Ash Characteristics of Various Wood Species

[madison]

I have burned locust (I think black locust) almost exclusively this yr, and have noticed a couple of things, most of which have been discussed, ie the locust burns hot, and long.

The unique characteristic which I have not seen discussed here is that the remaining ash is very dense, and requires cleaning out just about every third day. Last season, burning mostly black cherry, birch and some oak, I was cleaning out the stove much less frequently, and the ash was definately lighter/less dense.

When I am out west, burning lodgepole pine, the ash is almost non existent and really light.

Curious if others have noticed differences in the ash buildup and densities with different species of wood.

 

[LLigetfa]

The ashes from Poplar/Aspen are really fluffy like burning tissue paper and there is lots of it. It floats around inside the firebox and settles on the lip of the door. One cannot help but get it all over the house if not careful opening the stove. Same thing when shovelling the ashes out. I could overlook the low BTU value of Poplar. I could even tolerate the smell of it... well maybe not, but I cannot tolerate the ashes.

 

[pen]

Another wood that I find leaves very few coal chunks and more fine powder than other hardwoods around here is Ash.

pen

 

[gzecc]

Madison, I think I need to dissagree with your regarding the locust ash. I burn 50% locust and have very little ash. Do you reburn it, by raking it foreward and giving it some air to burn down more?

 

[begreen]

Locust for me on the west coast is a completely new experience. It is like no other hardwood I've burned. At times it seems more like burning coal than wood. It needs more air and attention, particularly after the secondary burn off stage which lasts quite a long time with this wood. But the ash from it hasn't been a big issue for me. Burning down the coals and therefore letting the stovetop temps drop is more an issue. It takes quite a while to really burn them down.

Just wondering if it could be while burning locust, you are also burning more wood to stay warm?

 

[derecskey]

+1 on lots of locust ash. I have a lot of locust this year, and I'm cleaning out my stove 2x or more a week.

 

[madison]

I do rake the ashes chunks front and center when reloading, which at times seems to make even more "cement" type ash, after that load is burned.

and i agree with the species needing more air, at least for most of the burn, except during the intense secondary period, where it is shut down completely, but only for a short period.

A picture of the wood i am calling black locust: https://www.hearth.com/econtent/index.php/forums/viewreply/250803/

 

[Flatbedford]

I Am burning a Locust/ Cherry mix and I am having a heck of a time burning up the coals. Even with full air, I am running the stove cooler than I'd like to burn up the coals for a few hours every day.

 

[waynek]

I burn a lot of Shagbark hickory and experience excess coal and ash build up in the stoves. I have to shake the grates frequently to settle the ashes in to the ash pit. A small inconvenience when you consider the excellent heating qualities. I very seldom burn it in my cook stove for heating purposes because the coals and ash build up in the small firebox. Now for maintaining a high oven temperature for baking , it is hard to beat. The coals and ash do not present a problem in the open hearth fireplace in fact it is essential to banking the fire.
jackpine

 

[RAY_PA]

I Am burning a Locust/ Cherry mix and I am having a heck of a time burning up the coals. Even with full air, I am running the stove cooler than I'd like to burn up the coals for a few hours every day.

Same here. Which is why I just shovel them out every other day and toss them. It takes too long and the stove temp drops too much to try and salvage what little heat is left in them.

 

[Flatbedford]

I Am burning a Locust/ Cherry mix and I am having a heck of a time burning up the coals. Even with full air, I am running the stove cooler than I'd like to burn up the coals for a few hours every day.

Same here. Which is why I just shovel them out every other day and toss them. It takes too long and the stove temp drops too much to try and salvage what little heat is left in them.

I've done that a couple times too. Now that there is some snow on the ground it is easier to dispose of them.

 

[LLigetfa]

I thought this thread was about ashes? Speaking about which, I need to clean them out eventually. I time the removal in anticipation of colder weather.

Of the three species of wood I burn here; Ash, Poplar, and Birch, only the Poplar ash is bad enough to avoid burning it. On the BTU chart they aren't all that far apart. I have lots of Poplar growing on my land and if it were not for the ashes, I'd be burning more of it. As it is now, when I cull out Poplar, if I need to drop it into my yard and clean up the mess, it goes on my woodpile. If however, I can drop it back into the bush, I just cut it up to lay flat and rot.

 

[madison]

Originally I was more interested in others observations on the "density" of the ash, this locust ash is literally like cement prior to adding water and sand, it is extremely thick, heavy and more importantly, is impervious to air, so the wood laying on the ash/coal mixture burns really slow compared to normal...

 

[WoodPorn]

I can't speak for the Locust but this year I'm burning 60-70% Maple (as opposed to my usual 75% Oak) and am finding the Maple is forcing me to remove the ashes and a portion of the coals twice as often as I usually do.

 

[LLigetfa]

I find that the texture of the ash varies with how hot I burn. Hotter fires tend to produce a coarse heavy ash. The ash up close to the doghouse gets downright crunchy.

 

[madison]

I find that the texture of the ash varies with how hot I burn. Hotter fires tend to produce a coarse heavy ash. The ash up close to the doghouse gets downright crunchy.

Very interesting. As with the blower I added this yr, i do believe that I am burning hotter, but stovetop temps do not reflect this with the blower on 24/7. I was thinking that with burning hotter, I would have less remaining ash, and less dense. Thanks for the comment.

I would add that crunchy and lumpy ash (not charcoal lumps) is another observation with this locust ash, almost like it had water added to it, and then dried.

 

[Jim K in PA]

For the first part of the season I was burning <GASP> white pine and hemlock, which left virtually no ash. What ash was left was relative low density. I had burned through most of the pine by early December when the temps finally dropped, and for the last 3 weeks have been burning a mix of red oak (60%), silver maple (30%) and ash (10%). I have easily twice as much ash, of much higher density, than I did with the pine. I burned for 6 weeks before I got a 5 gallon pail of ash out of the GARN. Now I get about a 5 gallon pail every two weeks or so.

FWIW, I saw about a 20% difference (less) in burn time with the pine, but the temp rise/time was pretty damned close to the hardwood, if not better.

 

[gzecc]

Jim, What hardwood are you burning?

 

[Jim K in PA]

Jim, What hardwood are you burning?

for the last 3 weeks have been burning a mix of red oak (60%), silver maple (30%) and ash (10%).

 

[gzecc]

Jim, I bet your oak is not fully seasoned yet. You are only getting 75% of its heat. It takes two years at least to bring it to 20%. I bet your pine is dry and your oak is not!

 

[Jim K in PA]

Jim, I bet your oak is not fully seasoned yet. You are only getting 75% of its heat. It takes two years at least to bring it to 20%. I bet your pine is dry and your oak is not!

Actually, I have to disagree. What prompts you to say that the oak is not seasoned? I can tell you that it is partially punky, with the outer sapwood (10% at most) being real soft. I have burned incompletely seasoned oak, and know well the difference it makes. I can quickly gauge the wood MC by my flue temps, which are excellent. I am routinely in the 425-475 deg F range before the last pass.

Pine has a GREATER energy density (Btu/lb) than oak, but a much lower physical density (mass/unit volume). What I was referring to was the rate of water temp rise/unit time, not the total rise. I am getting at least 350k Btuh from my hardwood, with a 20+ degree temp rise/hour, with a load on the GARN. Each load is probably 80-90 lobs total, with a burn time of 60-75 minutes/load of mixed hardwood. I would get a similar temp rise with the pine, with a load of about 60-80 lbs, which would be done in 45-60 minutes, albeit with a lower heat load in the shoulder season.

I keep my oak splits in the 4-6" range, while my pine splits are in the 6-10" range. I MUCH prefer carrying the pine, since it is so much lighter, but I have to carry more of it since it has less density per split.

Hopin' this all makes sense . . . ;-)

 

[gzecc]

I only imagined your oak wasn't dry because my pine burns hot and fast. No comparison to my oak. You obviously know what your doing. What kind of pine is it?

 

[Jim K in PA]

I only imagined your oak wasn't dry because my pine burns hot and fast. No comparison to my oak. You obviously know what your doing. What kind of pine is it?

I agree 100%, pine burns faster, and hotter, than oak. That is consistent with the burn times and Btu output I was tossing about. With the GARN, you can take advantage of the heat content of pine even if it burns fast because it absorbs so much of the heat into storage, rather than sending it up the flue.

I have been burning mostly EWP (Eastern White Pine) and some Hemlock. All of it has been split from medium to large logs; 24-36" rounds. Per the Btu chart over at sweep's library, here is a comparison of the Btu content per pound of what we are talking about (after doing a little division):

Red Oak: 6388 Btu/#

White Pine: 6395 Btu/#

Hemlock: 6406 Btu/#

So EWP and Hemlock have a little MORE energy per unit mass than Red Oak, but a lot LESS mass per unit volume (Pine is only 60% of the density of Oak). So, you have to burn a greater volume of pine to get the same total # of Btu's into storage (or your house), but the pine releases more energy during combustion.

Wow - Madison, I am sorry that your Ash thread has been hijacked so badly. :red: