Hydrobiologia 260/261: 15-23, 1993.A. R. O. Chapman, M. T. Brown & M. Lahaye (eds), Fourteenth International Seaweed Symposium.© 1993 Kluwer Academic Publishers. Printed in Belgium.

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Present and future needs for algae and algal products

Arne JensenInstitute of Biotechnology, University of Trondheim, N-7034 Trondheim, Norway

Key words: seaweeds, uses, phycocolloids, food, environmental aspects

Abstract

A review of the present needs, mainly for production of phycocolloids and food condiments, is given.Supply and demand vary from balanced, in some, to disproportionate in other fields. World-wideshortage of agarophytes contrasts with huge, unexploited beds of brown seaweeds.

In future, partly conflicting trends will decide the needs for algae and algal products. Growth in thehuman population, pollution, overexploitation of land and lack of freshwater will encourage use ofseaweeds. Modern biotechnology will favour this development, but will also be a serious threat to in-dustrial exploitation of seaweeds. Future uses of marine algae will be decisively influenced by the effortput into and the results coming out of seaweed research.

Introduction

According to classical theory, prices of commod-ities and services are a function of supply anddemand:

Price = f(supply, demand)

Whatever this function may be, it is commonlyaccepted that increasing demand pushes theprices up, while growth in supply is in some waynegatively related to the price. The demand itselfcreates the need for the raw material, finishedproduct or service involved and is based on someuse which the customer has adopted. This leadsto a consumption or flow, the volume of which isdetermined by supply and price. Again, one fac-tor is positively correlated to the flow, and thistime the supply holds this position, while theother, the price is negatively related. When we arediscussing the present and future needs for algaeand algal products we have to consider the uses

as the fundament, look at the supply and pricesand investigate present and future flows and vol-umes on this basis. This will actually describe ordefine the needs, qualitatively as well as quanti-tatively.

In previous times, and presently, the seaweedsare practically the only algal group that man hasdeveloped any need for. Some very limited usesof microscopic algae, such as the traditional con-sumption of Spirulina in Africa, the application ofDunaliella and other genera for pigment produc-tion and the more dubious use of Chlorella andSpirulina in health food form exceptions from therule. Indirectly, however, man together with manyother land-based consumers, depend heavily onthe marine phytoplankton, which are the primaryproducers in the oceans, and on which all marineanimals are absolutely dependent. The need forthese microscopic algal groups and the corre-sponding products is very real indeed, but will notbe included in the present treatise. We shall, how-ever, discuss briefly carbon binding by marine

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algae, macro- as well as microalgae, in a latersection.

The purpose of this presentation is to give anoverview of the past and present uses of seaweedsas a basis for the perspectives of the applicationof marine primary producers in the future. Amajor goal is to draw attention to the enormousunused potential the oceans have to provide en-ergy, raw materials, feed for animals and food forpeople, in order to underline the need for moremarine research.

Present uses of algae and algal products

In the Western world it is not fully realised thatthe major uses of seaweeds on a global scale arefound in human nutrition. As shown in Table 1

the total volume of seaweeds used in food is con-siderably larger than the sum of the industrialapplications, in weight and especially in value.While some 2 million tonnes of fresh weed areprocessed to nori, wakame and kombu annuallyand eaten, mainly in the Far East, about 1.5 mil-lion tonnes go to the industrial production, mainlyfor the phycocolloids alginate, agar and carrag-eenan. The value of the food products is morethan 6 times that of the industrial commodities.

The chemical composition and properties ofseaweeds

Faced with the fact that we use only around3.5 million tonnes of seaweeds out of a total bio-mass which is probably 100 times larger we mustlook for explanations for this poor exploitation.

Table 1. Present uses of seaweeds world-wide. (Indergaard & Jensen, 1991).

Products/value/spieces Product Raw materialtonnes/year tonnes/year f.w.

Alginate 230 mill. US$/yearMacrocystis sp., Laminaria sp. 27 000 500000Ascophyllum nodosum, Durvillaea sp., Lessonia sp.

Agar - 160 mill. US$/yearGelidium sp., Gracilaria sp., 11000 180000Gellidiella sp., Pterocladia sp.

Carrageenan - 100 mill. US$/yearEucheuma sp., Chondrus crispus, Gigartina sp., 15500 250000Furcellarea lumbricalis, Hypnea sp.

Seaweed meal - 5 mill. US$/yearAscophyllum nodosum, Fucus sp. 10000 50000

Manure ('Maerl') - 10 mill. US$/year 510000 550000

Liquid fertilizers - 5 mill. US$/year 1000 10000

Total industrial consumption of seaweeds 1540000

Nori > 1800 mill. US$/yearPorphyra sp. 40000 400000

Wakame - 600 mill. US$/yearUndaria sp. 20000 300000

Kombu > 600 mill. US$/year 300000 1300000

Total food use of seaweeds (f.w.) 2000000

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One reason is that vast resources are located inremote, noninhabited coastal regions, anotherthat harvesting exposed waters along rocky shoresis almost impossible. The main reason is, how-ever, to be sought in the chemical compositionand the physical properties of the algae and thealgal products. Table 2 gives a rough idea of themajor components found in brown, red and greenseaweeds.

A common feature is the high content of waterand the large fraction of minerals in all groups.This means expensive transport and high dryingcosts. The dominating minerals are sodium andpotassium chlorides, which are rather useless infood and feed, while valuable elements such ascalcium and phosphorus are very low in mostseaweeds. The low contents of protein and lipidsare very typical, and the seaweeds cannot func-tion as a basic source for these essential compo-nents, neither in man nor beast.

In addition to this, the carbohydrates whichdominate the organic content of the seaweeds arevery special, indeed. The structural complex ofcellulose and lignin found in land plants is sub-stituted by gel-forming and viscous polymers inthe seaweeds; alginates and fucose-containing,mixed and sulphated polysaccharides in thebrown, and sulphated galactans, xylans and othercomplex polymers in the red seaweeds. None ofthese can be digested by man or by non-ruminantanimals. As a result, the caloric food and feedvalue of most seaweeds is very low, and inclusionof more than a few percent in the diet or ration

Table 2. Approximate chemical composition of seaweeds.

Component Brown Red Green

Water') 75-90%/ 70-80 % 70-85%Minerals 2) 30-50% 25-35% 10-25%Carbohydrates 30-50 % 3) 30-60 % 4) 25-50 % 5)

Protein 7-15% 7-15% 10-15%Lipids 2-5% 1-5% 1-5%Cellulose 2-10% 2-10% 20-40%

1) of fresh weight; 2) of dry weight; 3) Mainly alginate andfucose-containing polysaccharides; 4) Sulphated polygalac-tans and xylans, resp. dominate; 5) Cellulose and starch arethe main components.

is not recommended. The unique compositionalso limits the industrial uses. The applications ofunusual polymers such as alginate, agar and car-rageenan do not require really large quantities,and the seaweeds as such are not suitable sourcesof bulk chemicals. Since they have flexible gelsinstead of solid cellulose-based structures, theycannot provide fibre or suitable construction ma-terial for clothing and housebuilding. In a sensethe seaweeds are much like many wild plants onland, such as the lichens and mosses, the heatherand shrub vegetation. They are important pri-mary producers of the ecosystem, but are of lim-ited importance to man and domestic animals,that rely completely on a few selected and bredcrop plants. It is in the light of this that we canunderstand the present needs for seaweeds andseaweed products.

Industrial uses

The alginates hold a dominating position amongthe industrial products made from seaweeds.These polysaccharides which give structure (gels,fibre) and viscosity to aqueous solutions and sta-bilize commonly used emulsions and dispersionsin a huge number of applications, from ice cream,shoe polish and paper sizing to oil drilling muds,represent a well established need for brown sea-weeds. The large brown seaweeds suitable foralginate production grow profusely in cold totemperate waters, and the major producers arelocated in the U.S.A., Norway, France, GreatBritain and Japan, with smaller factories operat-ing in Chile, China, Russia, India and other coun-tries. As shown in Table 1 the world productionamounted to ca 27 000 tonnes annually ( 1990),which represented some US $ 230 million. Theproperties of alginates originate in the uniquecomposition and structure of these polymericmolecules, composed as they are of blocks ofmannuronic and guluronic acid units in mostcases, but also of alternating chains of the twomonomers. Polymannuronic acid chains give vis-cosity to the alginate solutions, while blocks ofguluronic acid are responsible for the gel strength

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and the specific binding of divalent metal ions.Alternating chains are soluble in acid and givespecial features to the alginate they occur in. Thecomposition and structure, and thus the proper-ties of alginates, are species specific to a consid-erable extent (Haug, 1964; Skjdk-Braek, 1992).Most of the algal sources of the alginate industry,such as Laminaria digitata, (Huds.) Lamour,L. japonica, Aresch., Macrocystis pyrifera, (L.) C.Agardh and others are rich in mannuronic acid(mannuronic to guluronic acid ratios, M: G-ra-tios, around 1 or higher) and give alginates withhigh viscosity and medium gel strength. For thistype of alginate there is normally some sort ofbalance between supply of raw material and de-mand for the products. On a global scale largequantities of these types of seaweed are available,while a local shortage is felt in several countries.The US alginate industry has long felt a shortageof Macrocystis, and the Japanese industry importsraw material from other countries, while the Chil-ean alginate producer utilizes only a small frac-tion of the country's harvest of alginophytes.

The Chinese cultivation of L. japonica has attimes created some imbalance and disturbancesin the supply of raw material for the preparationof alginate. Originally this production was meantfor the domestic market, as a source of minerals,especially iodine, in the human diet. As this ap-plication did not develop to match the huge quan-tities of cultivated seaweed, up to 1 million tonnesfresh weight (f.w.) annually, new uses weresought, and alginate was one obvious option forpart of the biomass. China's own alginate indus-try is limited, and large quantities of L. japonicahave been offered on the international market atlow prices. The prices as well as the supplies andquality of the material have, however, not beenregarded as sufficiently stable, and there is con-siderable uncertainty as to what role cultivatedseaweeds will play in alginate production in thefuture. When it comes to alginates that are dom-inated by guluronic acid blocks, very few speciesof brown algae are available in sufficient quanti-ties for industrial exploitation. Norway has hugebeds of L. hyperborea, and the stipe of this plantis dominated by guluronic acid polymers (M:

G-ratios around 0.7 or lower), This forms thebasis for Norway's position as the second largestalginate producer in the world, and it's domina-tion in the field of high gel-strength alginates. Ona global scale there is a shortage of seaweeds withguluronic acid-rich alginates.

The markets for alginate have been growingsteadily over a long period and result from theopening of new uses and a loss of establishedones to cheaper products, such as carboxymeth-ylcellulose, phosphorylated starches and naturalplant gums (guar gum, locust bean gum etc.). Thismeans that there is a well established need forbrown seaweeds with mannuronic acid-rich alg-inates, as well as for materials with guluronicacid-dominated alginates, corresponding to half amillion tonnes of fresh algae annually. At presentthere are also fairly stable and growing marketsfor alginates amounting to a quarter of a billionUS $ per year.

The phycocolloids obtained from red algae,namely the agar group and the carrageenans, re-present together a need for seaweeds which equalsthat of the alginates (see Table 1), in monetaryvalue as well as in consumption of algal biomass.Agar and carrageenan are also gel-forming poly-mers or can give viscosity to aqueous solutions.They belong to the galactans and are sulphated toa variable degree. The agarose fraction of agar ispractically uncharged, while some of the carrag-eenans carry more than one sulphate group pergalactose unit in the native state (Painter, 1983;Craigie, 1990). The red algae prefer warmer wa-ters and dominate the benthic algal flora in theTropics and in warm areas.

Out of the nearly 200 000 tonnes (f.w.) of aga-rophytes that are processed every year the greaterpart is collected from natural beds. Gelidium spe-cies are the superior raw material, but increasingquantities are coming from a number of Gracilariaspecies, a growing fraction of which is cultivated.The more important agar manufacturers arefound in the USA, Japan, Denmark, Chile, Spainand France. In the case of agar we can definitelytalk of a real need for an algal product. The usein food in the Far East for several centuries es-tablished some sort of a need, but the application

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in bacteriology to solidify bacterial media resultedin a need so serious that large research and de-velopment programs were initiated during thesecond world war in the allied countries to secureagar when the access to the Japanese productswas closed. The resources of good agarophytesare limited due to the relative scarcity of the Ge-lidium species and to the slow growth which ischaracteristic of most members of this genus.While the traditional markets for agar in food andfeedstuffs have remained rather constant, newuses in meristem culture of ornamental plants andof vegetables have developed very rapidly, andthe use of agarose in pharmaceutical and finechemical industries for separation and purifica-tion of expensive products such as vaccines, hor-mones, enzymes and so on has nearly exploded.The need for good agarophytes and for agaroseitself is therefore larger than the available algalresources can carry.

The carrageenans also include gel-formingmembers as well as those which will provideviscosity and body to aqueous solutions andemulsions/dispersions. In this case more than halfof the 250 000 tonnes of raw material is cultivated,and the dominating species belong to the genusEucheuma. Simple vegetative propagation is re-quired, and cultivation techniques using nets orlines are well developed (Doty, 1978). This hasbeen sufficiently efficient to result in overproduc-tion at times and deflated prices. The Eucheumacultivation is a tropical activity with the Philip-pines and the Tropical Pacific as the centre, andwith African growers as competitive newcomerson the scene. In addition traditional sources arestill important. These are found in temperateareas, such as Ireland, Canada, Chile and Francewhich supply Chondrus, Gigartina and Iridaeaspecies.

The carrageenans form a varied group, involv-ing the potassium reactive kappa-carrageenanwhich gives strong gels, to lambda-carrageenanwhich is not gelling at all and which providesviscosity when used. These products find theirapplication mainly in the food industry, especiallyin dairy products and in bakery and confection-ery commodities. In a number of applications they

overlap with agar products and have taken oversome of the agar uses because of the scarcity andthe higher prices of the latter.

The need for carrageenans corresponds fairlywell with the production at present. Intermittentoverproduction of Eucheuma sometimes disturbsthe balance between supply and demand for theraw material, and it seems that competition fromAfrican growers may suppress the cultivation inthe Philippines and the Pacific area to some ex-tent in the near future. The major carrageenanproducers are often the more important proces-sors of agar and therefore located in the samecountries as the agar industry. Agars as well ascarrageenans and the alginates are naturally oc-curring polymers of rather complex structureswhich would be hard to synthesize chemically.Besides that, the fact that they are natural com-pounds gives them preference over syntheticproducts in most applications related to humanactivity. This means that competition from syn-thetic compounds is not very likely.

Food products and condiments

As pointed out above seaweeds are not, from achemist's point of view, especially suited to sat-isfy human needs and uses. In light of this theconsumption of 2 million tonnes of seaweed infood in the Far East is quite remarkable. It is inpart a result of real need for nutritive componentscontained in the seaweeds, brought about by thepopulation pressure in this part of the world. Nodoubt nori and wakame and even kombu maycontribute some protein and amino acids to theconsumer. Trace minerals, and in some cases,vitamins and growth factors may be provided aswell through the intake of algal products. Themajor reason for the widespread use of seaweedsin Japan and other Far East countries seems,however, to be related to taste and texture, to-gether with decorative effects brought about bythe algal ingredients.

The nori products which are made from Por-phyra species represent the most valuable singlegroup of products coming from the sea on a glo-

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bal scale (see Table 1). Cultivation of Porphyrawas initiated in the seventeenth century as a re-sult of the drastic decline in the natural stocks.Based on natural seeding of artificial substratethis cultivation, located mainly in the Tokyo Bay,grew to a large enterprise, covering several thou-sand hectares. The real break-through came afterthe revelation by the British phycologist KathleenDew of the life cycle of Porphyra, involving theConchocelis stage, as late as in 1949. Since thenthe Japanese Porphyra growers have had full com-mand of the whole life cycle of the alga and havedeveloped the world's most profitable seaweedindustry. The product, which is the thallus, pro-cessed in various ways to sheets, flakes, powdersand confectioneries of many forms, is an impor-tant ingredient in Japanese cuisine. The popular-ity of the products has secured markets whichhave kept the demand higher than the suppliesand given room for luxurious prices. Pollution ofJapanese waters has created problems recently,the production has suffered, and there is at presentconsiderable deficit of nori products world-wide,since the traditional uses are kept up both locallyin Japan and by the many people of Japanesedescent in foreign countries. Cultivation of Por-phyra for nori production has been attempted inthe US and in Canada, to cover American mar-kets. The fate of this endeavour is uncertain. Inaddition to Porphyra, large quantities of Undariaand of Laminaria japonica are cultivated, theformer mainly in Japan and Korea and the latterin China. For both species, the uses were origi-nally based on naturally occurring material whichcovered the demands up to the present century.Then the needs outgrew the supplies, and culti-vation was initiated. Wakame, made fromUndaria species, is almost as highly valued in foodas is nori, while the kombu products generallyappear to aquire somewhat lower prices. Theiruse is, however, well established and represents asolid need for these algae and the derived prod-ucts. It should be noted that while the Japanesestarted the kombu production and exported about25000 tonnes of dried Laminaria japonica toChina around 1890, the Chinese have completelyreversed this situation. In the best years the Chi-

nese fishermen cultivated up to 1 million tonnes(f.w.) of Laminaria japonica, and the flow of thisseaweed now goes from China to Japan.

Looking at the impressive and very lucrativeuses of seaweeds and derived products in the FarEast it is striking how these commodities devel-oped from the scarcity of food and raw materialof terrestrial origin to the luxury articles they areat present. Tradition and taste carried the poorman's food ingredients to the rich table of thewealthy people of today, where they reside alongwith other luxury items such as smoked eel andsalmon, oyster, caviar etc. The high prices of theproducts could carry the extra costs involved incultivation and gave rise to the impressive aquac-ulture of seaweeds. For most other purposes cul-tivation appears too expensive. The very efficient,rather straight forward cultivation based on veg-etative propagation of Eucheuma and Gracilariaspecies, in combination with low labour costs, isacceptable in the production of carrageenan andagar. Under the present conditions, cultivation ofalginophytes does not seem economically feasi-ble, even in China, as long as mechanical har-vesting of natural resources can cover the de-mand (needs) for alginate.

Future needs for algae and algal products

As shown in the previous sections, former andpresent uses of algae and the need for them werebased on the chemical composition of the nativematerial and the properties of the plants as such.These applications will of course develop further.However, more important for future uses are thenew perspectives that can be realized through ge-netic improvement of the algae, through com-pletely new applications, and because of environ-mental measures that involve algae.

Development of established uses

The steady growth of the alginate industry bysome 5% annually is expected to continue as aresult of population growth and increases in the

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standard of living in the industrialized countries.The growing consumption of glossy paper, pet-food, more elaborated food for people and ready-made dishes give rise to increased demands foraccessory ingredients such as alginates, pectin,agar, carrageenan and other plant gums. Newidiosyncrasies against synthetic compounds alsowork in favour of biopolymers, and alginatesometimes regains applications lost to carboxym-ethylcellulose and similar competitors.

Deeper insight into the nature of alginate andthe relationships between structure and functionof this polymer are constantly opening up newapplications of alginate, especially in biotechnol-ogy. Guluronic acid-rich alginates are superiorfor immobilization of cells and tissue (Skjik-Braek & Martinsen, 1991) in the preparation ofcomplex biomolecules such as hormones, en-zymes, vaccines etc. Even in large-scale pro-cesses, for example, fermentation of starch to eth-anol (Tanaka et al., 1986) and in industrialproduction of amino acids (Chibata et al., 1986)alginate immobilized cells are applied success-fully.

The use of alginates in slow-release systems forpharmaceuticals is developing rapidly, and we arefacing a break-through in in situ delivery of hor-mones, i.e. insulin in humans by means of trans-planted Langerhans islets encapsulated in com-bined alginate-chitosan capsules (Lim & Sun,1980; Soon-Shiong et al., 1992). Recently potentimmunoactivity has been demonstrated for cer-tain alginate fractions (Otterlei et al., 1991), andthis will very likely result in significant new ap-plications of alginate.

Quantitatively more important for the need ofalginate may be the successful attempts to de-velop alginate-based gels for micropropagation ofterrestrial plants (Draget, 1989). These can sub-stitute for the more expensive and restricted agarqualities that are used today. Future applicationin the planting of forestry trees would represent amajor increase in the demand for alginates. Thisadds up to expectations in the alginate industryfor significant growth in the near future, for bulkas well as for highly specialized alginates. Thealgal resources seem to be quite sufficient on a

global basis, but locally lack of suitable raw ma-terial, especially of guluronic acid-rich seaweeds,may easily occur. This may justify cultivation ofsuitable algae for special uses. If oceanic farming(see later) be realized the problem of raw mate-rial for production of bulk alginate will be solvedfor ever.

There are already on the market microbialpolysaccharides, such as xanthan gum, whichcompete with alginate for certain uses. As long asL. hyperborea and M. pyrifera are available inlarge quantities for mechanical harvesting, algi-nates will very likely compete successfully withmicrobial gums for most applications. Apparentlythe markets for nori, wakame and similar foodproducts will demand substantial growth in theprovision also of these products. The standard ofliving in parts of Asia is expected to improvefurther, and we should see growing needs for Por-phyra, Undaria and L. japonica as a result of con-tinued preference for traditional dishes in thepopulations involved. Continued spreading ofJapanese cuisine to Europe and America shouldalso add to the need for condiments and foodcommodities of this category. Finally there is littlereason to expect that the steady growth in theconsumption of agar and carrageenan will changeradically in the future. General growth in thehuman population and some improvement in thestandard of living will undoubtedly be reflected inincreasing demands for biopolymers such as agarand carrageenan, and the preference for naturalproducts that favour the use of alginate will alsoinfluence positively the application of the red algalcolloids.

Oceanic farming; C02-binding and other environ-mental aspects

It seems quite clear that the main established usesof seaweeds, namely as condiments in food andin the production of phycocolloids, will requireonly a small fraction of the potential for primaryproduction of the oceans. The really large-scaleapplications, i.e. for provision of energy, food andfeed and as raw material in the production of

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basic industrial chemicals, are not cost-effectivetoday, and will probably never be, as separateenterprises. The traditional energy sources, oil,gas and coal, are much cheaper than biogas orethanol from seaweed. Algae for staple food can-not compete with terrestrial crop plants, neitherin food value nor in price, and viewed separately,there is little reason to believe that the prices ofimproved algae will ever pay for the extensivebreeding efforts required to produce the improvedstrains. The same is valid for the production ofbulk chemicals from seaweeds by fermentation.As long as the production technology of the tra-ditional chemical industry is accepted, bioconver-sion of marine primary biomass is not likely to becompetitive.

Since the larger-scale uses of seaweeds are mu-tually exclusive in most cases, little improvementin economy may be gained by combining the en-terprises. The use of seaweeds for energy provi-sion excludes production of food, feed and chem-icals from the same material.

This explains to a large extent the former re-luctance of governments and private industry toinvest heavily in research and development ofmarine primary biomass. The situation is, how-ever, likely to change in the near future, for envi-ronmental reasons. If global warming is causedmainly by our extensive use of fossil carbon, in-creasing the primary production may becomenecessary both for the reduction of atmosphericCO2 and in the provision of non-fossil carbonsources. The change from traditional chemicalprocesses to bioconversion will have additionalbenefits beyond those related to the carbon bal-ance, e.g. for emission of nitrogen oxides, heavyhydrocarbons, soot, and for pollution by heavymetal and toxic by- products.

When we sooner or later shall have to ease thepressure of our intensive agricultural practices onthe terrestrial biotopes, marine production has tobe intensified instead, and marine algae will haveto substitute for terrestrial plants in several large-scale applications.

Tied to this we have the problem of eutrophi-cation of coastal waters caused by run-off of nu-trient salts from land, which calls for far better

solutions than the very expensive water treatmentsystems that are operating today and are plannedfor the near future. Large-scale cultivation of sea-weed reappears today as an interesting measurewhich would pick up nutrient salts, bind carbondioxide and provide useful biomass at the sametime.

We may thus be facing a completely new situ-ation which involves large-scale cultivation ofmarine algae to fight environmental problems ofinternational concern. In this connection short-term economy will not be decisive. Several indus-trialized countries are already levying taxes onautomobile fuel to reduce CO2-emission to theatmosphere; money that could be used to pay forthe binding of carbon dioxide by oceanic farming.

The concept of oceanic farming may actuallybe regarded as an extension of the large-scalecultivation of kelp for energy provision which wasinvestigated in the USA during the 70s as a con-sequence of the oil crisis (Bird & Benson, 1987;Flowers & Bird, 1990). The passing of the oilcrisis stopped this activity. When the problem ofglobal warming caused international concern tenyears later seaweed farming again became inter-esting, this time for the binding of atmosphericCO2. The Electric Power Research Institute inCalifornia arranged two workshops (EPRI, 1990)to discuss the role of large-scale oceanic farms inglobal change. Rough estimates indicated thatcultivation of 4 million km2 of seaweed, corre-sponding to 1% of the ocean's surface, wouldarrest the CO2 input to the atmosphere at the1988 level. Using the biomass produced for en-ergy provision and as a substitute for fossil car-bon material in the chemical industry, would re-duce significantly the use of fossil carbon sources.

Large-scale cultivation of macroalgae to coun-teract coastal eutrophication may be regarded aspart of the action against global warming. Bothactivities would provide huge quantities of sea-weed material at a negative price and would def-initely encourage large efforts to improve the sea-weeds genetically, to optimize the bioconversionto biogas and useful chemicals, an to develop newuses for the material.

In this situation successful conversion of se-

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lected seaweeds to animal feed, especially fish-feed, could be realized and become profitable. Animproved Alaria-plant with more laminaran andmannitol, somewhat higher protein content andless phenolics would be a very good raw materialin a fermentation process with yeast for the pro-duction of protein-rich feed for the farming ofmarine fish. In this way marine biotopes couldcontribute significantly in the provision of foodfor the growing human population, and allowsome release to the overstressed agriculture onland. Oceanic farming should also include micro-scopic algae. These will definitely contribute inthe binding of CO2 and could be used to providelarge quantities of valuable food for people viafilterfeeders such as mussels, shrimps and herbiv-orous fish. Large-scale engagement in the oceanicfarming concept on an international basis wouldinitiate a new era in seaweed and algal research,development and uses. The primary driving forceswill be the environmental concerns and the futurelack of food for people. The production of enor-mous quantities of algal biomas will represent aunique challenge for the seaweed scientists to findways to satisfy these needs, and would call forlong-term plant breeding programs that would ul-timately give us the algae for cost-efficient, sus-tainable utilization of the production potential ofthe marine environment.

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Painter, T. J., 1983. Algal polysaccharides, In G. O. Aspinall(ed.). The Polysaccharides. Acad, Press. London, Vol. 2:196-286.

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