3.6 Environmental Implications
47
on site. This involves neutralization, settling, biological treatment followed by sand
filtration before it is then released into the sea.
3.6.3 Solid Waste/By-Products
Protein extracted is recycled and reused as fertilizers or animal feed. The calcium
salts produced are used either deposited in landfill sites or spread on the roads as
road-filling material. The manner in which the by-products are processed, discarded
or reused depends on the regulations in the region of operation and company choice.
This will therefore vary from company to company. For every kg of chitin produced,
1.5 kg of calcium salt and 4 kg of protein are produced. The European company is
estimated to produce 2.84 kg protein per kg of chitin produced. These solid wastes
generated from the extraction of chitin find application as fertilizers and animal feed
in the case of the protein and as road fillers in the case of the calcium salt. Shrimp
shells are also often used as animal feed, and the diversion of shrimp shells for chitin
production which in turn results in additional pressure on other animal feed sources
such as barley and soybeans is partly compensated for by the use of the protein from
the extraction as animal feed. Similarly, crab shells are often sent to composting sites
where they are used as organic fertilizers. The use of the protein sludge as fertilizers
also partly compensates for the crab shells diverted from agricultural use to chitin
production.
3.6.4 Sodium Hydroxide
From the chemical-based extraction processes discussed, it is obvious that there is
a relatively large amount of acids and alkalis used from deproteinization to demineralization and even much more sodium hydroxide (up to 50%) is required for the
deacetylation of chitin to its more industrially relevant form, chitosan. This has a
lot of environmental impact, and the cost of the chemicals and the cost of disposing
them need to also be considered.
A life cycle assessment of sodium hydroxide which evaluated the environmental
impact of sodium hydroxide from the production to its use and disposal shows that for
every kg of sodium hydroxide used, 3.5 MJ of fossil energy is consumed, 0.6329 kg
of carbon dioxide is emitted which contributes to global warming, 1.298 g of 1,4
dichlorobenzene equivalents are released into the aquatic environment, 0.706 of sulfur dioxide equivalents are released into the atmosphere which further contributes to
acid rain and 0.4927 g of carcinogens are released to human exposure (Thannimalay
et al. 2013).
Mahtani Chitosan reports 1.3 kg sodium hydroxide used per kg of chitin and a
further 5.18 kg used per kg of chitosan produced from the chitin. Company X reports
47
on site. This involves neutralization, settling, biological treatment followed by sand
filtration before it is then released into the sea.
3.6.3 Solid Waste/By-Products
Protein extracted is recycled and reused as fertilizers or animal feed. The calcium
salts produced are used either deposited in landfill sites or spread on the roads as
road-filling material. The manner in which the by-products are processed, discarded
or reused depends on the regulations in the region of operation and company choice.
This will therefore vary from company to company. For every kg of chitin produced,
1.5 kg of calcium salt and 4 kg of protein are produced. The European company is
estimated to produce 2.84 kg protein per kg of chitin produced. These solid wastes
generated from the extraction of chitin find application as fertilizers and animal feed
in the case of the protein and as road fillers in the case of the calcium salt. Shrimp
shells are also often used as animal feed, and the diversion of shrimp shells for chitin
production which in turn results in additional pressure on other animal feed sources
such as barley and soybeans is partly compensated for by the use of the protein from
the extraction as animal feed. Similarly, crab shells are often sent to composting sites
where they are used as organic fertilizers. The use of the protein sludge as fertilizers
also partly compensates for the crab shells diverted from agricultural use to chitin
production.
3.6.4 Sodium Hydroxide
From the chemical-based extraction processes discussed, it is obvious that there is
a relatively large amount of acids and alkalis used from deproteinization to demineralization and even much more sodium hydroxide (up to 50%) is required for the
deacetylation of chitin to its more industrially relevant form, chitosan. This has a
lot of environmental impact, and the cost of the chemicals and the cost of disposing
them need to also be considered.
A life cycle assessment of sodium hydroxide which evaluated the environmental
impact of sodium hydroxide from the production to its use and disposal shows that for
every kg of sodium hydroxide used, 3.5 MJ of fossil energy is consumed, 0.6329 kg
of carbon dioxide is emitted which contributes to global warming, 1.298 g of 1,4
dichlorobenzene equivalents are released into the aquatic environment, 0.706 of sulfur dioxide equivalents are released into the atmosphere which further contributes to
acid rain and 0.4927 g of carcinogens are released to human exposure (Thannimalay
et al. 2013).
Mahtani Chitosan reports 1.3 kg sodium hydroxide used per kg of chitin and a
further 5.18 kg used per kg of chitosan produced from the chitin. Company X reports