Wednesday, April 30, 2008

The New Nuclear.

The UK Prime Minister, Gordon Brown, and his French counterpart, Nicolas Sarcozy have agreed joint strategies regarding nuclear power and illegal immigration. The two nations will undertake the construction of a new generation of nuclear power plants with the aim of curbing CO2, and will export the technology around the world. Almost 80% of France's electricity is made from nuclear energy which is a mature industry, while 20% of the UK's power is made from nuclear, but from reactors that are due for decommissioning within 10 - 15 years, once they reach their working lifetime.

The proposal will doubtless prove unpopular with many who regard nuclear as dangerous, not only per se, but in terms of the radioactive waste that it produces. There are strategies to deal with the latter which essentially involve sealing it into metal (copper) canisters and burying them underground in concrete bunkers, although time will prove the effectiveness of this which will be known only to future generations. It is hoped to create a new nuclear work-force which will be necessary to take nuclear-power into this next and challenging phase, since there is a shortage of nuclear engineers in the U.K., at least so colleagues in that industry tell me.

We can't have it both ways - i.e. maintain current energy use purely using renewables, at least not in short order. Hence, despite the "dirty" image of nuclear power in some quarters, there is an increasing view within the energy industry that "nuclear" could provide a lucrative energy market, certainly if the technology is indeed sold around the world. The nuclear agreement is one of a number of Anglo-French collaborations being discussed.

Another potential cooperation is a new initiative against illegal immigration. Britain is the last link in the European chain of movement and indeed trafficking of people, and many Britons feel that border-controls should be tightened and that this nation and France should act jointly to remove "failed" asylum seekers, who end-up in the U.K. via France. It is all a contentious issue, but the following actions have been identified:

Joint flights are proposed from Britain, stopping in France and then taking migrants back to various countries including Iraq, Iran and Afghanistan, alongside more checks being made on lorries at both UK and French ports. There is also an increase planned in the number of French officers working undercover to intercept gangs smuggling people into Britain.

My feeling is that the price of oil and hence the availability of lorries and other forms of transport will impact on the movement of people in general, illegal or legitimate, and populations will become increasingly more restricted as the cost of fuel continues to soar.

Related Reading.

Sunday, April 27, 2008

Grangemouth may Foretaste Peak-Oil.

The strike at the Grangemouth oil-refinery in Scotland has gone ahead, and while its duration is set for just 48 hours, it is debatable for how long the plant will be closed, in its wake. The news this morning on the BBC was optimistic and seemed to indicate that sufficient operations would be maintained that it could be brought back on-line within days, rather than the month or so originally feared. The whole business reminds me of the year 2000, when I was working in Switzerland, and my wife sent me regular e.mail-updates of the precarious situation in the U.K. at the time. On returning home, there was an "edge" to this normally apathetic and peaceful society, and I realised just how close we are to that fine-blade that divides civilization from anarchy.

At that time, it was a case of active-protest - unusual over here, as noted - that lorry-drivers had marched in London over rising fuel prices (I laugh at this one considering the price of fuel now!) and refineries and fuel-suppliers were blockaded resulting in the temporary but effective closure of 3,000 garages which were starved of fuel. To bring that number into reckoning, there are around 10,000 garages in the U.K. altogether, so it was a significant proportion and as I say, a very edgy time when I first began to realise the underlying fragility of my country, and by implication the entire world, being so entirely dependent on fuel. I must qualify the latter by saying that it is "oil" upon which we depend so much, since only 70% of it is refined into fuel while the rest (apart from a small amount in Europe that goes for heating-oil, and far less than is the case in the U.S.) serves as a chemical feedstock for industry.

The closure of the Grangemouth facility, since it is the only one of its kind in Scotland, will restrict supplies of fuel across not only that country but northern Ireland and the north of England. To cope with the shortfall, imports of fuel have been arranged from Gothenberg and Belgium, among other sources. The reason for the strike is dissatisfaction with changes in the pension-scheme for workers at the refinery, of whom 1,200 are involved. This is not uncommon, and similarly other organisations are abolishing so-called final-salary pensions, at least for newly appointed employees.

All in all, I see the combined-elements of this situation as both a metaphor and an inauguration for the post peak-oil time which I have termed the "Oil-Dearth Era" ( I am not as pessimistic as James Howard Kunstler that we are on the edge of an apocalypse and I believe we can survive, but forget about pensions, final-salary or of any kind. Dismiss too the transportation-driven economy and manner of living we are all used to in the West, whose prosperity has been literally fed by oil. "Literal" since all modern agriculture depends on oil and natural gas to run tractors and to synthesise fertilizers and pesticides. If transportation fails, people will tend to stay where they are and the morning and evening commute will be relegated to the pages of history. Paper-pages at that, once computers are crashingly expensive along with all other commodities.

Instead, the whole of civilization will take-on a more localised focus, while the concept of the mythical global village recedes into memory. We will depend on local economies, farms and businesses and what we can produce or grow for ourselves. Now there I do agree with Kunstler, as in his novel World Made by Hand, and I expect some of the nastier aspects he imagines will not prove to be far off the mark either, knowing human nature and the well-recorded history of inhumanity when the rules no longer can be enforced. I am thinking of former Yugoslavia, for instance and many African states.

I hope that chaos will not ensue in Scotland and the north, in some microcosm of the oil-dearth era. It is unlikely to be so severe because everybody knows that the refinery will come back on-line at Grangemouth within a short time, bringing back business as usual. But what will happen when there is nothing left or cheap enough to refine, there or anywhere else? We are not merely characters in a novel, all 6.7 billion of us.

Saturday, April 26, 2008

Concentration vs Mixing-Ratio.

Here is a reply to a colleague on the matter of "concentration" versus "mixing ratio" (as in my previous posting "Carbon in the Sky", Saturday, January 6th, 2007) which some readers might find interesting.

Dear Alexander,

I agree with your comments about the complexity of "concentrations". Chemists do indeed have various ways of expressing these things! Let's not mention "molality" versus "molarity" to describe the concentrations of solutions of various substances in liquids!

However, so as not to confuse the issue, it is probably better to refer to the amount of CO2 etc. in the atmosphere as "concentration" rather than as "mixing ratio". Yes, both terms are standard throughout the Anglo-American speaking world as far as I know.

For gas-phase species, the most commonly used units are ppm, ppb and ppt. These units express the number of molecules of pollutant found in a million, billion or trillion molecules of air. (Billion and trillion are US, not British). There is also pphm (parts per hundred million) which is sometimes used if the actual amounts of particular species make it a convenient unit. Alternatively, because numbers of molecules (or moles) are proportional to their volumes according to the ideal gas law: (PV = nRT), these units may be thought of as the number of volumes of the pollutant found in 10^6, 10^9 or 10^12 volumes of air, respectively.

This ratio of moles, molecules or volumes of the species to the number of moles, molecules or volumes of dry air is more commonly known as the "mixing ratio".

The use of mixing ratios is widespread for expressing the relative amounts of species at various altitudes throughout the atmosphere. Since the total air pressure and hence the number of molecules in a given volume decreases with altitude, a constant mixing ratio does not imply a constant concentration (i.e. as expressed in moles or molecules per unit volume).

Although not expressly stated in most cases, mixing ratios are usually referenced to dry air. If water vapour is included, the mixing ratio would vary with humidity, which could induce a variation of a few percent.

Although the term "concentration" is used frequently, if the units are ppm, ppb or ppt, it should be understood that this is really a mixing ratio. Some journals emphasize this by writing these units as ppm (v:v) etc. (i.e. to denote volumes explicitly)."

Related Reading.
"Chemistry of the Upper and Lower Atmosphere" written by Barbara J. Finlayson-Pitts and James N. Pitts, Jr. Published by Academic Press, New York, 2000, p 33, which puts the matter succinctly.

Friday, April 25, 2008

Cancer from Global Warming and Russian Peak Oil.

New research indicates that global warming may increase the risk of developing skin-cancer. The incidence of cancer measured in 10 separate regions of the US was found to be strongly correlated with both the local amount of sunlight falling per unit area and average maximum summer daily temperatures. The incidence of one type of skin-cancer called squamous cell carcinoma, was found to increase by 5.5% for every degree centigrade (C) rise in temperature. Similarly, basal cell carcinoma increased by 2.9%/degree C. This epidemiological data accords with previous tests on UV-irradiated mice which showed a 3 - 7% increase in the effect of the UV (e.g. in the "effective dose") per degree C rise in temperature.

Dr Jan van der Leun who conducted the research, concluded that only 80% of the variation in skin-cancer in the study could be accounted for by the local UV intensity alone. Additional factors, including genetic make-up and obviously how long people stay out in the sun for, and now it seems, temperature must be considered. The authors conclude that a 2-4% increase in mean summer temperatures could produce "substantial increases in incidence of skin-carcinomas", which among white-Caucasians have already increased dramatically during the past century.

If it is true that it is human-induced CO2 emissions that are responsible for increased global-warming, the following piece of news might appear as "good news". Namely that oil-production in Russia, second only to Saudi Arabia, has now peaked and is likely to decline during the coming years, according to Viktor Vekselberg, a co-owner of BP's TNK-BP venture company.

Russian companies are seeking tax-breaks to urge exploration and the development of new fields to prompt growth in production. Meanwhile, oil-production has fallen for the first time in the past 10 years as Soviet-era wells begin to dry-up and the likely costs of extracting oil from more challenging deposits, such as the Arctic, rally. In March, Russia produced 9.76 million barrels a day to be compared with 9.83 million barrels a day in December 2007. Such a fall in annual production would bring to an end a 58% increase in output since 1998, a point at which Russia defaulted on about $40 billion of domestic debt and devalued the Rouble. In 1998 a barrel of oil cost $12 while now it is almost $112 a barrel, in line with rising world oil prices.

As noted, cuts in oil-production and other fossil fuels might be taken as good news in terms of reducing global-warming and its effects, including more of us developing skin-cancer. The less carbon we have available to burn, the less CO2 we pump into the sky. However, by the time this offset helps reduce atmospheric CO2 levels, it is hard to see how civilization will be maintained, as these underpinning sources of energy to do so are depleted. We need a grand plan to address both and more immediately the latter.

Related Reading.
[1] "Russian oil has peaked". By Greg Walters and Maria Kolesnikova.
[2] "Global warming cancer warning." By Jon Edwards.
[3] Jan C. van der Leun, Photochem. Photobiol. Sci., 2008, DOI: 10.1039/b719302e

Wednesday, April 23, 2008

Saudi to Keep Oil for Itself.

King Abdullah of Saudi Arabia has commanded that some recent finds of crude oil be left untapped to preserve the nation's oil-wealth for future generations. Saudi is the world's greatest producer of oil at 11.3 million barrels per day which is predicted to be increased to 12.5 million bpd next year. The king is quoted as saying: "When there were new finds, I told them, 'no, leave it in the ground, with grace from God, our children need it'." World eyes are turned to Saudi to increase production to meet an inexorable thirst for oil, but when asked about the maximum likely production, the king said: "We'll get to 12.5 million barrels a day and then we'll see."

There is no longer any talk of output rising to 15 million bpd, and more likely, if the 12.5 million bpd is achieved, holding back 1 - 2 million bpd worth of spare-capacity, for the foreseeable future Saudi output is likely to be at around 9 - 11 million bpd. The vice president of Merrill Lynch, Tom Petrie commented: "The Saudis and other exporters are placing a new emphasis on elongating the petroleum exploitation and depletion cycle [i.e. the Hubbert Peak]. This stems from a growing awareness of the challenges of conventional resource maturity, as well as rising resource nationalism. This is likely to result in an earlier occurrence of global peak oil output than many customers yet recognize." With various existing estimates of the peak in world oil production at around 2012, this implies that a gap between supply and demand for world oil might occur within just a couple of years.

It is also possible that the Saudi fields are in reality approaching their maximum production, and there are varying estimates of how much oil they do have, with some commentators holding the opinion that Saudi has less recoverable oil than has been claimed, and that production of e.g. the giant Ghawar field has already peaked. Only time will tell, as it will over output from Russia, which according to Yuri Trutnev, the Russian Minister for Natural Resources, will fall this year, for the first time in 10 years. He believes that exports from OPEC, Russia and Mexico will in fact fall by 2.5 million barrels a day between now and 2012, which sounds to me that peak oil has arrived, to all intents and purposes.

All the countries in the Gulf have increased their own domestic use of oil and by 2015 Iran is predicted to use as much oil as they sell. It seems clear that the West simply has to find other ways to keep going that do not depend on oil, although as noted in many previous articles here, this is not an easy task. The major problem is transportation and the adaptation of modern civilization to use less of it. This is not a welcoming thought, including to this writer, but what other choice is there? Hydrogen is acknowledged to be years away if it will ever become a wholesale reality given its many challenges that need to be hence overcome and the world simply can't grow enough biofuels to replace the amount of oil-based fuels it gets through, even by severely compromising food production. Other possible technologies e.g. making diesel from algae and biomass-to-liquids (BTL) conversion are not available on the grand scale, as yet, and might also take years to implement.

Meanwhile oil, food and food prices rocket. Energy costs in general are on the up, notably in the United Arab Emirates (UEA) which apparently plans to double its energy use by 2015, and treble it by 2020. However, it appears very dubious what the actual state of play will be in the world by then, for any of us.

Related Reading.
[1] "Cheap energy in UAE is over." By Gundi Royle, Special to Gulf News.
[2] "Saudi King Abdullah drops quiet bombshell; U.S. media sleep through it." By Steve Andrews and Randy Udall.

Monday, April 21, 2008

Oil Price Rises Above $117 a Barrel.

This is more a note than a comment, to the effect that oil prices in Asia have exceeded $117 a barrel. This latest increase in the relentless rise in the cost of crude is blamed on an attack on an oil-pipeline in Nigeria. There have been remarks that OPEC will not push-up production and this belief is likely to bolster an increase in the price of oil. Shell has confirmed that a bomb had caused a leak in the pipeline for which the Movement for the Emancipation of the Niger Delta is believed responsible. This group have been assaulting the Nigerian oil-infrastructure since 2006 which has led to a decrease in production by 25%, thus urging oil prices. Nigeria is a major exporter of oil to the United States.

The pipeline has been isolated so that repairs can be carried out. The weaker dollar has also contributed to the rise in the price of oil above the $100 psychological-barrier. As the dollar falls, it brings investment in hard commodities like oil and gold, in an attempt to hedge against inflation. Simply too, the fall in the dollar makes these commodities cheaper for foreign buyers. The Secretary-General of OPEC has promised that it will not hesitate to ramp-up production if it is thought the higher prices are due to oil-shortages, but he noted that simply producing more oil will not bring its price down. For comparison, Brent crude is selling at just under $114 a barrel. I dare say we will see a parallel increase in fuel prices at the pumps.

The provision of fuel in Scotland is under threat too, by a strike over pensions. It is debatable how much any of us will get as a pension, if anything at all, especially in 10 - 20 years time, smack into the oil-dearth era, especially as unstable financial markets as we see them now will most likely oscillate in perpetuity. As the swings become more extreme there is a danger of panic on the markets which could bring some organisations, financial and otherwise to the verge of bankruptcy. I hope not, but I note that the British government is borrowing £50 billion ($100 billion) to prop-up the banking sector.

The Chief Executive of Ineos, who own the oil-refinery at Grangemouth, said that the union, Unite, was well-aware that a 48 hour strike will cause fuel-chaos across Scotland and northern England at this, the only such facility in the region. Rather like blast-furnaces, used to smelt iron-ore and make steel, oil-refineries cannot be simply switched off and on again. It can take weeks to get them up and running again, and sometimes some reconstruction is necessary. Like light-bulbs they are best kept burning! The Ineos workers are opposed to proposed changes in their pension-rites, particularly the ineligibility of new workers to a final-salary scheme. I expect a long battle ahead over fuel and pensions in the next decade and beyond. If the Grangemouth refinery is closed, it might take a month to get it back and running again.

The facility refines 200,000 barrels of oil daily which yields 9 million litres of petrol (gasoline). Farms and the haulage industry are expected to be hit hardest by the fuel shortages that will result if the 1,200 workers go ahead with their strike, while prices will increase as supplies become scarce. The result could be that the entire north-country, including Scotland is brought to a virtual standstill.

Related Reading.
[1] "Oil prices spike to record above $117 a barrel." By Thomas Hogue.
[2] "Strike threatens UK oil supplies."
[3] "Grangemouth strike threatens oil crisis." By Ian Robson and Sarah Robertson, Sunday Sun.

Sunday, April 20, 2008

Does algae solve the biofuel puzzle?

The following letter was published in "The Independent" newspaper on Saturday (the 19th of April).

Sir: I endorse Richard Pike's (he is CEO of the Royal Society of Chemistry) comments (letters, 16 April) about the need to find new sources of biofuels rather than those based on growing crops. The amount of land required to produce biofuels from crops on a scale commensurate with present human activities is vast, since the useful energy-capture from sunlight represents less than 1 per cent of the sunlight absorbed by the Earth's surface.

Hence there is necessarily a conflict between growing crops for fuel and crops for food because the area of arable land available to us is limited. But growing algae to make biofuel presents potentially a different proposition, and a Texas-based company, PetroSun, has just begun production.

With their figures showing that 4.4 million gallons (US) of diesel can be produced from 1,100 acres, we may deduce that 32.6 tonnes of diesel plus 116 tonnes of (other) biomass will be produced per hectare per year. Assuming the figure of 174 W/square metre (4.18 kWh/day), this amounts to a photosynthetic efficiency of 4.7 per cent, and is better than crop-based biofuel production by a factor of 10 to 20.

It is not necessary to use arable land nor divert valuable supplies of fresh water for biofuel, since the algae grow well in saline ponds, and could be placed on any land, or on water.

Professor Chris Rhodes

Caversham, Berkshire

Thursday, April 17, 2008

Biofuel from Algae: Vertical Reactors (HDVB).

I am indebted to a reader for bringing a new technology to my attention, namely the "High Density Vertical Bioreactor", or HDVB in contrast to open-pond systems, as alluded to in my recent posting, "Biofuel from Algae: Photosynthetic Efficiencies." The HDVB system is marketed by Valcent Products Inc. and consists of growing plants or algae in plastic pockets on clear vertical panels that move on a conveyor-belt arrangement. The strategy is designed to maximise the amount of sunlight and provide an ideal balance of nutrients to achieve optimum growth. It is proposed that such vertical growth systems might provide a solution to the problem of feeding urban populations so that urban living becomes sustainable.

Now, I like the sound of this, as it fits with my notion that once transportation begins to fail in consequence of cheap oil supplies waning in 5 - 10 years, humanity will relocalise into relatively small communities far less dependent on transport. The lack of urban growing space is counteracted by the very high efficiency of crop production in HDVB reactors. This form of agriculture as also soil-free, and uses perhaps 5% of the amount of water that is required to grow crops by conventional means, since the whole constitutes a closed-system with far less evaporation. Since these reactors can be placed anywhere (as can open-ponds) there is no necessity to compromise arable land which can still be used for standard agriculture.

However, the HDVB offers the potential of producing fuel as well as food, since algae can be grown in these systems too, and it is claimed in higher yield than in open-ponds. Thus in principle, food is grown locally, thus eliminating much of the fuel-costs borne in the carriage of crops from one part of the country to another or even across the world, by air or by ship, and also biodiesel can be made from oil extracted from algae grown using the technology, by transesterification with methanol or ethanol, as is done with plant-derived oils. Growing food both efficiently and locally also averts much of the spoilage that occurs on long hauls, during which as much as 50% of it is thus rendered inedible.

It is claimed that 100,000 gallons (US) of diesel can be produced per acre of HDVB area, which does seem very high. I commented in my article on photosynthetic efficiencies that the figure of 20,000 gallons/acre quoted in the wikipedia entry on "permaculture" looks to be well above the theoretical efficiency for a horizontal open-pond/algal system, but higher surface areas could be attained using vertical reactor arrangements; however, to install this paraphernalia on the very large scale is going to take a lot of plastic (derived from oil) and a lot of engineering, especially since the HDVB systems are more intricate than the basis I have indicated. Irrespective of whether the algae are grown in open-ponds or HDVB systems, there will also need to be a massive construction of transesterification plants and a source of methanol or ethanol must be found, in an amount equal to perhaps 10% of the diesel that is produced.

It sounds like a great idea and sits comfortably with most of my values and projections as to what precisely we need to achieve in order to form a stable, sustainable society. However, the scale-up will be a gargantuan task. If we can cut our fuel use to say 25% in relocalised communities, we still need to produce around 700 million tonnes of biodiesel annually (15 million tonnes just for the UK and 175 million tonnes for the US) and convert most vehicles to run on diesel-engines; but can this be done quickly enough to breach the demand/supply gap facing conventional oil production?

Related Reading.

Tuesday, April 15, 2008

Community in the Oil Dearth Era?

It's quite reasonable to grieve for the imminent loss of cheap oil, but the question remains, what are we going to do once it is gone? I am not a "peak oil doomer", and while looking into the uncomfortable realities of scale of renewables, biofuels etc. against the backdrop of current energy use, I have attempted to preserve some optimism. What I am saying is that we will have to live differently rather than not live at all. The extreme "survivalist" view is of a fellow sitting up all night with a shotgun, guarding his individual crop of vegetables, which does not strike me as being very sustainable, but I can envisage a community of male and female fellows each playing their own role in running a sustainable collective venture.

I am reminded of this basic premise by the article referenced below, entitled: "You are now entering an oil-free zone." This is, pretty much as you might think, a description of a small low-energy community - specifically, Totnes in Devon (the first such example), and then Falmouth and Stroud, as so named "transition towns" and the first transition village, Forest Row in Sussex. Significantly, Bristol and Brixton, in London, with its large Afrocaribean (initially Jamaican) community, are bringing the concept to larger urban conurbations. I say "significant" because the deconvolution of cities e.g. London with its population around 8 - 10 million (depending on where the borders are drawn) will pose the ultimate test of human adaptability and will to change in the direction of community living. The latter should be observed closely as linchpins of the entire process and measures of its likely success, or otherwise.

Life without oil is almost unimaginable or uncomfortably threatening when one does imagine it. Without oil-based plastics I would not be typing this, nor would there be the means of instant publication provided via the internet. Possibly this article and others of more local interest could be distributed via a small press in the form of a local newspaper. That said, I hope we do manage to hold-onto the net as otherwise we may simply disappear into a vacuum of small, isolated communities, which would be a thoroughly retrograde business. The notion of the "transition" town has been accredited to Rob Hopkins - not "Bob Hoskins" the actor, but the permaculture guru. The specific intention of these projects is the preparation for life post-oil.

I have commented on permaculture in previous postings both here and on ( a kind of on-line "New Scientist") where I write a monthly column. It's essential precept is energy efficiency, and so it should not fall victim to Jevons' paradox, where more available and hence cheaper energy (Jevons was referring particularly to coal and the steam-engine) ironically encourages the use of more energy and hence resources. In the utopia of permaculture, just sufficient energy and time are expended to fulfill the needs of a group of people in an immediate community, with the result that there is more time to devote to other activities, and one implication is that those living under such circumstances become more spiritually aware and imbued. It's a nice thought, especially as the world's financial markets take a down-turn on the roller-coaster ride they now offer and what meagre investments one has managed to squirrel-together over the years have plummeted in value during the past week.

The underpinning assumption for the transition town is that oil supplies will fall by around 3% a year beyond the peak in world-production, expected to arrive within a mere few years, which sits incongruously with such projections as an increased output from 84 million to 116 million barrels a day by 2030. It is also predicted that air-travel will have tripled by that same date, hence the necessity for a third runway at Heathrow airport and the demolition of a village that is inconveniently in the way of this development. What will they be putting in the fuel tanks by then, I wonder?

Transportation will be the major victim of peak oil, since 70% of all the 30 billion barrels currently produced in the world goes to fuel various forms of transportation, mainly its 700 million road vehicles. Fuel prices are already increasing and will continue to do so thus forcing vehicles of the roads. The net result will be a less mobile population and accordingly our focus will be increasingly on the local rather than the global, and thus we have potential transition towns brought into fruition in the light of what has been learned during the transitional period.

There is a political element too, in that as Hopkins points-out, people are getting fed-up with the government's lack of action in the face of peak-oil. Arguably there is an intention to avoid mass panic, but a gentle approach might well avert this by raising a kind of "Dunkirk Spirit", although that does impinge on matters of national identity which are now more complex that they were in 1945, partly in the pursuit of oil, as some ague. So how, as individuals, might we urge our own local communities into "transition"? I am thinking of the village of Caversham where my family lives (population around 9,000) and the larger conurbation of Reading, across the river Thames from us, a town with its population of 140,000.

As Hopkins admits, the answer is not entirely clear, but making the process attractive - the carrot not the stick - is key to making it a success. My own view is that an integration of the old with the new, rather than an overnight jump is necessary. We are not going to be instantly self-sufficient, and nor do we need to be. If we thus cut-back on our use of energy and resources by say a half, mainly through limiting transportation needs and other forms of energy efficiency, we are half way there. In this aim, we should rely increasingly on products and services from local farms and businesses, insulate our homes, grow some of our own food in back gardens and allotments, try to work locally and share our experience, the good and the bad. This by definition is "community".

Related Reading.
"You are now entering an oil-free zone". By Julie Ferry.

Friday, April 11, 2008

Price of Oil and Food Soars.

The price of crude oil has now hit above $112 a barrel, which is more than five times that of five or six years ago, while the price of rice has risen by up to 70% from last year. It is debatable what exactly is the reason for such a huge hike in oil prices, but the general costs of extracting it, including exploration, have increased markedly, as it becomes ever more difficult to secure enough oil to meet world demand of 30 billion barrels a year for it. All the major oil companies have needed to invest substantially in infrastructure and are angling in more costly regions e.g. in deep-sea locations and potentially the Arctic.

A new elephant field has not been found since the early 1980's, and it is thought that once the Middle East giants, especially Ghawar in Saudi, begin to decline, we are all in big trouble, living in a world utterly dependent on cheap oil. I doubt the price of conventional crude oil will ever come down, and unconventional sources even if fully exploited, will also become increasingly expensive to produce from, in the wake of the increasing costs of other resources of energy and water required to get oil from heavy crude and bitumen - for example in tar-sands. To exploit significant amounts of such resources, and if coal-to-liquids etc. are to be employed appreciably, will need massive new engineering, and I question just how much can be brought on-line within the crucial next decade, during which peak-oil and its consequences must be met head-on.

Some estimates of total conventional plus unconventional oil amount to 3.7 trillion barrels, but success in supplying the annual 30 billion barrels currently demanded, let alone satisfying projected requirements in a model of untrammelled economic growth, depends not on how big the resource is, but how quickly it can be extracted and processed. Providing enough platinum to fabricate hundreds of millions of fuel cells poses a similar dilemma, since while there is more than enough of the metal in the Earth per se, producing pure Pt is a very exacting process which limits its rate of production dramatically. A shortfall in oil, which I expect will prove the reality, means a deep decline in the world's transportation and a relocalisation of societies into small communities. It is indeed the issue of keeping transportation running, as conventional oil supplies fail to meet our urging for them, that is the linchpin of the human mechanism, and if this fails in an abrupt and unmanaged way, so will civilization.

Rice is the staple food for half the world's population of 6.7 billion; however, the price of rice has increased by up to 70% during the past year. In part, this is blamed on poor harvests in consequence of "extreme weather", rising populations and hence demand for food in countries that import rice from world markets, an expectation that things can only get worse leading to hoarding, and depleting stockpiles and insufficient investment in agriculture. In fact, the increasing cost of rice is but one example of an increase in world food prices overall. In an effort to protect their own internal food-provision and to curb inflation, main rice-producing nations, e.g. India, China and Vietnam, have imposed restrictions on exports. On the other side of the coin, net rice-importers such as Bangladesh, Afghanistan and the Philippines are suffering the consequences of an unstable and costly supply.

Rapid economic development in Asia has led to a more prosperous and more numerous middle class who eat more food, while land formerly used to grow rice is now used to host new housing developments, factories and in some regions, golf courses. The biofuels market has grown since 2006 providing a greater incentive for farmers to grow corn for ethanol than to produce rice, bringing global stockpiles to their lowest level for twenty years. Particular local factors have also contributed to the situation, such as the cyclone which destroyed much of Bangladesh's autumn rice crop last November, a total of almost one million tonnes. As a consequence of this, the country has imported 2.4 million tonnes of rice to avert a famine. Vietnamese rice-crops have also have suffered from a combination of adverse weather and infestations of pests.

There are fears that food-rioting may result, causing unrest and destabilisation across Asia and Africa, where half the world lives. The escalating price of rice and a weak US dollar has strained food-aid programmes, for example to feed the Myanmar refuges who are heading in large numbers toward the Thai border. I am reminded of the Hubbert analysis I have alluded to recently, that rather than the world population rising unchecked to 9 billion by 2050, it will instead peak at around 7.3 billion, somewhere close to the year 2025, and then decline to around 2.5 billion by the end of this century (2100). Possibly, we are beginning to glimpse the mechanisms by which this may occur, and that the greatest incidence of a population "die-off" will occur in the developing nations, i.e. Africa, Asia and South America, where the population growth has been greatest, especially during the past century.

Since most of this growth has been fed by mechanised agriculture, which only exists as underpinned by cheap oil and natural gas, it follows that the present number of people on Earth cannot be maintained during the imminent oil-dearth era. What other conclusion can be drawn?

Related Reading.
[1] "Food riots fear after rice price hits a high." By Peter Beaumont.
[2] "Asian states feel rice pinch."
[3] "Crude oil hits record price." By Loong Tse Min.

Wednesday, April 09, 2008

Oil from Algae: Photosynthetic Efficiencies?

There is much communicated on the prospect of growing oil-rich algae to convert into diesel as a replacement for the inevitably declining supply from crude oil. Now, PetroSun Inc. has announced that their Rio Hondo algae-farm in Texas will begin operations at its pilot commercial algae-to-biofuels facility [1]. The farm comprises 1,100 acres of salt-water ponds from which it is thought will be produced 4.4 million US gallons of algal oil along with 110 million pounds of biomass, annually. Expansion of the farm is intended in order to provide fuel to run existing or putative biodiesel and bioethanol refineries, owned or part-owned by PetroSun. Such an open-pond design effectively consists of a nutrient-loaded/fed aqueous culture medium (see "Could Peak Phosphate be Algal Diesel's Achilles' Heel?", posted here on 6-4-08), in which algae will grow close to the surface, absorbing CO2 from the atmosphere in the process through photosynthesis - hence the other vital ingredient is sunlight.

I am interested in the likely photosynthetic efficiency (PSE) of such processes, and of crop-agriculture too, hence I shall now attempt some illustrative sums regarding their PSE viability:

4.4 x 10^6 gallons (US) of oil = 4.4 x 10^6 gal x 3.875 l/gal = 1.7 x 10^7 l.
1.7 x 10^7 l x 0.84 kg/l = 1.43 x 10^7 kg = 1.43 x 10^4 tonnes of oil.

If 110 million pounds of biomass is also produced, this amounts to 110 x 10^6 lb/2200 lb/tonne = 5 x 10^4 tonnes. Hence the oil is 22% of the total "mass" produced.

1,100 acres/ 2.5 hectares/acre = 440 ha.

Therefore, the oil-yield = 1.43 x 10^4 t/440 ha = 32.6 tonnes/ha. To "grow" this much oil would take: 7.19 x 10^8 tonnes/32.6 t/ha = 2.21 x 10^7 ha.

If the total area of the US is 9.8 x 10^8 ha (that's land plus water), and the US fuel consumption may be estimated as 0.25 (one quarter if the world's total) x 0.7 (proportion of oil used for transport) x 30 x 10^9 barrels/7.3 barrels/tonne = 7.19 x 10^8 tonnes, to grow enough algae to produce an equivalent amount of algal oil would take:

2.21 x 10^7 ha/9.8 x 10^8 ha = 2.3% of total US area.

For the entire world, the requisite land area is 4 x that = 8.84 x 10^7 ha, to be compared with a total surface area of around 500 million km^2 (about 147 million km^2 being land), or <0.2% of it.

If the UK switched all its transportation over to diesel engines, which are more efficient in terms of tank to wheel miles than spark-ignition engines that burn petrol (gasoline), we would need 40 million tonnes of oil (assuming oil = diesel, since the actual yields of diesel from oil are uncertain).

This amounts to: 40 x 10^6 tonnes /32.6 t/ha = 1.23 x 10^6 ha, which is about 5% of the total area of the UK mainland.

So, what about the photosynthetic efficiencies incurred?

(1) I am taking a good-mean of 5 kWh/m^2/day. Quite often, values of W/m^2 are quoted over the whole year, which is a bit misleading, since the solar radiation hitting the Earth (insolation) varies from region to region and according to time of day and the changing seasons. However, dividing 5 kwh/m^2/day by 24 hours gives around 200 W/m^2, to be compared with around 350 W/m^2 hitting the top of the atmosphere, as an annual mean. This would correspond to a sunny clime, e.g. Arizona, Australia or central Africa; it is probably less than half this for northern Europe.

Expressing the insolation as kWh/day is more realistic however. Hence:

5 x 10^3 Wh/day x 365 days x 3600 s/h= 6.57 x 10^9 W/m^2/year. Since W = J/s, we have:

6.57 x 10^9 W/m^2/year x 10,000 m^2/ha = 6.57 x 10^13 J/ha/year (i.e. the amount of solar energy falling on each hectare of land).

If we assume that "diesel" uniformly contains 42 GJ/tonne of energy, each ha yields:

32.6 x 42 x 10^9 = 1.37 x 10^12 J.

Thus, the PSE on oil is: 1.37 x 10^12/6.57 x 10^13 = 2.1%.

But only 22% of the total is oil and the rest is (other) "biomass". If we assume that 1 tonne of biomass contains 15 GJ of energy (about the same as for glucose), we have:

32.6 tonnes x 15 x 10^9 x (100-22/22) = 1.73 x 10^12 J/ha, which gives a PSE of:

1.73 x 10^12/6.57 x 10^13 = 2.6%, and so the overall PSE for the PetroSun process is 2.1% + 2.6% = 4.7%

(2) Now this seems quite reasonable, and is in the 6% "ballpark" usually given for the amount of the total solar radiation that is used by plants in photosynthesis, as I have described previously. However, at 32.6 tonnes of oil per hectare, the yield is rather less than the 5,000 - 20,000 gallons/acre quoted in Wikipedia [2] for algal oil production.

5,000 gals/acre = 12,350 gals/acre = 12,350 x 3.875 = 47,856 l/ha, and assuming a density of 0.84 tonnes/m^2, this amounts to 40.2 t/ha, as the lower estimate.

[Assuming, again, a sunny 5 kWh/day or 6.57 x 10^13 J/ha/year], if 50% of the algae is oil with an energy content of 42 GJ/tonne, it contains: 40.2 x 42 x 10^9 = 1.69 x 10^12 J, which equates to a PSE of 1.69 x 10^12/6.57 x 10^13 = 2.6%.

Then there must be another 50% of "other" biomass, which at 15 GJ/tonne, amounts to:

40.2 x 15 x 10^9 = 6.03 x 10^11 J (PSE = 0.9%), and so the total energy of this high-oil crop = 1.69 x 10^12 + 6.03 x 10^11 = 2.29 x 10^12 J, giving a total PSE of 3.5%, which is also reasonable.

I am worried, however, about the upper Wikipedia limit of "20,000 gallons/acre". At 4x the above this implies a PSE of 3.5% x 4 = 14%! which seems far too high, being above the theoretical PSE limit, at which around 12.7% of the entire insolation is usefully absorbed by a photosynthetic entity. It is conceivable that special methods are employed to increase the yields, e.g. CO2-injection or forced-UV conditions to increase the PAR of the solar spectrum. At any rate it could not be achieved in standard open-pond systems. If someone can prove me wrong here I should be most interested in knowing the details.

Related Reading.

Monday, April 07, 2008


I seek for my answers but instead find madness,

amid the clamour of confused voices.

Nearly seven billion tongues pen

a million linguistic forms;

minds deliberate over dialects

and didaction, seeking meaning or God;

or just pleasing the moment

of global intercourse.

Finding a voice amid the babble -

the constant murmuring deafens.

Prophets and messiahs – true

or false? Who knows – there are so many?

Intolerance is neither sin nor

surprising when none can hear

another; individual heartbeats seem

merely virtual or alien, or the newest

con from sad, dusty fingers:

an S.O.S. to reach a calmer somewhere.

In this information overload,

I cannot withstand the flood

of disconnection, which liquidises

all permanent structures of belief.

I ache for silence from such mayhem;

to know the still echo of serenity,

which spoke all along,

under the thunder that is not thunder,

but the world's pain, in throng.

Christopher James Rhodes.

Sunday, April 06, 2008

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

The depletion of world phosphate reserves will impact on the production of biofuels, including the potential wide-scale generation of diesel from algae. The world 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 US the peak came in the late 1980's), 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 [1]. Consensus of analytical opinion is that we are close to the peak in world oil production too.

One proposed solution to the latter problem is to substitute oil-based fuels by biofuels, although this is not as straightforward as is often presented. In addition to the simple fact that growing fuel-crops must inevitably compete for limited arable land on which to grow food-crops, 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 "kick" of petrol, pound for pound.

In order to obviate the competition between fuel and food crops, it has been proposed to grow algae from which to make biodiesel. Some strains of algae can produce 50% of their weight of oil, which is transesterified into biodiesel in the same way that plant oils are. Compared to e.g. soy which might yield a tonne of diesel per hectare, or 8 tonnes from palm-oil, in excess of 100 tonnes (I shall assume 125 tonnes) per hectare is thought possible from algae, grown in ponds of equivalent area. Since the ponds can in principle be placed anywhere, there is no need to use arable land for them. Some algae grow well on salt-water too which avoids diverting increasingly precious freshwater from normal uses, as is the case for growing crops which require enormous quantities of freshwater.

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 km^2 to produce 40 million tonnes 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. I have used two different methods of calculation to estimate how much phosphate would be needed to grow enough algae, first to fuel the UK and then to fuel the world:

(1) I have taken as illustrative the analysis of dried Chlorella [2], which contains 895 mg of elemental phosphorus per 100 g of algae.

UK Case: To make 40 million tonnes of diesel would require 80 million tonnes of algae (assuming that 50% of it is oil and this can be converted 100% to diesel).
The amount of "phosphate" in the algae is 0.895 x (95/31) = 2.74 %. (MW PO4(3-) is 95, that of P = 31).

Hence that much algae would contain: 80 million x 0.0274 = 2.19 million tonnes 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 tonne of oil is contained in 7.3 barrels, this equals 30 x 10^9/7.3 = 4.1 x 10^9 tonnes and 70% of that = 2.88 x 10^9 tonnes of oil for transportation.

So this would need twice that mass of algae = 5.76 x 10^9 tonnes of it, containing:
5.76 x 10^9 x 0.0274 = 158 million tonnes of phosphate.

(2) To provide an independent estimate of these figures, I note that growth of this algae is efficient in a medium containing a concentration of 0.03 - 0.06% phosphorus; since I am not trying to be alarmist, I shall use the lower part of the range, i.e 0.03% P. "Ponds" for growing algae vary in depth from around 0.6 - 1.5 metres and so I shall assume a depth of 1 m for simplicity.

UK Case: I worked-out previously [3] that producing 40 million tonnes of oil (assumed equal to the final amount of diesel, to simplify the illustration) would need a pond/tank area of 3,200 km^2. 3,200 km^2 = 320,000 ha and at a depth of 1m, this amounts to a volume of: 320,000 x (1 x 10^4 m^2/ha) x 1m = 3.2 x 10^9 m^3.

A concentration of 0.03 % P = 0.092% phosphate, and so each m^3 (1 m^3 weighs 1 tonne) of volume contains 0.092/100 = 9.2 x 10^-4 tonnes (920 grams) of phosphate. Therefore, we need:

3.2 x 10^9 x 9.2 x 10^-4 = 2.94 million tonnes of phosphate, which is in reasonable accord with the amount of phosphate taken-up by the algae (2.19 million tonnes), as deduced above.

World Case: The whole world needs 2.88 x 10^9 tonnes of oil, which would take an area of 2.88 x 10^9/125 t/ha = 2.30 x 10^7 ha of land to produce it.

2.3 x 10^7 ha x (10^4 m^2/ha) = 2.3 x 10^11 m^2 and at a pond depth of 1 m they would occupy a volume = 2.30 x 10^11 m^3. Assuming a density of 1 tonne = 1 m^3, and a concentration of PO4(3-) = 0.092%, we need:

2.30 x 10^11 x 0.092/100 = 2.13 x 10^8 tonnes of phosphate, i.e. 213 million tonnes.

This is also in reasonable accord 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 tonnes (noting that we need 213 million tonnes to grow all the algae), and food production is already being thought compromised by phosphate resource depletion. The US produces less than 40 million tonnes 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 tonnes of phosphate. Hence, for the US, 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 tonnes and that in the US at 2,850 million tonnes (by a Hubbert Linearization analysis). However, as is true of all resources, what matters is the rate at which they can be produced.

I remain 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 energy-intensive 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 upon. 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, it will instead peak around the year 2025 at 7.3 billion, and then fall [1]. 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 [1]. It seems to me 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.

Related Reading.
[1] "Biofuels and the fertilizer problem,", By Tom Phillpott.
[2] "Chlorella" - Wikipedia.
[3] "Biofuel from algae - Salvation from Peak Oil?

Tuesday, April 01, 2008

Viva Vegetarians!

Meat-eating is seen as a sign of prosperity, and in China in 1962, the average person consumed just 4 kg of meat annually, now the figure is nearer 60 kg and increasing steadily. The UK has not been self-sufficient in food since the 18th century, and during WWI it was thought that the regular torpedo attacks on merchant ships from the colonies, as they then were, a part of the long since redundant British Empire, would starve the nation into surrender to Germany. Today we import 37% of our food, at a total cost of £22 billion, of which 68% comes from the European Union. London relies on imports for 80% of its food supply which makes me think that the Oil Dearth Era will be particularly harsh for such massive urban conurbations, which will not be readily devolved into self-sustaining communities.

Food prices have soared, and this applies to animal feed too, the cost of which must be passed-on to the consumer. It now costs £15 a month to feed a pig, or around double the cost of doing so a year ago. Wheat prices have also doubled, as we see in the rising cost of a loaf of bread. Fuel prices are on the "up" too. It is interesting that numerically, the price of a litre of diesel in pounds is the same as that in US dollars for a barrel of oil: i.e. £1.11 or $111 (more or less, but you get my point).

The average citizen of the United Kingdom eats 80 kg of meat per year, and the average American 124 kg. When I was a boy, meat was served up as a Sunday roast and then cold with "bubble and squeak, a strange British fare of the left-over potatoes and other vegetables, mainly cabbage, fried in "dripping", i.e. the fat which exudes from meat when it is roasted. Other than that I recall living on beans-on-toast, or cheese-on-toast. It did me no harm anyway! However, it is probably the reason why we British have such a poor reputation for the quality of our food, especially among the French, who are good cooks. However, I remember attending a conference on Zeolites in Southport, North West England, and meeting a nice Frenchman called Henri who said, "Ah it is not true that the British have bad food!" It was indeed a well-resourced conference and as I pointed-out, if the ingredients, meat and vegetables are of good quality, then the food here is fine.

Generally, I tend to cook at home and I think serve up something better than is normally presented in restaurants although these establishments too have improved vastly during the past 30 years. Pubs almost all do food these days and when I was in my late teens 30 years ago, they were exclusively drinking establishments, and food was a pork-pie or a bag of crisps - a scotch-egg or a pickled-onion if you were lucky! Interestingly, it requires 2 kg of grain to produce 1 kg of chicken but 7 kg for each kg of beef. I also recall when I was a kid that we all kept chickens! This was mainly for their eggs, and prior to battery-farming, chicken was an expensive (luxury) item, and indeed was often served-up at Christmas rather than turkey. Beef was relatively cheap, being home-produced, and lamb was (and still is) cheap as imported from New Zealand. Welsh lamb is far more expensive.

It might be argued that there is insufficient arable land on which to grow the grain to feed the animals that we kill to feed humans (which is never a pleasant notion). However, the facts are more complex. Specifically, in the United States, pesticides derived from hydrocarbons (i.e. oil) have increased in their use by 33 times. Practically all the food that we eat depends on oil or natural gas, the latter being converted into hydrogen which is combined with nitrogen to make ammonia via the Haber-Bosch process, and a substantial proportion of this is oxidised to nitric acid via the Ostwald process. The combination of the two provides ammonium nitrate, which is both a fertilizer and a high-explosive. The salient issue however is that 95% of all agriculture depends on hydrocarbons - oil and gas, either as a chemical feedstock or as a fuel.

Oil is a fulcrum of fertilizer-production, mechanised farming, transportation of food and the ubiquitous packaging that everybody loves to hate. Such modern farming methods have created an increase in grain production by 250% since 1950, and the cheapness of food held-back the rate of inflation and augured-in the post WWII consumer boom. In the global farmyard that is the modern world, prices have escalated at around 7.5% for bread, 15% for milk and other dairy products (e.g. cheese and eggs), while rice has increased its price by 60%. Food inflation runs at an average of 6.6% while the cost of a barrel of oil has risen by 70% (or 400% from its price of five years ago). We can only expect the cost of food and fuel to rise in accord with the raw price of oil.

Water-provision is another pressing matter. Less than 1% of the world's water is liquid freshwater - most water on earth comprises the oceans and is saline, while the bulk of freshwater is present as frozen ice, e.g. the massive shelves of Antarctica. Necessarily, the supply of freshwater is limited, and it takes anywhere from 100 to 1,000 times as much water to produce 1 kg of meat as 1 kg of grain. It has been pointed out that since 70% of all freshwater is used for farming, when buying food imported from elsewhere, in affect one is purchasing another country's water allocation. I hadn't thought of it that way, but it is true!

In a destructive synergy, rising oil prices, a real limit on how much land there is to grow food to feed either human or other animals, increasing demand for arable land to produce crops for biofuels, and the desertification of formerly arable regions in consequence to climate-change, the planet could not support a population of 6.7 billion meat-eaters. If we all turned vegetarian, this present number of us is probably sustainable for a while, but otherwise not. I recently estimated that in the absence of oil and gas based farming the Earth can probably support around 3 billion (Professor David Pimentel at Cornell University reckons closer to 2 billion), and there is a real threat of a die-off. It is interesting that by applying a Hubbert type population analysis, rather than the putative and often cited figure that by 2050 the world population will exceed 9 billion, I estimate that world population will peak at around 2025 at 7.3 billion, and then fall. By what means precisely this will happen is anybody's guess, but as is true of population analysis in general, of bacteria or humans, it is the underlying depletion of resources that determines precisely when and at what level this occurs.

Related Reading.
"Only a radical change of diet can halt looming food crises," By Rosie Boycott.