Evaluation of Low-Emissions Wood Stoves (Shelton & Gay)

[Renovation]

In this study, "green" was wood at 41% MC dry-basis (29% wet-basis, or % water by weight).

At the risk of asking a simple question, how do your "dry-basis" and "wet-basis" moisture measurements compare with what a prole like me might read on a moisture meter?

 

[Battenkiller]

In this study, "green" was wood at 41% MC dry-basis (29% wet-basis, or % water by weight).

At the risk of asking a simple question, how do your "dry-basis" and "wet-basis" moisture measurements compare with what a prole like me might read on a moisture meter?

Resistance moisture meter = dry-basis MC reading.

https://www.hearth.com/econtent/index.php/wiki/Determine_moisture_content_of_wood/

 

[Battenkiller]

Look at Fig. 7-16, which shows creosote vs burn rate. Green oak burned in the conventional stove (CG) at low rate turned in the worst readings of the entire group.

Clearly, low burn rates are dirtier across the board. What that tells me is that wood should be burned at higher rates, whether it is seasoned or not. Still, if you look at the cold-to-cold numbers, the green oak burned cleaner in the air-tight. It's not only this study that demonstrates this effect, it has been scientifically reported in at least half a dozen studies over the last 30 years. This is exactly opposite of what has anecdotal been observed by residential burners for years. Why is that? Are they burning the stoves correctly while the scientists haven't got a clue? Or does the subjective observation of gallons of creosote coming out of their chimneys influence their interpretation of how it really got there?

Shelton was a cutting edge researcher in this field in the years leading up to EPA Phase I. His work was instrumental (at least indirectly) in the development of the EPA testing protocol. If we assume that none of these scientists knows how to run a stove to get the best efficiency and the least amount of emissions, then we have to throw out the results of the EPA tests entirely, and with them, the quoted numbers used to sell the burn qualities of these stoves by the industry itself. I find it odd that so many would dispute these observations but willingly accept the manufacturers claims that were derived from the test procedures themselves.

Back during my little stint in research, I was a low level employee in training. I was hired because they had the budget dollars, but they really didn't know what to do with me at first. They kept me busy by going through hundreds of peer-reviewed publications to help me get up to speed on the nature of our research (circadian biology). To be honest, I learned very quickly not to get lost in the minutia of the methodology or the hard data itself. I assumed that if a scientist was good enough to get massive NIH and NSF funding, he or she was qualified to set the proper design parameters, develop a workable and repeatable methodology, accurately collect the data, and be able to analyze that data as it applied to their investigations. I also assumed that they were, perhaps, the very best qualified to interpret their own findings. So when I see a study like this, the first thing I want to see is the author's introduction and conclusions (usually in the abstract) and the discussion of the results..

The primary purpose of this study was to examine the effects of fuel and alliances on emissions and efficiency in order to provide a database that would help California Air Resources assess the impact of wood burning heaters on the environment. The conclusions were that burn rate had the greatest effect on emissions, that overall efficiency correlated very highly with low emissions, and that fuel choice had no substantial impact on these emissions in a given appliance. The recommendations were as follows:

1. Appliance design can have a very large effect on organic emissions. Requiring catalytic and other equally effective designs is likely to reduce emissions by a substantial amount -- on the order of a factor of 10.

2. Recommending use of seasoned instead of green fuels will not substantially reduce emissions from stoves. However, seasoned wood can reduce most emissions from open stoves and fireplaces by roughly a factor of two.

3. Catalytic and other low emitting chunk-wood stoves should be used according to manufacture's instructions: otherwise emissions may not be reduced. When operated with the bypass dampers open or doors open, there is little benefit. For catalytic stoves burning at medium to low burn rate will usually result in lower emissions than burning the same amount of wood in shorter but higher burn rate periods. Each kindling phase from a cold start can contribute as much emissions as an entire twenty-four hour day of steady use.

My interpretations of his recommendations are:

1. Appliance effect is huge

2. Fuel effect is negligible

3. Stoves that are efficient at low and medium burn rates are best run constantly, since cold starts alone can contribute as many emissions as running the stove all day.


And the take big home message? These things need to be run properly in order to receive the benefits of reduced emissions and better efficiency.


So, in order of importance: Appliance operator effect > appliance effect > fuel quality (seasoned or green).

 

[Renovation]

Each kindling phase from a cold start can contribute as much emissions as an entire twenty-four hour day of steady use.

I've wondered about that. Bad environmental news for masonry stove burners and others who are doing short, fast burns in big stoves?

 

[Battenkiller]

Each kindling phase from a cold start can contribute as much emissions as an entire twenty-four hour day of steady use.

I've wondered about that. Bad environmental news for masonry stove burners and others who are doing short, fast burns in big stoves?

It's all relative to the stove type. The EPA stoves (and masonry stoves even more) are so low in emissions during a regular run that the "kindling effect" has a much greater skewing of the emissions data than you might find in a conventional air-tight. The benefits far outweigh the negatives here. You are still much cleaner in total emissions starting a modern stove every day than running a conventional stove 24/7. At least that's what the data tells us.

 

[SolarAndWood]

So, in order of importance: Appliance operator effect > appliance effect > fuel quality (seasoned or green).

I assume that if one nails all of the above one is getting the most out of the fuel as well as pumping the least crap up the pipe?

Can we define appliance operator effect? I just mastered keeping the stove running for 7 months for the first time last year. Does this mean keeping a good coal bed, not letting the stove cool and running within the design output of the stove? Or are we getting into things like having the air set right for the amount of heat being sucked out of the stove by whatever means you have at your disposal through the entire burn cycle? i.e. keeping the temperature of the firebox within some tighter operating range through the entire burn cycle?

 

[Battenkiller]

Can we define appliance operator effect? I just mastered keeping the stove running for 7 months for the first time last year. Does this mean keeping a good coal bed, not letting the stove cool and running within the design output of the stove? Or are we getting into things like having the air set right for the amount of heat being sucked out of the stove by whatever means you have at your disposal through the entire burn cycle? i.e. keeping the temperature of the firebox within some tighter operating range through the entire burn cycle?

We all do what we have to in order to stay warm. We overload the stove because we want to wake up to a warm house, we cut the air down too far, we burn marginal wood if that's all we have, etc. As for me, I'm not competing with anyone here. The report verifies to me that these devices run pretty well over a wide range of variables. If you are getting good heat from your stove, I don't think you will be able to improve things much by micro-managing things. A few percent here and there... is it really all that important? The sensible heat losses that result from using a little more excess air than is ideal are well worth the added benefit of extra heat output to me.

In the last years of my father's life, he started to get ridiculous about the way he drove his car. He got obsessed with trying to save money on gas, and would accelerate at an absurdly slow rate, coasting down hills, driving too fast in school zones so he didn't have to slow down and then accelerate again, and so on. Drove us nuts. Did he save money? I don't know... maybe a little (didn't make us any richer when we settled his estate), but driving got to be a huge chore for him, and riding as a passenger got to be something we all dreaded. My feeling is, you buy a decently designed car and just get in it and drive normally. When they come out with a better model, you make your mind up to get it... or not.

I'm perfectly content to be heating with what some folks insist on calling a "smoke dragon". In fact, my stove is the same design used as an "air-tight" in this study, but I burn it 90% of the time with the bypass damper closed as it was designed to be. Maybe I could get a cleaner burn by burning it strictly like an old air-tight, and from the looks of the numbers, I'd have a 78% combustion efficiency (80% burning green oak), 38 g/hr PM burning seasoned oak (but only 20 g/hr if I burned green oak), and a 64% overall heating efficiency burning good, seasoned wood... which is one point higher than the arbitrarily assigned overall efficiency the EPA estimates for non-cats. Of course, even though I could burn cleaner burning wet wood, I get a 6% boost in total efficiency just by switching to wood in the 19-25% MC range. Which is what I aim for.

However, I feel I get more heat for a longer time by burning it the way it was designed to be burned, and I feel that my overall efficiency may be even higher, but I have no way to quantify that objectively. I may be making a bit more smoke (although I rarely can visibly detect it). Can I nail all of the operator effects down to get the absolute perfect numbers all around? Not likely, because when you plug up one leak, seems you get another one somewhere else. The smart operator lives within the design parameters of the stove, and that basically eliminates operator effect entirely. But if he or she goes far enough outside those parameters, operator effect then becomes the most significant one.

 

[BrowningBAR]

If folks would ever get their heads out of their asses about burning at low rates to save wood and get super long burns, we wouldn't even need cats, because the non-cats are superior when burned at high output. I never did understand the smoldering burn. Let it rip or let it go out. I wouldn't burn an oil burner with just the pilot light because I wanted to save fuel. I want heat out of the appliance.

This statement does not make any sense. I am not going to "let it rip" when it is 40 degrees out. And not everyone has basement installs like you. And the pilot light example an incorrect example.

 

[Battenkiller]

I simply mean to give the stove enough air to burn with an active flame. You can let a small fire "rip", you don't have to fill the box and blast yourself out of the house. What I'm against is closing down the air to get a long, smoldering burn. It's dirty and inefficient to burn that way, even if it seems you are saving on wood. Adding just enough excess air to clean things up will not send significant amounts of heat up the flue, and the increased combustion efficiency and heat output will more than compensate for the small amount of lost heat. Feel free to burn the way you want, I'm just making a generalized statement that is supported by the research being discussed here. This would be true for non-cat EPA stoves, but not necessarily for cat stoves.

Should I start a "BrowningBAR Thread" to discuss this further?

 

[BrowningBAR]

I simply mean to give the stove enough air to burn with an active flame. You can let a small fire "rip", you don't have to fill the box and blast yourself out of the house. What I'm against is closing down the air to get a long, smoldering burn. It's dirty and inefficient to burn that way, even if it seems you are saving on wood. Adding just enough excess air to clean things up will not send significant amounts of heat up the flue, and the increased combustion efficiency and heat output will more than compensate for the small amount of lost heat. Feel free to burn the way you want, I'm just making a generalized statement that is supported by the research being discussed here. This would be true for non-cat EPA stoves, but not necessarily for cat stoves.

Should I start a "BrowningBAR Thread" to discuss this further?

"If folks would ever get their heads out of their asses about burning at low rates to save wood and get super long burns, we wouldn’t even need cats, because the non-cats are superior when burned at high output."
-It goes with this statement. Which, again, is incorrect. Why would I want to start a bunch of small fires if I could have one long continuous low burn from a cat stove? And Explain the "non-cats are superior when burned at high output" because I do not see a difference.

 

[Battenkiller]

Well, when you get your very own test flue, you can report back here with your very own efficiency numbers. Folks like those at Woodstock and VC wouldn't be working on hybrid stoves unless they believed that peak combustion efficiencies occur at different burn rates in cats compared to non-cats.

 

[BrowningBAR]

Well, when you get your very own test flue, you can report back here with your very own efficiency numbers. Folks like those at Woodstock and VC wouldn't be working on hybrid stoves unless they believed that peak combustion efficiencies occur at different burn rates in cats compared to non-cats.

The VC clearly states that their efficiency numbers drop when in non-cat mode. And Woodstock is attempting to use both at the same time to increase it's efficiency even further. Not sure how that supports the "non-cats are superior when burned at high output" theory.

 

[BrowningBAR]

Should I start a "BrowningBAR Thread" to discuss this further?

And the point of that thread was to allow you the opportunity to propose experiments to be done to compare the non-cat stove to the Pre-EPA stove as you made several comments that my anecdotal stories of fuel savings offered no proof to greater efficiency. No idea why you took offense to that.

 

[Battenkiller]

Well, you're left to figure that one out on your own. What I do know is that when I was at the Woodstock factory, that was the essence of a short conversation I had with the owner of the company regarding the purpose of the dual technologies. If I misinterpreted him, you can call for yourself to verify I was wrong. I have other things to do besides spending all day defending statements I made in a now-defunct thread.

 

[Battenkiller]

Should I start a "BrowningBAR Thread" to discuss this further?

And the point of that thread was to allow you the opportunity to propose experiments to be done to compare the non-cat stove to the Pre-EPA stove as you made several comments that my anecdotal stories of fuel savings offered no proof to greater efficiency. No idea why you took offense to that.

Ordinarily that would be the topic of a PM I might receive from someone, not a ludicrous public thread that had my user name in the title. Don't worry about offending me, I gots rhino skin, but that action spoke volumes about you AFAIC.