Fossil Fuel or Not? – Not a simple choice.


Should we use it or not?  I mean, we are supposed to be an eco place, right?  So we should do everything by hand, so we don’t use fossil fuel, and thereby end up making a bigger impact on CO2 reduction, global warming and all that?
Well, if you look at the numbers, it isn’t that simple.
First of all, let us look at wood for heating.  We cut our own wood, every year, using a petrol-powered chainsaw or two.  Now, if we didn’t do that, and cut the trees down with a hand-saw and cut them up with a hand-saw, would we use less CO2?
This probably takes about 6 UK gallons of two-stroke petrol, each about 5 litres, and each litre uses about 10kwh of fossil-fuel energy.  That’s a total of 10x5x6 or 300kwh of energy.  Over the course of the year, this saves us approximately 35% of our gas bill, which is about 100kwh per month, or about 12,000kwh per year.  We save just over 1/3 of this, so about 5,000kwh per year by using wood fuel in our fire (which only heats the house, not the garage/workshop, at present).
But supposing we had to cut trees down and cut them up by hand?  Now, we are busy people, and have a day job as well as the woods.  And I am not in the best of health, something which is not my fault.  So if we did this by hand, we’d probably only have about half the amount of wood available, and so could only save about ½ as much, or 2500kwh per year.  We would reduce our fossil fuel use in petrol for the chainsaw by 300kwh, but increase our gas use by 2500kwh (and we keep the house pretty cold, have it properly insulated etc etc).  So we aren’t really saving anything if we do it this way.  Sure, if we only worked the land, and had all the time in the World to coppice trees, then it would be a different story.
So we think the use of petrol chainsaws produces a net reduction in our CO2 consumption and a net gain in our use of sustainable energy.  It is a compromise that in an ideal world we wouldn’t have to make, but we make it, and it works for us.
Likewise, we use a tractor in the woods.  Fossil fuel again.  But look what we get for that fuel!  We can clear dense bramble overgrowth and make new areas for establishing coppice and new habitat.  We can mow our meadows.  We can clear the wild flowers away from our newly-planted little trees.  We can move logs for habitat and fuel that would otherwise be beyond our capability.
Now, suppose we didn’t do this?  We already tried coping with managing our woods by hand, using either a small petrol strimmer, or a scythe.  It was fine in winter, until Spring happened, then we had no chance at all.  There are only 2 of us and 20 acres, and, as I said above, we have a day job (that funds the woods), and I am poorly.  20 acres is approximately 7 hectares, which, if our woods were average for the UK, would fix 35 tonnes of CO2 every year at a rate of about 5 tonnes per ha.  According to the Forestry Commission, this is about 2kg per average tree.  But if we didn’t do this, the loss rate among our saplings would be much higher, because inevitably, we would not be able to clear the undergrowth around all of them.  And those that survive would grow much slower due to competition from the herb layer.
It is realistic to assume that without assistance, the annual loss in our newly-planted woodland would be roughly 30% (with assistance it is down to 5%).  So an increased loss of 25%.  This is a modest estimate.  This would equate to about ¼ of 3.5hectares of area loss, so about 0.9ha – or 5 tonnes of CO2.
The tractor uses approximately 200 litres of fuel, at about 10kwh per litre, so 20,000kwh in a year.  This is approximately 0.5kg CO2 per kwh, or about 10 tonnes CO2 per year.   On the face of it, more than we gain by not allowing the trees to die.
But it isn’t that simple.  Dead trees break down and release CO2.  And it doesn’t take into account poor growth in other trees that don’t die, but also don’t grow well, and don’t fix much CO2.  And it takes no account of the benefits in terms of our meadows, or our habitat, or anything else that we do to improve the site for wildlife.  It also doesn’t take into account that this would be a compound loss i.e. 35% per year.  This is likely to account for at least as much CO2 again, annualised over a 5 year period.  We are likely to be at least carbon neutral, but with a much better outcome for the habitat, which would stay in its sorry state without our help to restore it to a much more natural habitat, and remove the impact of many years of animal grazing and other husbandry that has an adverse impact on the woodland structure.
AND it doesn’t take into account the CO2 fixed by our existing ancient woodland, which, at another 3.5ha, will more than offset the difference – some is slow-growing old wood, but some is coppice and newly-planted coppice, so we would expect it to be around the average 5 tonnes CO2 fixed per ha, or another 17,500 tonnes CO2.
So we are responsible for a net reduction in CO2, even though we use a high-consuming tractor for some of our work.
There are other benefits too. We couldn’t have visitors if we don’t create and maintain paths.  Why not?  I’m happy to walk off paths, and scramble through the woods, but the fact is, that if we don’t provide paths, most people won’t come.  Disabled people can’t come without good paths.  And we can’t satisfy the requirements of insurance and risk assessment for public use.  Allowing people to come to our woods is important to us, and it is important for people to see ancient woodland, and learn about it – and we are one of the few ancient woodlands available locally.
In an ideal world we could get this done without using carbon.  But the fact is, we can’t.  If we left things alone, the woods would deteriorate further, and we would lose habitat, and species, and diversity from an area in which these are incredibly valuable.   We don’t use more than we need to.  We use quite a minimum intervention approach in our woods.  We do a lot of things by hand too.  We are not shy of hard work – coppicing is VERY hard work, even using a chainsaw.  And one day we may have tractors, Land Rovers and chainsaws powered by sustainable electricity – we can but hope.  At the moment, we just have to make compromises to get things done.  Not without thinking about it, but the numbers still add up.

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