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 Global Contribution of Seaweed Culture to the Carbon Cycle

 Global Contribution of Seaweed Culture to the Carbon Cycle

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Table 3. A comparison between current and potential (see text) seaweed production from aquaculture

and seaweed wild harvest and cultivation in relation to the coastline in selected countries.



Coastline (t dw year−1)/


coastline km



if increased to

match China

dw year−1)/

coastline km

% of C


captured by

biomass at

Production the increased





potential C


(t year−1) by


















World Total

































































115, 612
































(Renaud and Luong-Van, 2006). Seaweed lipid can be directly converted to biodiesel with basically the same technology as other biomass feedstocks. Seaweed

carbohydrates and proteins can also be processed to useful fuels and chemical

feedstocks (Petrus and Noordermeer, 2006).

Seaweed oil is an interesting sustainable feedstock for biofuel/biodiesel manufacturing. It is a next-generation alternative to land-based biodiesel sources, like

soybean, canola, and palm. Seaweed oil can be extracted, processed, and refined

for various uses, including transportation, using currently available technology.

Other benefits of seaweeds as a potential feedstock are their availability. Seaweeds

can be grown nearly everywhere. One of the technical challenges for algae-based

biodiesel is the matching of seaweed growth requirements, performance, and

chemistry to each potential cultivation site and industrial use. Developing costeffective engineering of very large-scale farms and their operation are additional

keys to success in seaweed-based biofuel.

Seaweed farms are expected to locate mainly in two environments, one being

on the high seas (see Notoya, 2010) and in low value coastal lands and waters



close to CO2-emitting industrial centers and power plants. Typical coal-fired power

plants emit flue gas with up to 13% CO2. This high concentration of CO2 can

enhance uptake of CO2 by some seaweeds. Therefore, where the necessary lowvalue area is available, the concept of coupling a coal-fired power plant with an

algae farm provides an elegant approach to the immediate recycling of CO2 from

coal combustion into a useable liquid fuel.

6. Summary and Conclusions

The characteristics of the seaweed industry that make it suitable to contribute to

the abatement of climatic change and supply of biofuel are their widespread availability, diversity of species, high content of practical fuel biochemicals, independence from competition with food agriculture, high yields and CO2 uptake rates,

and low-cost technologies for large-scale production.

Seaweed aquaculture is expected to increase dramatically, both in monoculture and in IMTA. Seaweed coastal CO2 removal belts can be anticipated to

be developed in coastal waters together with sustainable seafood production

(see in Issar and Neori and in Notoya, 2010, this volume). Seaweeds can be a

considerable sink for anthropogenic CO2 emissions and excess nutrients in the

coastal waters of some countries. Increasing seaweed production to its full

potential, and appropriate use of the biomass could thus play a significant role

in the amelioration of greenhouse gas emissions and ocean nutrification and

the production of C-neutral fuels. The produced biomass can contribute to

some extent in meeting the global food, fodder, and pharmaceuticals requirements. It is clear that seaweed fuels will be produced. The timely transition to

renewable fuel from seaweed critically depends on scientific progress in three

areas, which are:

· Seaweed biology and biotechnology: identification and development of seaweed

varieties that maximize the production of biodiesel and other fuels

· Engineering: development of culture technologies and farm designs that

sustainably produce large quantities of seaweed feedstock at low cost

· Social sciences: communication to the relevant parties of the social, socioeconomic, and environmental benefits that large-scale seaweed fuel production can

have; overcoming opposition to innovation, gaining of socio-political support,

and public involvement

Critical to this and other innovative developments is the acceptance by the public

financial system of its obligation to support long-term research and innovation

programs, ensuring that emerging ideas that are explored consider overall societal

needs. Only the public financial systems, e.g., governments and the World Bank,

have the resources and time to fund the required investments. Such efforts need a

strong political will for their active steering in the right direction.



Preconditions for an accelerated development for industrial applications will be:

· Government regulations: shaping a competitive environment for the private sector

· Public–private partnerships: prototyping new processes by collaborations

between research and industry

· An educational infrastructure: drawing together the best possible human resources

When vigorously pursued, direct conversion of seaweed into fuel represents one of

the very few major options that humankind has to provide socially, economically,

and environmentally robust and resilient renewable fuel, whose production answers

additional major human necessities rather than creating them, and with energy

security that is guaranteed in a humanitarian instead of confrontational manner.

With scalable seaweed-fuel conversion technology, nations can become sustainable

producers and exporters at the level of regions, cities, communities, and individual

citizens. This may well give rise to a paradigm shift, from the current model where

fuel is provided at the lowest possible direct cost by large-scale industries, with

a considerable disregard for environmental and societal concerns, to an energy

system where fuel is a sustainable source of economic growth for the public that

principally owns its source of energy and the benefits that come with it.

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Biodata of Werner Reisser, author of “The Future is Green: On the Biotechnological

Potential of Green Algae”

Professor Dr. Werner Reisser is teaching General and Applied Botany at the Botanical

Institute of Leipzig University in Germany. He got his Ph.D. in 1977 from the University of

Göttingen, Germany, by studies on endosymbiotic associations of ciliates and algae.

His research interests center on taxonomy and ecophysiology of aeroterrestrial algae

and molecular ecology of soil ecosystems.

E-mail: reisser@rz.uni-leipzig.de


A. Israel et al. (eds.), Seaweeds and their Role in Globally Changing Environments,

Cellular Origin, Life in Extreme Habitats and Astrobiology 15, 373–383

DOI 10.1007/978-90-481-8569-6_21, © Springer Science+Business Media B.V. 2010




Institute of Biology I, General and Applied Botany, University

of Leipzig, D – 04103, Leipzig, Germany

1. Introduction

There are two main players that form the basis of nearly all global ecosystems in

converting solar energy to biomass: algae and plants. While plants are omnipresent

in public discussions dealing with such topics as climate change, bioreactors, biofuels

and green biotechnology, the role and potential of algae is usually known only

to experts. However, algae are present as primary producers in nearly all types of

ecosystems, their versatile physiology allowing them an impressive range of adaption

to aerial, terrestrial as well as aquatic habitats. As to its ecological impact, the

most important group of algae is the phytoplankton, especially the nano- and

picoplankton, which forms the basis of marine ecosystems. The phytoplankton

produces about the same amount of oxygen as all land plants and is also involved

in climatic processes by the production of volatile compounds and condensation

nuclei for the formation of clouds.

Tapping the biotechnological potential of algae has a long tradition in

human history (Spolaore et al., 2006). Algae, mainly kelps, are used as moisteners

in soil and as fertilisers for human or animal food production. The ability of algae

to absorb metals is used in biotreatment of contaminated soil. Microalgae are also

working in self-supporting life systems as they are used in space travel. A plethora

of algal products is on the market (Gantar and Svircev, 2008) obtained mainly

from cyanobacterian genera Aphanizomenon and Arthrospira (Spirulina) and from

chlorophycean genera Chlorella, Dunaliella and Scenedesmus. Algal products can

be found in ice cream, puddings, dietary products and cosmetics. From algal cultures, polyunsaturated fatty acids are obtained along with antioxidants, suppressors of hypertension, vitamins and natural pigments such as carotenoids and

phycobiliproteids. Microalgae also serve as food additives and are incorporated

into the feed for aquacultures, farm animals and pets. Nonetheless, in comparison

with plants, algae have played only a minor role in public awareness.

This may change now dramatically. The ever-increasing energy demand of

world economy is recognised as a threat to the world climate owing to an increase




in atmospheric CO2 (greenhouse gas) released by burning of fossil fuels (coal, oil,

natural gas). Therefore, there is a growing request for renewable energy sources

that do not release CO2 or – at least – do not emit additional CO2 (Schiermeier

et al., 2008). These are the classical sources of wind, water, solar, geothermal and

nuclear energy, but also the hopeful newcomers, hydrogen technology and fusion

power. However, although a lot of money has been and will be spent to exploit

those alternative energy sources, it is obvious that in the near future they can

cover only a small part of the world energy demand, either because they are more

or less exploited (e.g., hydropower in Europe), their public acceptance is limited

(e.g., nuclear fission power, wind plants) or financial resources are not as substantial as necessary (fusion power, hydrogen technology). What is more, it is obvious

that in the near future most energy needed for transportation purposes will be

used in combustion engines that require liquid fuels or gas. Therefore, it is desirable to try to replace fossil fuels by biofuels.

2. Biofuels

Biofuels (biogas, bioalcohol, biodiesel) are made from plant biomass, and are more

or less carbon neutral, since in burning they do not increase the overall CO2 content of the atmosphere but set free just the amount of CO2 that was fixed before

in photosynthesis of the plant (Schiermeier et al., 2008). Thus, in recent years,

plant biomass has gained growing importance as an alternative energy source.

Main current sources of bioalcohol (mostly bioethanol) are sugars of sugarcane

and starch of corn and wheat. Today, about 20% of the US corn harvest is used

to make bioethanol. This covers about 2% of the US demand for transportation

fuels (Chisti, 2007).

Biodiesel is made from plant oil, mainly from rapeseed, palm oil and jatropha.

Biogas is produced from different kinds of biomass. However, a serious flaw in the

ecobalance of traditional biofuels becomes obvious when the complete CO2 balance

is calculated, i.e., when CO2 costs for seed, fertilisers, herbicides, irrigation, harvest

and processing are taken into account. There is also growing concern in public discussion about the fact that the use of edible plants as energy sources may raise the prices

of food. It is also rather questionable to cut down tropical rainforests for planting oil

palms or jatropha when the plant oil is not processed locally but transported a long

way to the industrial countries. Therefore, for making biofuels it is desirable to use

plants (energy plants) with the modest requirements in soil quality and water supply

and that grow under conditions and at places not suitable for crop plants. Ideally, the

whole plant biomass can be used for fuel production and not just the special parts of

plants such as oil-containing fruits as in rapeseed or oil palm (‘first-generation energy

plants’). ‘Second-generation energy plants’ are already available, such as many prairie

grasses and microalgae.



3. Microalgae as Second-Generation Energy Plants

The use of microalgae for the production of biofuels has many ecological and

economical advantages. First of all, microalgae show a much higher efficiency in converting solar energy to biomass. From the biomass of corn grown on one hectare,

about 2,000 m3 biogas (methane) can be obtained; however, biomass of microalgae

grown on the equivalent area produces about 200,000 m3 (Solarbiofuels 2008). In

microalgal biomass, the percentage of compounds suitable for the production of

biofuels (e.g., starch, oil) is much higher than in crop plants, because there is no

need to divert energy to the synthesis of fibre material, vascular and absorption

tissues, etc. Microalgal cultures can be grown on a relatively small area that may

not be appropriate for agriculture and – at least in the case of ‘indoor systems’ –

they do not need irrigation and produce a high constant yield irrespective of outside environmental conditions such as temperature and draught. For producing a

given amount of biomass, indoor cultures need about 1,000 times less water than

crops. Preliminary data show that – on the same area – (Chisti, 2007) microalgal

cultures produce about 15× more oil for biodiesel production than rapeseed does.

To cover 25% of the US demand for transportation fuels by corn (Table 1), an area

of about 4.6× the area that is currently used for US agriculture is needed. When oil

from oil palms is used, about 12% of the agricultural area is required; however,

when microalgal cultures are used only 2–5% of that area would be sufficient.


For a large-scale culture of microalgae, two systems are used, the so-called ‘indoor’

and ‘outdoor’ systems (Figs. 1 and 2). Outdoor systems are sometimes also called

‘open raceway ponds’ and have a long tradition that can be traced back in history

Table 1. Crop efficiencies for the production of biodiesel. (Modified after Chisti, 2007.)


Yield of biodiesel (L × ha−1 × a−1)

Land area required (percentage of area covered

currently (ha × 106) by crops in the USA)a





Oil Palm

















To cover about 25% of all transportation fuels needed in the USA per year.

Oil content in algal biomass (by weight): 30%.


Oil content in algal biomass (by weight): 70%.










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