehydration reactions (Gallezot,
2007; Corey, 1988; Weissermel and Harpe, 2003).

6.3.4 Constrains faced during the production of bio-based
chemicals
The cost of raw materials is one of the major limitations as they may occupy about
50% of the total cost. The reaction rate and productivity also influence during the
production process. The installation of continuous reactor with recycling unit has
reduced the limitations associated with the production process. The genetic