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Global Contribution of Seaweed Culture to the Carbon Cycle
GAMZE TURAN AND AMIR NEORI
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)/
if increased to
% of C
Production the increased
(t year−1) by
(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
INTENSIVE SEA WEED AQUACULTURE
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.
GAMZE TURAN AND AMIR NEORI
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.
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
THE FUTURE IS GREEN: ON THE BIOTECHNOLOGICAL POTENTIAL
OF GREEN ALGAE
Institute of Biology I, General and Applied Botany, University
of Leipzig, D – 04103, Leipzig, Germany
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.
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.
THE FUTURE IS GREEN: ON THE BIOTECHNOLOGICAL POTENTIAL
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.
3.1. CULTURE SYSTEMS FOR MICROALGAE
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
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%.