What the wood stove particulate paper missed

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

cbrodsky

Member
Hearth Supporter
Jan 19, 2006
517
Millbrook, NY
From burningissues - the "bible" report often cited on stove particulate emissions missed what is possibly one of the simplest but most important opportunities to help people reduce emission levels. It is a shame they failed to see this in their data, but it does serve as further evidence of what I think all skilled woodburners already know - use dry seasoned wood!

-Colin


The average wood moisture by cordwood tree species ranged from 9.8% to 26.8% on a dry basis (9.0% to 21.1% on a wet basis) for Klamath Falls and from 18.1% to 112.1% on a dry basis (15.3% to 52.8% on a wet basis) for Portland.

First, burning some of this wood is downright wasteful in terms of moisture content. Wet wood is money up the chimney, and poor operating conditions for the stove that is bad for many reasons.

But more interestingly, I was very surprised by the notion that the authors concluded no correlation of wet wood with particulate emissions:

In addition, there was no clear statistical relationship (no R2 values greater than 0.9) between emission factors and either burn rate or fuel moisture for catalytic stoves, non-catalytic stoves or for both categories combined.

In fact, the "statistical test" was rather crude at best - simply plotting the data and looking for R^2 > 0.9 with a linear fit. What the authors cannot conclude is a linear correlation between moisture and particulate emissions.

Since this flies in the face of conventional wisdom as to best woodburning practices, using wood air dried to 20% or better moisture, I plotted these results and found there is in fact a very clear non-linear correlation between moisture level and particulate emissions. Wood at 20% or less moisture all had emission levels well below 10 g/hr. However, for wood above 20% moisture, 7 of 9 stoves had emission levels at or above 10 g/hr. This is pretty clear - it just requires using more than a simple linear R^2 test to observe it. I have to admit, this has me intrigued what else the report may have buried in it, but it also raises some concerns as to methodology throughout the study.
 
The report is invlid without the prior stove conditions, when chimneys were cleaned and no record of stoves being cleaned.
astute wood burner know their Cat combustors have to be cleaned to opperate effeciently, yet ther is no record of the cats condition or cleaning regiment

The whole study the way it was conducted is useless. It points out normal maintance keeps stoves preforming up to original specs . You are right about the particulate and moisture content again another flaw in this report. In general this report is not very scienctific
 
elkimmeg said:
thne report is invlid without the prior stove conditions when chimneys were cleaned and not record of stovves being cleaned.
astute wood burnerknow their Cat combustors are cleaned to opperate effeciently yet ther is no record of the cats condition or cleaning regiment

the whole study the way it was conducted is useless It points out normal maintance keeps stoves preforming up to original specs . You are right about the particulate and moisture content again another flaw in this report In general this report is not very scienctific

Elk -

I wouldn't dismiss it completely outright quite that quickly - I do think there is some valuable information in here. But you are right that this raises more questions.

One conclusion the authors made was that while some stoves were poorly maintained, the quality of maintenance did not correlate with emissions performance. That is interesting. If correct, it suggests these stoves are a little more bulletproof that we might believe - it suggests that even with lousy maintenance, they are still far better than pre-EPA stoves. If I have some time, I'd like to go back and re-analyze that result as well to see if it takes something more than a simple linear R^2 test to understand what is going on.

I don't think any of us would argue that a stove that is no longer factory fresh after many years might show a slight decline in performance, much like our cars with 80K miles are probably not at the same level as one with 10K miles. But the more interesting point was that no matter what, they are still well ahead of pre-EPA stoves, suggesting all this effort was indeed productive and a step in the right direction.

-Colin
 
Status
Not open for further replies.