1 r

10 15

Figure 5. Mean absorption characteristics of UV-absorbing compounds (OD at 330 nm/fresh weight (FW)) of Ceramium sp., Callithamnion gaudichaudii, Corallina officinalis, Porphyra columbina, Enteromorpha linza, Dictyota sp., and Ulva rigida exposed to UVR as a function of chl a concentration (OD(665 nm)/FW). (After Helbling et al., 2002.)

6. Algae as Food for Other Organisms

Macroalgae, as well as the environment where they grow, offer shelter and food for diverse organisms, mainly invertebrates. Although many studies have been carried out in different locations to evaluate the effects of solar radiation on the interactions between macroalgae and other organisms, very few studies have addressed this topic in the Patagonia area (Menchi, 2001; Helbling et al., 2002). Particularly, these studies evaluated the impact of UVR on the survival of the amphipod Ampithoe valida and the isopod Idothea baltica feeding on different macroalgae and differentially bioacu-mulating UV-absorbing compounds. The relationship between the optical density at 334 nm (i.e., an estimator of the concentration of UV-absorbing compounds) in the crustaceans and that of their diets is shown in Fig. 6. In I. baltica (Fig. 6a), there was a 5-,

1 I 1 I 0 1 2 Codium Enteromorpha

Polysiphonia

Polysiphonia

OD334 macroalgae

Figure 6. Optical density at 334 nm (OD334) in crustaceans as a function of OD334 in the macroalgae diet. (a) I. baltica; (b) A. valida. The symbols indicate the different algae used in this study: Codium sp. (▲) collected during February 2001; Enteromorpha sp. (•) collected during February and June 2000 and February 2001, and Polysiphonia sp. (■) collected during February 2000. The vertical and horizontal lines are the standard deviation.

a significantly higher concentration of UV-absorbing compounds when individuals were feeding on the Rhodophyte Polysiphonia sp. than when they were feeding on Chlorophytes. In A. valida (Fig. 6b), there was also an increase in the optical density at 334 nm, being low when the organisms were feeding on Enteromorpha sp. and significantly higher when they were feeding on Polysiphonia sp. Moreover, a higher concentration of UV-absorbing compounds was found in A. valida compared with that in I. baltica when feeding on Polysiphonia sp. This situation, however, was reversed when the two crustacean species were collected from Chlorophyte species. Survival experiments carried out with both species of crustaceans indicated a different ecological role of these compounds. In A. valida, and since a significant higher survival was observed when organisms were feeding on Rhodophytes compared with Chlorophytes, MAAs seem to provide an effective protection against UV-B radiation. In I. baltica, however, mortality was high and not significantly different in individuals feeding on rich and poor MAA diets. However, high amounts of MAAs in eggs/embryos of I. baltica suggested that these compounds might provide protection to the progeny rather than to adults.

7. Conclusions

The results of the in situ experiments summarized above indicate that the studied macroalgae are shade plants adapted to low light conditions during high tide favored by strong absorption and scattering of solar radiation in the water column. However, during low tide, organisms are damaged by high solar radiation exposure. Any further increase in solar UVR - for example, due to the continue decrease of the stratospheric ozone layer or the extent of influence of the Antarctic ozone 'hole' over Patagonia - would worsen this situation, leading to more inhibition of the algae. However, and so far, the studies have shown that the thalli protect themselves by actively shutting down the photosynthetic electron transport to recover during the subsequent low light phase. It is obvious that different species are adapted to different heights on the coast, and it can be concluded that the duration and intensity of solar radiation is a decisive factor in the habitat zonation of macroalgae in the Patagonian region.

8. Acknowledgments

This work was supported by Agencia Nacional de Promoción Científica y Tecnológica - ANPCyT (Project PICT N° 2005-32034 to VEV), Proalar (Project N° 2000-104 to EWH), the United Nations Global Environmental Fund (PNUD Project N° B-C-39 to EWH), Fundación Antorchas (Project A-13955/3 to EWH), the Deutsche Akademische Austauschdienst (Project Proalar N° T332 408 138 415-RA to D.-P.H), and Fundación Playa Unión. This is contribution N° 114 of Estación de Fotobiología Playa Unión.

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Biodata of Masahiro Notoya, author of "Production of Biofuel by Macroalgae with Preservation of Marine Resources and Environment"

Masahiro Notoya is currently a Professor in the Laboratory of Applied Phycology in the Tokyo University of Marine Science and Technology, Tokyo, Japan. He obtained his Ph.D. from Hokkaido University in 1978. Professor Notoya's scientific interests are in the areas of ecology of macroalgal and seagrass communities, i.e., "Moba ecology," integrated multitrophic aquaculture, algal bioremediation, biotechnology of useful algae, algal breeding technology, taxonomy, phylogeny and physiology of algae, and the life history of Porphyra.

E-mail: [email protected]

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

Cellular Origin, Life in Extreme Habitats and Astrobiology 15, 217-228

DOI 10.1007/978-90-481-8569-6_13, © Springer Science+Business Media B.V. 2010

PRODUCTION OF BIOFUEL BY MACROALGAE WITH PRESERVATION OF MARINE RESOURCES AND ENVIRONMENT

MASAHIRO NOTOYA

Notoya Research Institute of Applied Phycology, Mukojima-4, Sumida-ku, Tokyo 131-8505, Japan

1. Introduction

Biofuel production and environment are issues of concern in the world. First, the author describes the real needs of biofuel, and what kind of materials can serve this purpose. This is followed by the argument that under the present global circumstances, macroalgae are the most effective raw material for biofuel production. Seaweeds are the most important in the marine ecosystem for the preservation of marine bioresources and seawater quality by preventing pollution and eutrophication, and also in the absorption and fixation of CO2 aided by solar energy. The validity of macroalgae is also explained by various additional useful substances found in their tissues, and by having high productivities compared with terrestrial plants and commercial crops. Algae can be produced in the coast and unused vast ocean area within the exclusive economic zone. Finally, the author's idea for the construction of an effective production system of macroalgae is explained.

2. Environmental Destruction and Bioenergy Production

Threats to human life on a global scale in the near future is thought to include environmental destruction, shortage of drinking water and food, water pollution by the contamination of chemical substances or radioactivity, and energy problems. Most of these problems are due to unjustified destruction of natural environments, and they originated by spendthrift economy of mass production/consumption. It is also considered that a key factor of present global warming is CO2 emissions and other greenhouse gases emitted artificially by the excessive use of fossil fuel (fourth IPCC report). The need of energy production (bioenergy, physical energy from solar light, wind) with environmental conservation approaches without discharging CO2 is required. Therefore, in biofuel production, the technology using a lot of energy and discharging a lot of waste for producing the raw materials and for the conversion process for fuel is not suitable. Furthermore, neither the technology of changing food into energy nor the technology that uses a life place should be used.

3. Biofuel Production and Global Environment

Recent increases in atmospheric CO2 levels are also caused by the anthropogenic environmental destruction, such as the excessive consumption of fossil fuels, deforestation, and development of farmland. Thus, to enhance the accumulation of CO2 in a forest, stopping deforestation and developing farmland have been recommended among immediate measures to be taken in every corner of the world, until now. However, recently measures are moving to control the consumption of the fossil fuel and production of carbon-neutral energy.

Wood, weeds, corn, sugarcane, palm, sunflower, and rapeseed have all been evaluated as raw materials for carbon-neutral energy, such as alcohol or diesel engine oil. Physical energies have also been considered, such as solar, wind, geothermal, tidal, and current power. However, the energy for transportation that can replace petroleum should be liquid, or gas fuel. Land crop resources for carbon-neutral energy have also been used. However, land comprises only about 30% of the surface of the earth, and this includes mountains, deserts, and areas close to lakes and rivers; and besides using it as a region of economic activity, land also serves as a human being's region of livelihood, such as the city, farmland, and pasture. There was a feeling that not enough area has been allotted for the production of biofuel resources. Moreover, the shortage of food material in the world at present should be taken into consideration as well as the rapid increase in global population in the near future. Therefore, using up land space for the production of biofuel resources is considered a problem given the expected food crisis in the near future; thus all land space should be solely used for food production.

On the basis of the above-mentioned facts, production of biofuel resources should use marine plants rather than terrestrial plants. Especially in Japan, the small islands with a large exclusive economic zone require the development of technologies for large-scale culture of macroalgae on the coastal and offshore areas, such that the production of biofuel from macroalgae does not compete with that of food and does not destroy the environment. From our experimental trials, it was estimated that the annual bio-ethanol production was 20 million kiloliters from 10,000 ha (or 100 km2). This corresponds to about one third the amount of petrol used annually in Japan. Our project has estimated that a production of biohydrogen of about 4.7 m3/t wet weight of Ecklonia stolonifera Okamura is also possible.

4. Necessity of Preservation of the Coastal Environment and the Marine Bioresources

Generally, production of marine bioresources in coastal areas is greatly influenced by the ocean current and water temperature. Macroalgae grow well in coasts having lower temperatures generated by cold currents. Good fishing areas are formed at the boundaries of warm and cold currents.

In the coasts of Japan affected by cold currents such as those in the Pacific, from the north-east of Tohoku to Hokkaido, large amounts of brown macroalgae like Laminaria spp. can be found. Along the Pacific coast of Japan, the cold current flows from northeast to south and warm current flows from south to north. Both currents collide at the offing of the Tohoku region, and both make whirlpools where good fishing areas are found. However, the fish resources are continuously decreasing every year from these fishing areas. Moreover, on a global scale, large-sized wide-ranging fish resources are decreasing because of artificial destruction of the environment from various origins. In a certain shocking report, it has been predicted that the natural fish resources in the seas will almost disappear by 2050, addressing already exterminated fishes as well (Worm et al., 2006). On a global scale, it is shown that the coast and the ocean as well as the land and atmosphere are exposed to environmental destruction, and the preservation of the coastal and marine environment is needed.

About 48% of the coastline of Japan has been modified artificially until now, and the natural seashore and useful large macroalgal communities for fisheries have been destroyed by the construction of shore-protecting artificial seawalls from the viewpoint of seashore preservation (Ministry of the Environment, Government of Japan 1994). Generally, various algal species grow in this shallow coastal area, especially communities of large macroalgae such as Laminaria spp., Sargassum spp., and Ecklonia spp., together with sea-grass developing in the sand and muddy shallow bottoms. These areas are used as the spawning ground of fishes and shellfishes, the growing area of larval fish, and the feeding area of large-sized fish. Thus, this is an important area for the preservation of the environment as well as of useful animals and alga resources for fishery. Moreover, these areas in which macroalgae and sea-grasses grow also serve for water purification. Therefore, the shallow coastal area and the communities of marine organisms are important, as they receive the benefits of ecosystem services and environmental preservation.

In Japan, these useful areas of macroalgal communities and ecosystems for fisheries production have been specially called "Moba" since ancient times (Fig. 1). The definition of "Moba" in Japanese is "a useful and important economic area and/or ecosystem dominated by over-sized-seaweed and sea-grass communities in which marine resources are produced and preserved, and the environment has balanced functioning." "Moba" has been protected, managed, preserved, restored, and developed. It has also been advanced by the public works of country and local government. Besides the "Moba," there are various kinds of high productive areas and important ecosystems in tidal areas. There are various organisms involved in

Figure 1. "Moba" of Sargassum macrocarpum at a depth of about 6 m, and the algal frond length reaching 10 m, at Toyoda port, Nakanoshima Island, Oki Islands, Shimane Prefecture, Japan.

water quality purification in tidal flats, sandy regions, and salt marshes. However, in recent years these "Moba" and other natural tidal areas are greatly decreased by the coast development, and as a part of the project of "natural reproduction." In addition, the "Isoyake" phenomenon, which is covered with crustose coralline algae and the disappearing communities of the useful macroalgae, is spreading and progressing in the shallow waters along the coasts of Japan. There have also been eutrophication and pollution due to outflows of wastes from areas of fish and shellfish culture, and various economic activities of human beings along the coastal area. Occurrence of blooms of various photosynthetic organisms has also been observed. From the above-mentioned facts, invasion of the environment and its destruction can be seen from the near shore shallow waters to the offing, and we need to take immediate conservation measures both locally and globally. The restoration and preservation of seaweed communities, such as a "Moba" as a foundation of the coastal ecosystem, are needed.

5. Productivity of the Macroalgae Compared with Other Photosynthetic Organisms

The life cycles and major accumulation of carbon in most macroalgae is relatively short, taking about 1 year, or a few years. It is very short compared with tens to hundreds of years it takes for a tree in a forest to reach maturity.

Therefore, macroalgae, in which a lot of CO2 accumulates in a short time with high productive capacity, are more effective as a recycling resource for fuel than wood, in which CO2 accumulation and holding takes a much longer time. On the other hand, it is considered that the global production by the phytoplankton of ocean and terrestrial plants is almost equivalent. And the natural production by the macroalgae does not compare to it at all. However, the macroalgal production is limited by only the narrow attached area on the coastal line.

Yearly net production of macroalgae from the coast of Japan was reported to be 1.3 kg/m2 for Laminaria angutata (Fuji and Kawamura, 1970), 8.3 kg/m2 for Sargassum macrocarpum, 5.5 kg/m2 for Sargassum patensi (Taniguchi and Yamada, 1978), 3 kg/m2 for Ecklonia cava (Yokohama et al., 1987), and 1.9 kg/m2 for Sargassum yezoensis (Okamura, 2003). It was estimated that the terrestrial crop plants of the average productivity was approximately 2.3-10 kg/m2. Therefore, the productivity of macroalgae and terrestrial crop plants is similar. If it is possible to culture the macroalgae on the unused vast marine area for the biofuel resources, there is no bigger production of photosynthetic organisms of terrestrial crop plants or marine plants. On the other hand, with easy techniques and management of culture, the use of unicellular algae on land as a biofuel resource may also be considered. However, the filtration cost and cultivation area for the same amount of harvest of Laminaria or Sargassum are not comparatively equivalent. From the above-mentioned facts, since macroalgae (such as Laminaria spp. or Sargassum spp.) have high productivities and the growing periods are short (from 1 to few years), they should be considered as optimal resources for biofuel production.

6. Sargassum spp. and Laminaria spp. Algae as Raw Materials of Biofuel

Sargassum spp. grows in the shape of a tree with the help of a holdfast, and since the branches float on air vesicles, solar energy can be used efficiently. Laminaria spp. is heavier than seawater, and the leaf-like frond grows downward, or lies on the water surface, and more information is needed to devise good culture techniques for their optimal growth. The floating fronds of the Sargassum spp. are convenient, as they could be harvested just by separating their holdfasts from the culture system, which is very easy compared with the Laminaria spp.

Most species of Sargassum are grown in regions that have comparatively warm currents. Large communities are built on coastal areas, thus allowing the growth of useful fish and shellfishes as well as maintenance and preservation of marine resources (i.e., "Moba" are formed). Moreover, a few of the branches are floated out and they grow, and many fronds are accumulated and move with the current as the "flowing algae." It is well established that the "flowing algae" are used for spawning and as a habitat for various useful fish and shellfishes, such as yellowtail, Pacific saury, and rock fish, and also as a growing area for larval fish. Moreover, they are used as seeds for coastal fish farming. Therefore, artificial propagation and culture of Sargassum spp. is effective for the increase and preservation of marine fish and shellfish resources. In addition, owing to the macroalgae's nutrient uptake during their growth in the growing area, they can also be used for the function of restoring the eutrophication at the coast.

Laminaria species grow along the coasts of Japan, in the regions of Tohoku and Hokkaido, and they produce big quantities of fronds and form large community areas. Among the Laminariales, Ecklonia, Eisenia, and Undaria are grown on the warmer coasts of Honshu, Shikoku, and Kyushu. These species are also part of "Moba" and are useful for important marine resources and for their preservation. Therefore, it is necessary to consider whether Sargassum spp. or Laminaria spp. should be used according to the environmental characteristics of the coastal area.

Some years ago, the author considered and proposed the construction of an algal biofuel production system, which involved the cultivation of large amounts of macroalgae and the uptake and fixation of CO2 through solar energy in the vast unused offing ocean area. At the same time, various marine organisms of fish and shellfish would be attracted and preserved, and the marine ecosystem could be formed focusing on growing macroalgae, by which the production of marine resources would be greatly increased. This system is capable of using deep seawater, ocean power, wave power, wind power, and solar light energy. It will operate as a self-reliant energy production and consumption system, in which there are various self-reliant, zero-emission types of floating production that are complex, and can also be used for exploration, collection, and utilization of useful industrial raw materials contained in the sea and the seabed (Fig. 2).

General seaweed cultivation, such as Laminaria, Undaria, and Porphyra, has been performed in very calm regions of the inner bay. However, it is necessary to install a large-sized culture construction in the open sea for the production of biofuel resources. Therefore, new possibilities such as technology for large-sized culture construction and installation, production of seaworthiness facility, and harvesting technology for big amount of products will emerge. Then, the production and harvesting of algal biofuel resources, which do not use a culture facility, may be considered. That is, it involves the development of "artificial flowing algae" of Sargassum spp., harvest of grown algae at the points of flow and reach, and their use in biofuel production (Fig. 3).

For example, in the case of the western coast in the Japan Sea, if bits of Sargassum spp. branches are stocked in large quantities on the northern part of Kyushu, it can be "artificial flowing algae." These algae are flow along with the Tsushima warm current, and they go north, accumulating and growing. It takes at least around 2 weeks to go from the northernmost end of Kyushu to the entrance of Tsugaru Strait according to the reported movement of Nomura's jellyfish (Stomolophus nomurai). The northing route and attainment time of these algae change with the stock point and time. Although some algae drift along the shore in the direction of the flow, each flock of algae concentrates and reaches Tsugaru Strait or Soya Strait, and the "artificial flowing alga" does not disperse in the Japan Sea.

Figure 2. Image of the synthesic construction of a huge raft, self-reliant energy production and consumption, and zero-emission system on the ocean. The construction of each facility for the production, processing, research, as well as management, circulation, and a segment of the economy have been arranged in the upper and lower parts of the float, respectively.

Figure 2. Image of the synthesic construction of a huge raft, self-reliant energy production and consumption, and zero-emission system on the ocean. The construction of each facility for the production, processing, research, as well as management, circulation, and a segment of the economy have been arranged in the upper and lower parts of the float, respectively.

In fact, as far as the route or attainment time is concerned, if the highly precise simulation program developed by the group headed by Professor Yamagata of Tokyo University is used, it could also be said that it is possible to predict the correct position, which changes every moment, and the attainment time, and the course and time can also be specified arbitrarily.

Since all the culture facility and energy on the cultivation management of "artificial flowing alga" depends on natural ocean current and solar light, it is possible to produce low-cost resources for biofuel in large quantities.

In recent years, there have been global problems of the eutrophication and contamination of ocean water. We are also anxious about the same thing in the Japan Sea. Moreover, there are eutrophication problems by the loaded nutrients from the fish and shellfishes culture and from human activities on land, and its roads to blooming, such as red tide and green tide (Fig. 4) in coastal areas of each country.

To take up nutrients from large coastal or marine areas, it is important to cultivate or propagate useful macroalgae in large quantities in those areas, and

Figure 3. Images of the "artificial flowing alga" and "Moba" development for the macro-algal bio-fuel production with the preservation of global environment and marine resources.
Figure 4. Green Tide blooming of Ulva spp. at Park of Sea in Yokohama, Kanagawa Prefecture, Japan.

harvest and utilize them for our life. These macroalgae have also been used as foods since ancient times in some countries. Moreover, the substance is also used in various health foods and supplements, cosmetics, and fertilizers, and phycocolloid has been used as a food additive, recently. In addition, it is also used for integrated multitrophic aquaculture with fish and shellfishes. The author mentions that it is not proper to carry out burial or incineration disposal of the propagated plant. The extensive growing algae on a coast should be effective when utilized as "natural recycled resources." Therefore, these "artificial flowing alga" designs are multipurpose systems, such as a technology for sea water purification with the preservation of useful marine resources and the production of bioenergy resources.

7. Production of Algal Bio-fuel and Use of the Exclusive Economic Zone

The author has already spent about 6-7 years examining the biofuel production from macroalgae, about which several scientific reports were published and various scientific meetings (XIXth International Seaweed Symposium, March 28, 2007, Kobe, Japan and "The Challenges of Seaweed Bio-fuel Production and Preservation of Environment and Fisheries Resources.") were held.

Development of biofuel production technology is fundamental and the preservation of the prospective global environment should be considered. Therefore, as mentioned earlier, biofuel resources and their production area should not be compared with food and the living regions of a human being. Destruction of the environment and its ecosystems should not occur with the process of biofuel production. Natural energy should be used as much as possible, and the resources should be used without futility, at the same time avoiding waste output. The above-mentioned points are required for biofuel production. The type of development in the old capitalist profit-seeking system does not comply with the original meaning of biofuel production.

For that purpose, it may be necessary to establish a new field, for example, "biological energy," which converts steam gasification and synthesises gas with the help of an inorganic catalyst to directly produce useful and good-quality carbide from the fermentation system. As far as the biofuel production from the resources of algal organic matter is concerned, in addition to the former technology of fermentation of methane, alcohol, hydrogen, etc., various synthetic production systems should be developed, such as synthesis of gas by partial combustion. Effective technologies may also be developed using the analogy of pulp, refining of petroleum, or the production process of petrochemicals. About 40% residual substance waste is removed through several types of fermentation. These substances should also be used for the production of the high industrial commodity, ethanol, which is of added value for the substance of various cellulose systems.

In this design, the extensive stable supply of biomass materials is realized with a first premise. The way of thinking and conditions at the unique location of the vast exclusive economic zone of Japan is suited for algal culture and subsequent biofuel production. Views of new, eco-friendly synthetic technology development in global and marine resource preservation will help in Japan's global contribution.

8. References

Ministry of the Environment, Government of Japan (1994) National survey on the natural environment. 1-400 (in Japanese). Murata, Y. (1980) Photosynthesis and production, In: S. Miyachi and Y. Murata (eds.) Photosynthesis and Dry Matter Production. Rikougakusha, Tokyo, pp. 475-510 (in Japanese). Okamura, D. (2003) Sargassum yezoensis, In: M. Notoya (ed.) Seaweed Marine Forest and Its Developmental Technology. Seizando-Shoten, Tokyo, pp. 75-81 (in Japanese). Taniguchi, K. and Yamada, Y. (1978) Ecological study on Sargassum patens C. Agardh and S. ser-ratifolium C. Agardh in the sublittoral zone at Iida Bay of Noto Peninsula in the Japan Sea. Bull. Jpn. Sea Reg. Fish. Res. Lab. 29: 239-253. Taniguchi, K. and Yamada, H. (1988) Annual variation and productivity of Sargassum horneri population in Matsushima Bay on the Pacific Coast of Japan Sea. Bull. Tohoku Reg. Fish. Res. Lab. 50: 59-65 (in Japanese).

Worm, B., Barbier, E.B., Beaumont, N., Duffy, J.E., Folke, C., Halpern, B.S., Jackson, J.B.C., Lotze, H.K., Micheli, F., Palumbi, S.R., Sala, E., Selkoe, K.A., Stachowicz, J.J. and Watson, R. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790. Yokohama, Y., Tanaka, J. and Chihara, M. (1987) Productivity of the Ecklonia cava community in a bay of Izu Peninsula on the Pacific Coast of Japan. Bot. Mag. Tokyo 100: 129-141.

Biodata of Christopher J. Rhodes, author of "Biofuelfrom Algae: Salvation from Peak Oil?"

Professor Chris J. Rhodes is currently a visiting professor at the University of Reading and Director of Fresh-Lands consulting. He was awarded a D.Phil from the University of Sussex in 1985 and a D.Sc in 2003. He has wide scientific interests (www.fresh-lands.com) which cover radiation chemistry, catalysis, zeolites, radioisotopes, free radicals, and electron spin resonance spectroscopy, and more recently have developed into aspects of environmental decontamination and the production of artificial fuels. He has published more than 200 peer-reviewed papers and three books.

E-mail: [email protected]

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

Cellular Origin, Life in Extreme Habitats and Astrobiology 15, 229-248

DOI 10.1007/978-90-481-8569-6_14, © Springer Science+Business Media B.V. 2010

BIOFUEL FROM ALGAE: SALVATION FROM PEAK OIL?

CHRISTOPHER J. RHODES

Fresh-Lands, P.O. Box2074, Reading, Berkshire, RG4 5ZQ, UK

1. Introduction

There is practically nothing in the modern world that does not depend on the resource of plentiful, cheap oil. The majority of crude oil is refined into fuel for transportation, but it also provides a feedstock for a myriad of industries, producing products ranging from plastics to pharmaceuticals. In total, it is reckoned that worldwide some 86 million barrels of oil are consumed daily, which amounts to just over 31 billion barrels a year. Around one quarter of all oil is used in the USA, which was formerly the world's main oil-producing nation. Now that accolade is with Saudi Arabia, which delivers an almost ten million barrel daily aliquot to the world oil markets, while Russia exhumes an almost equal quantity. In 1999, the price of a barrel of oil was $12, but reached almost $150 in the summer of 2008 preceding a world stock market crash and a fallback to $25 a barrel (Rhodes, 2008). The price rose during the following year and, writing in August 2009, it is now around $70 a barrel. There are many factors held culpable for such frenetic activity in the marketplace, including a seemingly inexorable demand for oil (and indeed all kinds of energy resources) from rising economies such as China and India, a weakening US dollar, and that oil is becoming harder to produce, as a general principle. Over all of this looms the specter of peak oil, which is the point at which production meets a geological maximum, and beyond which it must relentlessly fall. The combination of these factors must culminate in a gap between rising demand and ultimately falling supply. Within a decade or less, the world economies will no longer be able to depend on some limitless growth in oil output. For these reasons, attention is being turned toward "Alternatives," which ideally are also "Renewables," but the issue of biofuels is more complex than is generally realized, and it is at best a partial solution bearing its own attendant environmental costs (Rhodes, 2005).

In addition to the simple fact that growing fuel crops must inevitably compete eventually for limited arable land on which food-crops are to be grown, there are vital differences in the properties of biofuels, e.g., biodiesel and bioethanol, from conventional hydrocarbon fuels such as petrol and diesel, which will necessitate the adaptation of engine designs to use them; for example, in regard to viscosity at low temperatures, e.g., in planes flying in the frigidity of the troposphere. Raw ethanol needs to be burned in a specially adapted engine to recover more of its energy in terms of tank to wheels miles, otherwise it could deliver only about 70% of the energy content of petrol, pound for pound in accordance with its lower enthalpy of combustion (29 MJ/kg) than is typical for an oil-based fuel like petrol (gasoline) or diesel (42 MJ/kg) (Rhodes, 2005).

Of the various means that are being considered, at least in terms of growing our way out of the oil crunch, is making biofuel from algae. There are many advantages claimed as we shall see, but in particular, the quoted yields of oil that might be derived from algae per hectare are high, even when compared with those from high-oil-yielding plants such as jatropha and palm, which translate to around 6 t of diesel per hectare (see Section 6). Most biofuel in Europe is biodiesel and is made, for example, from rapeseed oil, which yields perhaps 1 t of diesel per hectare. In contrast, it is reckoned that some species of high-oil-yielding algae might furnish more than 100 t of diesel per hectare - an attractive prognosis indeed, since an area, say the size of the southern UK, could fuel the entire world (Rhodes, 2005). Algae offer further advantages that they can be used to absorb CO2 from smokestacks at fossil-fuel-fired power stations, they can be grown on saline waters or wastewaters (cleaning the latter in the process), and furthermore there is no necessity to use arable land for algae production since the tanks they are grown in can be placed anywhere, including brownfield land or on the open ocean. Thus, the competition between fuel and food production is avoided.

The author attempts an overview of some specific aspects of a subject that is, however, not quite as straightforward as it first appears.

2. The Peak Oil Problem

The prediction of peak oil was made in 1956 by Marion King Hubbert (Hubbert, 1956), a geophysicist working for the Shell Development Corporation. Hubbert predicted that the lower 48 states in the USA would peak (hit maximum production) during 1965-1970, depending on his estimate of the total volume of the reserve. At that time, the USA was awash with oil and his prediction was not taken seriously. Hubbert's analysis is based on the logistic function, the first derivative of which gives a peak. Mathematically, this kind of curve can be represented by the logistic differential equation (1).

In Eq. (1), P is the production rate, as shown by its equality to the rate of change of cumulative production Q (i.e., the sum quantity of oil recovered from a given source to date), Qt is the total amount of oil that will ever be recovered from it, and k is the logistic growth rate (a sort of % compound interest). In Hubbert's original paper (Hubbert, 1956), he assumed two scenarios for the lower 48 states in the USA: (1) there were 150 billion barrels worth of oil and (2) there were 200

billion barrels as a total recoverable reserve, Qt. In those days before computers, he simply reckoned the amount of oil represented by each square on his sheet of graph paper, and drew a curve by hand that enclosed an area equal to the estimated volume of the reserve. For case (1), he predicted that the peak in production would arrive in 1965 and for (2) around 1970. Thus, the method was not predictive of the volume of oil that would be recovered in total; this had to be reckoned first. In fact, US production peaked in 1971, so establishing both his fame and credibility in the basic method. In a later paper (Hubbert, 1982), Hubbert surveyed the mathematics behind all this, from which an alternative and predictive method coined the Hubbert Linearization (Deffeyes, 2005) was derived. The basis of this is that Eq. (1), which is a quadratic, can be rewritten in the form of Eq. (2), which is a linear equation of familiar form y = mx + c.

By plotting annual production divided by cumulative production (i.e., P/Q ) versus cumulative production alone (Q), a straight-line plot is obtained, with a y-axis intercept equal to k and a slope of -k/Qt. Thus, both essential parameters of the logistic peak, k and Qt, may be estimated without prior assumptions, an improvement on the original approach (Hubbert, 1956). The method is still used extensively in the oil industry, although now with modern PCs, it is easy to fit directly logistic and all other kinds of functions to oil production data using programs like Origin. Having established values for k and Qt, they can be used to construct the logistic curve with considerable accuracy. Because of the symmetry of the curve, when the peak is reached, half the reserve has been extracted, beyond which production falls inexorably. For the entire world, a value for Qt of around two trillion barrels is estimated, of which we have used close to half. It is expected that once the peak is reached, there will be a decline in world oil production by 3% per annum. This approach is not without its critics, however. Some maintain that it is an oversimplification, and does not allow for future discoveries of oil or the production of unconventional oil and that it is more likely that the postpeak outcome will be a more steady plateau followed by a gradual depletion in supply rather than a mirror-fall of the growth phase. The oil industry actually uses a number of methods of geophysics, e.g., seismic measurements, to estimate the volume of a reserve, and their final predictions are often based on a combination of physical data and various kinds of mathematical and numerical modeling procedures, including "Hubbert."

Various estimates have been given for the time of arrival of peak oil. If all production, ignoring tar sands and natural gas liquids (NGL), is considered, the peak famously reckoned by Kenneth Deffeyes (2005) to arrive on November 24, 2005 (thanksgiving day!), is predicted. If all production including NGL is included, the peak shifts forward to mid-2006. All studies that place peak oil in 2010 and beyond use other methods, but generally consider the rates of depletion of existing oil fields and projections about developing fields. Such studies are termed "bottom-up analysis." Chris Skrebowski, a researcher for the Energy

Institute in Britain, told delegates at a recent oil conference that the world oil supply will peak in 2011 or 2012 at around 93 million barrels a day (it is presently 84 million barrels a day), in line with a general consensus among industry experts there that the peak will arrive by 2012 (Low, 2007). Key pieces of evidence for this include the falling rate of discoveries of new oil fields; the age of the largest fields; geopolitical threats to future oil supplies; and the sustained high price of crude oil. Coincidentally, the CEO of Shell stated earlier this year that he expects to see a gap between supply and demand for oil sometime during 2010-2015. However, the truth is that we will only know retrospectively exactly when peak oil did occur: its effect being to pull down supply while demand continues to rise, thus enlarging the gap from both sides. There is much speculation as to how high oil prices will go. Goldman Sachs predicted in May that we may see the new psychological benchmark $200 barrel within 6-24 months (Rhodes, 2008). In the wake of the record $139 barrel, Morgan Stanley predicted $150 by the beginning of July. This did not happen, in fact, and the price has fallen below $120 a barrel. More alarmingly, the CEO of the Russian Gazprom, Alexey Miller, is talking about a barrel of oil costing $250, which would mean an increase in fuel prices at the pump of 60 p/l and that is before fuel taxes are applied on top of this. Fuel would then cost in excess of £2.00/l (Rhodes, 2008).

3. Conventional Biofuels

Most biofuels produced in Europe are made from plant oils (biodiesel) with a smaller amount of bioethanol that is produced from sugar beet (Duffield et al., 2006). In the USA, the situation is reversed and huge amounts of corn are turned over to the production of "corn ethanol." The ethanol industry in Brazil is mature, as it is made from sugarcane, which grows well there, with the USA as its major customer for exports. As it is not thought that the Brazilian ethanol industry compromises land on which food crops could be otherwise grown, there is a strong objection made with increasing volume to the diversion of corn grown in the USA from the world food markets to making ethanol. Indeed, part of the huge increases in the price of basic staple foods has been blamed on the use of arable land to produce biofuels rather than to grow food (Elgood and Eastham, 2008). There are consequently shortages of rice and wheat, and a significant reduction in the market stockpile of corn, all of which contribute to a potential food crisis particularly in developing nations, including China and India. The yields of biodiesel that can be produced from a hectare of land suitable for different "fuel crops" are shown in Table 2.

4. Biofuel from Algae

There are some truly astounding figures about the amount of biodiesel that might be obtained from farming algae, rather than from growing crops. For example, whereas the yield of biodiesel from soybean is 357 kg/ha/year and 1,000 kg/ha/ year from rapeseed, it is 79,832 kg/ha/year from algae, i.e., about 80 t/ha. There are some algae that yield around 50% of their own weight of oil, and from one study it might be deduced that the yield is around 125 t/ha on the basis that 200,000 ha of land could produce 7.5 billion gallons (one quad) of biodiesel (Maio and Wu 2006).

(Since there are 3.875 l to the US gallon, it equals 7.5 x 109 x 3.875 = 2.91 x 1010 l. Since there are 159 l to the barrel and 7.3 barrels to the ton (accepted average), it amounts to 2.91 x 1010/(159 x 7.3) = 2.51 x 107 t of biodiesel produced from 200,000 ha, i.e., 2.51 x 107/200,000 = 125.5 t/ha).

Some rough calculations are presented to indicate some estimates of scale. In the UK, around 57 million tons of oil are used to run transport - cars, planes, and the whole lot. Another 16 million tons are used as a chemical feedstock for industries etc. However, only the fuel budget is described here. Diesel engines are more efficient in their tank-to-wheel use of fuel than spark-ignition engines, which burn gasoline (petrol), meaning that we could reduce that total by 30%, i.e., to 40 million tons, by switching all forms of transport to run on Diesel "compression" engines. If we take the optimistic 125 t/ha figure for the yield of biodiesel from algae, it implies a crop area of 40 x 106/125 = 320,000 ha, or 3,200 km2.

Now this is only 1.3% of the area of the UK mainland, which does look feasible, especially in comparison with values of up to five times the entire area of arable land present that has been deduced, which would be necessary to provide sufficient biofuels derived from land-based crops.

There is no need to use arable land in any case, since the algae would be grown in ponds, and these could be installed essentially anywhere, even in offshore locations, i.e., growing the material on seawater, because salt concentration appears to assist the algal growth.

We can make some guess as to the thickness of the algae too. One hectare = 100 x 100 m = 10,000 m2. Hence, 320,000 ha = 3.2 x 109 m2. The volume of 40 million tons of biodiesel at a specific gravity of 0.84 (based on 79,832 kg = 95,000 l; so, 80 t = 95 m3) = 4.76 x 107 m3. Hence, spread over 3.2 x 109 m2 gives a thickness of 4.76 x 107 m3/3.2 x 109 m2 = 0.015 m = 1.5 cm. So, assuming that 50% of it is "oil," it gives a thickness of around 3 cm, which seems reasonable.

How much water would be needed to fill the tanks? Let us assume they are 1-m deep (with the algae floating on top of that), i.e., 3.2 x 109 m2 x 1 m = 3.2 x 109 m3. Since this amounts to 3.2 km3, it is a significant volume of water, and if freshwater would account for about 2% of the UK's total. However, as it has been indicated, seawater can be used instead, or the "ponds" could be fashioned from floating "boon" structures offshore. Closed ponds might be better, since that would permit a much closer control of nutrient supply, and if they were covered, it would restrict the potential for invasion by algae with a lower oil yield.

This might be the only way to provide significant amounts of "oil" post peak-oil (other than by coal liquefaction), and large-scale production should be attempted as soon as possible - well before the world's supply of naturally occurring petroleum begins to wane significantly, which gives us just a few years. The "crop" would take up CO2 from the atmosphere, thus reducing the burden of greenhouse gas that many are worried about, and that amount of carbon would be re-emitted once the fuel was burned, but with a continual crop production working in symbiosis with the CO2 content of the atmosphere, taking it up through photosynthesis. There would be no additional CO2 emitted, other than in the production of an alcohol, methanol, or maybe ethanol, which is needed to transesterify the initial oil into the final biofuel. This would be in a proportion of about 10% of the oil yield, and could be provided from agricultural waste, e.g., wheat grass, some minor compromise of food crops, say to grow sugar beet to ferment into ethanol, and ultimately by hydrolysis and fermentation of cellulosic material once that technology is underway, thought to be by 2015.

What about costs? If we assume a cost per hectare of $80,000, that would equate to $80,000 x 320,000 = $25.6 billion, or around £13 billion. Annual maintenance/operating costs have been estimated at $12,000 per hectare, which is about £2 billion. Assuming a price of $60 a barrel, that may be compared with an annual cost for 40 million tons of oil of $60 x 40 million x 7.3 (barrels/t) = $17.5 billion or about £9 billion. This would mean money that is not going out of the country to unstable regions of the world, and it would break completely UK's dependence on imported oil. It would also reduce the nation's CO2 emissions by probably 30%. Biodiesel could even be used to substitute for coal in power stations and cut the UK's dependence on coal imports, while reducing CO2 emissions still further.

5. Chemical Composition of Algae

Algae are made up of eukaryotic cells. These are cells with nuclei and organelles. All algae have plastids, which are chlorophyll-containing species that can perform photosynthesis. However, different algal types have different combinations of chlorophyll molecules. Some have only Chlorophyll A, some A and B, whereas other lines have A and C.

All algae primarily contain proteins, carbohydrates, fats, and nucleic acids, but in varying proportions. As the percentages differ with the type of algae, some algae contain up to 40% of their overall weight in the form of fatty acids. It is this fatty acid component (oil) that can be extracted and converted into biodiesel (Table 1).

The interest in algal oil is not recent, though the widespread interest in making biodiesel from algal oil is. Algae oil is produced for the cosmetic industry, principally from macroalgae (larger-sized algae) such as oarleaf seaweed etc. Most current research on oil extraction from algae is, however, focused on microalgae.

Table 1. Chemical composition of algae expressed on a dry matter basis (%) (Becker, 1994).

Strain

Protein

Carbohydrates

Lipids

Nucleic acid

Scenedesmus obliquus

50-56

10-17

12-14

3-6

Scenedesmus quadricauda

47

-

1.9

-

Scenedesmus dimorphus

8-18

21-52

16-40

-

Chlamydomonas rheinhardii

48

17

21

-

Chlorella vulgaris

51-58

12-17

14-22

4-5

Chlorella pyrenoidosa

57

26

2

-

Spirogyra sp.

6-20

33-64

11-21

-

Dunaliella bioculata

49

4

8

-

Dunaliella salina

57

32

6

-

Euglena gracilis

39-61

14-18

14-20

-

Prymnesium parvum

28-45

25-33

22-38

1-2

Tetraselmis maculata

52

15

3

-

Porphyridium cruentum

28-39

40-57

9-14

-

Spirulina platensis

46-63

8-14

4-9

2-5

Spirulina maxima

60-71

13-16

6-7

3-4.5

Synechoccus sp.

63

15

11

5

Anabaena cylindrica

43-56

25-30

4-7

-

Algal oil is very high in unsaturated fatty acids. Some UFAs found in different algal species include arachidonic acid, eicospentaenoic acid, docosahexenoic acid, gamma-linolenic acid, and linoleic acid.

Algal oil is very high in unsaturated fatty acids. Some UFAs found in different algal species include arachidonic acid, eicospentaenoic acid, docosahexenoic acid, gamma-linolenic acid, and linoleic acid.

Table 2. Yield of various plant oils (http://oilgae.com).

Castor 1,413

Sunflower 952

Safflower 779

Palm 5,950

Soy 446

Coconut 2,689

Algae 100,000

6. Comparison of Average Oil Yields from Algae with That from Other Oilseeds

Table 2 presents indicative oil yields from various oilseeds and algae. Please note that there are significant variations in yields even within an individual oilseed depending on where it is grown, the specific variety/grade of the plant, etc. Similarly, for algae there are significant variations between oil yields from different strains of algae. The data presented here are indicative in nature, primarily to highlight the order-of-magnitude differences present in the oil yields from algae when compared with other oilseeds (Becker, 1994).

7. Oil Content of Fixed Oils

Cereals only contain about 2% by weight oil, compared with oilseeds that contain much higher levels. The oil content of oilseeds varies widely from one type to the other. It is about 20% in soybeans and as high as 50% in some new Australian varieties of canola (the oil content of canola seed varies from 35% to 50%, and is usually considered to be averaging 40%). Sunflower has one of the highest oil contents among oilseeds - about 55%. Castor seeds have about 45-50% comprising oil. Safflower has about 40% of its contents as oil, and cottonseed has about 20% of its weight as oil. Hemp has 30-35% oil content. Copra, the dried coconut meat, has about 60% (sometimes close to 65%) oil content. Peanuts contain approximately 50% oil on a dry weight basis. Palm kernel has about 50% oil. Corn has only 5-10% of its dry weight as oil. The average oil content of mustard is about 40% - yellow mustard have only about 27% whereas brown mustard have about 36% oil; some oriental mustard have up to 50% oil. Flaxseed has about 45% oil content. For jatropha, the oil content is 35-40% in the seeds and 50-60% in the kernel (Becker 1994) (Table 3).

8. Extraction of Oil from Algae (http://oilgae.com)

Oil extraction from algae is currently a hotly debated topic because this process is one of the more costly features, which can determine the sustainability of algae-based biodiesel. In terms of the concept, the idea is quite simple: Extract the algae from its growth medium (using an appropriate separation process), and use the wet algae to extract the oil (Note: It is not necessary to dry the algae prior to extracting the oil from them). There are three well-known methods to extract the oil from oilseeds, and these methods should apply equally well for algae too:

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Table 3. Oil content (% of dry weight) - average values.

Soy

20

Canola/rapeseed

40

Sunflower

55

Castor

45