Wood burning stove/boiler

[Dave2002]

Not having the scientific know-how which you mention above, my one very strong reason for being in favour of woodburnrs is that wood is a renewable resource. So we must keep renewing it, i.e. getting energy directly from the sun. We must stop exploiting millions of years of past sun-energy in each mined lump of coal or gallon of oil. Anyone listening to Bill Gates' talks on R4?

It is very debatable whether wood is a renewable source. One of the reasons why coal replaced wood in the 18th and 19th centuries was because there was too much demand for wood, and stocks were being depleted. So coal replaced wood - yet another fossil fuel, until eventually oil and gas came along. Electricity, if it can be generated cleanly, is much better, but there is a big "IF" there.

[oddoneout]

As is so often the case the more one looks into a subject the more there are questions to be answered. A great deal of the talk around green matters such as emissions, pollution free, sustainable, seems to be accompanied deliberately or otherwise by a very narrow point of view. Thus electric cars are 'pollution free' - if you disregard their manufacture and the production of the power that drives them, and other pollutants such as brake and rubber particulates.
There are undoubtedly issues with burning wood or solid fuel, but they need to be viewed from all angles not just one or two. In the same way the suggestion that heat pumps should replace gas boilers overlooks that they are not like for like - not least as a hot water tank will be needed, something which combi boilers eliminated.
Following up an article about the experiment in Gateshead to replace natural gas with hydrogen in a domestic setting threw up more such side issues

https://www.theguardian.com/business/2021/feb/16/first-uk-homes-with-hydrogen-boilers-and-hobs-to-be-built-by-april

https://www.theguardian.com/science/2020/mar/21/is-hydrogen-the-solution-to-net-zero-home-heating

This is being considered as part of the drive to carbon neutrality, but there are questions to be answered about the carbon load of producing the hydrogen. Then there is the issue of what hydrogen combustion produces, and I must confess this was not something I knew (actually that may not be true but my chemistry education was a very long time ago...), namely NOx

https://www.icax.co.uk/Advantages_Burning_Hydrogen_Heating.html

So - domestic use would reduce carbon emissions(depending on manufacture?), but produce another undesirable emission - and in a setting where humans are exposed to it; bring the street pollution into your home?
And linking back to the thread topic, the table here is interesting re NOx https://www.engineeringtoolbox.com/n...ls-d_1086.html

As an aside I notice that educational material from the beeb and elsewhere didn't differentiate between 'air' and oxygen' when discussing the combustion products of hydrogen.

[oddoneout]

It is very debatable whether wood is a renewable source. One of the reasons why coal replaced wood in the 18th and 19th centuries was because there was too much demand for wood, and stocks were being depleted. So coal replaced wood - yet another fossil fuel, until eventually oil and gas came along. Electricity, if it can be generated cleanly, is much better, but there is a big "IF" there.

Well it is renewable when compared with oil, or coal, or indeed peat? Whether it can be renewed within a suitable timescale and in sufficient quantity( and without unacceptable ecological cost) is perhaps another matter.

[french frank]

It is very debatable whether wood is a renewable source.

Linguistically, there is no debate. It is renewable because it can be renewed. It could be argued that coal and peat are also 'renewable', but since it takes millennia for that to happen, by which time the human species might even have been wiped out, the use of the word in that sense would be considered nonsensical.

Timber, generally speaking, if planted and harvested according to a sustainable cycle, is constantly renewed. It's therefore a renewable resource. Contrary to the flawed argument, when you cut trees down you don't have to wait for their replacements to grow. Their replacements were planted roughly 30 years earlier in anticipation. That is sustainability.

[Dave2002]

Well it is renewable when compared with oil, or coal, or indeed peat? Whether it can be renewed within a suitable timescale and in sufficient quantity( and without unacceptable ecological cost) is perhaps another matter.

It's renewable in the sense that new trees can grow in place of old ones. Here are a few details about just one oak tree - https://sylva.org.uk/oneoak/tree_facts.php

I guess it would burn (perhaps it already has ...). I expect some of us would be able to burn that tree in one or two years for heating, so that would be 222 years of growing "used" in a fraction of that time.

Probably some other trees would be better in that regard, but I feel that to use the word "renewable" to any of them in the sense that we really want is just a fraud. You think it's renewable because someone else with a vested interest tells you, and you believe them. Ideally we'd like the rate of production to just about match the usage rate, and hopefully with an overall reduction in CO2 emissions rather than a net increase.

One might still burn wood knowing it's not completely renewable because it might still be the best option for individual circumstances, but don't pretend it's really renewable unless the full life cycle over a realistic timescale is considered, and the data is verified.

[french frank]

Probably some other trees would be better in that regard, but I feel that to use the word "renewable" to any of them in the sense that we really want is just a fraud.

You've fallen into the same logical trap as I've just mentioned. It's the combination of renewability and sustainability.

[oddoneout]

It's renewable in the sense that new trees can grow in place of old ones. Here are a few details about just one oak tree - https://sylva.org.uk/oneoak/tree_facts.php

I guess it would burn (perhaps it already has ...). I expect some of us would be able to burn that tree in one or two years for heating, so that would be 222 years of growing "used" in a fraction of that time.

Probably some other trees would be better in that regard, but I feel that to use the word "renewable" to any of them in the sense that we really want is just a fraud. You think it's renewable because someone else with a vested interest tells you, and you believe them. Ideally we'd like the rate of production to just about match the usage rate, and hopefully with an overall reduction in CO2 emissions rather than a net increase.

One might still burn wood knowing it's not completely renewable because it might still be the best option for individual circumstances, but don't pretend it's really renewable unless the full life cycle over a realistic timescale is considered, and the data is verified.

Hence my comment about ecological cost. And no, I don't think or believe that.

[Dave2002]

Hence my comment about ecological cost. And no, I don't think or believe that.

"You" wasn't addressed at you specifically.

Most of what we do is environmentally damaging, but has to be weighed against other factors. In the limit we perhaps just have to admit that "we wanted to do it".

[Dave2002]

Our wood burner is actually a dual fuel burner. I queried whether it was OK to mix coal or other similar fuel with the wood, and warned not to do that because of undesirable chemical effects.

Either burn wood, or burn smokeless coal.

I wonder whether an occasional burn with the smokeless coal will reduce future problems with the chimney - for example a week or two before having the flue swept.

[gradus]

I don't know how hot smokeless fuel burns or whether it chemically reacts with tar deposits to make them easier to remove, but I know that burning a really hot wood fire periodically will help. The heat transforms the tar 'glazing' into something which has a crisp honeycomb texture, easily removed by the sweep's brush.

[ardcarp]

I wonder whether an occasional burn with the smokeless coal will reduce future problems with the chimney - for example a week or two before having the flue swept.

It is possible to get a product...a powder...which you can add to the glowing embers of a wood fire. It claims to 'crumble' the tar in the flue if done regularly. We just add a couple of lumps of smokeless fuel, which according to our chimney sweep is just as effective.

[Dave2002]

According to the expert from the burner company, smokeless fuel burns hotter - which I imagine might loosen the tar. Mixing the fuels was definitely not recommended. It is also possible that different woods would give different results. Some people have suggested using driftwood, but now it seems that that is also not recommended.

From this table - https://startwoodworkingnow.com/how-hot-does-wood-burn/ it seems that Birch, Beech and Oak burn considerably hotter than some other woods. The articled suggests that Ash also burns hot - around 1000C, but there is also mention of Victorian Ash which seems to burn at a lower temperature.

Smokeless fuels most probably burn even hotter than most woods.

We haven't had the flue swept since the installation of the burner, so don't know how difficult that will be, or whether there will be any problems.

[ardcarp]

Mixing the fuels was definitely not recommended.

Any reason given? Surely a multi-fuel stove......

[french frank]

Any reason given? Surely a multi-fuel stove......

Just looking at the documentation for mine. It specifies fitting a "multifuel liner' so perhaps that is the problem Dave2002 has with his flue - not the correct liner? It looks as if fitting the new flue pipe and the liner cost at least the same, if not more, than the stove.

[oddoneout]

Any reason given? Surely a multi-fuel stove......

Coal and wood have different requirements in terms of air flow etc, and to get proper burning the grate needs to be set up for each - open for coal and closed for wood on my stove(and one of the other models has two side plates that have to be inserted for coal) - so it's either/or. The term multi-fuel means that it can burn a range of fuels, but doesn't imply they can be mixed in one burn. Having said that, of course many users doubtless do mix fuel.
For me a benefit of sticking to just wood is that I don't need to clean out the grate before each use as the wood burns on a bed of ash, and when I do empty it the ash can go on the compost heap or be dug into the garden, rather than having to be externally disposed of.