Page 424 - Refining Biomass Residues for Sustainable Energy and Bioproducts

382 Refining Biomass Residues for Sustainable Energy and Bioproducts

three-dimensional, and cross-linked biopolymer having phenylpropane units with
relatively hydrophobic and aromatic properties. Due to these differences in their
chemical composition and structure, cellulose, hemicellulose, and lignin have dif-
ferent chemical reactivities. In addition to the complex nature of bioresources, the
inert chemical structure and the compositional ratio of carbon, hydrogen, and oxy-
gen in molecules in biomass present difficulties in the chemo-catalytic conversion
of biomass to fuels and chemicals. Therefore besides using the natural lignocellu-
losic biomass as a reactant, researchers often use model compounds for conver-
sion process studies.
Francavilla et al. (2015) targeted biooil and char as pyrolysis end products from
an algae species Dunaliella tertiolecta. In this case, to increase the economic value
of the biomass, the lipid fraction was extracted before the pyrolysis for recovery of
beta-carotene, phytosterols, and fatty acids. Integrated use of medium-value bulk
products (lipids, proteins, carbohydrates) in combination with the valorization of
residual biomass is a biorefinery approach that received attention once biodiesel
production was found feasible only at a longer term (Wijffels et al., 2010). Algae-
based proteins offer excellent nutritional quality by delivering all amino acids,
including all essential amino acids and can be used for human food as well as ani-
mal feed. Microalgae-derived starch can serve as a substrate for further microbial
fermentation processes. Microalgal polysaccharides find application as water-
soluble lubricants and thickening agents such as agar. Production of high-value
products coupled with residual biomass use is currently the most economically
attractive and feasible biorefinery approach considering the limited amount of algae
biomass that is available today. The target high-value markets are often associated
with nutraceuticals, cosmetics, and pharmaceutics. This residual biomass can be
valorized through energy applications, as fertilizer or for aquaculture or other food
and feed application, presuming no solvent application was employed in the extrac-
tion process. These are essential aspects to take into account when elaborating a
biorefinery-based value chain. Once the algae biomass is cultivated, one of the
main challenges during the biorefinery process is to preserve the compounds in the
remaining fractions, especially their bioactive properties.

16.6 Conclusion

Agricultural wastes are major source of biomass energy and bio-based materials.
Proper utilization of agrowastes could lead to sustainable rural development in
countries such as India that requires benign, viable resources of energy. The biore-
finery mode operates for converting agroindustrial residues into various products,
including biofuels and chemicals through a cascade of modern technologies such as
pyrolysis, gasification, Fisher Tropsch, and other catalytic processes. The develop-
ment of the agroindustrial waste-based biorefineries can help to stabilize the econ-
omy of the rural areas by offering a clean energy service through the replacement
of fossil fuel and creating energy security. A great extent of rigorous effort is