272
12 Collagen
used for fishmeal. Collagen production from fish waste therefore serves a significant
role in helping to manage the waste generated from fisheries whether captured or
farmed.
12.6.3 Water Consumption
The water consumed is used in different aspects of collagen production, in the washing of the fish biomass prior to pretreatment, washing the pretreated biomass where it
has been pretreated with alkali and the water used in the main extraction. The purity
of water varies from clean tap water to ultrapure water which requires additional
energy to clean. In the washing stage using the hydrothermal method for extraction
of collagen from fish scales (Olatunji et al. 2014) as an example, water is used in an
estimated ratio of 13:1 (volume of water in ml to mass of fish waste in grams), in
the washing following pretreatment this usually requires repeated washing before the
water becomes neutral after sodium hydroxide pretreatment (in the case of extraction
from fish scales). If we assume it is washed six times after pretreatment in the same
water to fish waste ratio, this means for the cleaning and pretreatment stage about
91 ml of water is required per gram of fish scales. In the extraction process, more
water is used as the solvent for the extraction. For each gram of fish scales, 10 ml of
water is used. This makes an estimated 10 ml of water for every gram of collagen
produced from fish scales. The water from washing could be recycled either on site
or sent to water treatment plant. The water used in the extraction could be recovered
during the drying process by condensation, although this will then require further
energy and material consumption for these additional operations.
12.6.4 Energy Consumption
In the enzyme extraction process, less energy is consumed in heating as the extraction
is carried out at low temperature. However, energy is required for cooling. Where
the average room temperature in cold climates is around 16 °C and in hotter climates
could reach much higher temperatures of around 30 °C, energy input is required to
remove heat from the system such that at least 50 J is required per gram of water
being heated. Where hydrothermal extraction at 80 °C is used, energy is required
to heat the system from room temperature (assuming this to be about 25 °C) to
80 °C. This heating will require an input of about 230 J per gram of the water being
heated for the entire duration of the extraction. Additional energy is then utilized
in drying; this can be done either by freezing and sublimation in freeze drying or
by evaporation. Other operations requiring more energy input include operating the
centrifuge for separation at about 2500 rpm for about 15 min, the power consumed
per centrifuge cycle depends on the volume of the centrifuge and the power efficiency
of the particular unit.
12 Collagen
used for fishmeal. Collagen production from fish waste therefore serves a significant
role in helping to manage the waste generated from fisheries whether captured or
farmed.
12.6.3 Water Consumption
The water consumed is used in different aspects of collagen production, in the washing of the fish biomass prior to pretreatment, washing the pretreated biomass where it
has been pretreated with alkali and the water used in the main extraction. The purity
of water varies from clean tap water to ultrapure water which requires additional
energy to clean. In the washing stage using the hydrothermal method for extraction
of collagen from fish scales (Olatunji et al. 2014) as an example, water is used in an
estimated ratio of 13:1 (volume of water in ml to mass of fish waste in grams), in
the washing following pretreatment this usually requires repeated washing before the
water becomes neutral after sodium hydroxide pretreatment (in the case of extraction
from fish scales). If we assume it is washed six times after pretreatment in the same
water to fish waste ratio, this means for the cleaning and pretreatment stage about
91 ml of water is required per gram of fish scales. In the extraction process, more
water is used as the solvent for the extraction. For each gram of fish scales, 10 ml of
water is used. This makes an estimated 10 ml of water for every gram of collagen
produced from fish scales. The water from washing could be recycled either on site
or sent to water treatment plant. The water used in the extraction could be recovered
during the drying process by condensation, although this will then require further
energy and material consumption for these additional operations.
12.6.4 Energy Consumption
In the enzyme extraction process, less energy is consumed in heating as the extraction
is carried out at low temperature. However, energy is required for cooling. Where
the average room temperature in cold climates is around 16 °C and in hotter climates
could reach much higher temperatures of around 30 °C, energy input is required to
remove heat from the system such that at least 50 J is required per gram of water
being heated. Where hydrothermal extraction at 80 °C is used, energy is required
to heat the system from room temperature (assuming this to be about 25 °C) to
80 °C. This heating will require an input of about 230 J per gram of the water being
heated for the entire duration of the extraction. Additional energy is then utilized
in drying; this can be done either by freezing and sublimation in freeze drying or
by evaporation. Other operations requiring more energy input include operating the
centrifuge for separation at about 2500 rpm for about 15 min, the power consumed
per centrifuge cycle depends on the volume of the centrifuge and the power efficiency
of the particular unit.