Tải bản đầy đủ - 0 (trang)
 Could Peak Phosphate be Algal Diesel’s Achilles’ Heel?

 Could Peak Phosphate be Algal Diesel’s Achilles’ Heel?

Tải bản đầy đủ - 0trang



population has risen to its present number of 6.7 billion in consequence of cheap

fertilizers, pesticides, and energy sources, particularly oil. Almost all modern farming has been engineered to depend on phosphate fertilizers, and those made from

natural gas, e.g., ammonium nitrate, and on oil to run tractors, etc. and to distribute the final produce. Worldwide production of phosphate has now peaked (in the

USA, the peak came in the late 1980s), which lends fears as to how much food the

world will be able to grow in the future, against a rising number of mouths to feed

(Phillpott, 2008). Consensus of analytical opinion is that we are close to the peak

in world oil production too.

The algae route sounds almost too good to be true. Having set up these ponds,

albeit on a large scale, i.e., they would need an area of 3,200 km2 to produce 40

million tons of diesel, which is enough to match the UK’s transportation demand

for fuel, if all vehicles were run on diesel engines (the latter are more efficient in

terms of tank-to-wheels miles by about 40% than petrol-fuelled spark-ignition

engines), one could ideally leave them to absorb CO2 from the atmosphere (thus

simultaneously solving another little problem) by photosynthesis, driven only by

the flux of natural sunlight. The premise is basically true; however, for algae to

grow, vital nutrients are also required, as a simple elemental analysis of dried algae

will confirm. Phosphorus, though present in under 1% of that total mass, is one

such vital ingredient, without which algal growth is negligible. Two different methods of calculation have been used here to estimate how much phosphate would be

needed to grow enough algae, first to fuel the UK and then to fuel the world:

1. The analysis of dried Chlorella (Wikipedia, 2009b) has been taken as an

illustration, which contains 895 mg of elemental phosphorus per 100 g of algae.

UK Case: To make 40 million tons of diesel, 80 million tons of algae would

be required (assuming that 50% of it is oil and this can be converted 100% to


The amount of “phosphate” in the algae is 0.895 × (95/31) = 2.74 %. (MW

PO43− is 95, that of P = 31).

Hence this amount algae would contain: 80 million × 0.0274 = 2.19 million

tons of phosphate.

World case: The world gets through 30 billion barrels of oil a year, of which

70% is used for transportation (assumed). Since 1 t of oil is contained in 7.3 barrels,

this equals 30 × 109/7.3 = 4.1 × 109 t and 70% of that = 2.88 × 109 t of oil for transportation.

So, this would need twice that mass of algae = 5.76 × 109 t of it, containing:

5.76 × 109 × 0.0274 = 158 million tons of phosphate.

2. To provide an independent estimate of these figures, it has been noted that

growth of this algae is efficient in a medium containing a concentration of 0.03–

0.06% phosphorus; the lower part of the range, i.e., 0.03% P is used here. “Ponds”

for growing algae vary in depth from around 0.6 to 1.5 m and so a depth of 1 m

could be assumed for simplicity.

UK case: Previously, the author has worked out (Rhodes, 2009) that producing

40 million tons of oil (assumed equal to the final amount of diesel, to simplify the



illustration) would need a pond/tank area of 3,200 km2. An area of 3,200 km2 is

equal to 320,000 ha, and at a depth of 1 m, this amounts to a volume of: 320,000 ×

(1 × 104 m2/ha) × 1 m = 3.2 × 109 m3.

A concentration of 0.03 % P = 0.092% phosphate, and so each cubic meter

(1 m3 weighs 1 t) of volume contains 0.092/100 = 9.2 × 10–4 t (920 g) of phosphate.

Therefore, we need:

3.2 × 109 × 9.2 × 10–4 = 2.94 million tons of phosphate, which is in reasonable accord with the amount of phosphate taken up by the algae (2.19 million

tons), as deduced earlier.

World case: The whole world needs 2.88 × 109 t of oil, which would take an

area of 2.88 × 109/125 t/ha = 2.30 × 107 ha of land to produce it.

2.3 × 107 ha × (104 m2/ha) = 2.3 × 1011 m2 and at a pond depth of 1 m they

would occupy a volume = 2.30 × 1011 m3. Assuming a density of 1 t = 1 m3, and

a concentration of PO43− = 0.092%, we need:

2.30 × 1011 × 0.092/100 = 2.13 × 108 t of phosphate, i.e., 213 million tons.

This is also in reasonable accordance with the figure deduced from the mass

of algae accepting that not all of the P would be withdrawn from solution during

the algal growth. Indeed, the ratio of algal phosphate to that present originally in

the culture medium (i.e., 158/213) suggests that 74% of it is absorbed by the algae.

Now, world phosphate production amounts to around 140 million tons (noting

that we need 213 million tons to grow all the algae), and food production is already

being thought to be compromised by phosphate resource depletion. The USA produces less than 40 million tons of phosphate annually, but would require enough to

produce around 25% of the world’s total algal diesel, in accord with its current

“share” of world petroleum-based fuel, or 53 million tons of phosphate. Hence, for

the USA, security of fuel supply could not be met by algae-to-diesel production

using even all its indigenous phosphate rock output, and imports (of phosphate) are

still needed. The world total of phosphate is reckoned at 8,000 million tons and that

in the USA at 2,850 million tons (by a Hubbert Linearization analysis). However, as

is true of all resources, what matters is the rate at which they can be produced.

13. Conclusions

Some aspects of the practicalities of algae-to-fuel conversion, including field

trials, have been discussed previously (Gao and McKinley, 1994; Miyamoto, 1997;

Christi, 2007; Sheehan et al., 1998). The author remains optimistic over algal diesel, but clearly if it is to be implemented on a serious scale, its phosphorus has to

come from elsewhere than phosphate rock mineral. There are regions of the sea

that are relatively high in phosphates and could in principle be concentrated to the

desired amount to grow algae, especially as salinity is not necessarily a problem.

Recycling phosphorus from manure and other kinds of plant and animal waste

appears to be the only means to maintain agriculture at its present level, and certainly if its activities will be increased to include growing algae. In principle too, the



phosphorus content of the algal waste left after the oil-extraction process could

be recycled into growing the next batch of algae. These are all likely to be energyintensive processes, however, requiring “fuel” of some kind, in their own right.

It is salutary that there remains a competition between growing crops (algae)

for fuel and those for food, even if not directly in terms of land, for the fertilizers

that both depend on. This illustrates for me the complex and interconnected nature

of, indeed Nature, and that like any stressed chain, will ultimately converge its

forces onto the weakest link in the “it takes energy to extract energy” sequence.

A Hubbert analysis of human population growth indicates that rather than

rising to the putative “9 billion by 2050” scenario quoted from WHO figures, it will

instead peak around the year 2025 at 7.3 billion, and then fall (Phillpott, 2008). It is

probably significant too that that population growth curve fits very closely both

with that for world phosphate production and another for world oil production

(Phillpott, 2008). It seems to be highly indicative that it is the decline in resources

that will underpin our demise in numbers as is true of any species: from a colony

of human beings growing on the Earth, to a colony of bacteria growing on agar

nutrient in a petri dish.

14. References

Becker, E.W. (1994) In: J. Baddiley et al. (eds.) Microalgae: Biotechnology and Microbiology. Cambridge University Press, Cambridge/New York, p. 178.

Christi, Y. (2007) Biodiesel from microalgae. Biotechnol. Adv. 25: 294–306.

Deffeyes, K.S. (2005) Beyond Oil. Hill & Wang, New York.

Duffield, J.A., Shapouri, H. and Wang, M. (2006) Assessment of biofuels, In: J. Dewulf and H. Van

Langenhove (eds.) Renewables-Based Technology. Wiley, Chichester.

Elgood, G. and Eastham, T. (2008) Biofuels blamed for food price crisis, http://uk.reuters.com/article/


Fraser, J. (2008). http://thefraserdomain.typepad.com/energy/2008/03/fyi-petrosun-to.html.

Gao, K. and Mckinley, K.R. (1994) Use of macroalgae for marine biomass production and CO2 remediation – a review. J. Appl. Phycol. 6: 45–60.

Global Green Solutions (2006). http://www.globalgreensolutionsinc.com/s/VertigroFAQ.asp.

Hubbert, M.K. (1956) Nuclear energy and the fossil fuels. Presented before the Spring meeting of

the Southern District, American Petroleum Institute, Plaza Hotel, San Antonio, TX, March

7–9, 1956.

Hubbert, M.K. (1982) Techniques of production as applied to oil and gas, In: Glass SI (ed.) Oil and

Gas Supply Modelling, Special Publication 631. National Bureau of Standards, Washington

DC, pp. 16–141.

Low, D. (2007) ASPO conference confirms a peak in global oil production by 2012. http://www.energybulletin.net/35127.html

Maio, X. and Wu, Q. (2006) Biodiesel production from heterotropic microalgal oil. Bioresour. Technol. 97: 841–847.

Miyamoto, K. (ed.) (1997). Renewable biological systems for alternative sustainable energy production

(FAO Agricultural Services Bulletin – 128).

Phillpott T. (2008) Biofuels and the fertilizer problem. http://www.energybulletin.net/print.


Rhodes, C.J. (2005) Energy Balance: http://ergobalance@blogspot.com.



Rhodes, C.J. (2008) Oil calculator. Chemistry and Industry, July 7, p. 12.

Rhodes, C.J. (2009) Oil from algae; salvation from peak oil? Sci. Prog. 92: 39–90.

Sheehan, J., Dunahay, T., Benemann, J.R. and Roessler, P. (1998) A Look Back at the U.S. Department

of Energy’s Aquatic Species Program – Biodiesel from Algae, NREL/TP-580-24190.

Valcent (2009) http://www.valcent.net/s/TomorrowGarden.asp.

Wikipedia (2009a) Algaculture, http://en.wikipedia.org/wiki/Algaculture.

Wikipedia (2009b) Chlorella, http://en.wikipedia.org/wiki/Chlorella.

Biodata of Leila Hayashi, Anicia Q. Hurtado, Flower E. Msuya, Genevieve

Bleicher-Lhonneur, and Alan T. Critchley, authors of “A Review of Kappaphycus

Farming: Prospects and Constraints”

Dr. Leila Hayashi is currently a Postdoc of the Universidade Federal de Santa

Catarina, Brazil. She obtained her Ph.D. from Universidade de São Paulo, Brazil,

in 2007, and continues her studies and research at the Universidade Federal de

Santa Catarina. She gives classes to undergraduate and postgraduate students and

has participated in projects regarding the commercial viability of Kappaphycus

alvarezii in Brazil. Her scientific interests are in the areas of seaweed cultivation

and commercial processing, extraction of value-added products, and integrated


E-mail: leilahayashi@hotmail.com

Anicia Q. Hurtado is currently a Visiting Scientist of the Aquaculture Department,

Southeast Asian Fisheries Development Center, Tigbauan, Iloilo, Philippines.

She has been there since 2006 after serving the Center as Senior Scientist for 20

years. She finished her Doctor of Agriculture at Kyoto University, Kyoto,

Japan. She works mainly on the aquaculture of Kappaphycus as a Consultant

to international and local, nongovernment organizations directly involved with

seaweed farmers. At present, she is developing “new strains” of Kappaphycus

using tissue culture techniques for possible sources of propagules for commercial


E-mail: aqhurtado@gmail.com

Leila Hayashi

Anicia Q. Hurtado


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

Cellular Origin, Life in Extreme Habitats and Astrobiology 15, 251–283

DOI 10.1007/978-90-481-8569-6_15, © Springer Science+Business Media B.V. 2010



Flower E. Msuya is currently working as a Senior Researcher at the Institute of

Marine Sciences of the University of Dar es Salaam in Zanzibar, Tanzania.

She obtained her Ph.D. from Tel Aviv University, Israel, in 2004 and continued

her research at the Institute of Marine Sciences. Dr. Msuya’s scientific interests

are in seaweed farming, physiology, ecology, and value addition; Integrated

mariculture; and socio-economic studies in marine science and associated fields.

E-mail: flowereze@yahoo.com

Genevieve Bleicher-Lhonneur is currently working as a senior Strategic Raw Materials

Procurement manager for Cargill. She has spent her entire career in procurement,

putting her expertise at the disposal of the industry. Her contribution to many

seaweed farming projects and fair support to the farmers are widely recognized.

She is still involved in developing new sources and improving farming conditions for

the benefit of the farmers and the whole industry. To reach this objective, Cargill is

financing specific studies related to strain selection or environmental impact on

cultivated seaweed properties in close cooperation with outside scientists.

E-mail: Genevieve_Bleicher-Lhonneur@cargill.com

Flower E. Msuya

Genevieve Bleicher-Lhonneur



Alan T. Critchley is a reformed academic. He graduated from Portsmouth

Polytechnic, UK, and had a university career in Southern Africa teaching phycology,

marine ecology, and botany (KwaZulu Natal, Wits and Namibia). He moved to

the “dark side” in 2001 and took up a position in a multinational industry with

Degussa Texturant Systems (now Cargill TS), where he was responsible for new

raw materials for the extraction of the commercial colloid carrageenan. It was

here he began a love affair with Kappaphycus and its cultivation. Since 2005,

he has worked as head of research for Acadian Seaplants Limited working on

value addition to seaweed extracts and on-land cultivation of seaweed for food and

bioactive compounds. Not able to turn his back on the academic world entirely, he

is currently adjunct professor at the Nova Scotia Agricultural College. It has been

his absolute priviledge and pleasure to work with such excellent scientists and

friends as Leila, Anne, Flower, and Genevieve on research into the production

and improved quality of carrageenan-producing seaweeds.

E-mail: Alan.Crithley@acadian.ca







Depto. BEG, Centro de Ciências Biológicas,

Universidade Federal de Santa Catarina, Trindade, 88040-900

Florianópolis, Santa Catarina, Brazil


Aquaculture Department, Southeast Asian Fisheries

Development Center, Tigbauan, Iloilo, 5021, Philippines


Institute of Marine Sciences, University of Dar es Salaam,

P.O. Box 668, Zanzibar, Tanzania


Raw Material Procurement, Cargill

Texturizing Solutions, 50500 Baupte, France


Acadian Seaplants Limited, 30 Brown Ave., Dartmouth, NS,

Canada B3B 1X8

1. Introduction

Global warming is of increasing concern worldwide. The question of how to

mitigate the CO2 released into the atmosphere is the most topical issue, and

sustainable solutions are constantly being sought. Aquaculture has been proposed

as one method for the sequestration or immobilization of CO2 through filtration

or mechanical/chemical processes for long-term storage (Carlsson et al., 2007).

However, the development of new sustainable technologies are but in their infancy,

as the aquaculture sector moves to becoming more efficient and sustainable.

In the above context, Chopin (2008) suggested that if limitations to nutrient

emission are to be put in place, extractive species such as seaweeds could be

considered as suitable for nutrient credits (e.g. for the extraction of nitrogen,

phosphorus, etc.), in a similar system to that of carbon credits, which are becoming

increasingly acceptable to be traded in the global economy.

Kappaphycus alvarezii, commercially recognized as “cottoni,” is considered

the main source of kappa carrageenan, while Eucheuma denticulatum, known as

“spinosum,” is the main source of iota carrageenan. Both species are responsible for

approximately 88% of raw material processed for carrageenan production, yielding

about 120,000 dry tons year−1 mainly from the Philippines, Indonesia, and Tanzania

(Zanzibar) (McHugh, 2003). Considered as two of the most commercially successful

species, they could be potential candidates for carbon and nutrient credits, if

research and technology are developed, since the farms have the potential to




increase the area occupied for seaweed cultivation, thus improving the carbon

dioxide sequestration and acting as a nutrient sink when cocultivated with other

organisms, thereby improving water quality to some extent.

A review of Kappaphycus (broadly including Eucheuma) farming is presented,

including the current possibilities and challenges with the goal of contributing to

sustainable mariculture management practices.

2. Worldwide Trends of Kappaphycus Production

The world’s geographical area for the Kappaphycus farming lies within ±10°

latitude (Fig. 1), notably from the Southeast Asian countries extending to East

Africa and Brazil. However, the Southeast Asian region, primarily the Brunei–

Indonesia–Malaysia–Philippines (East Association of Southeast Asian Nations

(ASEAN) Growth Area – BIMP-EAGA – integrated countries) has by far the

greatest potential for expanded tropical seaweed cultivation, consisting 60% of

the sites in the world. In particular, Indonesia, Malaysia, and the Philippines

provide sheltered areas that are favorable for cultivation (IFC, 2003).

The current and estimated increase in Kappaphycus production in the

BIMP-EAGA region is shown in Fig. 2. Although the production of the southern

Philippines and Sabah combined is about 100,000 t dry weight year−1, with the

potential to increase by approximately 50%, the shared projected capacity of

West, Central, and East Indonesia is huge (approximately 450,000 t) (IFC, 2003).

The high potential of Indonesia can be attributed to its extensive coastline, which

fits 100% within the tenth parallel latitude, where tropical seaweeds grow abundantly and robustly and, most importantly, where typhoons seldom occur. On the

other hand, the single largest area of Kappaphycus production in the Philippines

(Sitangkai, Tawi-Tawi) offers considerable potential for expansion since it has

60,000 ha available for mariculture purposes, even though only an estimated

10,000 ha are presently used for cultivating Kappaphycus (PDAP, 2007). Sabah

(Malaysia) had a total production of 50,000 t fresh weight (around 6,250 t dry

weight), which was grown on 1,000 ha (= 50 t ha−1 year−1) in 2005 (Neish, 2008).

Projection for this area aims an expansion to 12,000 ha in 2010, with a target

production of 250,000 t fresh weight.

Figure 1. The world’s potential geographical area for the Kappaphycus farming.



Figure 2. Major areas of Kappaphycus cultivation and potential dry weight production in the BIMPEAGA region (IFC, 2003).

Table 1. World production of Kappaphycus (cottonii) in 2006 (Hurtado, 2007).


Volume (ton dry weight)

Total (%)































The Kappaphycus (cottonii) world production for commercial extraction of

kappa carrageenan shows that the BIMP-EAGA region produces 96.5% of the

total production, of which 55% comes from the Philippines, followed by Indonesia

(38%) and Malaysia (2.5%). The rest of the producing areas contribute relatively

very small volumes (Table 1).

3. Cultivation Techniques and Post-harvest Management

Since the first successful farming of Kappaphycus in the Philippines in 1970, the

cultivation technique has undergone many modifications. The main commercial

Tài liệu bạn tìm kiếm đã sẵn sàng tải về

 Could Peak Phosphate be Algal Diesel’s Achilles’ Heel?

Tải bản đầy đủ ngay(0 tr)