Having written many reports on forestry, and in particular the brutal methods of clearfelling for sawlog only recovery… When burning wood/fibre/biomass, the Carbon Pool/Footprint analysis is littered with contradiction after contradiction.
It is as though there is documentation related to, and supporting, whatever point of view you personally want to take… However, what is not so easy to dispute, and in relation to a couple of the posts above, is cold hard scientific fact, that is more difficult to dilute in favour of alternate opinion… Viz:
The only time Below ZERO Emissions Scenario can occur: ‘Is when fine narrow diameter woody material is burnt in a controlled furnace environment… Instead of being left on the forest floor where they would rapidly rot and release methane gas’
In short, burning all wood will release harmful emissions to atmosphere. However, the toxicity levels from greenhouse gas methane (rotting down method), are far higher than those emitted from a controlled furnace, such as bioenergy in a combined heat & power plant. Hence the below zero calculation. Similar perspective with burning fossil fuels over biomass. They all emit various levels of toxicity into the atmosphere, it is just how the calculations are presented.!
In leaving woody materials to rot down upon the soil, the structure and balance of the soil becomes impacted to such a degree that regeneration of trees and plants are put at risk. Especially on the sites of monoculture softwood plantations (conifer, spruce etc), as soil requires various nutrients to make it healthy, something it is deprived of when the forest or woodland are of single species. If there are any gardeners out there wondering why their flower beds, or vegetable plots are not producing the goods… especially after digging in fresh sawdust-woodchip-bark mulch into the soil… then wonder no longer, check out the nitrogen leaching that occurs between them.!
It is to be remembered most of the monoculture plantations, certainly in Scotland, were brought about by the lack of available timber in the war efforts of the last century, and how vulnerable it left the whole country. It was then a case of plant the fast growing species (softwoods), to service the timber industry (approx 35-40yr harvest period, as opposed to the narrow/broadleaved hardwoods of 75-90yr harvest period). Burning wood in all forms back in the day held little priority.
Thinning out trees serves a few purposes. a) Thinning the canopy lets light through to encourage undergrowth, which in turn encourage insect life, which brings birds, whom bring seeds etc for regeneration and so on.
Main reason for thinning out is to preserve the healthy (stronger) trees to reach full term, with a healthy girth and straight bole for increased sawmill value. This occurs because less competition amongst the stand for growing (straight), upwards for light.
It must be remembered though, that with biomass, it can be replenished quite easily, something it holds advantage over when it comes to fossil fuels that had taken zillions of years to form.
Important to remember that the concern is about three aspects - GHGs, black carbon, and PM2.5. The amount of GHGs is really a function of the mass of wood, though obviously burning releases them more quickly. The problem of PM2.5 is really relative - I don’t think twice about it in the woods of West Quebec, but in an urban environment the problem is different due to source density.
Black carbon is trickier, essentially a component of PM2.5 that also causes climate change. That is where better standards for stoves/fireplaces can make a massive impact. Controlled airflows can dramatically reduce black carbon output. The insert we installed a couple of years ago has a fan system that has dramatically cut down visible smoke.
Remember N_N… if you get a log fire, might make sense to get a stove with a glass front, instead of an open fire type, otherwise the flue will draw any and all hot air/temp from within the room.
Got to agree though, nothing better than looking at a wood log fire roaring away… just a small price to pay putting extra logs on to compensate the draft element
one further thing I like to add. We have just had a new boiler and some relacement (not all) radiators installed for free via a Welsh Government scheme to increase home heating efficiency. No means testing or future obligations, nothing
Basically we were given a free EPC survey, which lead to what measures could be taken to improve that rating by a certain amount. Some properties in our area were given solar panels etc.
Great scheme for us. The downside being there’s always more that can be done but far better than passing the buck to residents.
Reminds of what I was told many years ago. Crematoriums have/need a strict minimum distance between each other… Apparently, when burnt, the human body produces arsenic gas that emits to atmosphere and depending upon weather dispersion (or NOT), can return to land…
Just hoping modern day filtration has resolved that worry
Is that to improve secondary burn? My insert has a fresh air intake piped directly into the stove through an air brick on the side of the house but it doesn’t even have a secondary burn function let alone a fan.
I was on a budget, and bought it from France as wood stoves in the UK are eye-wateringly expensive.
I’m thinking of adding a plate at the back of the fire to create almost a false back to divert air above the fire. The fire has brilliant draft but would like to be using the wood to its full capacity and burning off that extra smoke that escapes the initial burn.
The fan system serves a couple of functions, one of which is improving combustion - essentially secondary burn. It also serves as a form of temperature control, although there are passive dampers involved with that as well. The third function is it provides the primary mode of heat diffusion. The combustion occurs inside an interior chamber that is vented to the outside, any smoke is directed out through a relatively small aperture. The fans flow air around that chamber, and out the slots you can see at the side. So the heated air has no smoke content at all.
Visually, I don’t find it very different from a traditional fireplace, but the efficiency effect is staggering. We use much less wood with these inserts than with an open fire. It is hard to provide a reliable measure, but without question we are using a fraction of the wood and usefully extracting far more energy from it. In the city house, what we had before was basically a wood-fired television, any heat effect was in the immediate area of the fire, and almost certainly offset by increased cold air draw in while venting most of the heat out of the house. By contrast, with this unit we had multiple evenings last winter where the thermostat shut down the furnace while it was -20C or colder, letting the fireplace take over heat load well into the night - yet we used less wood on any given night. More overall, because we used it more. I cannot quantify any savings, because with lockdowns and virtual school, our natural gas consumption was higher than in a normal year.
All that to say, in at least some contexts heat load can be met with burning wood, but doing it with inefficient combustion and sending 90% of the energy up a flue just doesn’t work.
The pine beetle problem though was a direct result of climate change.
Basically recent winters have not been cold enough to kill the beatle (as in the normal cycle). This lead to explosion in population decimating the pine.
It’s quite a hot topic here given the push for native forests vs plantation forests (radiata pine). It has both cultural and climate aspects (Māori heritage and billion trees program).
Radiata pine has short rotation (20 years) it locks up lots of carbon quickly both in soils and biomass. Natives on the otherhand are slower growing and sucking carbon for 100 years. So lots of debate on this topic. Both sides with pros and cons.
The thinning that occurs here is used to help biomas growth for the plantation forests. As you say it’s mainly to improve growth of main stem, but they are reluctant to let it be used for other purposes given nutrients. Monoculture of plantations seen as high risk for climate change and pests and disease.
I was curious about your below zero emission statement (perhaps I missunderstood) but my understanding is that half the carbon captured by a tree is stored in woody biomass above ground. The rest is with roots and micro flora below ground. Given mass balancing surely most applications of wood would have below zero net balance? (Obviously extent varies by tree, climate, soil type) but by simple mass balance is some carbon is captured underground that means there must be less carbon available?
Did you read the story about how, during the Second World War, both sides would build decoy tanks, planes, airfields, hangars etc.
The Germans spent weeks building a large airfield, hangars, planes, vehicles all out of wood in an attempt to deceive the Allies.
The problem was that the RAF caught wind of this from an early stage. They did nothing but waited for the Germans to finish. When the decoy base was finally completed, the RAF sent one sortie over the airfield and dropped a single, wooden, bomb.
