Burn 100 pounds of firewood. Where does the mass go?

[wahoowad]

I saw this posted elsewhere and everybody gave wacky responses. I'm hoping to get more educated responses here.

Say I burn 100 pounds of seasoned oak firewood. I'm probably left with a pound of ashes at most. Did 99 pounds of particles go up the chimney as smoke? If moisture content accounts for 15 or 20%, does that mean 15 pounds of water vapor released and 99-15 = 84 pounds of particles/smoke up the chimney?

 

[BrotherBart]

I figure most of that weight was carbon and hydrogen and they get oxidized and turn into CO2 which goes right up the pipe.

 

[Mike Wilson]

Burn 100 pounds of firewood. Where does the mass go?

Into the ether, where else?!

-- Mike

 

[moralleper]

The mass is turned into energy, heat. mass is energy there is a fairly famous equation for this, E=mc2

 

[Turner-n-Burner]

When you burn a hydrocarbon - any hydrocarbon- the bonds between the hydrogen and the carbon atoms are broken and replaced with more stable bonds between hydrogen and oxygen and carbon and oxygen. So in addition to the 15 lbs or so of water that was present in the wood and is given off as water vapor, your stove is actually MAKING water as fuel is burned and oxygen is fed from your home to the fire.

Ideally, all of the hydrogen in the wood would be converted to water, and all of the carbon into carbon dioxide. What you are calling smoke is mostly water vapor and carbon dioxide just like the exhaust of your car. Other things are present of course - including soot particles that make up the stuff you can actually see.

in an efficient and clean buring stove, there should be very little soot going up the chimney, the vast majority of the weight of the wood should be converted to water vapor and carbon dioxide.

to keep the math simple, assume that hydrogen, oxygen and carbon atoms all weigh the same amount:

, for a 100 lbs of wood call it 20 lbs of water, plus 40 lbs of hydrogen plus 40 of carbon.

40 lbs of hydrogen would mate with 20 lbs of oxgen making 60 lbs of water vapor.
40 lbs of carbon would mate with 80 lbs of oxygen to make 120 lbs of carbon dioxide.
plus you have your original 20 lbs of water which is heated to steam.

ignoring the insignificant amount of ash left in your stove, and the soot that goes up the stack your 100 lbs of wood is converted to 200lbs of "smoke" .

Now just wait for some chemist to correct me with the real math... Either way, you get the point - nearly everything becomes h20 and co2 - but significantly more than you started with!

 

[Martin Strand III]

Burning Wood 101

Complete combustion of wood results in giving off heat, light, and the gases carbon dioxide and water vapor.

So, since wood is composed of

Carbon 41%
Hydrogen 4.5%
Oxygen 37%
Water 16% (air dry approx)
Ash 1.5%

the weight of any fuel load can be calculated.

PROBLEM: Burning wood in a stove does not produce complete combustion. Therefore, the above calculations are not "real world".

With incomplete combustion of wood, other noxious substances are produced:

Wood smoke: contains carbon monoxide, oxides of nitrogen and VOC's (volatile organic compounds; ie, smog)
Toxic pollutants: benzene, formaldehyde and others
Particulate matter: PM10, PM 2.5 (those dirty little buggers in 10 and 2.5 micron size that cause lung cancer and can enter your blood stream from your lungs)

The above nasties make up as much as 60 Grams/hour (yes, per hour) if you burn wood in a pre-Phase II stove and are reduced to 2 - 7.5 Grams/hour if burned in a more modern Phase II stove. Relative amounts may vary with different stoves and vary even with the same stove with different fuel loads.

The bottom line is the numbers themselves aren't important; they just underscore the logic to burn hot fires in a modern Phase II stove using dry wood.

Aye,
Marty

 

[Turner-n-Burner]

Burning Wood 101

Complete combustion of wood results in giving off heat, light, and the gases carbon dioxide and water vapor.

<snip>

The bottom line is the numbers themselves aren't important; they just underscore the logic to burn hot fires in a modern Phase II stove using dry wood.

Aye,
Marty

C'mon - I want to see someone bust out the real numbers and calculate the WEIGHT of the light that is emitted from the fire anyone remember what a photon weighs?

LMAO!

 

[Gibbonboy]

The Mass. goes somewhere just to the north of Conn., no?

 

[DriftWood]

Burning Wood 101

Complete combustion of wood results in giving off heat, light, and the gases carbon dioxide and water vapor.

<snip>

The bottom line is the numbers themselves aren't important; they just underscore the logic to burn hot fires in a modern Phase II stove using dry wood.

Aye,
Marty

C'mon - I want to see someone bust out the real numbers and calculate the WEIGHT of the light that is emitted from the fire anyone remember what a photon weighs?

LMAO!

Nice discussion these Web pages have the equations,charts and real world problems in burning wood clean.

Burning of wood, Heat release and fire spread

(broken link removed)

Burning Rate of Solid Wood Measured in a Heat
Release Rate Calorimeter

(broken link removed)

Theory of Design of an Efficient Wood-Burning Appliance

http://mb-soft.com/juca/print/314.html

 

[babalu87]

At least a woodstove operates somewhere in the vicinity of 60%

Think of how many pounds of gasoline you burn every week, now think of the horrible efficiency that an internal combustion engine has (30% is about right)

 

[Mike Wilson]

The mass is turned into energy, heat. mass is energy there is a fairly famous equation for this, E=mc2

Dude, if this were true I could lay firey waste to a 10 mile radius around my home with the mass from one split... Hey honey, warm enough for you??? Hey, where the hell did all your skin go?

-- Mike

 

[citizanken]

Is any carbon monoxide produced when you burn wood? I am having an insert installed and was curious if I should get a CO detector

 

[Rhone]

Yes, and yes you should get a CO detector. Usually with wood most often the CO is pulled down with chimneys with more than one flue. If your insert is exhausting and the flue that runs the boiler right next to is back-drafting the fumes coming out your chimney from your insert can be sucked down the flue of your boiler filling your basement (if that's the location of your boiler/furnace) with CO. So, having the CO in the living area above and hanging out in the basement could be deadly if you didn't also have one down there as well. Put a CO detector on all floors at a minimum.

 

[smirnov3]

The mass is turned into energy, heat. mass is energy there is a fairly famous equation for this, E=mc2

Actually, that's not quite right: E^2 = m^2c^4 + p^2c^2.

Where p is the momentum of your firewood.

So the faster your firewood is moving, the more energy it has.

 

[Mike Wilson]

The mass is turned into energy, heat. mass is energy there is a fairly famous equation for this, E=mc2

Actually, that's not quite right: E^2 = m^2c^4 + p^2c^2.

Where p is the momentum of your firewood.

So the faster your firewood is moving, the more energy it has.

So what, I should throw it into the stove instead of placing it there? :lol:

-- Mike

 

[Corey]

Wahoowad - I haven't seen anyone give a clear, simple answer, but essentially, the answer is yes, the extra mass leaves as not just smoke, but "products of combustion". The basic equation is :

hydrocarbon (HC's) + oxygen (O2) --> water (H2O) + carbon dioxide) CO2

This is very simplistic equation and doesn't take into account some things such as burning wood in air (oxygen, nitrogen) as opposed to pure oxygen, etc.

So you chuck a piece of wood into the stove. The mass leaves the stove as:

carbon dioxide
water vapor (created from burning the wood - equation above)
water vapor (boiled from the wood)
particulate matter (fly ash, smoke particles, carbon soot)
carbon monoxide
nitrogen oxides
other gasseous chemical compounds (this list should pretty much cover it- http://burningissues.org/table2.htm )

non-combustible ash in the pan

That should cover almost all the weight - CO2, water, particulates being the major players. There is no E=MC2 matter/energy conversion in the fire...no more so than the natural radioactive decay of elements in the wood - which would make up a VERY small amount of mass...probably on the order of single atoms worth.

The wiki has a good fire article at:

http://en.wikipedia.org/wiki/Fire

Corey

 

[coldinnj]

Sorry the E=MC2 is not correct. Unless of course you have one of those SNAP generators or some other type of nuclear reactor.
This would be more appropriate.
First you would determine the enthapy of the observed reaction (combustion in your case). .d.H(c) = sum(.d.H (f) products) - sum (.d.H (f) reactants).

[Reads enthalpy of compustion equals the sum of the enthalpies of the products minum the sum of the enthalpies of the reactants.}

The heats of formation could be obtained experimentally, computationally, or from data tables.

This would be the molar enthalpies. To find the energy of a certian mass of material, factor in the molecular weight.
But of course we won't get technical. Lets just say: No mass is lost. No energy is lost.
We have balance in life grasshopper.

 

[wg_bent]

The mass is turned into energy, heat. mass is energy there is a fairly famous equation for this, E=mc2

Dude, if this were true I could lay firey waste to a 10 mile radius around my home with the mass from one split... Hey honey, warm enough for you??? Hey, where the hell did all your skin go?

-- Mike

Mike, you'd have to get a PE Summit in order to do that.

 

[Roospike]

Sorry the E=MC2 is not correct. Unless of course you have one of those SNAP generators or some other type of nuclear reactor.
This would be more appropriate.
First you would determine the enthapy of the observed reaction (combustion in your case). .d.H(c) = sum(.d.H (f) products) - sum (.d.H (f) reactants).

[Reads enthalpy of compustion equals the sum of the enthalpies of the products minum the sum of the enthalpies of the reactants.}

The heats of formation could be obtained experimentally, computationally, or from data tables.

This would be the molar enthalpies. To find the energy of a certian mass of material, factor in the molecular weight.
But of course we won't get technical. Lets just say: No mass is lost. No energy is lost.
We have balance in life grasshopper.

If ya can't dazzle 'em with brilliance, baffle 'em with bullshit.

:lol: on said calculations

 

[Roospike]

If ya can't dazzle 'em with brilliance, baffle 'em with bullshit.

:lol: on said calculations

It's getting contagious.....aaaalllllllrrrrriiiiightt!![/quote]

Just rib-n ya ;-)

 

[coldinnj]

Just wanted to have fun as we all know the calculations are just a little banter here.
As for the information I posted... I do not in any way pretend to be brilliant... however the information is not bullshit either.
Check with a PHD chemist if you like.
"If you can't dazzle em with brilliance
baffle em with bullshit
or just tell the truth and really amaze them"

 

[jldunn]

Does anyone know the half life of pine? Is its half life generally longer than that of hardwoods?

I'm sure it depends on a ton of variables, like how long the wood has been seasoned, if it is split, etc.

 

[coldinnj]

Yes Grasshopper
the Harmonic is important...
However is there Harmony when two are STRUCK?
"One must find harmony in nature"