10.6 Environmental Implications
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10.6.2 Solid Waste Generation
Compared to lignocellulosic land plants such as corn and sugarcane, algae biomass
has simpler composition. Brown algae, for example, comprise 15% laminarin, 18%
mannitol, 32% alginate and 35% ash and salts. Lignocellulosic plants, for example, corn stover, contain 35% cellulose, 19% hemicellulose, 16% lignin and other
compounds up to 27% (Konda et al. 2015). This means the solid residue generated
from the extraction of protein from algae results in less diverse range of compounds
which make the utilization of this waste less complex compared to residue from
lignocellulosic biomass.
10.6.3 Water Consumption
In extraction of proteins, water is used as the main extraction medium. Water is
also consumed in the washing of the biomass prior to extraction. In the cultivation
process, aquatic plants and algae have one major advantage over terrestrial plants of
not requiring freshwater. They can, in fact, be used to clean up water by extracting
the nutrients in the water for their metabolism. However, careful control of the levels
of the different nutrients is required for optimal growth and control of the yield of
the desired biopolymer from the aquatic plant or algae. In the extraction of protein
from Spirulina platensis, for example, 1 g of biomass required 15 ml of distilled
water as extraction medium (Yucetepe et al. 2018). Much of the water used in the
extraction process is then evaporated in the drying process, and this requires some
energy input. The water used in washing is either sent to external water treatment
plants or recycled internally. Where acids or alkalies are used, the water needs to
be neutralized and this requires the use of either more acid or alkali in the water
treatment.
10.6.4 Acids and Alkali
Although the enzyme extraction method relies on enzymes to break down the cell
walls with the aim of eliminating or at least minimizing the need for additional
chemicals, in some cases it is necessary to use acids or base to achieve the required
pH for enzymes to function optimally. Enzymes are proteins, and the activity of
these proteins is determined by their configuration as well as conformation (O’Brien
et al. 2012). The conformation is dependent on the pH of the environment within
which they are acting, therefore for specific enzymes, a specific pH is required. For
example, while alcalase is used, a pH 8 was required (Safi et al. 2017). This will
require the addition of an alkali to achieve this pH. However, this is relatively mild
as it is close to a neutral pH.
221
10.6.2 Solid Waste Generation
Compared to lignocellulosic land plants such as corn and sugarcane, algae biomass
has simpler composition. Brown algae, for example, comprise 15% laminarin, 18%
mannitol, 32% alginate and 35% ash and salts. Lignocellulosic plants, for example, corn stover, contain 35% cellulose, 19% hemicellulose, 16% lignin and other
compounds up to 27% (Konda et al. 2015). This means the solid residue generated
from the extraction of protein from algae results in less diverse range of compounds
which make the utilization of this waste less complex compared to residue from
lignocellulosic biomass.
10.6.3 Water Consumption
In extraction of proteins, water is used as the main extraction medium. Water is
also consumed in the washing of the biomass prior to extraction. In the cultivation
process, aquatic plants and algae have one major advantage over terrestrial plants of
not requiring freshwater. They can, in fact, be used to clean up water by extracting
the nutrients in the water for their metabolism. However, careful control of the levels
of the different nutrients is required for optimal growth and control of the yield of
the desired biopolymer from the aquatic plant or algae. In the extraction of protein
from Spirulina platensis, for example, 1 g of biomass required 15 ml of distilled
water as extraction medium (Yucetepe et al. 2018). Much of the water used in the
extraction process is then evaporated in the drying process, and this requires some
energy input. The water used in washing is either sent to external water treatment
plants or recycled internally. Where acids or alkalies are used, the water needs to
be neutralized and this requires the use of either more acid or alkali in the water
treatment.
10.6.4 Acids and Alkali
Although the enzyme extraction method relies on enzymes to break down the cell
walls with the aim of eliminating or at least minimizing the need for additional
chemicals, in some cases it is necessary to use acids or base to achieve the required
pH for enzymes to function optimally. Enzymes are proteins, and the activity of
these proteins is determined by their configuration as well as conformation (O’Brien
et al. 2012). The conformation is dependent on the pH of the environment within
which they are acting, therefore for specific enzymes, a specific pH is required. For
example, while alcalase is used, a pH 8 was required (Safi et al. 2017). This will
require the addition of an alkali to achieve this pH. However, this is relatively mild
as it is close to a neutral pH.