[Stoves] Fwd: Re: Shields E450c as a way to test char-making stoves (attn: GACC testers)

Crispin Pemberton-Pigott crispinpigott at gmail.com
Tue Oct 22 12:20:04 MDT 2013

Dear Paul


I can't keep track of who you are sending that to. I will continue here.


>NOTE:   There is char remaining at the end of the batch.  Crispin wants 
the unburned char to be counted as fuel used.   Others want the char to 
be valued as fuel for other stoves or as biochar or as atmospheric CO2 
removed.   This debate is AN important question if discussing the amount 
of original FUEL that is used.   But it is not THE important question 
concerning the stove efficiency of ENERGY released (with some amount 
captured in the pot so that ENERGY efficiency can be calculated).
I feel it necessary to add the words missing from the above:
Crispin wants the unburned char to be counted as fuel used if that char
cannot be considered fuel for the stove being tested at the time.
This is not a fine point, It is basic to the rating and prediction of fuel
In many cases (I am chasing a new one) the remaining char is fuel for
another stove. Fine. That stove will be rated according to how it uses that
char, and what is unburnable leftovers will be considered 'consumed' by that
char burning stove. The point is no one gets to double dip on the energy,
altering (lowering) the claimed fuel consumption by pointing out that the
'energy used' is a lower number.  Used energy is always a lower number than
available, but that should not distract us.
>We really do need to differentiate between the FUEL and the ENERGY, 
especially when a substantial amount of energy is not extracted from the 
fuel, as is the case of the remaining charcoal.
Exactly! Thank you.
>This was not a problem when the only stoves available essentially took 
all of the energy out of the fuel.   But that is no longer the case and 
we need better definitions of "efficiencies".
Well, in the 1980's it was recognised as a problem and the Eindhoven Group
and VITA both started discarding all remaining fuel as lost. They never, as
far as I know, even tried using the leftovers that were burnable as part of
the fuel in the next cycle, even when it was obvious that was happening on
the ground. From what I can find, testes were always started with 100% new
raw fuel.
>With fossil fuels, we calculate that we get all of the energy released 
from the fuel.   BUT those are PROCESSED fuels like LPG and kerosene or 
even "fuel oil".  If you consider all of the original fuel (such as 
crude oil), then there is a great amount of ENERGY in the "other stuff" 
that is not available via the stove.    Should that be called "non-fuel" 
and be counted against the processed fuel's efficiency?   No, not 
really.    Other derivatives of the crude oil have their own uses and 
values, of which some are not even for energy (such as asphalt).
It is reasonable to make such a system analysis of the raw material. The
point we face as testers is that we are asked what happens with this stove
using that fuel. Period. 
>Charcoal made from wood fuel is no longer wood.  And therefore the FUEL 
efficiency denotes the 100% disappearance of the wood.   But in terms 
for ENERGY efficiency, 100% of energy in wood = energy in charcoal  +   
That is one way to look at it.
>Crispin argues that Fuel efficiency needs to be reported.   This can be 
important in areas of severe deforestation.   But that thinking is 
deficient in three regards:
Let's look:
>1.  Tradition has used the term FUEL as if the amount of fuel could / 
should / must be equated to the amount of ENERGY that is released.   But 
that equivalence is no longer the case when a significant "left-over" 
(by-product or co-product) is created, as in the case of the charcoal.
The view is correct for certain fuel types, but it is not for biomass
because of the way it burns. 
>2.  Tradition has focused on wood as if it were the only biomass fuel 
that truly matters in cookstoves.    That is no longer the case now that 
pyrolytic microgasifiers that use many other forms of biomass are 
acknowledged to be serious candidates as clean cookstoves.   [And that 
acknowledgement is certainly less than 8 years old, and maybe not even 
acknowledged by some still today. Sad but true.]
Well..charcoal has long been recognised as a biomass fuel. How it was
produced varied. Gasifiers have been around for a long time, making
>3.  Therefore, if FUEL conservation (or efficient usage) is the battle 
cry of the testers for fuel efficiency, then the use of NON-wood fuels 
means that the micro-gasifier stoves need to be credited with using NO 
wood from the forests and are therefore far superior than the 
wood-burning stoves in regard to the saving of forests (and watersheds 
and animal habitats and biodiversity, etc.).
That is unfortunately not the case - though some are still trying to make it
(because it has certain merits). The availability of non-woody biomass is
not a 'given' in many places. There are huge amounts of wasted biomass
(burned to get rid of it) but that does not mean a generalisation is
possible. Looking at the UNFCCC rules for what constitutes 'sustainable
biomass' can lead to the conclusion that fuel efficiency (whatever the form
of the biomass) is important. That is a general case, however there many
places with an excess of something and others where everything is used. 
A policy manager might conclude that in their target region there is plenty
of non-woody biomass and to save the forests from chopping, they will use
the alternative. This does not have to be put into pyrolysers, it needs to
be burned 'somehow' and a pyrolyser is one way to do it. It might be made
into pellets or briquettes or powder. We should be technology neutral when
making rules.
>Summary statement and plea:   Let's get off of the "wood standard" and 
get on the energy standard.
We can do that, if we do not at the same time create a rating method for
stove performance that lies about the fuel consumption. 
The issue for me has been that test methods have been mis-reporting actual
performance and misleading programme managers who make decisions about what
technology they want to support with their $$. 
1.       Stoves with equal performance shall receive equal ratings.
2.       Stoves with unequal performance shall not receive equal ratings. 
If the mathematics of the test method provides a rating that contradicts
either of those rules, it needs to be investigated and corrected. If a
metric is the actual problem, change the metric (calculate something else
that is representative of performance). 
When it comes to mass of fuel consumed, the energy in it and so on, the lab
is agnostic. There are no holy stoves and there are no holy fuels. The stove
does what it does, emits what it emits, and consumes what it consumes. We
just report it. Don't shoot the messenger.
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