Hutton Scholar Blogs: Powering the Blue Economy

AFS Hut­ton Junior Fish­eries Biol­o­gy Schol­ar, Katy Zhen, shares insights from her sum­mer in RAEL and con­duct­ing field work at the water, fish­eries, and ener­gy nexus

Starting the Summer

I am Katy, a 2025 Hut­ton Schol­ar of the Amer­i­can Fish­eries Soci­ety. This sum­mer I am work­ing with Alexan­dra Grayson and Dr. Daniel Kam­men at the Renew­able and Appro­pri­ate Ener­gy Lab­o­ra­to­ry, who, with Tufts Uni­ver­si­ty and the Uni­ver­si­ty of Cal­i­for­nia San Diego, have been answer­ing ques­tions at the nexus of wave ener­gy and the blue econ­o­my. The main task that I will be assist­ing with is “gen­er­at­ing ener­gy demand pro­files for blue econ­o­my indus­tries”. I will vis­it aqua­cul­ture farms on the west coast with my men­tor Alexan­dra to val­i­date some of the ener­gy demand datasets we’ve devel­oped and learn about the ener­gy effi­cient strate­gies these farms are imple­ment­ing. I will also be help­ing devel­op load pro­files, mod­els of ener­gy demand and where the demand is com­ing from, which dif­fer depend­ing on sea­son, time of day, and day of the week. 

I am par­tic­i­pat­ing in the Hut­ton Junior Fish­eries Biol­o­gy Pro­gram because of my inter­est in the envi­ron­men­tal sci­ences which was inspired by my child­hood grow­ing up in the height of the pol­lu­tion cri­sis in Chi­na. I felt called to fish­eries sci­ence specif­i­cal­ly because of my iso­la­tion from bod­ies of water as a child and my sud­den intro­duc­tion to aquat­ic habi­tats when I immi­grat­ed to San Fran­cis­co. Liv­ing next to the Bay and the pacif­ic ocean, I was intro­duced to the impor­tance of these habi­tats and inspired to pro­tect the health of the oceans.

Farmed fish and its growing demand

The glob­al pop­u­la­tion has grown dra­mat­i­cal­ly over the past decade, and the demand for food has risen accord­ing­ly. The lack of space and resources on land for ani­mal farm­ing has pushed many toward aqua­cul­tures as the response against food inse­cu­ri­ty. This sec­tor has extreme poten­tial con­sid­er­ing the fact that 70% of the plan­et is ocean but only 2% of human food pro­duc­tion comes from it. In fact, accord­ing to the 2024 edi­tion of The State of World Fish­eries and Aqua­cul­ture (SOFIA), the glob­al aqua­cul­ture pro­duc­tion has already increased by 4.4% since 2020 and will only con­tin­ue grow­ing in the next decades. How­ev­er, as the demand for aqua­cul­ture grown foods increas­es, so does the demand for ener­gy to pow­er these farms. In order to ensure that the indus­try grows sus­tain­ably, the Food and Agri­cul­ture Orga­ni­za­tion of the Unit­ed Nations (FAO) has pro­posed the Blue Trans­for­ma­tion, a vision to “expand aquat­ic food sys­tems and increase their con­tri­bu­tion to bet­ter pro­duc­tion, bet­ter nutri­tion, bet­ter envi­ron­ment and bet­ter life”.

In addi­tion to farm­ing fish for food, fish are often spawned and har­vest­ed at hatch­ery facil­i­ties for con­ser­va­tion. Recent­ly my men­tor Alexan­dra and I vis­it­ed Nim­bus Hatch­ery in Gold Riv­er, CA to val­i­date our fin­fish hatch­ery load pro­file data. There, we were intro­duced to their process of spawn­ing and rais­ing both salmon and steel­heads to be released back into the Amer­i­can Riv­er. The hatch­ery was orig­i­nal­ly built in com­pli­ance with a Cal­i­for­nia law which states that each com­pa­ny that builds a dam must be respon­si­ble for fund­ing a near­by hatch­ery to mit­i­gate for the loss of fish habi­tat. While vis­it­ing Nim­bus, I learned that an ener­gy inten­sive process at the hatch­ery was low­er­ing the water tem­per­a­ture through a cool­ing sys­tem. Female salmon are extreme­ly sen­si­tive to changes in water tem­per­a­ture and will only spawn eggs when the tem­per­a­ture is below a cer­tain threshold. 

There are mul­ti­ple types of aqua­cul­tures that are cur­rent­ly being uti­lized to farm seafood, with the main three being recir­cu­lat­ing aqua­cul­ture sys­tem (RAS) inland aqua­cul­ture sys­tem, non-RAS inland aqua­cul­ture, and off­shore marine aqua­cul­ture. Nim­bus hatch­ery accli­mate juve­nile fish they spawn using race­ways, which is a non-RAS aqua­cul­ture. Cer­tain types of non-RAS aqua­cul­ture, by many met­rics, are con­sid­ered the least sus­tain­able option due to their pol­lut­ing of fresh­wa­ter drink­ing sources and alter­ation of nat­ur­al land­scapes due to the large amount of land nec­es­sary. The hatch­ery man­ag­er men­tioned to us that he has been push­ing for the change to RAS aqua­cul­tures but lim­its in fund­ing have pre­vent­ed the switch. RAS aqua­cul­tures are a bet­ter alter­na­tive but they are extreme­ly ener­gy inten­sive. How­ev­er, with inno­va­tions in renew­able ener­gy, it has the poten­tial to be sus­tain­able and play a key role in grow­ing aqua­cul­ture pro­duc­tion and con­ser­va­tion needs in the future. The main issue with both of these options is that they are inland and there­fore com­pete for space with human and ani­mal pop­u­la­tions. Marine aqua­cul­tures are a loop­hole through this prob­lem due to the ocean’s expan­sive size, mak­ing it the choice with the most poten­tial for expand­ing pro­duc­tion. How­ev­er, off­shore aqua­cul­ture is not with­out its draw­backs, pos­ing harm to the marine ecosys­tem and the sov­er­eign­ty of trib­al nations by con­fin­ing non-native fish species in open-water cages and rais­ing the risk of dis­ease and pol­lu­tion. In 2017, the fail­ure of a Puget Sound net pen facil­i­ty released non-native salmon which com­pet­ed with native species for food and habitat. 

While marine aqua­cul­tures bypass the com­pe­ti­tion for land space, they also require large amounts of ener­gy. This is espe­cial­ly the case for off­shore aqua­cul­tures which are grow­ing in pop­u­lar­i­ty around the world. Ener­gy require­ments for these farms vary depend­ing on the species farmed but can include desali­na­tion, clean­ing, refrig­er­a­tion, mon­i­tor­ing, and light­ing. Feed­ing is often the most ener­gy inten­sive process, at times account­ing for 90% of ener­gy use, in fin­fish and crus­tacean farm­ing. Mol­lusks and oth­er low troph­ic marine (LTM) species often require less ener­gy because feed­ing is not nec­es­sary as they can direct­ly extract dis­solved nutri­ents from the marine envi­ron­ment. These species are com­mon­ly farmed on the west coast espe­cial­ly in Wash­ing­ton which is the num­ber one pro­duc­er of mol­lusks in the coun­try. In order to ensure that marine aqua­cul­ture can remain a sus­tain­able farm­ing option even as the mar­ket expands, the Pacif­ic North­west Nation­al Lab­o­ra­to­ry (PNNL) has been look­ing into how aqua­cul­tures can turn to renew­able ener­gy sources to ful­fill many of its ener­gy requirements. 

The off­shore renew­able ener­gy source with the most poten­tial for imple­men­ta­tion into aqua­cul­ture sys­tems is marine hydro-kinet­ic (MHK) ener­gy which derives ener­gy from the mechan­i­cal motion of ocean water, includ­ing waves, tides, and cur­rents. The PNNL sug­gests a method called co-loca­tion which would pair MHK ener­gy devices with aqua­cul­ture devel­op­ments. This arrange­ment can be mutu­al­ly ben­e­fi­cial for the two sec­tors. MHK ener­gy would pow­er aqua­cul­ture oper­a­tions, while aqua­cul­ture farms would pro­vide the marine ener­gy indus­try with an appli­ca­tion space and pro­mote fur­ther devel­op­ment in the field. As the co-loca­tion method is deployed across dif­fer­ent case stud­ies around the world, it is obvi­ous that the method has clear ben­e­fits includ­ing cost sav­ings on ener­gy use, abil­i­ty to min­i­mize envi­ron­men­tal effects by low­er­ing green­house gas emis­sions, and the abil­i­ty for excess pow­er from MHK devices to pro­vide pow­er to onshore facil­i­ties like hatch­eries and pro­cess­ing facil­i­ties. The main bar­ri­ers to imple­ment­ing co-loca­tion in aqua­cul­ture oper­a­tions are the high costs asso­ci­at­ed with device instal­la­tions and the uncer­tain­ty regard­ing licens­ing and con­sent­ing pro­ce­dures since there is cur­rent­ly a lack of clear reg­u­la­to­ry frame­works due to the nascent­ness of MHK, espe­cial­ly in the US.

Oth­er than imple­ment­ing renew­able ener­gy into aqua­cul­ture devel­op­ments, there have also been oth­er strate­gies devel­oped to improve ener­gy effi­cien­cy with four notable ones being: under­wa­ter and autonomous feed­ing, LED lights, heat pumps, and bat­tery stor­age. In most cur­rent fin­fish aqua­cul­ture farms, salmon and oth­er fin­fish are fed through pneu­mat­i­cal­ly dri­ven, mechan­i­cal feed­ing sys­tems where feed is blown through tubes into indi­vid­ual pens. The fair­ly recent devel­op­ment of under­wa­ter feed­ing reduces the amount of ener­gy need­ed by 50–60% by trans­port­ing feed through the feed­ing hoses using water pres­sure. Sim­i­lar­ly, LED lights have 60% less ener­gy demand and dou­ble the life span com­pared to the halo­gen lights com­mon­ly used in the indus­try today. Cur­rent­ly, aqua­cul­ture farms that require heat­ing use elec­tri­cal heat­ing pan­els dur­ing the win­ter to main­tain a sta­ble tem­per­a­ture. How­ev­er, a more ener­gy effi­cient option is uti­liz­ing water to water heat pumps which can pull heat from the envi­ron­ment and deliv­er between 1.5–4.5 times the ener­gy they receive from the grid. Last­ly, ener­gy demand can be reduced through peak shav­ing by charg­ing bat­tery packs at hours with low demand to be used dur­ing peak hours.

As the demand for aqua­cul­ture foods con­tin­ues to grow, it is vital that we are meet­ing the demand with sus­tain­abil­i­ty in mind. Research has demon­strat­ed the ben­e­fits of expand­ing the off­shore aqua­cul­ture indus­try and it is cru­cial that we adapt accord­ing­ly in order to guar­an­tee food secu­ri­ty for the future. This is espe­cial­ly impor­tant in the Unit­ed States where we import 90% of our seafood and are falling behind oth­er coun­tries like Chi­na and Nor­way in terms of aqua­cul­ture farm­ing capabilities. 

Sources:

Mont­gomery, Kat. “Oppor­tu­ni­ties and bar­ri­ers fac­ing off­shore fin­fish farm­ing in the US.” (2019).

FAO. “The State of World Fish­eries and Aqua­cul­ture 2022: Towards Blue Trans­for­ma­tion.” (2022)

Free­man, M., et al. “Off­shore aqua­cul­ture: a mar­ket for ocean renew­able ener­gy.” Report for Ocean Ener­gy Sys­tems (OES) (2022).

Krause, Gesche, et al. “Prospects of low troph­ic marine aqua­cul­ture con­tribut­ing to food secu­ri­ty in a net zero-car­bon world.” Fron­tiers in Sus­tain­able Food Sys­tems 6 (2022): 875509.

Møller, Sofie. “Reduc­tion of CO2 Emis­sions in the Salmon Farm­ing Indus­try: The Poten­tial for Ener­gy Effi­cien­cy Mea­sures and Elec­tri­fi­ca­tion.” MS the­sis. NTNU, 2019.

Hen­riks­son, Patrik. “Ener­gy effi­cien­cy of aqua­cul­ture.” Glob­al Seafood Alliance, 1 Sept. 2010, www​.glob​alseafood​.org/​a​d​v​o​c​a​t​e​/​e​n​e​r​g​y​-​e​f​f​i​c​i​e​n​c​y​-​a​q​u​a​c​u​l​t​u​re/.

Hardy, Ronald W. “Best man­age­ment prac­tices for salmon feeds.” Glob­al Seafood Ini­tia­tive, 1 Apr. 2004, www.globalseafood.org/advocate/best-management-practices-for-salmon-feeds/#:~:text=Feeding%20frequency%20and%20delivery,of%20feed%20that%20is%20lost.

Meeting Critical Minerals Demand using the Ocean

With the rise in pop­u­lar­i­ty of elec­tric vehi­cles, com­pa­nies like Tes­la have been increas­ing their pro­duc­tion rates. In fact, in 2024 alone, Tes­la pro­duced almost 2 mil­lion vehi­cles that each require bat­ter­ies made from crit­i­cal min­er­als like lithi­um and cobalt. The Ener­gy Act of 2020 defines a crit­i­cal mate­r­i­al as any non-fuel min­er­al, ele­ment, sub­stance, or mate­r­i­al that has a high risk of sup­ply chain dis­rup­tion and serves an essen­tial func­tion in one or more ener­gy tech­nolo­gies. This increase in demand for crit­i­cal mate­ri­als rais­es con­cerns that sup­plies might be insuf­fi­cient to meet these demands. Researchers have been work­ing on mod­el­ing future demand for these mate­ri­als. How­ev­er, detailed sce­nar­ios of met­als based on both sup­ply and demand have not emerged because there are more than 60 com­mon­ly used met­als in mod­ern tech­nol­o­gy and it is dif­fi­cult for these met­als to sub­sti­tute each oth­er, not to men­tion glob­al resources of met­al are not well quantified. 

One such study that quan­ti­fies future crit­i­cal min­er­als demand was devel­oped by the Cen­ter of Indus­tri­al Ecol­o­gy at Yale Uni­ver­si­ty and its four sce­nar­ios were inspired by the 17 Sus­tain­able Devel­op­ment Goals. Its results show that the “Secu­ri­ty Fore­most” sce­nario will have the least sub­stan­tial cumu­la­tive ener­gy demand. In this sce­nario, secu­ri­ty over­shad­ows oth­er val­ues and envi­ron­men­tal gov­er­nance is con­sid­ered low pri­or­i­ty. Tech­no­log­i­cal inno­va­tion and infra­struc­ture devel­op­ment and main­te­nance take a back seat, thus low­er­ing ener­gy use in many areas. In con­trast, the sce­nario that will cause the most cumu­la­tive ener­gy demand is the “Equi­tabil­i­ty World” sce­nario where all sec­tors work col­lec­tive­ly to sup­port the Sus­tain­able Devel­op­ment Goals. Envi­ron­men­tal issues are heav­i­ly focused on and hous­ing and ener­gy become gen­er­al­ly avail­able to all. The devel­op­ment in terms of infra­struc­ture rais­es the demand for crit­i­cal mate­ri­als. The results from this study show that the more invest­ment there is in renew­able ener­gy and eco­nom­ic growth, the greater the demand for crit­i­cal mate­ri­als will be. How­ev­er, this is not to dis­cour­age grow­ing the renew­able ener­gy mar­ket as the results also demon­strate that even with a lack of invest­ment in renew­able ener­gy, the sup­ply of these mate­ri­als would still fail to meet future demand. The future we want will hinge upon our abil­i­ty to appro­pri­ate­ly meet demand as we con­tin­ue to inno­vate sustainably.

Researchers at the Col­orado School of Mines did a com­par­a­tive review of 150 resource demand mod­els to deter­mine the pro­ject­ed scale of growth of renew­able ener­gy sources and how crit­i­cal mate­r­i­al short­ages will impact clean ener­gy. A wide vari­ety of min­er­al demand mod­els have been cre­at­ed based on the abil­i­ty to pre­dict the deploy­ment of clean ener­gy tech­nolo­gies and then cal­cu­lat­ing the mate­ri­als need­ed to build those tech­nolo­gies. How­ev­er, these mod­els all pro­duce vast­ly dif­fer­ent results depend­ing on what sources are used and what the mod­el­ers pri­or­i­tize. In fact, the review found that even among mod­els that used the same sce­nar­ios, results var­ied dras­ti­cal­ly and led to dif­fer­ent con­clu­sions. Although it is dif­fi­cult to spec­u­late if min­er­al mar­kets are advanc­ing fast enough to meet demand, this review states that the most plau­si­ble way to meet demand esti­mates is by min­ing remain­ing reserves. Anoth­er pop­u­lar sup­ply-side strat­e­gy is met­al recy­cling. While met­al recy­cling is impor­tant for the sus­tain­abil­i­ty of crit­i­cal min­er­als, total demand can­not be met through this process alone due to high dis­si­pa­tion rates and long prod­uct life times. 

How­ev­er, for many crit­i­cal min­er­als, min­ing reserves would only meet sup­ply demands for a few more decades. For exam­ple, extract­ing all 25 mil­lion tonnes of ter­res­tri­al reserves of cobalt would result in only anoth­er 30 years of sup­ply. This is the rea­son why many are now look­ing toward sea­wa­ter min­er­al har­vest­ing as the solu­tion for crit­i­cal min­er­al demand. Many rare earth ele­ments (REE) like lithi­um, ura­ni­um, and cobalt are more abun­dant in sea­wa­ter than on land.

Sea­wa­ter con­tains abun­dant amounts of min­er­als and gas­es that are even­ly dis­trib­uted unlike land-based min­er­als which are con­cen­trat­ed in cer­tain geo­log­ic struc­tures and geo­graph­ic loca­tions. In addi­tion, extract­ing min­er­als from sea­wa­ter is more envi­ron­men­tal­ly friend­ly and pos­si­bly more eco­nom­i­cal depend­ing on the method uti­lized. The most eco­nom­i­cal method is pas­sive adsorp­tion where the ocean cur­rents deliv­er sea­wa­ter to the adsor­bent for extrac­tion. To increase adsorp­tion, an elec­tri­cal field can be applied to the adsor­bent mate­r­i­al which will also pre­vent adsorp­tion of non-tar­get min­er­als through an elec­tro­chem­i­cal process. Anoth­er method being uti­lized is a mechan­i­cal­ly dri­ven extrac­tion sys­tem where the adsor­bent mate­r­i­al is exposed to sea­wa­ter and then dri­ven to the sur­face plat­form where min­er­als are extract­ed in a sol­vent bath. If the ener­gy used by the sys­tem is gen­er­at­ed from a marine ener­gy device, there is a sig­nif­i­cant cost reduc­tion because there would be no more need for trans­port ves­sels to deploy and retrieve adsor­bents. Marine ener­gy har­vest­ed at sea has the poten­tial to pow­er an elec­trolyz­er, per­form elec­tro­chem­i­cal extrac­tion, mechan­i­cal­ly dri­ve an active adsor­bent sys­tem, and pow­er on-site tech­ni­cal needs. An exam­ple of a mechan­i­cal­ly dri­ven sys­tem is the Sym­bi­ot­ic Machine for Ocean uRa­ni­um Extrac­tion (SMORE) which uses absorbent shells that are incre­men­tal­ly spaced along a chain. Recent research also shows that ele­ments with mul­ti­ple reduc­tion-oxi­da­tion states can poten­tial­ly be direct­ly extract­ed from sea­wa­ter using more tra­di­tion­al elec­tro­chem­i­cal process­es but this option is still unproven and nascent. 

Over­all, as demand for crit­i­cal min­er­als increas­es with the rise in renew­able energy,electrical vehi­cles, and glob­al eco­nom­ic growth, sea­wa­ter min­er­al har­vest­ing is emerg­ing as an incred­i­bly viable solu­tion. More envi­ron­men­tal­ly and social­ly friend­ly than ter­res­tri­al and deep-sea min­ing, sea­wa­ter min­er­al har­vest­ing is also more eco­nom­i­cal espe­cial­ly when paired with marine hydro-kinet­ic energy. 

Sources:

Elshka­ki, A., Graedel, T. E., Ciac­ci, L., & Reck, B. K. (2018). Resource demand sce­nar­ios for the major met­als. Envi­ron­men­tal sci­ence & tech­nol­o­gy, 52(5), 2491–2497.

Calderon, J. L., Smith, N. M., Bazil­ian, M. D., & Hol­ley, E. (2024). Crit­i­cal min­er­al demand esti­mates for low-car­bon tech­nolo­gies: What do they tell us and how can they evolve?. Renew­able and Sus­tain­able Ener­gy Reviews, 189, 113938.

Haji, M. N., & Slocum, A. H. (2019). An off­shore solu­tion to cobalt short­ages via adsorp­tion-based har­vest­ing from sea­wa­ter. Renew­able and Sus­tain­able Ener­gy Reviews, 105, 301–309.

Mass­a­chu­setts Insti­tute of Tech­nol­o­gy Sym­bi­ot­ic Sys­tems for The Future of Energy,Water, and Food. [Avail­able online at: https://ilp.mit.edu/sites/default/files/2020–01/Slocum.2017.China_.pdf]