useful in studies focusing on the bioremediation service of seaweed
cultivation [45].
The use of impact categories from well-known methods supports comparability of results among different studies. However,
practitioners can create new impact categories to include aspects
relevant for the aquaculture sector, such as sea surface occupation
[46, 47], sea bottom impact [48], and phosphorus-limited marine
eutrophication [45]. Other impacts such as on biodiversity have
been developed for other systems; however, no characterization
factors have been set up for marine environment yet [30, 49–51].
5.1 Impact
Categories Used in
Seaweed Sector
Climate change is the most common impact category used in LCA
of seaweed production. Thanks to the photosynthesis, seaweed acts
as a temporary storage of carbon and reducing the concentration of
carbon dioxide in the atmosphere. The management of biomass
defines where and when the carbon is released, the carbon balance
of the system, and possible interaction with the nitrogen cycle. The
end-of-life scenario is a key process to describe when calculating the
net carbon balance. When modelling a biorefinery system for production of fuel, fertilizer, and fish feed, part of the carbon remains
in the soil for more than 100 years, delivering a carbon sequestration service [52]. When seaweed is converted in an energy vector,
the balance between absorption and emissions (during use phase) is
considered neutral [53]. However, a thorough mass balance of the
carbon and nitrogen within the system boundary can reveal if other
greenhouse gases emissions occur, e.g., methane loss during
storage [40].
Cumulative energy demand (CED) [54], energy return on
energy investment (EROI), [55] and fossil depletion [41] are
useful impact categories for studies focusing on biofuel production
[12, 14, 16, 45]. These categories consider the total energy
(or fossil resources) required from society to produce 1 unit of
available energy. The result is a quantification of energy efficiency
of the process and can highlight the best performance between
seaweed-based biofuels and their fossil alternatives.
Seaweed cultivation is often considered as a bioremediation
technology to reduce eutrophication [56, 57]. During the growth
phase, seaweed can absorb up to 32 kg nitrogen and 17 kg phosphorus from the water per ton dry weight [45]. Eutrophication
impact categories help the practitioner to evaluate the balance
between seaweed bioextraction and system emissions during processing and end-of-life phases. The CML method offers a single
impact category that converts both emissions of nitrogen and
phosphorus in units of phosphate equivalents [42]. ReCiPe and
ILCD methods differentiate between marine eutrophication,
assumed to be nitrogen limited, and freshwater eutrophication,
phosphorus limited. Marine eutrophication is therefore quantified
Life Cycle Assessment
111
cultivation [45].
The use of impact categories from well-known methods supports comparability of results among different studies. However,
practitioners can create new impact categories to include aspects
relevant for the aquaculture sector, such as sea surface occupation
[46, 47], sea bottom impact [48], and phosphorus-limited marine
eutrophication [45]. Other impacts such as on biodiversity have
been developed for other systems; however, no characterization
factors have been set up for marine environment yet [30, 49–51].
5.1 Impact
Categories Used in
Seaweed Sector
Climate change is the most common impact category used in LCA
of seaweed production. Thanks to the photosynthesis, seaweed acts
as a temporary storage of carbon and reducing the concentration of
carbon dioxide in the atmosphere. The management of biomass
defines where and when the carbon is released, the carbon balance
of the system, and possible interaction with the nitrogen cycle. The
end-of-life scenario is a key process to describe when calculating the
net carbon balance. When modelling a biorefinery system for production of fuel, fertilizer, and fish feed, part of the carbon remains
in the soil for more than 100 years, delivering a carbon sequestration service [52]. When seaweed is converted in an energy vector,
the balance between absorption and emissions (during use phase) is
considered neutral [53]. However, a thorough mass balance of the
carbon and nitrogen within the system boundary can reveal if other
greenhouse gases emissions occur, e.g., methane loss during
storage [40].
Cumulative energy demand (CED) [54], energy return on
energy investment (EROI), [55] and fossil depletion [41] are
useful impact categories for studies focusing on biofuel production
[12, 14, 16, 45]. These categories consider the total energy
(or fossil resources) required from society to produce 1 unit of
available energy. The result is a quantification of energy efficiency
of the process and can highlight the best performance between
seaweed-based biofuels and their fossil alternatives.
Seaweed cultivation is often considered as a bioremediation
technology to reduce eutrophication [56, 57]. During the growth
phase, seaweed can absorb up to 32 kg nitrogen and 17 kg phosphorus from the water per ton dry weight [45]. Eutrophication
impact categories help the practitioner to evaluate the balance
between seaweed bioextraction and system emissions during processing and end-of-life phases. The CML method offers a single
impact category that converts both emissions of nitrogen and
phosphorus in units of phosphate equivalents [42]. ReCiPe and
ILCD methods differentiate between marine eutrophication,
assumed to be nitrogen limited, and freshwater eutrophication,
phosphorus limited. Marine eutrophication is therefore quantified
Life Cycle Assessment
111