Wood burner emission comparisons
- Thread starter rik_uk3
- Start date
That is really interesting. I have just been thinking about passive wood gas fired vs fan driven wood gas fires in terms of smoke produced and how well the wood is turned into ash.
When everything is perfect the bushbuddy seems to work well, but it still seems to cycle through smoky periods where it isn't burning that well. In contrast I can get a more consistent burn, with consistently less smoke than the bushbuddy from the honey stove
But the fan driven spenton consistently burns with little smoke. So I have recently been wondering if a fan driven non wood gas stove might be just as efficient as a passive wood gas stove.
This paper suggests this may be the case and that stoves like the Spenton, biolite and vital may be that little bit more environmentally friendly than the alternatives.
Not that it's likely to be that simple, but interesting nine the less.
Graham
When everything is perfect the bushbuddy seems to work well, but it still seems to cycle through smoky periods where it isn't burning that well. In contrast I can get a more consistent burn, with consistently less smoke than the bushbuddy from the honey stove
But the fan driven spenton consistently burns with little smoke. So I have recently been wondering if a fan driven non wood gas stove might be just as efficient as a passive wood gas stove.
This paper suggests this may be the case and that stoves like the Spenton, biolite and vital may be that little bit more environmentally friendly than the alternatives.
Not that it's likely to be that simple, but interesting nine the less.
Graham
It would be interesting to see where a canister powered propane/butane burner would sit in comparison.
It's much more complicated of course as you need to factor in the production of the gas, the manufacture of the cylinders, and the transportation from factories to the user.
It would still be interesting to see a comparison however.
Graham
That paper is quite old and things have moved on, some of the newest stuff is incredible..
To get efficient, consistent gasification of fuel in a wood stove it needs draw.
To get draw, a fan or a chimney effect is needed. Without enough draw, the gases cant get through the fuel stack at the optimum rate and incomplete combustion results.
A fan solves the issue of having to cart around a chimney to push air through and makes things much easier to get good combustion. An efficent gasifying wood stove is actually more efficient than most of our modern heating technology and gets up to 90% efficiency.
FWIW, unless the bushbuddy is top lit and the fuel stacked properly, it isnt gasifying-its simply an efficent fire. The efficiency of a gasifying stove comes from burning the fuel in an oxygen controlled environment-the volatiles are driven off from the wood and burnt remotely from the fuel, leaving a good percentage of charcoal which is then burnt to provide more heat. It effectively burns the wood twice. Burning the fuel straight to ash is simple combustion, as in a honey stove for example.
The reason why the bushbuddy smokes is because it is choked by the inlet holes. A fan draught gasifier should be recieving 5-1 primary(bottom holes) to secondary( top holes) ratio of air by volume.
The Bushbuddy is 3-1 to compensate for the air flow resistance of the fuel stack and explains why it burns perfectly sometimes (more fuel in usually) and smokes at others.
If you want to find out about adding a fan to a fire, check out 'fan forges' ; theyre very powerful but not very efficient IME compared to a gasifying wood stove -passive or not.
To get efficient, consistent gasification of fuel in a wood stove it needs draw.
To get draw, a fan or a chimney effect is needed. Without enough draw, the gases cant get through the fuel stack at the optimum rate and incomplete combustion results.
A fan solves the issue of having to cart around a chimney to push air through and makes things much easier to get good combustion. An efficent gasifying wood stove is actually more efficient than most of our modern heating technology and gets up to 90% efficiency.
FWIW, unless the bushbuddy is top lit and the fuel stacked properly, it isnt gasifying-its simply an efficent fire. The efficiency of a gasifying stove comes from burning the fuel in an oxygen controlled environment-the volatiles are driven off from the wood and burnt remotely from the fuel, leaving a good percentage of charcoal which is then burnt to provide more heat. It effectively burns the wood twice. Burning the fuel straight to ash is simple combustion, as in a honey stove for example.
The reason why the bushbuddy smokes is because it is choked by the inlet holes. A fan draught gasifier should be recieving 5-1 primary(bottom holes) to secondary( top holes) ratio of air by volume.
The Bushbuddy is 3-1 to compensate for the air flow resistance of the fuel stack and explains why it burns perfectly sometimes (more fuel in usually) and smokes at others.
If you want to find out about adding a fan to a fire, check out 'fan forges' ; theyre very powerful but not very efficient IME compared to a gasifying wood stove -passive or not.
Clearly its going to loose out on a life cycle energy balance vs a sustainable wood gathered to runa honey stove or similar but the comparison in by products of partial burning and their life effects make the whole Thing interesting.
At work we are designing industrial scale gasifiers and fired heaters. The issues are the same.
Tepee,
Can you explain how you get consistent gasification with the bushbuddy, because I am obviously not very good at it, hence me questioning how much benefit I am actually getting from it.
I would also be interested in some pointers to the incredible new stuff.
Thanks,
Graham
Can you explain how you get consistent gasification with the bushbuddy, because I am obviously not very good at it, hence me questioning how much benefit I am actually getting from it.
I would also be interested in some pointers to the incredible new stuff.
Thanks,
Graham
I assume that although the issues are the same, it's still going to be easier to get consistent results at an industrial scale, compared to the variation in conditions and users with bushbuddy's or even the domestic scale stoves in the paper.
Graham
If the fuel is stacked into the burn chamber and lit from the top, it will burn at at its most efficient. The key to gettiing it to work is to make sure that the fuel stack is dense enough to stop hot embers falling to the bottom and ignitin gthe fuel there. If its too dense though, air cant pass through the fuel stack. Theres no hard and fast rules as all fuel is different. Making sure the fuel is all the same size and pencil thickness is a good guide.
For me though, its too much of a faff to cook on like this. In terms of effort, it much better just to have normal little fire in it and take advantage of its clean burn.
Theres lots of effort and being put into biomass energy and its moving from passionate open development to bigger business it seems. Bioenergy lists is a good place to look with people all over the world developing stoves, but the site is down until they get new software
. Might be worth keeping a check to see when it comes back on.IMO, the Biolite stove is impressive and if it sells well, it'll change the world.
The Champion Tlud stove has been tweaked and now burns incredibly cleanly.
Rocket stoves are burning more cleanly than ever, too many to list.
The worlds lightest gasifier is worth a look-made of ally foil
Theres also the Worldstove site with its very clever co-axial gasifier.
You design for a spec of feedstream. On a fired heater thats quite definable but for a municipal or sorted waste feed to a gasifier its hard to predict how the mix will change of the twenty to thirty year design cycle. Some of our fired heaters though are still running well into their 60th years.
The issue with any bushcraft hob as you say is that the feedstock is completly variable, dry wood, wet wood, sappy sugary wood etc. the OP article research is trying to address the smog from three brick fires across rual asia and african contenents.
I'm torn between using a little unleaded petrol stove that has an energy optimised supply infrastructure, clean burn flame, little soot or CO produced against perhaps more sustainable (non fossil fuel) burn of wood on an open fire that smells better (woodsmoke) feels greener but perhaps damages the environment via warming affects of the gases produced or particulate impacts. Not to mention the odd scraps of plastic or coated paperwaste that people often throw into the fire. Who knows what mix of long living molecules that releases when partially combusted at the low temperature of a wood fire.
Best bet is to chew nettles or eat all your food cold. I'm not ready for that though. Most recently i've used propane and butane as it burns the cleanest for boiling water and wood for zapping food.
Thanks for this, and it's nice to know you too find getting the bushbuddy to gasify is too much of a faff as well. I need to read more about the efficiency and the pollutants produced. Not that I believe my stove burning makes much difference, but I like the principle.
I agree about the Biolite, and I hope to get one once the first generation has been better tested in the wild, but my spenton works well, fan driven by solar power, and the fire box enclosed so it's still good in windyish conditions. But it's abut bulky and heavy.
Graham
As I just said to Teepee, I suspect our hobby use of stoves isn't going to make much difference. With no expertise at all, my gut feeling is that if you look at the whole life cycle, the small wood burning stoves, which use tiny amounts of wood, whether gasified or not, seems a greener approach. But I would be interested if any one has any figures that might suggest the correct answer?
Graham
