[Stoves] Emissions fromResidentialWoodCombustion:EffectofMoisture on Emissions

Sun Dec 31 16:47:29 CST 2006

Dear Tom,

I agree that experiments need to be explained in detail. The UCB revised
Water Boiling Test goes to great lengths to control confounding variables to
maintain international comparability of tests while attempting to account
for variables like different fuels and different moisture content. The
intention is for an International Standard test that could be followed to
standardize testing protocol. The WBT includes wood species and moisture
content in the Excel spreadsheet that calculates results.

Obviously, the Controlled Cooking Test and Kitchen Performance Tests are NOT
comparable between places because different fuels, different pots, different
fire tending techniques, different cooking times, etc are used. So the CCT
and KPT can only be used to show differences in one place between different
stoves. That's probably the most valuable info for the local stove project.
But it is also valuable to have a test that can be used to compare results
internationally.

The WBT is the only one of the three International Standard tests that tries
to create comparability between stoves tested by different folks in
different places. That's why the WBT takes into account variables like
different wood species and moisture content. 

Any test is an partial snapshot of performance when variables are controlled
(WBT) and when they are not as controlled (CCT, KPT). That's why the
conferences that created these three tests (WBT, CCT, KPT) suggested doing
all three tests to create a multi-dimensional picture of effectiveness.
Because the KPT can be a lengthy procedure, Aprovecho most frequently uses
the WBT/CCT combination, both with emissions, including the KPT when
time/effort/funding is available. 

By the way, Dana and David of CEIHD are getting more and more practice doing
KPTs with emissions, and learning how to get good results in less time.

All Best,

Dean

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Tom Miles
Sent: Sunday, December 31, 2006 9:48 AM
To: 'Discussion of biomass cooking stoves'; 'Crispin Pemberton-Pigott'
Cc: 'Marlis Kees'; 'David Hancock'
Subject: Re: [Stoves] Emissions
fromResidentialWoodCombustion:EffectofMoisture on Emissions

Thanks Dean. 

As a general comment we would all benefit if everyone included more detail
about the fuels they burn, species, moisture content, size, etc. As to fuel
species, there are differences in the way that hardwoods, softwoods and
woods of different densities decompose during gasification and combustion
that affect the design and efficiency of the stove. More information will
help us understand a particular local application or test.

Thanks

Tom 

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Dean Still
Sent: Saturday, December 30, 2006 11:40 PM
To: 'Discussion of biomass cooking stoves'; 'Crispin Pemberton-Pigott'
Cc: 'Marlis Kees'; 'David Hancock'
Subject: Re: [Stoves] Emissions from
ResidentialWoodCombustion:EffectofMoisture on Emissions

Dear Tom,

I hope to get the ok from the publisher to have an 'early release' of
results for ETHOS but we'll see. 

All Best,

Dean

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Tom Miles
Sent: Saturday, December 30, 2006 6:26 PM
To: 'Discussion of biomass cooking stoves'; 'Crispin Pemberton-Pigott'
Cc: 'Marlis Kees'; 'David Hancock'
Subject: Re: [Stoves] Emissions from Residential
WoodCombustion:EffectofMoisture on Emissions

Dean,

You presented some charts of the results of those tests in your ETHOS
presentation last year but we haven't seen complete reports with data tables
that show the different stoves, tests, fuels, conditions, etc. Will you be
putting more complete information from your benchmark tests on the Aprovecho
website?

Thanks

Tom   

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Dean Still
Sent: Saturday, December 30, 2006 5:51 PM
To: 'Crispin Pemberton-Pigott'; 'Discussion of biomass cooking stoves'
Cc: 'Marlis Kees'; 'David Hancock'
Subject: Re: [Stoves] Emissions from Residential Wood
Combustion:EffectofMoisture on Emissions

Dear Crispin,

The wood used in the Aprovecho tests is Douglas fir which is a hard
softwood. The UCB WBT accounts for wood type. 

The proposed benchmarks were not based on Rocket stoves. They were based
instead on testing many different types of stoves (more than 30 now) ranging
from the three stone fire to very clean burning stoves. Rocket types are in
the middle range.

Emissions do change depending on the moisture of the wood. So does fuel
used. The University of California at Berkeley revised Water Boiling Test
Excel spreadsheet accounts for moisture content in wood used. The wood we
have used averages around 10% moisture content in the winter. 

As I pointed out yesterday the WBT is designed to minimize confounding
variables to highlight the performance of the stove. The UCB revised
Controlled Cooking Test which follows the WBT uses all local cooks, pots,
fuels, food, techniques. The Kitchen Performance Test is the third test in
this series, a larger survey of stoves in use in kitchens. 

The proposed benchmarks are based on the WBT because Aprovecho has a
'library' of WBT tests (done under an emissions hood). One fine day we hope
to have a similar 'library' of CCT and KPT results (with emissions) from
which to evolve definitions of improved performance. 

All best,

Dean

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Crispin
Pemberton-Pigott
Sent: Saturday, December 30, 2006 2:14 PM
To: Stoves
Cc: Marlis Kees; David Hancock
Subject: Re: [Stoves] Emissions from Residential Wood Combustion:
EffectofMoisture on Emissions

Dear Testers

I reviewed the paper by Fernando Preto and noticed interesting and important

things throughout the document.

For example, testing done with softwood gives consistently higher CO than 
hardwood. Higher moisture content gives consistently lower CO, all the way 
to 35% moisture (dry weight basis I believe).

This means that benchmarks proposed for emissions which have been based on 
low moisture softwoods (as is the case in the draft proposal forwarded for 
discussion in Bonn for WHO, could be quite misleading. We could set a lower 
permissible level for CO.

The reasons for this is that the proposed benckmarks were based on Rocket 
Stoves mostly optimised (dimensions and operator technique) for low CO in 
ppm.  The emissions may have been significantly lower had the wood contained

15 to 35% moisture, and the PM 2.5's would have been affected either up or 
down.

The vast majority of particulate emissions from wood fires are PM 2.5's 
(something over 85%) and they seem to follow a path inverse to the CO 
production.

It is clear that testing of stoves has to be done with wood that is 
reasonably moist and comparable with field conditions, and then the stove 
dimensions optimised to that fuel. Also, the operator of the stove has to be

familiar with how to operate it with that particular fuel.  Reproducing the 
exact method as used with very dry fuel will not perhaps give the best 
result.

Both the USA and Canada seem to be leaning towards using a dry weight basis 
for testing and certification.  This is inconvenient for us with our simple 
scales, but it is only a matter of mathematics and can be resolved on the 
spreadsheet.

One must again remember that these tests by Preto are 'device dependent' and

do not constitute the expected emission of cooking stoves, only standard 
(three sets or types) of box-stoves for space heating.  Surprise still might

be lurking.  I would not be surprised to find improved cooking stoves are 
cleaner than space heating stoves.

If a stove is going to be primarily used with hardwood, it should not be 
tested with softwood because the emissions are quite different.  The biggest

difference of all is between dry softwood, as used in APROVECHO standardised

testing, and moist hardwood, especially in CO production.  As make cook in 
fact use moist hardwood of many species (softwood being a lousy fuel) the 
relevance of APROVECHO's standard fuel test results is suspect.

It is likely that the target emissions or benchmarks for CO and particulates

can be reduced if Preto's work is borne out for improved cooking stoves.

A very interesting set of developments!

Regards
Crispin

----- Original Message ----- 
From: "Tom Miles" <tmiles at trmiles.com>
To: "'Discussion of biomass cooking stoves'" <stoves at listserv.repp.org>
Sent: Saturday, December 30, 2006 2:24 PM
Subject: [Stoves] Emissions from Residential Wood Combustion: Effect 
ofMoisture on Emissions

Emissions from Residential Wood Combustion: Effect of Moisture on Emissions
Fernando Preto, Canmet Energy Technology Center, Canada, Paris, October 21,
2005
 <http://www.ieabcc.nl/meetings/task32_Paris_ssc/Preto.pdf>
http://www.ieabcc.nl/meetings/task32_Paris_ssc/Preto.pdf (1.3 MB pdf)
http://stoves.bioenergylists.org/en/canmetiea32paris
<http://stoves.bioenergylists.org/en/canmetiea32>

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