Burning 1 kg plastic generates 3kg of CO2

[Getonit]

One of my associates from FB posted a video making the claim that burning 1kg of plastic generates 3kg of CO2. I tried to google the answer and the only thing I got out of this was this is stated as a very common "fact". Before I argue this point with her I want to understand the science. My chemistry was too long ago and my grasp of it was even weaker so I can't answer logically. Intuitively it doesn't make sense, I think the answer is conservation of matter or something like that, but looking for hard scientific answers.

Any answers appreciated.

Mark

 

[Henning]

One of my associates from FB posted a video making the claim that burning 1kg of plastic generates 3kg of CO2. I tried to google the answer and the only thing I got out of this was this is stated as a very common "fact". Before I argue this point with her I want to understand the science. My chemistry was too long ago and my grasp of it was even weaker so I can't answer logically. Intuitively it doesn't make sense, I think the answer is conservation of matter or something like that, but looking for hard scientific answers.

Any answers appreciated.

Mark

When you burn (rapidly oxidize) a hydrocarbon you replace hydrogen with oxygen and create H20 and CO2. Since oxygen is heavier than hydrogen. With the atomic mass of Hydrogen being just above 1 and the atomic weight of Oxygen being just shy of 16, the premiss seems ok.

 

[EdFred]

Assuming no carbon residue remains 1kg of the polyethylene molecule chain will produce approximately 3.142kg of CO2 and 1.285kg of water.
Each kg of PE (0.857kg carbon, 0.142kg hydrogen) takes 3.428 kg of oxygen out of the atmosphere during the reaction.

3.142 + 1.285 = 0.857 +0.142 + 3.428 (approximately)

 

[JHW]

oh if it were only like that.

the problem with burning plasitcs is not the water and CO2, it's the other stuff that will kill you if you breath too much of it, and that will poison the fish if too much of it gets washed off into a stream. I find it amazing that the religion of MMGW is so strong that we worry about benign & natural gasses with no mention of poisons.

 

[Henning]

oh if it were only like that.

the problem with burning plasitcs is not the water and CO2, it's the other stuff that will kill you if you breath too much of it, and that will poison the fish if too much of it gets washed off into a stream. I find it amazing that the religion of MMGW is so strong that we worry about benign & natural gasses with no mention of poisons.

If you mentioned the poisons, then MMGW wouldn't be the argument and burning oil would be under much greater risk, and we can't have that because it would cost profits over the next few quarters to rectify. It is however noticed by those who care.
http://www.theguardian.com/environment/2009/apr/09/shipping-pollution

 

[EdFred]

oh if it were only like that.

the problem with burning plasitcs is not the water and CO2, it's the other stuff that will kill you if you breath too much of it, and that will poison the fish if too much of it gets washed off into a stream. I find it amazing that the religion of MMGW is so strong that we worry about benign & natural gasses with no mention of poisons.

Well, yeah, nothing in the plastics is absolutely clean, or burns 'perfectly' that's why we get CO emissions instead of just water and carbon dioxide - even burning NG and propane.

 

[Cap'n Jack]

If you mentioned the poisons, then MMGW wouldn't be the argument and burning oil would be under much greater risk, and we can't have that because it would cost profits over the next few quarters to rectify. It is however noticed by those who care.
http://www.theguardian.com/environment/2009/apr/09/shipping-pollution

Apples & oranges, Henning.

The article mentioned the sulfur in the fuel. The PE plastic being used as an example in this thread doesn't contain sulfur.

The sulfur in fuel can be removed, and is removed in automobile gasoline, to avoid "poisoning" the catalytic converter.

Most diesel sold in the world, except possibly for marine application, is 10 to 50 PPM sulfur. In the USA, they started phasing out the marine diesel last year, at 500 ppm, replacing it with 10 ppm fuel.

The toxins from burning PE plastic at low temperature are mostly soot and aromatic hydrocarbons (benzene, napthalene, ect). This is avoided by burning it at higher temperature and more oxygen (air).

Chlorinated and flourinated plastics (PVC, PTFE) are a whole 'nother story- HF or HCl are formed (capture these in a scrubbing stack), also polyhalogenated aromatics. These last are very difficult to be rid of since they actually re-form as the gas cools- some of my undergrad research was on these compounds.

So, burning plastics is bad if they are halogenated. A proper facility can burn other plastics.

If one agrees with MMGW, one should reduce their burning of non-renewable hydrocarbons and products therefrom.

If you cite a reference, make it pertinent to the conversation.

 

[SixPapaCharlie]

Assuming no carbon residue remains 1kg of the polyethylene molecule chain will produce approximately 3.142kg of CO2 and 1.285kg of water.
Each kg of PE (0.857kg carbon, 0.142kg hydrogen) takes 3.428 kg of oxygen out of the atmosphere during the reaction.

3.142 + 1.285 = 0.857 +0.142 + 3.428 (approximately)

Duh..

 

[weilke]

Here is a secret. Burning 1kg of 'green' natural gas will also produce 3kg of CO2.

 

[EdFred]

Here is a secret. Burning 1kg of 'green' natural gas will also produce 3kg of CO2.

2.75kg actually. Assuming it's a clean burn. Also uses 4kg of oxygen to get it done.

I assume we are talking pure Methane - though NG isn't pure.

Ethane is 2.93:1
Propane is 3:1
Butane is 3.03:1

 

[Palmpilot]

...the religion of MMGW...

People's views on the subject seem to be mainly correlated with their politics. It's true of both sides of the political spectrum, as far as I can tell.

 

[Henning]

Here is a secret. Burning 1kg of 'green' natural gas will also produce 3kg of CO2.

However you use the gas to release energy will, however if you use a fuel cell for the process, it is much easier to reclaim the CO2 (and water) and reprocess it into new fuel through introducing both to algae.

 

[JeffDG]

The big thing you're forgetting in the "conservation of matter" equation is the air around the burning plastic. The extra mass (ie the extra 2 kg) comes from the oxygen in the air.

 

[Henning]

The big thing you're forgetting in the "conservation of matter" equation is the air around the burning plastic. The extra mass (ie the extra 2 kg) comes from the oxygen in the air.

Yep, and that's the beauty of hydrogen fuel cells, for 1kg of hydrogen shipped, you ship 9kg of water and the energy of 3kg of gasoline, (not to mention the extra heat energy value released in the conversion process) because the atmosphere carries the rest for free.

 

[ChemGuy]

Those numbers look right.

I blame the moles.

Although there is less CO2 if we use low temp and a reducing flame. Maybe that will make the enviro-nazis happy. Just make more particulates and less CO2.

 

[Cap'n Jack]

Yep, and that's the beauty of hydrogen fuel cells, for 1kg of hydrogen shipped, you ship 9kg of water and the energy of 3kg of gasoline, (not to mention the extra heat energy value released in the conversion process) because the atmosphere carries the rest for free.

Yeah, hydrogen works fine if you pipe it. Less so in vehicles due to the low energy density.

You've never answered this:

<SNIP>

Here's some numbers for you...you ran some of them already, but you didn't run the last set.
A kilogram of gasoline gives 47 MJ energy
A kilogram of hydrogen gives 130 MJ / Kg, this is liquid hydrogen, but we'll assume gaseous hydrogen has the same energy (it has less, because it is less dense)

Sounds great so far, sounds like a win for hydrogen, doesn't it?

Take the next step.
Assume gasoline is 0.71 kilograms/ liter ( this is the light end of the range)
Liquid hydrogen is 70.99 grams per liter (0.07099 kg/ liter)

Now...do the calculation- how many liters of hydrogen is required to give the same energy as a liter of gasoline?

This is the best possible case, with current storage technology, right now. It is really a lot worse. For the time being, other technologies do a lot better. If they solve the fuel storage issue, I'll be with you cheering hydrogen on.

Please let me know what numbers you come up with. How many liters of liquid hydrogen are needed to replace a liter of gasoline?

Please note I gave you every benefit here, and allowed you liquid hydrogen, which you aren't going to get. The only way you'll get that amount of energy density of hydrogen is at 33 degrees kelvin.

 

[Henning]

One Kg of H2 produces the equivalent energy out put in vehicles as 1 gallon of gas. Most car manufacturers have the equipment ready to roll, Toyota even put all their patents into Public Domain to try to get things rolling. Fight it all you want, it's doable and being done already in LA, Iceland, and elsewhere.

 

[Cap'n Jack]

One Kg of H2 produces the equivalent energy out put in vehicles as 1 gallon of gas. Most car manufacturers have the equipment ready to roll, Toyota even put all their patents into Public Domain to try to get things rolling. Fight it all you want, it's doable and being done already in LA, Iceland, and elsewhere.

And what is the volume of that one Kg of H2, even as liquid?

 

[weilke]

2.75kg actually. Assuming it's a clean burn. Also uses 4kg of oxygen to get it done.

I assume we are talking pure Methane - though NG isn't pure.

Ethane is 2.93:1
Propane is 3:1
Butane is 3.03:1

So it's 3kg.

Add to that 4-5% of 'unaccounted for gas' that leaked somewhere between wellhead and burner tip, and your carbon balance of burning 'green' natural gas vs. coal or local plastic garbage starts to even out further.

 

[JeffDG]

And what is the volume of that one Kg of H2, even as liquid?

Don't get him started on Hydrogen...he thinks it's magic and produces energy with no input.

 

[EdFred]

Don't get him started on Hydrogen...he thinks it's magic and produces energy with no input.

It is magic, and you can milk it from unicorns!

 

[oldShar]

Here is a secret. Burning 1kg of 'green' natural gas will also produce 3kg of CO2.

HORRORS

The alternative name for Natural Gas is (horrors) METHANE
-- you're going to send the environmentalists into apoplexy mentioning the word GREEN and METHANE in the same sentence

 

[weilke]

HORRORS

The alternative name for Natural Gas is (horrors) METHANE
-- you're going to send the environmentalists into apoplexy mentioning the word GREEN and METHANE in the same sentence

Dont tell them about water vapor.

 

[Henning]

And what is the volume of that one Kg of H2, even as liquid?

Well, the Ford Explorer version manages 350miles a fill, so it's manageable, Mercedes is building and operating them in SoCal in B chassis with 134mile range as well.

 

[Lindberg]

And what is the volume of that one Kg of H2, even as liquid?

Is it about 14 liters?

 

[Palmpilot]

Dont tell them about water vapor.

Water vapor is an effect, not a cause, because it enters and leaves the gaseous state at normal atmospheric temperatures. That's not true of either carbon dioxide or methane.

 

[Henning]

Water vapor is an effect, not a cause, because it enters and leaves the gaseous state at normal atmospheric temperatures. That's not true of either carbon dioxide or methane.

Also water vapor can be condensed and reclaimed/reused as can the CO2 if the NG is utilized through a solid oxide fuel cell.

 

[Cap'n Jack]

Well, the Ford Explorer version manages 350miles a fill, so it's manageable, Mercedes is building and operating them in SoCal in B chassis with 134mile range as well.

Why can't you answer the question?

You have this habit of either changing the story ( as with the discussion with Wing and Rotor about the boat yard signs), or lying, or not answering the question if it doesn't support your premise.

Those vehicles are either experimental, with no cargo capacity, or not very useful out here, where there are places off the interstate where gas stations are not common.

So what is the volume of a kilogram of liquid hydrogen? Do you think gaseous hydrogen would have a greater or lesser volume?

 

[Henning]

Why can't you answer the question?

You have this habit of either changing the story ( as with the discussion with Wing and Rotor about the boat yard signs), or lying, or not answering the question if it doesn't support your premise.

Those vehicles are either experimental, with no cargo capacity, or not very useful out here, where there are places off the interstate where gas stations are not common.

So what is the volume of a kilogram of liquid hydrogen? Do you think gaseous hydrogen would have a greater or lesser volume?

Volume of a gas depends on pressure, and the H2 services are, and will be, pressurized gas for the near term future.

The typical automotive tank is 8.5kg of H2 in a 0.2m3 tank. The energy density of the H2 is 33 kWh/kg (more than twice that of the 14 kWh/kg of NG).

 

[Cap'n Jack]

Volume of a gas depends on pressure, and the H2 services are, and will be, pressurized gas for the near term future.

The typical automotive tank is 8.5kg of H2 in a 0.2m3 tank. The energy density of the H2 is 33 kWh/kg (more than twice that of the 14 kWh/kg of NG).

And that's why I tried to make it simple for you and asked for the volume of a kilogram of liquid hydrogen.

A typical automotive gasoline tank isn't 0.2 cubic meter, which is 200 liters, and about 53 gallons. This mean a lot of space is lost just for the hydrogen fuel in these vehicles with such a gas tank. The cars I've seen get the range from just carrying people, with no cargo space. Look at the Marai and ix35.

It is a bit of a red herring to only look at energy as a function of energy per unit weight. The energy per unit volume also plays a role. The Marai is a nice car but can't carry much, 4 people and no cargo because of the low energy density of hydrogen. Of course, that is fine for going to and from work.

If batteries can be charged more quickly, making them as convenient as gasoline, they could outstrip hydrogen in energy density.

 

[Henning]

And that's why I tried to make it simple for you and asked for the volume of a kilogram of liquid hydrogen.

A typical automotive gasoline tank isn't 0.2 cubic meter, which is 200 liters, and about 53 gallons. This mean a lot of space is lost just for the hydrogen fuel in these vehicles with such a gas tank. The cars I've seen get the range from just carrying people, with no cargo space. Look at the Marai and ix35.

It is a bit of a red herring to only look at energy as a function of energy per unit weight. The energy per unit volume also plays a role. The Marai is a nice car but can't carry much, 4 people and no cargo because of the low energy density of hydrogen. Of course, that is fine for going to and from work.

If batteries can be charged more quickly, making them as convenient as gasoline, they could outstrip hydrogen in energy density.

So? There is plenty of volume in the driveshaft tunnel which an electric vehicle doesn't need. This is not a problem in the slightest, especially in America where a Ford Explorer is an average sized vehicle.

 

[weilke]

Water vapor is an effect, not a cause, because it enters and leaves the gaseous state at normal atmospheric temperatures. That's not true of either carbon dioxide or methane.

It is both, effect and cause. While carbon dioxide doesn't turn liquid, it does get sequestered by natural mechanisms, no different from water vapor.

 

[Henning]

It is both, effect and cause. While carbon dioxide doesn't turn liquid, it does get sequestered by natural mechanisms, no different from water vapor.

Yep, bubble it through water with algae, then feed the rest into a greenhouse and you turn it into fuel and food. Dump it into the atmosphere at the rate we do while simultaneously cutting down those natural sequestration mechanisms called trees though and you add insulation to the atmosphere.

 

[Cap'n Jack]

So? There is plenty of volume in the driveshaft tunnel which an electric vehicle doesn't need. This is not a problem in the slightest, especially in America where a Ford Explorer is an average sized vehicle.

Most passenger cars don't have a drive tunnel anymore- front wheel drive, So that space doesn't exist to be taken by tanks. Even so, the current fuel cells cars don't have trunk space.

SUVs are common, but there are more cars on the road, even here in Nebraska, if observing the types of vehicles counts.

 

[Henning]

Most passenger cars don't have a drive tunnel anymore- front wheel drive, So that space doesn't exist to be taken by tanks. Even so, the current fuel cells cars don't have trunk space.

SUVs are common, but there are more cars on the road, even here in Nebraska, if observing the types of vehicles counts.

You're trying to infer a problem that doesn't exist. The only thing keeping fuel cell cars from populating the streets is lack of clean H2 production which is simple to solve if the energy industry wasn't worried about milking every last cent out of the public. The car makers are ready already.

 

[Cap'n Jack]

You're trying to infer a problem that doesn't exist. The only thing keeping fuel cell cars from populating the streets is lack of clean H2 production which is simple to solve if the energy industry wasn't worried about milking every last cent out of the public. The car makers are ready already.

And you are making up "facts" again. Most cars don't have a drive tunnel, being front wheel drive. As someone that is supposed to know cars and engines, you should know that. Most vehicles driven are cars.

I'm not inferring a problem that doesn't exist. Take a look at the Toyota or Hyundai offerings. They are hybrid cars. Space only for people. Large batteries and hydrogen tanks. I question if the reported range is from the hydrogen tank only, or a combination of hydrogen and battery.

Toyota reportedly loses $100,000 on each car they sell at $57,000. Maybe they'll make it up in volume.

 

[Henning]

And you are making up "facts" again. Most cars don't have a drive tunnel, being front wheel drive. As someone that is supposed to know cars and engines, you should know that. Most vehicles driven are cars.

I'm not inferring a problem that doesn't exist. Take a look at the Toyota or Hyundai offerings. They are hybrid cars. Space only for people. Large batteries and hydrogen tanks. I question if the reported range is from the hydrogen tank only, or a combination of hydrogen and battery.

Toyota reportedly loses $100,000 on each car they sell at $57,000. Maybe they'll make it up in volume.

There is no reason a tunnel cannot be reformed. There is no reason that a chassis cannot be built to deal with whatever. They lose money because the volume of sales does not make up for the R&D costs of the program already spent, not just the construction costs. You are correct, with volume that goes away which is why they are pushing the industry.

For some unknown reason you assume technology remains static. An Apple Watch has far more computing power than a PDP-12 did which took up 2 rooms. As technology becomes more popularly used, the price decreases and capability increases as more thought and investment is introduced.

 

[Cap'n Jack]

There is no reason a tunnel cannot be reformed. There is no reason that a chassis cannot be built to deal with whatever. They lose money because the volume of sales does not make up for the R&D costs of the program already spent, not just the construction costs. You are correct, with volume that goes away which is why they are pushing the industry.

For some unknown reason you assume technology remains static. An Apple Watch has far more computing power than a PDP-12 did which took up 2 rooms. As technology becomes more popularly used, the price decreases and capability increases as more thought and investment is introduced.

The tunnel has been "reformed". It is filled with batteries and fuel tanks. It is actually 2 tunnels, under the seats. One (under the front seat) holds a battery, the other holds a hydrogen fuel tank (back seat) It wasn't enough capacity, so there is another tank in the "trunk". The front of the car, where the engine used to be, is the fuel cell. Going to be a pain in the neck (or back) putting groceries on the back seat.

Apples and oranges again, with the technology. There was a lot of improvement possible in computers, one can't change the laws of physics. Rather, the laws of physics allowed for a lot of improvement in computers. If they get another method of sequestering hydrogen to improve its energy density, it will be a great improvement over what we have now. some interesting work in hydride chemistry, but they aren't nearly there yet.

They are marketing those cars incorrectly. They could make a great commuting car. The range works, the carrying capacity works for that too. But electric cars also work fine within the same use-niche. The end user price is competitive between the two.

 

[Palmpilot]

It is both, effect and cause. While carbon dioxide doesn't turn liquid, it does get sequestered by natural mechanisms, no different from water vapor.

Yes, but how quickly? According to climatologists, the reason CO2 acts as a forcing and H2O does not is that disturbances in atmospheric CO2 levels persist much longer.

 

[ClimbnSink]

Cool so if I burn one car tire I get three car tires out of it. Crap that didn't work I took a tire off my moms car and burned it and now there are only three left. U guys math is messed up. She is going to be ****ed when she gets home from rehab.