The Achilles' Heel of Algal Biofuels - Peak Phosphate. - An Update.

The following is an update to a previous posting http://ergobalance.blogspot.co.uk/2012/02/achilles-heel-of-algal-biofuels-peak.html If anything, the situation might be worse that I had concluded then, but the issue of phosphate rock reserves is more complex than I had deduced. So, this article is as written before, but with a few more numbers worked through, to account for "real" phosphate rock, rather than my initial model of it being pure fluorapatite [Ca₅(PO₄)₃F (calcium fluorophosphate)]. The references are as appended to a full article on this subject that will appear in the next issue of the journal, Science Progress http://www.ingentaconnect.com/content/0036-8504

The depletion of world rock phosphate reserves will restrict the amount of food that can be grown across the world, a situation that can only be compounded by the production of biofuels, including the potential large-scale generation of diesel from algae. The world population has risen to its present number of 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 produce². If a peak in worldwide production of rock phosphate will occur within the next few decades, this will restrict the amount of food that the world will be able to produce in the future, against a rising number of mouths to feed. Additionally, there is a consensus of analytical opinion that we are also close to the peak in world oil production. One proposed solution to the latter problem is to substitute oil-based fuels by biofuels, although this matter 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 in 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 (high compression ratio) engine to recover more of its energy in terms of tank to wheels miles, otherwise it could deliver only about 70% of the energy contained petrol, or diesel, weight for weight. In order to obviate the competition between fuel and food crops, it has been proposed to grow algae from which to make biodiesel²⁷. Some strains of algae²⁸ can produce 50% of their weight of oil, which may be transesterified into biodiesel in the same way that plant oils are. Compared to, e.g. rapeseed, which might yield a tonne of biodiesel per hectare, or 8 tonnes from palm-oil, perhaps 40─90 tonnes per hectare²⁹ is thought possible from algae, grown in ponds of equivalent area. Since the ponds can, in principle, be placed anywhere, there is no compromise over arable land, unlike fuel/food crops. Some algae grow well on salt-water too which avoids diverting increasingly precious freshwater from our normal uses for it, as opposed to the case for land-based crops which require enormous quantities of freshwater.

Diesel engines are more efficient²⁷ by about 40%, in terms of tank to wheels miles, than petrol-fuelled spark-ignition engines, and so, in the spirit of energy efficiency, we shall assume that all vehicles are converted to run on diesel. This means that a total of around 40 million tonnes/year of diesel would need to be substituted for. To produce an equivalent amount of algal biodiesel, and assuming a yield of 40 tonnes/hectare (the lower end of the 40─90 t/ha range²⁹), the algae ponds would require a total area of 10,000 km². Ideally, the algae plants could be integrated with fossil fuelled power plants, to absorb CO₂ from smokestacks by photosynthesis, driven only by the flux of natural sunlight. However, for the 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 are now used to estimate how much phosphate would be needed to grow this amount of algae: (1) to fuel the UK and (2) to fuel the world:

(1) An analysis of dried Chlorella [http://en.wikipedia.org/wiki/Chlorella} is taken as illustrative, 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 %. (The Formula Weight, FW of PO₄^3- is 95, while that of P is 31).

Hence this much algae would contain: 80 million x 0.0274 = 2.19 million tonnes of phosphate. By initially assuming the chemical composition of the rock to be that of fluorapatite, Ca₅(PO₄)₃F, FW 504, we can conclude that this amount of PO₄^3- is contained in 3.87 million tonnes of it. However, actual mined rock phosphate is a more impure material than this, and that normally used for fertilizer production is reckoned to contain 29─34% P₂O₅ (to be compared with 42.3% as may be deduced from the chemical formula of pure fluorapatite, above). Following the calculations so far for the quantity of PO₄^3- involved, and by using the ratio of FW for 0.5 P₂O₅/PO₄^3- (71/95), we may conclude that there are (71/95) x 2.19 million = 1.64 million tonnes of P₂O₅ contained in this amount of PO₄^3-. Taking the range average of 31.5% for the mineral P concentration, reckoned as P₂O₅, this would accord with 5.20 million tonnes of actual “rock phosphate”, yielding a conversion factor of 1.34 up from the value reckoned for pure fluorapatite. We may use the latter in the remaining calculations.

World Case: The world produces and consumes 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 10⁹/7.3 = 4.1 x 10⁹ tonnes and 70% of that = 2.88 x 10⁹ tonnes of oil for transportation.

Assuming that 50% of it is water, we would require twice the deduced mass of algae = 5.76 x 10⁹ tonnes of it, which contains: 5.76 x 10⁹ x 0.0274 = 158 million tonnes of phosphate. As before, by taking the chemical composition of the material as fluorapatite, Ca₅(PO₄)₃F, FW 504, this amount of "phosphate" is contained in 279 million tonnes. Applying the factor of 1.34 as arrived at above, to account for the typical degree of impurity in the mineral, we obtain a requirement of 374 million tonnes of actual mined rock phosphate.


(2) To provide an independent estimate of these figures, we may note that growth of this algae is efficient in a medium containing a concentration of 0.03─0.06% phosphorus. To avoid being alarmist, we may use the lower part of the range, i.e 0.03% P. "Ponds" for growing algae vary in depth from 0.3─1.5 m, but we now assume a depth of 0.3 m.

UK Case: assuming (vide supra) 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 10,000 km². 10,000 km² = 1,000,000 ha and at a depth of 0.3 m, this amounts to a volume of: 1,000,000 x (1 x 10⁴ m²/ha) x 0.3 m = 3 x 10⁹ m³.

A concentration of 0.03 % P = 0.092% phosphate, and so each m³ (assuming a density of 1t/m³) of volume contains 0.092/100 = 9.2 x 10^-4 tonnes (920 grams) of phosphate. Therefore, we need:

3 x 10⁹ x 9.2 x 10^-4 = 2.76 million tonnes of phosphate, which is in reasonable accord with the amount of PO₄^3- taken-up by the algae (2.19 million tonnes), as deduced above. This corresponds to 4.87 million tonnes of Ca₅(PO₄)₃F, and if the 1.34 “impurity factor” is applied, to 6.53 million tonnes of rock phosphate.


World Case: To meet the requirements of the entire world would demand the substitution by algae fuel of 2.88 x 10⁹ tonnes of crude oil, and an installation to produce this amount would occupy an area of 2.88 x 10⁹/40 t/ha = 7.20 x 10⁷ ha of land.

7.2 x 10⁷ ha x (10⁴ m²/ha) = 7.2 x 10¹¹ m² and at a depth of 0.3 m the ponds would occupy a volume = 2.16 x 10¹¹ m³. Assuming a density of 1 tonne = 1 m³, and a concentration of PO₄^3- = 0.092%, we need:

2.16 x 10¹¹ x 0.092/100 = 1.99 x 10⁸ tonnes of PO₄^3-, i.e. 199 million tonnes. This corresponds to 352 million tonnes of Ca₅(PO₄)₃F, or (x1.34) 472 million tonnes of actual mined rock phosphate.

This is also in acceptable 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.


Rock phosphate production¹⁰ in 2011 amounted to 191 million tonnes, against which must be compared the 472 million tonnes we have estimated would be needed to grow sufficient algae to fuel the world with algal biodiesel. Since food production is already being thought compromised by rock phosphate resource depletion, finding such a significant additional quantity is probably impossible. Currently, the U.S. produces less than 30 million tonnes of rock phosphate annually, but would require 104 million tonnes of the material to produce 22% of the world's total algal diesel, in accord with its current "share" of world petroleum-based fuel. Hence, for the U.S., security of fuel supply could not be met by algae-to-diesel production using even all its indigenous rock phosphate output, and significant imports would still be needed. This is in addition to the amount of the mineral necessary to maintain agriculture. In principle, phosphate could be recycled from one batch of algae to the next, but how exactly this might be done remains a matter of some deliberation, e.g. the algae could be dried and burned³⁰, and the phosphate extracted from the resulting “ash”, or the algae could be converted to methane in a biodigester^31,32, releasing phosphate and other nutrients in the process. Clearly there are engineering and energy costs attendant to any and all such schemes and none has been adopted as yet.


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 mineral rock phosphate. 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 beyond the peak for rock phosphate, and certainly if additionally, algae are to be produced in earnest. 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. A recent study³³ concluded that growing algae could become cost-effective if it is combined with environmental clean-up strategies, namely sewage wastewater treatment and reducing CO₂ emissions from smokestacks of fossil-fuelled power stations or cement factories. This combination appears very attractive, since the impacts of releasing nitrogen and phosphorus into the environment and also those of greenhouse gases might be mitigated, while conserving precious N-P nutrient and simultaneously producing a material that can replace crude oil as a fuel feedstock.

It is salutary that there remains a competition between growing crops for fuel, and those for food, even if not directly in terms of land, for the fertilizers that both depend upon. There is a dissonance in that apparently clean, renewable sources of biofuels, in reality depend on inputs of a mined and finite reserve, which not only is growing more scarce, but its recovery leaves radioactive waste as a legacy (phosphogypsum)¹⁸. In principle, at least, recycling phosphorus from one batch to the next, in algae production, might be done more readily than for land-based crops. Along with the higher relative areal yields that are possible with algae, this might alleviate the rising demand for phosphate rock. The above, however, illustrates the complex and interconnected nature of, indeed Nature, which as any stressed chain, will ultimately converge its forces onto the weakest link in the "it takes energy to extract energy" sequence. It seems quite clear that with food production already stressed, the production of (algal) biofuels will never be accomplished on a scale anywhere close to matching current world petroleum fuel use (> 20 billion barrels/annum)²⁷. Thus, the days of a society based around personalized transport powered by liquid hydrocarbon fuels are numbered. We must reconsider too our methods of farming², to reduce inputs of fertilisers, pesticides and fuel. Freshwater supplies are also at issue², in the complex transition to a more localised age that uses its resources much more efficiently.

References.

(2) Rhodes, C.J. (2012), Sci. Prog. 95, 203.

(27) Rhodes, C.J. (2008) Sci. Prog., 91, 317.

(28) Rhodes, C.J. (2009) Sci. Prog., 92, 39.

(29) Rhodes, C.J. (2012) Making Fuel from Algae: Identifying Fact Amid Fiction, in Gordon, R. and Seckbach, J. Eds. The Science of Algal Fuels: Phycology, Geology, Biophotonics, Genomics and Nanotechnology. Dordrecht, Springer, p177.

(30) Knoshaug, E.P. and Darzins, A. (2011) Chem. Engin. Prog., March, 37.

(31) Sialve, B. et al. (2009) Biotech. Adv. 27, 409.

(32) Heaven, S. et. al. (2011) Biotech. Adv., 29, 164.

(33) Clarens, A.F. et al. (2010) Environ. Sci. Technol., 44, 1813.

Energy Institute: Potential for Hydropower on the River Thames.

The following is cobbled together from some notes taken at this event, hosted at the Energy Institute (London) on January 28th (2013): http://www.energyinst.org/events/view/909

The thread is, that since we have the river (Thames) close to us, surely we can use its flow of water to produce energy. Thus, weirs in particular, might be considered as assets, of which there are 44 on the Thames, owned by the Environment Agency. Each weir has been screened for its potential in hydropower generation, with consideration to: the "head" (i.e. the drop between the flowing water at the upper and lower parts), and the prevailing flow of the river there. Along the Thames, the head range is 0.7--2.7 metres, with an average of 1.8--1.9 metres. Since this is in the region of the 2 metres reckoned to be viable for power generation, the prospects appear favourable; however, environmental impacts must be considered too. It is the duty, after all, of the Environment Agency (EA) to protect the environment.

Interestingly, it is developers rather than the EA who build hydropower installations, to whom the EA grant a lease for their use of the weir. Romney weir - work on which started in September 2011, and is due to be completed in March 2013 - has some spare capacity for water flow as a flood relief channel (most weirs still need to be kept for flood defence).

Here are some points of consideration taken from, the Environment Agency - Consultation on river flow and water abstraction standards for hydropower : https://consult.environment-agency.gov.uk/portal/ho/br/standards/hydro

*Flows, constraints and water abstractions

*Monitoring of environmental impact - In Europe some schemes taken out because of environmental damage.

*Impoundment licence - authorises holder to obstruct or impede flow.

*Flood risk assessment - flood defences.

*Planning permission.

*Fish pass approval from national panel - there are both sea trout and salmon in the Thames.

*Hydropower is possible at Teddington, for which an application is close to being placed. The anticipated output is 450--490 kW, from 3 screws.

*The most fish-friendly kind of turbine is the Archimedes screw, which accordingly is the preferred technology.

*The existing Thames weirpools, especially gravels, are valuable for fish spawning, and the cumulative impact on spawning grounds mist be considered.

*Since there is no such thing as a "typical year", the impact on wildlife will be monitored over 15 years, to get a kind of "average".

*The proposed installation at Goring (and Streatley) http://ergobalance.blogspot.co.uk/2011/11/further-proposed-hydroelectric-power-on.html was mentioned, over which there is apparently some concern from local residents about noise. I believe that to install the three turbines needs and investment of £2.5 million, hardly a trivial sum! The Goring scheme has taken years to get moving, and is intended to be funded by sale of shares (e.g. 500 investors putting in £5,000 each?). The maximum power output is reckoned at 300 kW, with an average of probably 140 kW. A 3 blade screw is envisaged for Goring, a design on which tests have been made with live fish - most of which survived. Goring is a community led project, as is that at Osney.

*At Romney, a 5 blade screw is planned, which computer models suggest should be fish friendly, but the proof of this will be with actual fish, once it has started. If it proved to be a fish-shredder, it would have to be shut down, as is the case for all such schemes, should they prove to result in damage to the environment

*20-22 sites are being pursued, but because weirs were not designed to be used as hydropower installations, they are subject to a lengthy approval process.

Useful sources of info: Hydropower: A guide for you and your community / Generating energy / Publications / Home (England) - Energy Saving Trust England : http://www.energysavingtrust.org.uk/Publications2/Generating-energy/Hydropower-A-guide-for-you-and-your-community

Setting up a low carbon community group: from kitchen table to willing & able | Low Carbon Hub : http://www.lowcarbonhub.org/advice/2011/12/05/setting-up-a-climate-change-community-group-from-kitchen-table-to-willing-able

Protecting the environment by promoting the use of hydropower: British Hydropower Association : http://www.british-hydro.org/index.html
 
And a few final points (some from the lectures, and some of my own):

Hydropower is a critical feature of electricity generation in many countries http://en.wikipedia.org/wiki/Hydroelectricity, most notably Norway which gets 98+% from its water systems, closely followed by Brazil (86%) and Venezuela (69%); hydropower provides 61% of Canada's electricity, while for the United States it is a little under 6%, and the U.K. nearer 1%.

On the Thames, a working facility exists at Mapledurham http://ergobalance.blogspot.co.uk/2011/11/100-kw-hydroelectric-turbine-at.html although this is privately owned, rather than by the EA. The head is 2.05 m. Once all the planning permission, licenses etc. have been secured, practical challenges remain: e.g. it is not easy to undertake construction on a river, since access to the work area is often difficult. In the case of Teddington, the river is tidal as well as fluvial and hence it flows up and down continually. To avoid environmental contamination, biodegradable oil is recommended to lubricate the hydraulics in plant machinery.

Impacts on wildlife must be considered, i.e. protected species, invasive species, fish rescue. In the event of an emergency, contingency plans must be in place, e.g. in the case of a flood, plant & coffer damns should be removed, then simply move out & let it flood! The final weir in the line is at Richmond, and is owned by Port of London authority, with a half lock and barrage. It is tidal and is left open for part of the day. Caversham weir has too low a head and is not suitable for hydro. A facility with Sunbury proposed 4 screws is proposed at Sunbury. Although, 3 screws would be the most efficient, it has been decided that having 2 fixed speed plus 2 variable turbines is the best compromise for the overall prevailing river conditions there. The EA is considering the prospect of removing some of the weirs that are not needed for navigation, as part of the overall strategy.

Other documents:
Goring & Streatley Hydro-electricity project (PDF slides) http://www.chilternsaonb.org/uploads/files/ConservationBoard/PlanningDevelopment/Dave%20Holt.pdf

Small scale hydropower rejected sites https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/47952/755-wag-report-annex-4.pdf

Reading: English Town to Adopt Biogas Buses.

Reading is the town where I live, in the south east of England, and is famous for the three Bs that used to be produced here - beer, bulbs and biscuits - and probably also for its gaol, famously written about by Oscar Wilde, in "The Ballad of Reading Gaol." The latter is an epic poem, about a prisoner being hanged for murder, and written by Wilde during his exile in France. Wilde's downfall was brought about by an ill-considered private prosecution that he issued against The Marquis of Queensbury, who devised the Queensbury Rules of British boxing, and was also the father of Lord Alfred Douglas ("Bosie"), Wilde's lover.

The law suit against Queensbury was provoked by his leaving a card at Wilde's club, with the words penned, "For Oscar Wilde, posing as somdomite" (the misspelling is Queensbury's, not mine). However, the tables were turned on Wilde, and in the case then brought against him, he was convicted of gross indecency and served two years hard labour in Reading Gaol. On his release, Wilde left for France, where he spent his last few years in dissolution, finally dying of cerebral meningitis, aged just 46. Wilde was a brilliant writer, and it is ironic that it was the judgement of his novel, "A Picture of Dorian Gray", as an "immoral book" that precipitated an inquisition into Wilde's own moral character.

Reading is more recently in the headlines http://www.bbc.co.uk/news/uk-england-berkshire-21243654 since it's local authority has ordered 20 new buses which run on methane: both compressed natural gas, and biogas generated from cattle manure and food waste. The vehicles are 12 m (39 ft) in length and carry 40 passengers, and are fitted with a gas tank on the roof to hold the methane. The outlay for the buses is £3.5 million ($5.6 million) but their running costs are less, and they are quieter than are conventional diesel buses. The ride is said to be smoother too.

The bio-gas component of the fuel is to be supplied from a farm in Sussex - which is relatively local, especially as compared, say, with importing gas from Qatar or Russia - and it is better from an environmental standpoint to convert manure and food waste to methane in a biodigester, rather than simply letting it rot and release greenhouse gases (methane and carbon dioxide) into the atmosphere. Reading is by no means the first town anywhere to adopt "green" buses that run on methane, since there are many such examples in Europe and in the wider world, e.g. the town of Augsburg in Germany, whose buses all run on compressed natural gas.

According to a life cycle analysis (LCA) http://www.clickgreen.org.uk/research/data/123546-biogas-powered-buses-cause-the-least-environmental-damage,-study-finds.html for city of Kaunas, in Lithuania, where 60% of transportation is public, compressed biogas powered buses were found to cause the least environmental damage, when the entire fuel chain is accounted for, mainly because the gas is produced by a local wastewater treatment plant, as compared with non-renewable inputs like imported crude oil and natural gas. As part of an overall European aim to make public transport sustainable, and to reduce the number of cars on the roads, the energy requirements and impacts on human health, ecosystems and resources were taken into account. The "well-to-wheel" cycles -  extraction, transportation, production, distribution and use - were compared for buses running on diesel, compressed natural gas, compressed (locally sourced) biogas and trolleybuses powered by electricity generated from natural gas or from heavy fuel oil.

As expected, there was some variation, according to the type of vehicle and the source of the fuel, and it was found that buses running on compressed biogas consumed the most fuel (although their emissions are of biological origin), while the smallest consumption was from trolleybuses that ran on electricity generated from natural gas. Most significantly, it was found that rather than using natural gas directly as a fuel, it was almost twice as energy-efficient to instead generate electricity from it first to power trolleybuses.

Other salient conclusions are that:

• While similar emissions occur from buses running on compressed natural gas or compressed biogas, the levels of carbon dioxide are greater as emitted from compressed biogas buses (albeit that this is of biological origin) than from compressed natural gas buses.

 • The greatest ecosystem damage was found to result from emissions of greenhouse gases from buses powered by compressed natural gas.

• High levels of particulates, nitrogen oxides and carbon monoxide emitted from diesel buses pose the greatest threat to human health.

It is concluded that while LCA is a useful approach by which to plan for public transport in urban areas, its input parameters must be adapted to meet the particular characteristics of each city or town.

In the case of Reading, the new biogas buses may be perceived as part of the Reading Climate Change  Partnership scheme, which intends to substantially reduce carbon emissions across the town by 2020 http://www.reading2020.org.uk/

Low Energy Light Bulbs Not So "Green" After All?

Making choices about the kind of light bulbs we should be using, on the simple basis of energy consumption, and hence carbon emissions, may be a little short-sighted. Thus, the old fashioned incandescent bulbs are no longer commonly on sale, though there is something of a black market in them, due to the poorer quality of light given out by their alternatives - low-power CFLs (compact fluorescent light bulbs) and LEDs (light emitting diodes).

The first incandescent (filament) bulb was invented by Joseph Swan, who gave the first public demonstration of the device at a lecture in Newcastle upon Tyne, in the north east of England, on 18 December 1878. Swan later illuminated his house, in neighbouring Gateshead, by means of the technology. Credit for the incandescent bulb is often, but incorrectly, given to Thomas Edison, who invented it independently, but later than Swan. In 1881, the Savoy Theatre in London was lit by Swan incandescent light bulbs; the first theatre and the first public building in the world to be lit entirely by electrical power. The basic principle of the incandescent bulb has changed little in the past 135 years, of which the main criticism is that most of the energy consumed by the bulb is discarded as heat, rather than providing useful light.

Despite the wide, and almost exclusive, adoption of CFLs and LEDs in place of the original design, a life-cycle analysis http://pubs.acs.org/doi/abs/10.1021/es302886m has shown that there may be an environmental legacy, beyond carbon emissions, or their reduction, in the form of toxic metals, especially copper, lead, mercury and zinc, with smaller amounts of arsenic and antimony, which needs to be given greater consideration. The analysis accounts both for the metals that are present and their expected lifetimes in the environment, and concludes that both CFLs and LEDs should be classified as hazardous waste, in particular because of their lead content, which can be leached at 132 and 44 mg/l, respectively, and well above the accepted threshold of 5mg/l.. The amount of copper is also at issue, being 111,000 and 31,600 mg/kg respectively, in comparison with the accepted limit of 2500 mg/kg.

In their favour, both devices last far longer and consume considerably less power than do incandescent bulbs; nonetheless, the presence of heavy metals is concluded to impart some 3 -- 26 times the environmental burden for CFLs, while LEDs are deemed to be worse overall by a factor of 2 -- 3 than their more established counterpart. It is concluded that not only must energy consumption be taken into account, but that a reduction in the levels of toxic materials incurred in the manufacture of such "green" technology should be factored in to the design.

These results represent an alternative reality, in terms of our use of materials, since they tacitly illustrate the point that the final disposal/reuse of materials used in the manufacture of all appliances and devices must be designed-in to the processes through which they are created. The supply of various elements is at issue, and efficient means for recycling them is the only way to avoid running out of, e.g. indium, helium, and many other vital materials within only a decade or so http://ergobalance.blogspot.co.uk/2012/07/shortage-of-resources-for-renewable.html. The notion of the circular economy http://en.wikipedia.org/wiki/Circular_economy is the overarching example of this line of thinking, which follows the patterns of Nature, in which there is no such thing as "waste". Everything in the natural world is recycled, e.g. though such agencies as the soil food web, where energy and materials are exchanged among an holistically interacting community of organisms, which may number in their billions, in a single teaspoonful of soil http://en.wikipedia.org/wiki/Soil_food_web.

In principle, we can reuse materials to fabricate new and replacement technology, so long as we have sufficient available energy to do this. It is the loss of cheap energy, particularly in the form of liquid fuels refined from petroleum, that will set an ultimate limit to the extent by which human civilization is underpinned by technology. When this begins to fail, we may nonetheless draw from the design models of nature, in adopting lower energy, intermediate technology paradigms, such as are found in the principles of permaculture  http://www.permaculture.org.uk/. Hence the environmental problems accorded from low energy light bulbs, and carbon emissions, will no longer be a feature for us, once we have become reconnected with the natural world.

Gold Mining in Space... has no one heard of EROEI?

The prospect of exploration in space for minerals has been the substance of science fiction, but in the face of a rapid depletion of non-renewable resources, and a likely downturn in funding for space projects in general, in these times of austerity, "mining asteroids" has emerged as an apparently serious proposition. Two companies, "Planetary Resources" and "Deep Space Industries", have now unveiled their plans to look for precious metals, such as gold, platinum, and rare earth elements, on asteroids. It is believed that water, which is costly to send up in space, might be present as water-ice, and so might be converted to rocket fuels to support space vehicles, or even breathable oxygen, for the new industry. It is postulated that a space fuel-station might be in operation by 2020, and from where, fuel such as hydrogen could be transferred down to earth orbit to refuel commercial satellites or spacecraft.

Deep Space Industries intends to send out smaller (25 kg mass) vessels - "Fireflies" - fitted with low-cost CubeSat components to explore asteroids for potential bounty, and their launching-costs would be brought down by being launched with heavier, commercial communications satellites. It is anticipated that the first launch will take place in 2015, and that the fireflies will be sent on a journey of 2-6 months, equipped with telescopes that can sense from remote the presence of particular elements. Having targeted a likely source-rock, larger craft - "Dragonflies" - would next be sent out, on round trips of 2-4 years, to physically recover up to 70 kg of material.

It is thought that only by mining resources in space, can permanent space-development be made economically viable. Initially, Deep Space Industries intends to sell observation platforms in orbit around Earth to prospecting services, as the industry opens-up on a free-market basis, but that actual mining will be underway during the next decade. There are thousands of asteroids that pass fairly close to Earth, which it is considered might be ripe for harvesting. Space-tourism also appears to be another potential income stream.

This is very much a case of playing the longer game, and it might be decades before investors get their money back, if they ever do. Apparently, a mission by NASA to recover material from an asteroid to Earth is expected to cost about $1bn http://www.bbc.co.uk/news/science-environment-17827347. On this basis, it would be necessary to bring back around 20 tonnes of pure platinum (at the current price of ca. $1,600/ounce) - not a mere 60 g... and of unprocessed rock at that - to break even financially, and one might only guess at the likely economic loss, let alone the minuscule actual EROEI should these materials be used for actual energy generation, reaped in undertaking this approach on a commercial basis. Hence, the case for a viable industry on this basis is not compelling. Most likely, whatever materials that are recovered in space, would be best used in space, so that their value is increased by virtue of not having to transport them from earth, e.g. for their use in space stations. That said, the likelihood of establishing a self-sustaining space-based, space-industry must be questionable, in terms of the energy and other resources, including actual metal extraction and device fabrication, that would be required.

As far as mining gas and oil on asteroids is concerned, in terms of EROEI the notion is no more than a pipe-dream, and rather we must confront the falling EROEI for such resources as already pertains on earth, since the emerging "hole" in conventional crude oil and gas production must increasingly be filled by unconventional versions, that are more laborious and thus more expensive to provide.