80
4 Alginates
Seaweed cultivation, although requires less land space, does not always involve
less resource usage when compared to terrestrial crops such as corn, sugar beet or
potatoes. The resource consumption varies for different methods of cultivation, and
brown algae cultivation is particularly more resource intensive as the reproductive
process of brown algae is a more complex alternating reproductive cycle compared
to those which reproduce vegetatively. Aquaculture of cush algae generally requires
more resource use than wild-sourced seaweed. Because some seaweed cultivation
involves permanent or partial occupation of aquatic environment, this could have
further impacts such as blockage of sunlight for aquatic life below and mechanical
displacement. Cultivation of seaweed, however, reduces problems such as loss of
seaweed species through overharvesting of wild stocks.
Contrary to algae grown for direct food consumption which are mostly grown on
a commercial scale in aquaculture, seaweed for algae production is best grown wild
and harvested from natural source. Seaweed harvest for algae production, therefore,
requires less resource consumption outside of transport and the much less temporary
impact of the process of harvesting.
4.6.2 Chemicals
Based on the sample case study (Konda et al. 2015) which is representative of a
typical bench-scale extraction process, producing 26 mega tones of sodium alginate
pellets requires 720 MT formalin at a concentration of 0.1%, 835 MT of HCl at 0.38%
concentration, 73 MT of sodium carbonate at 10% concentration for extraction, 500
MT of calcium chloride at 10% concentration for the formation of insoluble calcium
alginate salt and a further 4.2 MT of sodium hypochlorite at 5% for bleaching. More
HCl is then used for neutralization after bleaching requiring a further 150 MT of 3.6%
concentration. Sodium carbonate is then added again to reform the sodium alginate
salt and this requires about 80 MT at 10%. Finally, the extracted product is purified
and dried using around 140 MT of air and 281 MT of a mixture of ethanol, methanol
and acetone at around 48% or as required. Although alginate is a biopolymer from
a natural renewable source, the use of mineral-based acids and alkali and other
chemicals may have contradictory impact on the objective of alginate as a greener
alternative to synthetic fossil-based polymers.
4.6.3 Land Use
A general advantage of aquatic sourced raw materials for biopolymers is that the
raw materials do not require large land areas for production; rather, they make use of
aquatic space. This is significant as land spaces for human habitation are becoming
more limited due to the increasing population of humans and the need for more
land space to grow food crops and rear land animals for survival of the population.
4 Alginates
Seaweed cultivation, although requires less land space, does not always involve
less resource usage when compared to terrestrial crops such as corn, sugar beet or
potatoes. The resource consumption varies for different methods of cultivation, and
brown algae cultivation is particularly more resource intensive as the reproductive
process of brown algae is a more complex alternating reproductive cycle compared
to those which reproduce vegetatively. Aquaculture of cush algae generally requires
more resource use than wild-sourced seaweed. Because some seaweed cultivation
involves permanent or partial occupation of aquatic environment, this could have
further impacts such as blockage of sunlight for aquatic life below and mechanical
displacement. Cultivation of seaweed, however, reduces problems such as loss of
seaweed species through overharvesting of wild stocks.
Contrary to algae grown for direct food consumption which are mostly grown on
a commercial scale in aquaculture, seaweed for algae production is best grown wild
and harvested from natural source. Seaweed harvest for algae production, therefore,
requires less resource consumption outside of transport and the much less temporary
impact of the process of harvesting.
4.6.2 Chemicals
Based on the sample case study (Konda et al. 2015) which is representative of a
typical bench-scale extraction process, producing 26 mega tones of sodium alginate
pellets requires 720 MT formalin at a concentration of 0.1%, 835 MT of HCl at 0.38%
concentration, 73 MT of sodium carbonate at 10% concentration for extraction, 500
MT of calcium chloride at 10% concentration for the formation of insoluble calcium
alginate salt and a further 4.2 MT of sodium hypochlorite at 5% for bleaching. More
HCl is then used for neutralization after bleaching requiring a further 150 MT of 3.6%
concentration. Sodium carbonate is then added again to reform the sodium alginate
salt and this requires about 80 MT at 10%. Finally, the extracted product is purified
and dried using around 140 MT of air and 281 MT of a mixture of ethanol, methanol
and acetone at around 48% or as required. Although alginate is a biopolymer from
a natural renewable source, the use of mineral-based acids and alkali and other
chemicals may have contradictory impact on the objective of alginate as a greener
alternative to synthetic fossil-based polymers.
4.6.3 Land Use
A general advantage of aquatic sourced raw materials for biopolymers is that the
raw materials do not require large land areas for production; rather, they make use of
aquatic space. This is significant as land spaces for human habitation are becoming
more limited due to the increasing population of humans and the need for more
land space to grow food crops and rear land animals for survival of the population.