Research comparing cordwood & compressed bricks (Biobricks)

[Hawk.Hill]

I'm sorry if this is a repeat, I searched and couldn't find this question addressed...

Does anyone know of actual research that compares firewood to the compressed sawdust bricks, like BioBricks (I don't know a term for these)? I am looking for an analysis of both fuels and then a comparison of the results. I assume something exists (so many universities in N America and Europe do research on wood and wood composites), but I have only found claims and statements made by retailers, eco-websites, and manufacturers.

For example...long ago I worked with renewable energy and the idea of how much energy is embodied (or embedded?) in solar panels came up a lot. Back then, a solar panel took about 5 years to generate the energy that had been used to produce it. How much does it take to make, package, deliver, etc. the bricks? My firewood is harvested, processed, and delivered from woods within 30 miles of our home. I'd also like to see a comparison of a cord vs. pallet on btu's. You get the idea...

Why? I am trying to determine the more environmentally friendly option. We burn nearly 6 cords each year (NE Connecticut), and a friend of ours is trying to sell us on the BioBricks...so much less ash, better for the environment, etc, and I saw my wife look interested. That said, our friends just moved here and this is their first year running a VC Resolute stove; also, I'm sure the wife is dead-set against wood because it's "too messy." I think I'm committed to cordwood and would like to see some research to back up my gut -- or convince me to change.

I've already read some excellent posts here about the differing qualities of bricks, associated dangers and warranty issues, and cost compared to cordwood. It's all been very helpful and informed me of things I hadn't considered. So thanks for that.

I plan to search a bit more for info and will post again here if I find something...If you made it to here, thanks for staying with me!

 

[j7art2]

Do you plan on buying them or making your own?

I made about 50 bio bricks this year from shredded newspaper. They work fine, but even with a professional press (which I bent, and returned, mind you) they are ridiculously time consuming. The time it takes me to make 25 biobricks I can C/S/S a whole face cord. Not to mention, it took almost a truckload of newspaper to make those 50.

 

[Fastdonzi]

Let her cut the check for the Fuel/Heat Bill. All the sudden Heating with wood becomes a wonderful idea and she'll be wanting to help Split & Stack...

 

[blades]

On the basis of environmentally favorable - cord wood hands down. See the bio blocks, even if raw material is repurposed, still has to be reduced to a compatible form ( hammer mill) then heated and dried to 8-12% moisture ( if not already in that area), now into the press - package blocks and transport; so there is a lot of expended energy in their creation/ distribution - either electric from some source and/or petroleum or both. They do provide some reduction in landfill quantities but that savings is only a smidgen in the over all picture.

 

[iamlucky13]

For starters, make sure your friend is aware compressed wood bricks usually expand when burned, forcefully enough they can damage secondary burn tubes if they overfill it.

For your main question, the results should be similar to those for wood pellets, which there have been life cycle analyses on. For example, this student assessment I found by searching for "wood pellet life cycle analysis" estimates that production of the pellets uses about 17% as much energy as the pellets contain.

http://publications.lib.chalmers.se/records/fulltext/141464.pdf

It doesn't compare burning cordwood, although I suspect you can find similar assessments for that. I'd expect the overall impact to be close, slightly favoring cordwood over pressed blocks - you've got increased processing and energy input competing against the potential to get slightly better efficiency and slightly lower emissions from a more uniform, drier fuel.

To throw another consideration into the mix, if cordwood is less expensive, which frees up more money to invest in other improvements to your home, like better insulation, a heat-recovery ventilator, or perhaps solar panels, you'd arguably be better off going that route.

I'd also like to see a comparison of a cord vs. pallet on btu's.

This part of your question, fortunately, is more straightforward.

Perfectly dry wood has a heat value of approximately 8600 BTU/pound. At the typical 8% moisture that compressed wood products are dried to, it's about 7900 BTU/pound. A pallet is usually right around 1 ton, so that's 15.8 million BTU per pallet. If you can get them for $300 per pallet, you're looking at $18.99 per million BTU.

For firewood, the BTU per cord output varies, but because the density of wood also varies, it actually usually tracks pretty close to that 8600 BTU/po24.und value (Pine and other high sap woods may be higher, because sap has a higher BTU content, but it's still in the same ballpark). In fact, I think most firewood charts simply calculate a heat value by converting 8600 BTU/pound to a 20% moisture basis (~6800 BTU/pound), and multiplying by the density.

So supposing you can get red oak for $250/cord at a dry weight (20% moisture) of 3600 pounds per cord. That's about 24.5 million BTU/cord, which is similar to what most firewood charts suggest, and works out to about $10.21 per million BTU.

As your friend noted, pressed wood bricks are very neat and easy to use (already seasoned and ready to use), and in fact, quite compact to store. Between their density and ease of stacking, a pallet of Biobricks takes up 3/8 the volume of your cord of oak but offers 2/3 the heating value. Compared to lower BTU fuels, the space savings are even more significant.

 

[kennyp2339]

I'm certainly not a scientist by any means but both products have there pro's / con's with different variables in between; firewood is definitely harder to have a control test environment.
Here's how I think without getting a headache... I shoot for about 5 /6 cords of wood each year. I cut, split, and stack it, it sits for 3 years drying out. When it is time to burn I shoot for a moisture content of 15 - 18 % I know if its that dry then my stove will burn it clean and I will hold the stove to its efficiency standard and grams per hour test to meet the epa rules. If I burn crappy wet wood I'm going to smoke a lot and not get the right heat out of the wood, therefor I will be polluting more than what my stove was tested for.
Bio Bricks - I do like them but I'm not sure how much energy it takes to create them (meaning from the forest to my door step) It seems as though that it requires more energy than my cutting, splitting, stacking and leaving for 3 years. They do burn clean though, actually they burn to good for my stove (I tend to get more smoke with them in my stove because the cat gets overwhelmed and cant burn it all) but the ease of use is fantastic, just a little pricy. I hope that helps, both bio bricks and cord wood are a renewable resource's and carbon neutral if used properly, I just think of the amount of energy it takes to get the final product which is a warm house without fossil fuels.

 

[iamlucky13]

(I tend to get more smoke with them in my stove because the cat gets overwhelmed and cant burn it all)

Have you tried stacking them tighter to slow down the burn?

 

[kennyp2339]

I have, when it gets real cold I turn my t-stat up and have a hotter fire box, that when I notice more smoke, when I burn them on a low setting it's not as prevelant, a few other BK owners have noted similar experiences, the fire is just to rich for the cat to totally burn off, cord wood is not as dense (comparing it to oak and maple) now my father has an epa tube stove and he rocks bio bricks, it literaly looks like has not burning at all on any air setting.

 

[jdogg]

I kinda thought the purpose of bio bricks was to mix with unseasoned wood. At $18 and change per million BTUs I would just burn oil. Last fill was $2.48 per gallon (Feb 16 2015) aprox 143,000 BTUs per gallon. I think LP is like 93k BTUs per gallon. Not sure what LP is going for?

 

[EJP1234]

I have a cat stove, and I have been mixing in Eco Bricks with my splits. I get better burns, longer burns, and a better sustained temp. Next year I am going to get two pallets of them to mix in with the splits during the coldest times of the winter. I really enjoy them and think they are a great product.

 

[mass_burner]

I kinda thought the purpose of bio bricks was to mix with unseasoned wood. At $18 and change per million BTUs I would just burn oil. Last fill was $2.48 per gallon (Feb 16 2015) aprox 143,000 BTUs per gallon. I think LP is like 93k BTUs per gallon. Not sure what LP is going for?

I agree. If you got the wood, burn it.

 

[mstoelton]

One consideration you may not have thought of is that the biobrick type fuels have to be stored in a dry environment without any contact with water whatsoever. If they get wet at all they start to expand and lose their shape. They can be stored in a shed or garage as long as they are off the ground, but will need a roof and splash protection. This could cause some storage issues.

Cordwood on the other hand usually only needs to be top covered and is less moisture sensitive.

 

[kennyp2339]

One consideration you may not have thought of is that the biobrick type fuels have to be stored in a dry environment without any contact with water whatsoever. If they get wet at all they start to expand and lose their shape. They can be stored in a shed or garage as long as they are off the ground, but will need a roof and splash protection. This could cause some storage issues.

Cordwood on the other hand usually only needs to be top covered and is less moisture sensitive.

Yes yea and yes, the bio bricks need to be away from moisture, one of my buds bought a few packs and left them outside directly on the ground with a tarp over them ( insert dumb @&$) them when they blew up to marshmallows he started to tell me how much they stunk.. I said well you didn't think it through enough, it's your fault.. Lol, the nice thing though is on cord of wood equals one 4x4x4 pallet so it has a low space impact