Jet Fuel, Additives, Water, and Green Jet Fuel.

Rns

Member
But it isn't....it is all part and parcel of the entire premise.

This is not to mention that once there is demand the land previously used for crops will be converted to oil seed.

I know what they claim as it is only to be used as a rotation crop but when you remove the rotation crop you have removed the purpose of rotation crops which is to revitalize the soil and add back in the plant mass to hold the soil
 

MikeC

Closed Account
Mike you are insisting that there is magic going on with synthetic jet fuel

In what way is anything I've said "magic"?

Perhaps you could enlighten me on just how the plant oil based fuels and or blends can get lower consumption rates while also reducing emissions while also giving the same thermal output.

I have no idea - where did I say any such thing?

Of course the sulfur will be eliminated but that is not the only newest emission reduction claims that I am seeing in the whiz bang "green" jet fuel world.

AFAIK the emission advantages are that the production of the fuel is not adding NEW carbon to the atmosphere as fossil fuels do - nothing at all about the actual makeup of the exhaust being significantly different.
 

MikeC

Closed Account
But it isn't....it is all part and parcel of the entire premise.

This is not to mention that once there is demand the land previously used for crops will be converted to oil seed.

I know what they claim as it is only to be used as a rotation crop but when you remove the rotation crop you have removed the purpose of rotation crops which is to revitalize the soil and add back in the plant mass to hold the soil

algae is one of the new technologies that "promises" to generate much more fuel per land area than any crops - hence lessening the need for more land.

Plus of course we already do grow enough food for everyone anyway......
 

MikeC

Closed Account
It is not cost competitive

Nowhere do I see where the cost per pound/gallon of finished fuel is stated.

It is more government money paid out which we all pay for in taxes.

how can you conclude that it is all subsidized if you cannot find het actual costs?? :confused:

It didn't take much of a search to find some information on the topic, so I guess you didn't try very hard:


The US Federal Aviation Administration (FAA) has a goal that one billion gallons of renewable jet fuel is consumed by the US aviation industry each year from 2018. We examine the cost to US airlines of meeting this goal using renewable fuel produced from a Hydroprocessed Esters and Fatty Acids (HEFA) process from renewable oils. Our approach employs an economy-wide model of economic activity and energy systems and a detailed partial equilibrium model of the aviation industry. If soybean oil is used as a feedstock, we find that meeting the aviation biofuel goal in 2020 will require an implicit subsidy to biofuel producers of $2.69 per gallon of renewable jet fuel. If the aviation goal can be met by fuel from oilseed rotation crops grown on otherwise fallow land, the implicit subsidy is $0.35 per gallon of renewable jet fuel. As commercial aviation biofuel consumption represents less than two per cent of total fuel used by this industry, the goal has a small impact on the average price of jet fuel and carbon dioxide emissions. We also find that, as the product slate for HEFA processes includes diesel and jet fuel, there are important interactions between the goal for renewable jet fuel and mandates for ground transportation fuels.
Content from External Source
Or less academically here -


The eye of the needle for this sunny renewable biofuel future has been twofold.
First, the cost – no one has yet been able to produce renewable Jet A-1 at a cost comparable to hydrocarbon Jet A-1.
The second problem derives from the first, in that no one has yet been able to produce renewable Jet A-1 in commercial quantities at a competitive rate.
But this might all be about to change.
Content from External Source
 
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Rns

Member
Yes - as I said



the standard for Jet A1 is Def Std 91-91 - AFAIK rev 7 is the latest and is available on the web if you search
I read it but your link did not render more than the first page.

I had forgotten the requirement of even the more severly hydro processed petroleum stocks for added oxygen stabilizers.

I still stand by my contention that the plant based fuels as a whole carry more bound water than their petroleum counterparts.

There is no spec in your Std for bound water only free water as I knew.
 

Rns

Member
how can you conclude that it is all subsidized if you cannot find het actual costs?? :confused:
I am in farm country and know what it takes ball park to get a crop from seed to bunker.

I ran the numbers numerous times several years ago and the break even point then with a lower fuel equipment and seed cost was 170 to 180 BBL of crude to be viable.

I will search and find the list of subsidies already spent to get the bio jet fuel going.

I will offer this Mike

I will put up 5 dollars that within three years we will hear about more contrails and plant based fuels will be a contributing factor to the increased vapor.

We seem to have spun back to the myopic vision that CO2 is the only greenhouse gas we should be concerned with and it isn't at all.
 

MikeC

Closed Account
You wanted a link to the thermal value - not the bound water specs!! There is no bound water in kerosene - which is why there is no standard for it. Water can be emulsified or "suspended", but usually settles out overnight, which is why fuel drains are usually done first thing in the morning. Any solubility of water in JetA1 is insignificant.

The thermal capacity at combustion is given as a minimum of 42.8 Mj/Kg in Table 3 of the standard, which opens fine for me.
 

MikeC

Closed Account
I am in farm country and know what it takes ball park to get a crop from seed to bunker.

Argument by association...yawn...

We seem to have spun back to the myopic vision that CO2 is the only greenhouse gas we should be concerned with and it isn't at all.

I haven't spun back there at all - it has never been part of the discussion I was having, and it is well known that water vapour is far and away the most important greenhouse gas due to the sheer bulk of it in the atmosphere.

looks to me like you're changing the topic and avoiding any meaningful discussion.....o_O
 

Rns

Member
You wanted a link to the thermal value - not the bound water specs!! There is no bound water in kerosene - which is why there is no standard for it. Water can be emulsified or "suspended", but usually settles out overnight, which is why fuel drains are usually done first thing in the morning. Any solubility of water in JetA1 is insignificant.

The thermal capacity at combustion is given as a minimum of 42.8 Mj/Kg in Table 3 of the standard, which opens fine for me.
That is the minimum for military yet your supplied plant oil link listed a range that goes above and below it.

Let me ask you then where does the water for contrails come from?
 

Rns

Member
Argument by association...yawn...



I haven't spun back there at all - it has never been part of the discussion I was having, and it is well known that water vapour is far and away the most important greenhouse gas due to the sheer bulk of it in the atmosphere.

looks to me like you're changing the topic and avoiding any meaningful discussion.....o_O
I appreciate you mocking me and telling me that I didn't do what I did in looking at the situation.

I must of dreamed all the numbers I did in looking at an oil plant here in the area.

Have a nice night and do you or do you not accept my wager?
 

Svartbjørn

Senior Member.
Let me ask you then where does the water for contrails come from?

The main products of hydrocarbon fuelcombustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can raise the relative humidity of the air past saturation point. The vapor then condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails. The time taken for the vapor to cool enough to condense accounts for the contrail forming some way behind the aircraft's engines. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly condense. Exhaust contrails rarely occur below 8,000 m (26,000 ft), only if the temperature there is below −40 °C (−40 °F), and if the relative humidity is over 60%.[3]
http://en.wikipedia.org/wiki/Contrail
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I think that will answer your question @Rns. While there may be some very very very small amounts of water in the fuel itself, its more of a result of carbon being expelled in the exhaust providing something for the water molecules in the air to cling to, creating contrails.. which (IIRC) has been explained several times. If I also recall, there are methods built into the fuel systems of aircraft to bleed out the moisture so that the risk of crystallization damage from ice is minimized.
 

Mick West

Administrator
Staff member
The main products of hydrocarbon fuelcombustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can raise the relative humidity of the air past saturation point. The vapor then condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails. The time taken for the vapor to cool enough to condense accounts for the contrail forming some way behind the aircraft's engines. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly condense. Exhaust contrails rarely occur below 8,000 m (26,000 ft), only if the temperature there is below −40 °C (−40 °F), and if the relative humidity is over 60%.[3]
http://en.wikipedia.org/wiki/Contrail
Content from External Source
I think that will answer your question @Rns. While there may be some very very very small amounts of water in the fuel itself, its more of a result of carbon being expelled in the exhaust providing something for the water molecules in the air to cling to, creating contrails..

Not really. It's the water created by burning the fuel that raises the humidity high enough to trigger condensation.
 

Jazzy

Closed Account
biofuels burn a little cooler which will in many instances increase apparent water vapor at the exhaust and in current jets would seem very likely to increase the likelihood of visible contrails.
That's true, but future integrated air traffic control systems will be able to send aircraft through less-saturated air, effectively reducing visible contrail pollution to occasional small accidents. That'll be nice. :)
 
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