Study points to metal powders as potential replacement for fossil fuels

December 9, 2015
Could metal particles be the clean fuel of the future?
Stabilized flames of different metal powders burn with air, compared to a methane-air flame. Credit: Alternative Fuels Laboratory/McGill University

Can you imagine a future where your car is fueled by iron powder instead of gasoline?

Metal powders, produced using clean primary energy sources, could provide a more viable long-term replacement for fossil fuels than other widely discussed alternatives, such as hydrogen, biofuels or batteries, according to a study in the Dec. 15 issue of the journal Applied Energy.

"Technologies to generate clean electricity - primarily solar and wind power - are being developed rapidly; but we can't use that electricity for many of the things that oil and gas are used for today, such as transportation and global energy trade," notes McGill University professor Jeffrey Bergthorson, lead author of the new study.

"Biofuels can be part of the solution, but won't be able to satisfy all the demand; hydrogen requires big, heavy fuel tanks and is explosive, and batteries are too bulky and don't store enough energy for many applications," says Bergthorson, a mechanical engineering professor and Associate Director of the Trottier Institute for Sustainability in Engineering and Design at McGill. "Using metal powders as recyclable fuels that store clean primary energy for later use is a very promising alternative solution."

Novel concept

The Applied Energy paper, co-authored by Bergthorson with five other McGill researchers and a European Space Agency scientist in the Netherlands, lays out a novel concept for using tiny metal particles - similar in size to fine flour or icing sugar - to power external-combustion engines.

Could metal particles be the clean fuel of the future?
Proposed metal-fuelled engine and range of possible applications. Credit: Alternative Fuels Laboratory/McGill University

Unlike the internal-combustion engines used in gasoline-powered cars, external-combustion engines use heat from an outside source to drive an engine. External-combustion engines, modern versions of the coal-fired steam locomotives that drove the industrial era, are widely used to generate power from nuclear, coal or biomass fuels in power stations.

The idea of burning metal powders is nothing new - they've been used for centuries in fireworks, for instance. Since the mid-20th century, they've also been used in rocket propellants, such as the space shuttle's solid-fuel booster rockets. But relatively little research has been done in recent decades on the properties of metal flames, and the potential for metal powders to be used as a recyclable fuel in a wide range of applications has been largely overlooked by scientists.

Recyclable after combustion

The idea put forward by the McGill team takes advantage of an important property of metal powders: when burned, they react with air to form stable, nontoxic solid-oxide products that can be collected relatively easily for recycling - unlike the CO2 emissions from burning fossil fuels that escape into the atmosphere.

Using a custom-built burner, the McGill researchers demonstrated that a flame can be stabilized in a flow of tiny metal particles suspended in air. Flames from metal powders "appear quite similar" to those produced by burning hydrocarbon fuels, the researchers write. "The energy and power densities of the proposed metal-fueled heat engines are predicted to be close to current fossil-fueled internal combustion engines, making them an attractive technology for a future low-carbon society."

Iron could be the primary candidate for this purpose, according to the study. Millions of tons of iron powders are already produced annually for the metallurgy, chemical and electronic industries. And iron is readily recyclable with well-established technologies, and some novel techniques can avoid the carbon dioxide emissions associated with traditional iron production using coal.

Next step: building a prototype

While laboratory work at McGill and elsewhere has shown that the use of metal fuels with heat engines is technically feasible, no one has yet demonstrated the idea in practice. The next step toward turning the lab findings into usable technology, therefore, will be "to build a prototype burner and couple it to a heat engine," Bergthorson says.

"Developing metal recycling processes that don't involve CO2 emissions is also critical."

Co-author David Jarvis, head of strategic and emerging technologies at the European Space Agency, adds: "We are very interested in this technology because it opens the door to new propulsion systems that can be used in space and on earth. The shift away from for vehicle propulsion is a clear trend for the future. While not perfected and commercialized today, the use of low-cost metallic fuels, like iron powder, is a worthy alternative to petrol and diesel fuels. If we can demonstrate, for the first time, an iron-fueled engine with almost zero CO2 emissions, we believe this would then trigger even more innovation and cost reduction in the near future."

Explore further: Gasification of oil palm biomass to produce clean producer gas for heat, power generation

More information: J.M. Bergthorson et al. Direct combustion of recyclable metal fuels for zero-carbon heat and power, Applied Energy (2015). DOI: 10.1016/j.apenergy.2015.09.037

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Steelwolf
2 / 5 (16) Dec 09, 2015
It still does not address the oxygen depletion problem that is the more dangerous flipside of the carbon problem. Each Carbon grabs 2 Oxygen atoms, so not only is there being more of the carbon tied up in the atmosphere, it also ties up atmospheric Oxygen, which we HAVE to have a minimum amount of in the air or we plain die.

The focus on Carbon in the CO2 equation is not what can kill us in the short term, using up the levels of oxygen to create an even Lower level than we have now is very dangerous. We used to consider normal oxygen content at around 20%, now we have been creeping down to 18 % and lower, and it is no wonder that so many folks need anti-depressants or anti-anxiety drugs to deal with the anoxia signals telling them they have to get fresher air...and they are outside!

More needs to be said about the O2 depletion, more study needs to be done before we start combusting metals too!
my2cts
3.4 / 5 (5) Dec 09, 2015
Metal oxide, this is brilliant.

SW, you miss the point.
The metal oxide and the oxygen will be recycled.
Gigel
1 / 5 (1) Dec 09, 2015
Apparently oxygen is at about 20.9% of normal air, so no problem there.
Isotherm7
3 / 5 (2) Dec 09, 2015
It would be nice to see some crude estimates for system efficiency, including the regeneration of the metal powder. I bet that for an automobile sized system it is pretty low. The corresponding automobile would resemble, in its modus operandi, a Stanley Steamer. I would also guess that the combustor would be very susceptible to build-up of oxide crud.
hemitite
3 / 5 (2) Dec 09, 2015
Re iron oxide recycling: Hydrogen produced by solar power, along with the heat from concentrated sunlight, could be used to reduce this oxide back to iron producing only water as a byproduct.
Wolf358
3.3 / 5 (3) Dec 09, 2015
We can use Aluminum wire. Feed it under water to an arc, and you get nice Hydrogen, and Aluminum Oxide as a byproduct. Aluminum Oxide is recyclable with electricity... Simpler than metal oxides...?
krundoloss
2.5 / 5 (2) Dec 09, 2015
Sounds like someone is getting funded! It sounds interesting, but I am wondering where the energy is coming from in this cycle, with the energy needed to produce the powder, the energy required to recycle it, and transport it, the fact that it wont flow like a liquid, sounds like more trouble that it is worth in the long run.
haroldo_macedo
3 / 5 (2) Dec 09, 2015
Anything you get from inside the earth and throw onto the atmosphere will pollute.
antigoracle
2.1 / 5 (7) Dec 09, 2015
Imagine sitting in your car and saying "Check out the fireworks". Other than that, this is just another stupid idea which, unlike fireworks, will never take off.
warmonger
4.4 / 5 (13) Dec 09, 2015
The comments so far are pretty bad.

Steelwolf - Run out of oxygen? Seriously where to begin. This idea would help us to get off the fossil fuels driving up CO2.

Isotherm - True, but system efficiency could easily be comparable to a combustion engine, which we know to be very low.

Wolf - Interesting idea, but aluminum oxide generally IS considered a metal oxide.

Krundloss - Metal oxides are just for energy storage, the energy comes from somewhere else. Hopefully from renewables.

Haroldo - Iron is not toxic, and you don't need a tremendous amount of it. Just a few kilos per person, which we probably already have. And you wouldn't be "throwing it onto the atmosphere", it falls into the collector, and practically all of it would get recycled.

Antigoracle - Using metal oxides a cool idea, but still may never be feasible. Fireworks? Huh, you mean like the ones you see inside your car piston? Btw, how many of your brilliant ideas have panned out? Give the dudes a chance.
ab3a
4.2 / 5 (5) Dec 09, 2015
One of the interesting features of hydrocarbons is that they offer a great deal of energy per unit volume and per unit mass.

My obvious question are the mass and volume per calorie of heat for metals "burned" this way? Is this fuel practical for anything other than a stationary plant of some sort? I have my doubts.
my2cts
3.7 / 5 (6) Dec 09, 2015
Al(OH)3 or Al2(SO4)3 would be excellent candidates. These have similar enthalpies of formation per weight to CO2.
If in doubt do a little research of your own.
Eikka
5 / 5 (5) Dec 09, 2015
My obvious question are the mass and volume per calorie of heat for metals "burned" this way? Is this fuel practical for anything other than a stationary plant of some sort? I have my doubts.


The energy density for metals is quite high because they have a high binding energy. For iron, 2Fe2O3 + 3C -> 4Fe + 3CO2. I seem to remember that the reaction is endothermic, so more energy is added by heat than is present by transferring the oxygen to the carbon, so it can be estimated that an atom of iron burns with roughly the same energy, if not slightly more as an atom of carbon.

Iron is roughly twice as heavy, so the energy density would be about half. Around 3 kWh per kg.

In a modern high efficiency stirling engine, or in a compound turbine, the efficiency can be 50% so the practical energy density would be around 1.5 kWh/kg which is still 7-8 times higher than the best lithium batteries
Eikka
4.5 / 5 (4) Dec 09, 2015
However, as you see from the above chemical equation, the easiest way to turn iron oxide back into iron is by using carbon. A common way it's done is by burning natural gas with little air to get a flow of heated CO gas, which is then pumped through the iron oxide.

If you can make methane by conversion of renewable power, or if you can make very hot CO gas somehow on demand, you've got that part figured out, but unfortunately the efficiencies of such processes are currently around 40% so the cost of turning renewable power to iron powder will naturally be enormous.

There exists a method for reducing iron with hydrogen at 500 C but I can't find any details of the process. It would also imply producing hydrogen, which is not very efficient either.
my2cts
3.7 / 5 (6) Dec 09, 2015
Sulfates have the highest enthalpies and aluminium beats iron in molar and in weight enthalpy.
Hydroxides are the best option because OH is much lighter than SO4 and there is less risk of pollution.

https://en.wikipe...a_table)
Al(OH)3: 1277/78 kJ/g
CO2: 395/48 kJ/g
Al(OH)3 has twice the energy density of CO2 !
Initially you have just Al or C so
Al: 1277/27 kJ/g
C: 395/12 kJ/g, H: 120 kJ/g
Al is as good as the alkanes.
Eikka
5 / 5 (4) Dec 09, 2015

Hydroxides are the best option because OH is much lighter than SO4 and there is less risk of pollution.


Wouldn't that imply some sort of a battery?

Disposable aluminium or zinc batteries have been proposed, where you would insert plates of metal and return the spent chemicals to a recycling facility by collection points wherever you refuel.

The problem has always been the high cost of reducing the metal back to its original state. Aluminium for example is made where you have plenty of steady and very cheap electricity production, such as hydroelectric power. Norway is a large aluminium producer.

These processes don't lend themselves easily to intermittent renewable power such as solar or wind, because it's done by molten electrolysis, and if there's no power then the pool freezes solid and takes days of wasted power to get going again.

And they use carbon electrodes which are consumed into CO2 in the process.
loneislander
not rated yet Dec 09, 2015
Pointless. How is this different (better) than hydrogen? It's just a battery no matter what the combustion process might look like.
tomb
2.3 / 5 (3) Dec 09, 2015
The cost of making the energy from solar or wind would already be twice the cost from oil or natural gas. Than you use a very energy intensify process to produce the reduced iron powder or Al wire. The cost of the resulting fuel would be at least twice to four times that of oil or natural gas. The rich do not care, the rest of us, the peons, can walk.
Grallen
2.3 / 5 (3) Dec 09, 2015
Apparently recycling aluminum makes solar power more feasible for grid supply too.

http://www.treehu...any.html
Osiris1
5 / 5 (1) Dec 10, 2015
Like the hydrogen cycle better. Burn H2...get water. Solar power splits water to H2 and O2. Release the O2 and keep the H2 recycled gas and use it again. Use in internal combustion engine and release both. Take sea water and use solar to split that. Get all the solutes, various useful salts as a by product. One use, lol, would be on fish sticks! Use the H2 and release the O2 just like above and let the natural water cycle do the rest.

Better yet use the hydrogen in a fuel cell to power the cars by electricity in plug-in hybrids like the Chevy Volt and other machines. MUCH MORE efficient. Do away with the Otto Cycle engines and Stirling Cycle engines to total electric and get rid of a LOT of waste heat in the process.
Mike_Massen
2 / 5 (8) Dec 10, 2015
Osiris1 says
.. hydrogen cycle better. Burn H2...get water. Solar power splits water to H2 and O2. Release the O2 and keep the H2 recycled gas and use it again. Use in internal combustion engine and release both
No, staggeringly inefficient !

Electrolysis Very wasteful to produce H2 ie. Always do something better with electricity, besides H2 damages conventional engines re embrittlement

Osiris1 said
Take sea water and use solar to split that. Get all the solutes, various useful salts as a by product..
No, far more efficient to evaporate re ponds in sun !

Osiris1 says
Use the H2..
No, see above

Osiris1 says
.. use the hydrogen in a fuel cell to power the cars
No, see above

Osiris1 says
Do away with the Otto Cycle engines..
Only for smaller ones, not prime movers (yet), comparative efficiency vs transport vs power density ie Not as simple as U desire...

This better http://www.hazergroup.com.au

Yes I have shares... ASX:HZR
Colbourne
2 / 5 (2) Dec 10, 2015
Metal powders may be the ideal fuel for Mars, as you could probably burn magnesium with the CO2 atmosphere in some form of internal combustion engine.
It could possibly even be used as fuel for jets and even with rockets with tanks of CO2 filled cheaply from the atmosphere
antialias_physorg
5 / 5 (9) Dec 10, 2015
It still does not address the oxygen depletion problem that is the more dangerous flipside of the carbon problem. Each Carbon grabs 2 Oxygen atoms, so not only is there being more of the carbon tied up in the atmosphere, it also ties up atmospheric Oxygen

Really? I mean...seriously? Really? What kind of a braindead argument is that? Do you have any idea what "precent" even means? And how it compares to ppm (which is what CO2 concentrations are measured in)

CO2 is currently at 400ppm (i.e. 0.04%). If we were to reach the tipping point (read: full global catastrophe) of 600 ppm then atmospheric oxygen would have dropped from 20.8% to 20.78%. To give you an idea what this means in 'breathability'. This is about the same 'depletion' you experience if you go to the third floor (reduced atmospheric due to 10 meters height. This pressure drop is equivalent to lower oxygen concentration with regards to breathability).
antialias_physorg
5 / 5 (7) Dec 10, 2015
One of the interesting features of hydrocarbons is that they offer a great deal of energy per unit volume and per unit mass.

So do metal powders (note that they didn't use gasoline rocket boosters on stuff like the Shuttle. Weight/volume was paramount. So you can well assume that metal powders are right up there -or beyond- what gasoline can deliver)
Is this fuel practical for anything other than a stationary plant of some sort?

Large scale (national) energy storage?

Though there's a qualifier here from the article:
hydrogen requires big, heavy fuel tanks and is explosive

...metal powders are pretty explosive as well. And whereas a hydrogen explosion doesn't leave any residue behind (except water) a metal powder explosion does so - with possible ecological side effects.

How is this different (better) than hydrogen?

Higher energy density. Less problems with prolonged storage. Easier transport by existing infrastructure (trucks).
Steelwolf
3.5 / 5 (2) Dec 10, 2015
I know that my info seems like crackpottery, However, I was a trained Navy Firefighter, Damage Controlman and Helo Crash Crew trained. I was a radiation worker and asbestos remover, sometimes working in 'hot' areas. So, it is not like I have not actually been trained on the subject and then watched the oxygen percentage numbers drop right along with the CO2 going up. We were trained that 20 % to 21% was normal, and then watched numbers slide to 19 as the lower number in later training, and then, since, it has gotten down to 18% with 19 as the Higher number, which is close to where we were previously told the 'cutoff' point is. So, with all of our cars and factories BURNING Fuel, it takes the Oxygen out of the air. Very Very simple science and even just plain common sense. We also know that we are impacting the sea life in such a way that it too is being depleted of oxygen, with devastated dead areas. Seas affect land too.

Do you Really think that it Cannot happen on land too?
Steelwolf
3.5 / 5 (2) Dec 10, 2015
The huge numbers of things that we do that consume oxygen and our ecosystem has been damaged so that we are not getting the return/replacement as we should. Many of the articles here point to that, 16% greater deforestation in the Amazon, the Indonesia Fires, the heavy industrialization in China. We used to have their haze problem, then moved our dirty machines there.

It is not only CO2, but ALL of the MANY combustive processes which we use, combined, that have led to the depletion, that and ecological destruction limiting the speed of replacement/recycle by carbon capture in the ecosystem.

Yes, many trees in some areas have responded with extra growth, which must have some offsetting effect on O2, but overall there HAS been a decline since 1981 when I had my training, and today I see the numbers running low, it reminds one of the rest of the carbon-oxygen cycle that we don't see all the time, taking it for granted it will always be there, and That is dangerous thinking.
Steelwolf
3.5 / 5 (2) Dec 10, 2015
Ok, some quick checking and I find some of my past data faulty and those past sites suspect, However, this study from the British Institute of Science in Society has some very good data on this, complete with the proper, needed numbers.

http://www.i-sis....sing.php

And it shows some interesting things just with CO2 and plants, not even touching out huge industrial oxygen consumption. As the article states, the O2 Budget is something that is overlooked in the whole Carbon debate, and yet it is of higher priority than the CO2. The climate change can cause havoc over years and decades, yet all it would take is atmospheric O2 to drop just once below our sustainability level, and it is pretty much all over for the human race unless you have a bunker and ways to grow in an enclosed environment such as greenhouses and domes.

This is not a new idea, and it IS pertinent to the problems being faced presently.
antialias_physorg
5 / 5 (6) Dec 10, 2015
I know that my info seems like crackpottery, However, I was a trained Navy Firefighter, Damage Controlman and Helo Crash Crew trained.

None of this seems to have trained you to read simple graphs (or do simple math).

Yes, oxygen has been droppingwhile CO2 has increased (some extreme papers put this at quadruple rate). But here's the simple math:

Oxygen (current): 208000 ppm
CO2 (current): 400ppm
Rise of CO2 since 1980s: roughly 60ppm

If we posit that O2 is dropping at quadruple that rate that's a drop by 240ppm in 35 years

Hypoxia starts at 19.5% O2 (read: 195000 ppm). Which means that if we continue burning fossil fuels at current rates we will have to worry about hypoxia issues roughly in the year 4000 (Note that we have fossile fuel reserves for only a tiny fraction of that time).

There's plenty of things to worry about with regards to CO2. Oxygen depletion, however, is not one of them.
katesisco
3.4 / 5 (5) Dec 10, 2015
Reading the back and forth, I wonder if there is not a bigger problem than seen. Most of us once hospitalized know how close to dying the lack of oxygen is. Even with a nasal canula, it feels like not enough O2. P Ward has written several books on past extinction events and he associates high O2 low CO2 times with new species and low O2 and high CO2 with extinction events. I believe we have a more fragile balance than the figures imply.
Mike_Massen
2.8 / 5 (9) Dec 10, 2015
@Steelwolf,
In respect of the relative magnitudes antialias_physorg is correct, adding biggest problem is the rate of rise of CO2 coupled with its selective property of infra-red (IR) resonance, this means it interferes with IR light (heat) leaving Earth consequence raises water vapour too which also interfere, ie
http://cbc.arizon.../sim/gh/

O2 is transparent to visible as is IR & despite comparative change in short term CO2 will increase some plant growth beneficially though re food plants it may shift their equilibria so they produce cyanogens ie Poison, this already happens re Cassava & Clover (food for cattle) similar propensity.

CO2 radiative interference is called 'forcing' & details here:-
https://en.wikipe..._forcing

Over the ~4000 yr period antialias_physorg suggests, its very likely we could well adapt, if need be & if nothing else changes re CO2 rate, much like living at higher altitude I understand, not desirable...
gkam
1.9 / 5 (9) Dec 10, 2015
Why combustion? We are more likely to see metal-air batteries for our electric vehicles. We tested them at EPRI in the 1980's.
TheVissigoth
2 / 5 (4) Dec 10, 2015

Answer: There are several reasons combustion cycle is superior. First it produces much, much high power density than batteries because reaction runs at high temperatures (2000 K or higher) and in accordance with the Arrhenius exponential reaction law is many orders of magnitude faster at high temperatures. Second, metal fuels for combustion unlike for batteries can be low purity and thus are much less expensive. There is also no need for an additional "infrastructure" such as expensive catalysts, electrolyte etc. The batteries also have comparatively low life span whereas "metal engine" will last as long as ICE or even longer.
TheVissigoth
2.6 / 5 (5) Dec 10, 2015
The cost of making the energy from solar or wind would already be twice the cost from oil or natural gas. .....The rich do not care, the rest of us, the peons, can walk.


It does not looks economical at all if you compare metal fuels with fossil hydrocarbons. But if you look for chemical energy carrier to replace hydrocarbons than, if you think carefully, nothing beats metals. I will give you the analogy of early 20th century dilemma of automobiles and horses. Automobiles at that time were absolutely crazy idea from the point of economics. Horses are self-manufacturing, don't need high-quality roads, can feed on grass etc. And look around now. Do you see horses? If you need to go fast from point A to point B you need a car. If you want to eliminate CO2 in delivering clean energy to consumers y
Eikka
3 / 5 (2) Dec 11, 2015
Apparently recycling aluminum makes solar power more feasible for grid supply too.


Up to a point.

the plant will be able to adjust the power consumption of the 290-megawatt smelter up and down by about 25 percent.


In other words, assuming that the intermittent power is on and off with a 50/50 split in respect to time, they can absorb a quarter of their energy input, approaching up to a third, of intermittent renewable energy.

That still leaves the 75% that they can't, which has to come from something reliable and dirt cheap. If they can't get cheap power, the whole factory is shut down and relocated somewhere they can, because the customers won't buy more expensive aluminium when there's less expensive aluminium made elsewhere.
Eikka
5 / 5 (1) Dec 12, 2015
Automobiles at that time were absolutely crazy idea from the point of economics. Horses are self-manufacturing, don't need high-quality roads, can feed on grass etc.


Horses are not "self-manufacturing", and the carts they're pulling do need some level of road infrastructure or you'll just break down all the time.

If you leave horses to manufacture themselves, all you get is wild horses. It takes years of upkeep and costly expert training to "make" one, and then they require continued maintenance and fuel even when you're not using them, and they often act erratically, run away, cause accidents and eventually break their leg or die on the street and you're left with a 500 kilo rotting corpse to dispose of.

The procedure of starting up a horse in the morning requires hired servants unless you want to spend your time grooming them, and they shit -everywhere- which is also something you have to pay to deal with.

Even a bad automobile beats a horse in economic terms.
Eikka
5 / 5 (1) Dec 12, 2015
The first cars were pretty simple affairs, nothing more than four bicycle wheels under a buggy, and their main purpose was to get people from point A to B without much fuss.

http://www.thehen...dbig.jpg

The major stumbling block at the time was the lack of standardized precision manufacturing, so every part from the simplest nut and washer were all custom made for each car, and that's what made them relatively expensive. You couldn't go to a hardware store to get a standard M8 machine screw - it had to be made for you, and different shops made slightly different size screws.

They also broke down a lot due to the same reason, but for whomever could afford one it was much more economical and practical than horsing around with a chariot just to go downtown.

Stavros
1 / 5 (1) Dec 13, 2015
0rison
1 / 5 (1) Dec 13, 2015
Previously:

Zinc powder will drive your hydrogen car
http://www.israca...px?id=51

Magnesium: Alternative Power Source - Phys.org
http://phys.org/n...rce.html

The car that makes its own fuel - Phys.org
http://phys.org/n...uel.html
Manfred Particleboard
2 / 5 (4) Dec 13, 2015
Has no one picked up on what metal oxides do to moving parts? The word Abrasive springs to mind.
snerdguy
5 / 5 (1) Dec 14, 2015
It has potential if the energy cycle can maintained with only renewable energy sources. It takes a lot of energy to mine and refine metals and a lot of energy to produce pure metal powders. It also would require special storage because metal wants to oxidize and metal powder can even self ignite is some conditions. That brings up the worst part. Metal powders are highly explosive and can release a lot more energy in a much shorter time than a petroleum product. Powdered aluminum is use make certain explosives and solid rocket fuel. How are you going to safely store the quantities needed to operate a practical power plant? A lot of research is still needed.
wkingmilw
5 / 5 (1) Dec 14, 2015
As we've seen with natural gas fueled and electrically powered vehicles, access to fueling stations is the biggest limitation to adoption of cleaner technologies. This is usually never considered by the inventors or the article writer during announcement development. Its a tough business to break into. You almost have to have finance the infrastructure as well as the invention in order to have any chance at being successful.

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