[Stoves] Particulate Matter Norms

[Crispin Pemberton-Pigott]

Dear Ranyee

 

For those who may be new to the metrics involved I will add just a little on
one point you raise in explanation (and thank you for that).

 

>The IWA metrics do not include emissions per mass of fuel used.

 

For some this may seem odd as a lot of the US regulations state emissions
per kg burned. When the emissions are measured per unit of energy (usually
per MegaJoule) the number becomes 'translatable' or 'portable as I like to
call it. If you have an emission per MJ then if you know the energy content
of any fuel means it is a simple matter to make the conversion to emissions
per unit mass (just divide the emissions number by the net heat energy per
kg or per pound).

 

On the other hand, if you are given the emission per kg and do not know the
energy content of the fuel, you cannot make the translation back to 'mass
emitted per MJ'. 

 

For this reason, it is wise to always report things per unit of energy so
anyone can make use of the number in their local methodology.

 

Lately we are seeing reported the 'emission per net energy delivered'. There
is great utility for this in the stove community. If you have the emission
mass per MJ delivered into the pot, or pots, or the room if it is space
heating, you have a metric that can be used to make a direct comparison
between different stoves and fuels without having to do any conversions at
all. 

 

It a stove emits 10 mg PM 2.5 per MJ and the thermal efficiency to the pot
is 35%, then the emission per Net MJ is 10/0.35 = 28.6mg/Net MJ

 

A different stove emitting 14 mg PM2.5 per MJ with a heating efficiency of
49% is:

 

14/0.49 = 28.6mg/Net MJ which is exactly the same amount of PM 2.5 to do the
same cooking task (at that power level).

 

Thus if you are comparing two stoves one of which emits 14 mg and other 10
mg per MJ of heat from burning the fuel, it is misleading unless you also
consider the efficiency of heat transfer as well. The two are combined by
reporting the emissions per net MJ of heat delivered.

 

Some national standards use the net heat delivered as the denominator in the
equation but is it relatively uncommon.

 

Regards

Crispin

 

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