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.
-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.
