Eucalyptus biomass

I’m sure you can tell that I am a big fan of Eucalyptus biomass and firewood.

Being a newcomer to rural Ireland, I was quite surprised that some households in the rural community were buying firewood ! To me it appeared that they could simply grow their own. A cheap form of winter fuel in the form of Eucalyptus biomass, either for firewood logs or coppice.

My experience with turf has been good, though turf does leave a lot of fine ash to be cleared up most mornings. Burning timber, provided it is dry provides equivalent heat with a fraction of the ash. Although I haven’t yet, as of September 2018, been able to verify that Eucalyptus firewood leaves even less ash than most other varieties such as Ash and Spruce, this is what I am led to believe.

Eucalyptus biomass

Eucalyptus is ideally suited to biomass in Ireland due to it’s fast growth rates. Many varieties of Eucalyptus will coppice, giving a high yield over a thirty year lifespan. Eucalyptus is considered to be a perennial biomass crop, i.e. a harvest can be taken each year.

Because Eucalyputs can grow in a wide variety of poor soils, with many varieties thriving in wet ground, they are a commercial proposition on degraded land which otherwise would yield no revenue. Again I am surprised that growing Eucalyptus biomass isn’t more popular.

How does Eucalyptus biomass compare with other varieties as a firewood crop.

Below are my own personal experiences and results of research.

My experience:

  • It’s very noticeable when you burn Ash, just how long it lasts and how much heat it gives off. Likewise when you burn softwood like spruce, it’s very evident how much more quickly it burns, though it does burn hot.
  • Wood needs to be dry before it will burn well. This is important ! Seasoning is a relative term. The summer of 2018 was particularly hot, and a small Irish Alder I cut up for firewood was dry in a few weeks ! It brunt well, not as good as Ash, but certainly it is acceptable firewood.
  • As below wood becomes fibrous and tough as it seasons. This is my experience of Ash and Spruce. The chain saw cuts through it with ease when it’s fresh. Try cutting it with the chain saw when it’s been drying for a few months and you would think the saw is blunt.

My research:

  • Generally conifer, Ash, Oak, Beech and the other mainstays of the Irish firewood market need to be seasoned for at least a year unless kiln dried. It’s suggested that Eucalyptus be seasoned for a couple of years. It grows at least twice as fast as the other species, so that shouldn’t be an issue. NOTE what I say above though, everything is relative and subject any tree wood to hot dry conditions and it will dry out more quickly than in cold damp conditions.
    My current view after burning some of my Eucalyptus wind fall is that it will require no more seasoning / drying that Ash, Spruce or Alder all of which I have personally cut and burnt.
  • BTU values for Eucalyptus suggest equivalent heat value to Oak, though there are over 700 varieties which grow in various habitats from the coast to the high mountains and everything in-between. Therefore it is likely that the BTU values will differ depending on the variety. A general rule of thumb would be the heavier the wood the more dense it is, and therefore the more heat it will produce per given volume. White Ash produces about 60% more BTU than white pine and about 30% less than Oak. NOTE these figures will always only be a guide ! trees even of the same variety will differ to some degree or another.
  • I would generally consider Eucalyptus biomass coppice varieties such as Gunnii to be equivalent to Willow (sallys). The Ash comparable firewood log varieties as the Nitens, Viminalis and Johnstonii.
  • Those that burn Eucalyptus as firewood love it. The caveat is that you need to process it within a week or so of cutting it down, assuming you are splitting it with an axe. DON’T leave three metre logs in your mini forest to season. The wood will become fibrous and tough. As above though, my experience has been similar with native species such as Ash and Spruce.
    If you process it within a week or so and store it in a log store with a poly carbonate roof, then it will dry out in a year easily. Β Cut up logs will have more surface area exposed for moisture to evaporate from. The shed / greenhouse I built in Scotland could reach temperatures of over 50℃ during the summer, and often over 30℃ on a sunny day during the winter. It was a simple wood structure, though with a polycarbonate roof and windows.

Quotes from firewood for life Eucalyptus Firewood 

  • “Overall, eucalyptus is a good choice for firewood. The wood produces heat somewhat comparable to oak and it leaves a nice bed of hot coals.”
  • “Eucalyptus firewood is known for burning very hot.”

World Forest Industries suggests that Eucalyptus has a BTU of 34.5 with Live Oak having a BTU of 36.6. Most of the species are native to the US. One that is shared with Ireland is Sitka Spruce which has a BTU of 21.7.
A personal comment on the BTU value for Eucalyptus would be that it does not state which variety of the 700 was tested.

Climate change

Is having an impact. This is no longer a debate. Sustainable heating fuel is therefore going to be more valuable in the near future. Ash dieback is affecting the mainstay of the Irish biomass (firewood) industry, and a good substitute, in fact a better alternative is growing Eucalyptus trees as Eucalyptus biomass.

With the right preparation of the ground and planting from large plugs, Eucalyptus will establish quickly and grow rapidly. If you are planting small plugs, then they will still establish quickly, though you will need to do vegetation control for a year until the trees are large enough to outpace the surrounding vegetation.
Some of Eucalyptus varieties, notably the Swamp Gums and also Regnans grow so vigorously that even the small plugs will require minimal vegetation control.

Eucalyptus planted for biomass and firewood is a sustainable carbon neutral fuel.

After what can only be described as a very poor year for growth generally; food crop yields are about sixty percent of average in the 2017 / 2018 season, this is what my mini forest looks like, with several trees approaching two metres after eighteen months.

Bog Lizard - Eucalyptus Viminalis biomas mini forest 271018
Bog Lizard - Eucalyptus Viminalis biomas mini forest 271018 detail

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