System engineering design that will fit the chosen location in the
harsh marine environment is a challenge. Attaching seaweeds to
ropes, lines, or nets is a traditional way of cultivation since installation
and maintenance costs are very low. One of the cultivation methods
is done by seeding directly to the ropes [14]. Another approach is via
transplantation: seedlings are grown indoors, then cultured in greenhouse tanks and finally the small fronds are transplanted onto ropes
in the sea. The ropes should be tensed to reduce diffusion boundary
layers surrounding the thalli, thus increasing water exchange for
efficient nutrient availability and fast growth [15, 16]. Horizontal
and vertical ropes systems were also discussed by Peteiro and Freire
[14]. A system with concentrically horizontal ropes was tested in Ref.
[17]. Seabed planting can be cited as well as cage system (opentopped cage anchored to the seafloor) for nearshore cultivation
[18]. Co-management with other offshore systems like wind farms,
for instance, was considered [19–22] and discussed as the environmentally and economically advantageous approach [23].
Optimizing downstream processing of the biorefineries is a complex task, which depends upon the species choice, their chemical
composition, available technologies, human resources, and economic and environmental impacts. Exergonomics, introduced by
Yantovsky for the analysis of energy systems [24], links invested and
operational exergy expenditures and allows one to find optimal
exergy efficiency of production systems [24, 25]. Yantovsky also
suggested that “for more reliable decision making, the simultaneous
optimization of three target functions: exergy, money, and pollution,
is needed” [24]. However, the designer should reduce not only
pollution from the system. The designer must also consider the
multiple complex effects the energy system—especially, a large scale
renewable energy system—has on the ecosystem services of the surrounding environment. In the next section, we will examine the use
of environmental exergonomcis, a recently developed tool for energy
and production system analysis [26], and for design and analysis of
offshore marine biorefineries. Environmental exergonomics includes
mechanical (technological efficiency of system), capital efficiency of
system, and environmental efficiency, measured by the eco-exergy
(exergy contribution of ecosystems to the biorefinery).
ä
Fig. 2 (continued) marked in red, and those permitting biomass production only at deeper waters marked in
blue. (b–d) Monthly estimates of (b) productive surface area; (c) mean biomass production potential; and (d)
total production potential within the five NDBP (red boxes and associated abbreviations in panel a) and
integrated globally (denoted GLB). Colors denote different months of the year. The analysis is performed over
locations associated with water depth of 100 m or shallower. The + signs mark annually integrated biomass
production potential at each region. Assumed biomass density of 4 kg m
À2
. Production potential will change
linearly with changes in assumed biomass density. Abbreviations: East Asia offshore waters (EAS), North
Atlantic (NAT), South America offshore waters—East (SAE), South America offshore waters—West (SAW),
West Africa offshore waters—South (WAS). Figure adapted from Ref. [75] with permit
14
Alexander Golberg et al.
harsh marine environment is a challenge. Attaching seaweeds to
ropes, lines, or nets is a traditional way of cultivation since installation
and maintenance costs are very low. One of the cultivation methods
is done by seeding directly to the ropes [14]. Another approach is via
transplantation: seedlings are grown indoors, then cultured in greenhouse tanks and finally the small fronds are transplanted onto ropes
in the sea. The ropes should be tensed to reduce diffusion boundary
layers surrounding the thalli, thus increasing water exchange for
efficient nutrient availability and fast growth [15, 16]. Horizontal
and vertical ropes systems were also discussed by Peteiro and Freire
[14]. A system with concentrically horizontal ropes was tested in Ref.
[17]. Seabed planting can be cited as well as cage system (opentopped cage anchored to the seafloor) for nearshore cultivation
[18]. Co-management with other offshore systems like wind farms,
for instance, was considered [19–22] and discussed as the environmentally and economically advantageous approach [23].
Optimizing downstream processing of the biorefineries is a complex task, which depends upon the species choice, their chemical
composition, available technologies, human resources, and economic and environmental impacts. Exergonomics, introduced by
Yantovsky for the analysis of energy systems [24], links invested and
operational exergy expenditures and allows one to find optimal
exergy efficiency of production systems [24, 25]. Yantovsky also
suggested that “for more reliable decision making, the simultaneous
optimization of three target functions: exergy, money, and pollution,
is needed” [24]. However, the designer should reduce not only
pollution from the system. The designer must also consider the
multiple complex effects the energy system—especially, a large scale
renewable energy system—has on the ecosystem services of the surrounding environment. In the next section, we will examine the use
of environmental exergonomcis, a recently developed tool for energy
and production system analysis [26], and for design and analysis of
offshore marine biorefineries. Environmental exergonomics includes
mechanical (technological efficiency of system), capital efficiency of
system, and environmental efficiency, measured by the eco-exergy
(exergy contribution of ecosystems to the biorefinery).
ä
Fig. 2 (continued) marked in red, and those permitting biomass production only at deeper waters marked in
blue. (b–d) Monthly estimates of (b) productive surface area; (c) mean biomass production potential; and (d)
total production potential within the five NDBP (red boxes and associated abbreviations in panel a) and
integrated globally (denoted GLB). Colors denote different months of the year. The analysis is performed over
locations associated with water depth of 100 m or shallower. The + signs mark annually integrated biomass
production potential at each region. Assumed biomass density of 4 kg m
À2
. Production potential will change
linearly with changes in assumed biomass density. Abbreviations: East Asia offshore waters (EAS), North
Atlantic (NAT), South America offshore waters—East (SAE), South America offshore waters—West (SAW),
West Africa offshore waters—South (WAS). Figure adapted from Ref. [75] with permit
14
Alexander Golberg et al.