Page 422 - Refining Biomass Residues for Sustainable Energy and Bioproducts

380 Refining Biomass Residues for Sustainable Energy and Bioproducts

Figure 16.5 Advances on waste valorization (Arancon et al., 2013).
Options for valorization of the entire algae biomass include (1) the use of intact
algae cells or (2) of disrupted whole cell content, or (3) fractionation of the biomass
into different fractions via biorefinery (Fig. 16.7).
Many cascading biorefinery approaches are elaborated to separate various
marketable fractions from the same algal biomass (Bastiaens et al., 2017). The production
of low-value compounds (like energy) combined with the valorization of remaining resid-
ual biomass (category 1) has been reviewed (Bastiaens et al., 2017; Maurya et al., 2016).
The ability to use sunlight as process energy and the potential to shift toward a more car-
bon neutral production turn algae-based bulk products into future sustainable and economi-
cally attractive products. Whole algae or oil extracts are convertible into a kind of fuel
applications including liquid-ethanol, biodiesel, and gaseous transport fuels—biogas and
biohydrogen—via catalytic cracking, enzymatic saccharification, and transesterification/
hydrogenation bioprocesses. Neutral lipids constitute the basis for biodiesel while sugars
can be converted into ethanol. In case of lipids as the target compound, deoiled parts of
algal biomass (remaining fraction) contain carbohydrates and proteins mainly and are
marketable for many applications including energy carriers, algae meal for animal and
fisheries feed, biosorbent to remove heavy metals, bioplastics production, and compost
making. Deoiled algae biomass with a high carbon:nitrogen (C:N) ratio is beneficial for
the production of methane, ethanol, and biohydrogen while a low C:N ratio means high