Here are my workings, if you spot any glaring errors, please leave a comment. It's all round figures, I'm not going to bicker about anything more accurate than the first significan figure.
How many trees would we need to clear the backlog?
CO2 in atmosphere = 3,000 billion tonnes (3 x 10^12)
One-third of that is the increase since 1850 = 1,000 billion tonnes, this is apparently the Bad and Planet Warming portion. 1850 level is accepted as beneficial.
World population = 8 billion
Bad CO2 per person = 125 tonnes.
Trees consist of mainly CO2 by mass, plus a bit of H.
My mistake 1 - see comments - about half of the weight of a live tree is water.
An 80 foot tall hardwood tree = 9 tonnes
Let's say an average medium sized tree = 5 tonnes.
(A four foot long section of tree trunk with diameter 2 foot = 1 tonne, so if the main trunk is 16 feet high (two storeys of a house) plus 25% for boughs and branches, that's 5 tonnes)
So we'd need to grow another 25 trees per person to catch up. Sure, those trees will take decades to grow, but you have to start somewhere.
Ongoing emissions
At present, total CO2 in atmosphere is going up by 1% a year.
My mistake 2 - see comments - probably closer to 0.5%
1% x 3,000 billion tonnes = 30 billion tonnes.
30 billion ÷ 8 billion people = 4 tonnes per person.
Let's say each tree soaks up 0.1 tonnes of CO2 per year while it's growing (from above - 5 tonnes divided by 50 years)
That's 40 trees per person i.e. each person plants that many to offset the element of their lifetime emissions which aren't being soaked up naturally. This sort of overlaps with the 25 from above for older people, but hey.
The maths gets super tricky after that. People are born and they die. Older trees would have to be cut down once they reach maturity and are soaking up little additional CO2, then stored somewhere dry - to be replaced by new trees that are soaking up carbon as they grow. So I won't bother looking that far ahead.
Land area needed
25 to clear the backlog, plus 40 for ongoing = 65 per person.
Number of trees in the world = about 400 per person
So broadly speaking, an increase in tree cover of one-sixth
Forests (and presumably other wooded areas) = 31% of global land area
So that would have to go up to 36%, which seems do-able.
Applied to the UK
Decent sized trees per acre = 200. (In the dense wood at the top of my road, there are fairly big trees whose trunks were about 5 or 6 yards apart, so each tree has its own circle = 24 sq yards. 4,840 sq yards ÷ 24 sq yards = 200)
So the UK would need to 65 trees per person/200 trees per acre x 70 million people = 23 million acres, or 40% of the UK land area.
There's not that much suitable land (Scottish grouse moors, marginal farmland and such like) in the UK, but maybe we could get half-way there?
Countries like the UK that don't have enough land area per person and especially city-states like Monaco or Hong Kong will have to buy up some land in Canada or Siberia, where the land costs pennies, and let their trees grow there.
Alternative calculations welcome!
UPDATEs:
1. The two mistakes seem to largely cancel out. Trees only soak up half as much CO2 per tree as I thought, but we only need to soak up half as much CO2 = overall 90 not 65.
2. The Welsh government reckons that they need about 30 trees per person to be 'carbon neutral'. I assume (rightly or wrongly) that this is just to deal with ongoing CO2 increases and not clear the backlog, so ballpark, our figures are in agreement.
Sunday, 30 January 2022
Trees and CO2 capture - fun with numbers
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23 comments:
I don't think you are right to say CO2 goes up 1% per annum, it is about half that, net. Emissions are indeed 1% but half of it goes into various sinks. Currently the CO2 cycle, so-called, is not what you'd call well-described. We don't know which sinks absorb what quantity with enough accuracy to do this sort of calculation accurately. And, of course, it is all interlinked..
Trees consist of CO2. With a bit of H.
This is where the Warmists confuse us. Conflating Carbon and Carbon Dioxide.
Is your H also combined with Oxygen?
Me, I think that Oxygen is the bad element.
Worst greenhouse gases? Water vapour and CO2.
What is common?
That sneaky Oxygen. Just sits in background while poor old Carbon takes the flak.
Mony a mickle makes a muckle. There are lots of little bits of waste around the UK that could grow a few trees and there are all the miles of hedgerow which could also be used, plus more hedgerow could be planted. Ever since WWII, the government has pursued a cheap food policy. Farms have had to become ever more efficient, but that efficiency has been measured in how cheaply they could produce food, not how much food they could produce per acre of land. That has resulted in the removal of thousands of miles of hedges, much of which could be put back without impacting efficiency in terms of food per acre.
GT: "I don't think you are right to say CO2 goes up 1% per annum"
I did it this way. CO2 levels forty years ago were 340 ppm, now they are 420 ppm. That's 24% over 40 years, actually closer to 0.5% than 1%, but I rounded up. Could round down to 0.5%, so instead of 25 for the backlog it's 10 or 15.
Dh, that is an excellent theory!
B, farmers want to maximise profit. Land is subsidised, labour is heavily taxed. So output per unit labour has improved; output per unit land has worsened.
My example is - look at allotments. Land is expensive to rent (£50/year for maybe one-tenth of an acre allotment compared to £100/year for farmland) and there are people beavering away all the time (their own fruit and veg and the labour inputs being 'hobby' are untaxed).
So heck knows how much we could turn over to trees (for a given amount of total food grown) if we used the best land properly - like the Dutch, where it's covered in polytunnels, or like in the old days where it was all labour-intensive small holdings??
But I think 40% is pushing it.
The point is that farmers don't profit, only landowners profit. Yes, a lot of farmers are also landowners, but they are profiting as landowners, not as farmers.
I think a living mature tree better approximates to a vertical column of water compared to a vertical column of molecular C. At least that's what I've found when I weighed some freshly logged wood and then again 3 years later when it had dried.
Which is good because while it's growing that water might otherwise enter rivers and then the sea.
But to your point about UK massively increasing forest cover - easily done and already happening - but could go further and quicker by stopping the subsidies to farmland owners based on land area and permitting GMO. Let's do it.
From https://www.sciencedirect.com/science/article/pii/S0301479702001767 , "The total length of the main five types of field boundaries in GB was estimated to be around 1.5 million kilometres at the three periods. The two most widespread categories were Hedge and Fence, i.e. about 75% of the total length of boundaries at any time."
75% of 1.5 million kilometres is 1.125 million kilometres If the trees are spaced 5m apart, that is 225 million trees. At a wild guess, say 15% of those trees are already there, that would be approx 200 million new trees, almost half your new tree requirement and you haven't started planting up the verges of all the roads yet.
Well, that was easy wasn't it? What's more, it's probably less than you have calculated as grass consumes more CO2 than trees. Also, there is 'enough land' in the UK. Broadly.
So yet again we find that the CO2 alarrmists have not thought things through. Probably because they don't want to.
B, let's not get into that.
AC, excellent point. Let's say live tree is half water (I dried out some logs and weighted them after a year). Happily, this mistake is equal and opposite to the mistake pointed out by GT above, so the end result is unaffected.
B, thanks for looking that up. But I'm not sure it gets us much closer. Assuming my 65 trees/person to be 'about right', 65 x 70 million = 4.5 billion trees. So your 200 million extra trees barely touch the sides (as desirable as they may be for other reasons).
L: "grass consumes more CO2 than trees". Can you get 5 tonnes of grass from 24 sq yards? I doubt it, my back lawn is 50 sq yards and it's a wheelie bin full when I mow it. Also, grass is constantly growing, dying and rotting again, it doesn't lock it away semi-permanently like trees do.
MW. Apparently because grass keeps growing and getting cut/eaten it does take in more CO2 than a slow growing tree. The internet told me that so it must be true...
L, the internet can say what it likes. Quite possibly growing grass soaks up more C02 per unit area than growing trees. But it then dies and rots or gets eaten and the CO2 gets breathed or farted out again.
The good thing about trees is they lock in CO2 semi-permanently, then you cut them down at maturity and store them somewhere dry. Until the whole country is covered with drying logs.
Mark, whoops, out by an order of magnitude.
Farts are CH4, methane, which, yes, I know, is supposed to be a greenhouse gas but 1) how do we know? 2) this is all about reducing CO2, not greenhouse gases. If we were serious about reducing greenhouse gases we should be tackling the real offender, H2O and 3) there's even less CH4 in the atmosphere than there is CO2 (1.9 versus 412ppm). Added to that, the vast majority of the carbon in grass eaten by herbivores comes out of the other end as shit, which ends up as humus in the soil.
B, CH4 is a GHG just as much as CO2, i.e. not at all.
Nonetheless, I just wanted to work out whether CO2 offsetting by allowing trees to go is a viable option (certainly the cheapest and easiest) and it would appear that it is.
Welsh govt says 30 trees/person, I reckon it's more like 90. Both are do-able.
Then when temps keep rising even though CO2 is going down, it will be Emperor's new clothes time.
Yeah, but they won't. Soon the Earth will leave its warming cycle and start cooling again, all the Alarmists will shout "hurrah, didn't we do well, see, deniers, we were right all along" The cooling will go on and everyone will round on the Alarmists and say, "It's getting colder and you're to blame".
Update 2): there's so much bollocks in that article, I wouldn't know where to start. Basically the Welsh are upset because the Saes are trying to buy up their land and that always pisses them off.
Google censors yet more science, in the name of science.
https://dailysceptic.org/2022/02/04/this-is-the-satellite-temperature-graph-google-doesnt-want-you-to-see/
The biggest problem is where do we put the trees!
There is not much land which is not useful to either people or wildlife.
A lot of rare butterflies for example in the UK live in grasslands.
B, going by the Roman and Mediaeval Warm Periods, we're in for a few centuries of nice weather.
"Basically the Welsh are upset because the Saes are trying to buy up their land and that always pisses them off."
There's an excellent article on that topic here!
LF: "The biggest problem is where do we put the trees!"
Exactly, I thought I covered that. If my numbers are correct, we'd need to allow trees to cover 40% of the UK, which is clearly not do-able. So we'd do what we can and then buy up cheaper land in Canada or Ireland or heck knows where.
6% worldwide seems tricky to be honest but I am not sure.
LF, 6% seems high, but it must be do-able, seeing as a few thousand years ago trees covered half the land area, we just chopped down a lot for farming.
Roughly speaking, Russia is 10% of world land area. Canada, Brazil and USA are 6% each. Australia and China are also about 6%, but they are mainly desert AFIAA.
Of that list of countries, Canada is the only trustworthy one, and is already half trees. So that's 3% straight out of the blocks and the rest we can do elsewhere. Like Ireland and Scotland and Scandinavian countries, which are basically empty.
MW, you really think Canadia is trustworthy? Seriously?
RS, compared to USA, Brazil or Russia? Definitely.
Talking to my Indian colleagues recently, they were saying how corrupt their system is. I replied "but ours is just as corrupt. Just that we have legalised the corruption". They kind of got it, but would not concede because it meant they could no longer make way with their blame game. It's pure psychological denial of course. Would you fall into the same category?
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