B Waste-to-energy question (not homework)

[Elli1]

TL;DR Summary

Burning waste in a waste-to-energy plat, can more energy be produced by turning the trash to ash, then the amount of energy needed to turn the trash to ash?

Burning waste in a waste-to-energy plat, can more energy be produced by burning the trash then the amount of energy needed to heat the trash to the point it vaporises? (to turn it to ash)
eg we have 100 J of energy inside some rubbish, and this energy would all be released when we incinerate the rubbish,
So and we used 50 J of energy to turn the rubbish to ash, is this possible?
Or would it always cost more energy to turn the TRASH TO ASH then the energy we get from turning the trash to ash.
Thanks in advance!

 

[russ_watters]

I would expect this to depend on the quality of the trash, specifically if it has a high content of noncombustibles like water and metal.

 

[jrmichler]

Search terms waste to energy will provide a lot of good information.

 

[hmmm27]

"trash to ash" might be a cute marketing term but you'd have to define what you mean by "trash", first. Also if you "vaporize" something, you don't get ash... by definition.

 

[Lnewqban]

Not trash, but a somehow similar process, and what it takes:
Please, see:
https://en.m.wikipedia.org/wiki/Charcoal

 

[bobdavis]

Is this equivalent to the question of whether the trash material can sustain its own combustion without further energy input?

 

[hmmm27]

I think that was the original question, but the OP hasn't bothered to define what the material is, nor what exactly is meant by "burning".

 

[Elli1]

Is this equivalent to the question of whether the trash material can sustain its own combustion without further energy input?

yes

 

[Elli1]

I think that was the original question, but the OP hasn't bothered to define what the material is, nor what exactly is meant by "burning".

the would be things like plastic, wood, metal, banana peals, and burning would be heating until most of the mass has 'disappeared'

 

[Elli1]

Summary:: Burning waste in a waste-to-energy plat, can more energy be produced by turning the trash to ash, then the amount of energy needed to turn the trash to ash?

Burning waste in a waste-to-energy plat, can more energy be produced by burning the trash then the amount of energy needed to heat the trash to the point it vaporises? (to turn it to ash)
eg we have 100 J of energy inside some rubbish, and this energy would all be released when we incinerate the rubbish,
So and we used 50 J of energy to turn the rubbish to ash, is this possible?
Or would it always cost more energy to turn the TRASH TO ASH then the energy we get from turning the trash to ash.
Thanks in advance!

when using a car the fuel is used up and you have energy left over to make the car move, so when burning waste (fuel) you use up the waste and have energy left over, it seems like this breaks the conservation of energy-mass in both cases

 

[russ_watters]

when using a car the fuel is used up and you have energy left over to make the car move, so when burning waste (fuel) you use up the waste and have energy left over, it seems like this breaks the conservation of energy-mass in both cases

Why do you think it violates conservation of energy/mass? For the mass part; no, mass is not consumed when you burn something. The mass of the products is equal to the mass of the reactants. But the reactions produce output energy. If you don't understand how that works even for a car, I suggest trying to work some simple chemistry combustion equations, such as burning methane.

Anyway, this link does indicate that typical municipal waste does contain excess energy, so when it is burned it is self-sustaining and you can produce electricity:
https://www.eia.gov/energyexplained/biomass/waste-to-energy-in-depth.php

 

[Elli1]

Why do you think it violates conservation of energy/mass? For the mass part; no, mass is not consumed when you burn something. The mass of the products is equal to the mass of the reactants. But the reactions produce output energy. If you don't understand how that works even for a car, I suggest trying to work some simple chemistry combustion equations, such as burning methane.

Anyway, this link does indicate that typical municipal waste does contain excess energy, so when it is burned it is self-sustaining and you can produce electricity:
https://www.eia.gov/energyexplained/biomass/waste-to-energy-in-depth.php

As we are taking something 'not useful' (waste) and getting 'free energy' from it is why it didn't seem to make sense to me, But so the process of burning trash is the same as combustion in a car and thus more energy is produced by the trash then is put into the trash (it is self sustaining). Until the fuel runs out.

 

[sysprog]

I know a guy who regularly turns waste cooking oil from restaurants into diesel for his Mercedes-Benz 300 SD $-$ along with the usual nasty products of diesel combustion emissions, his exhaust makes it smell like there's a White Castle or Chinese take-out nearby.

 

[OmCheeto]

Thanks!

I needed an easily solved homework problem this morning.

Source of data: https://www.co.marion.or.us/PW/ES/disposal/Pages/mcwef.aspx