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Green Building Bible, Fourth Edition
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Data and monitoring: Cars, houses and trees

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1 to 29 of 29

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      CommentAuthorSteamyTea
    • CommentTimeAug 4th 2012 edited
     
    Was pondering while working on a 'new marine energy device' and also from a comment I made the other day about maybe tackling transport would be a faster way to reduce CO2 than tackling housing.
    So decided to try and calculate how many trees I would need to plant for the mileage that my car has done since it was new.
    It is a ten year old Scenic, has emissions of 157g/km (http://carfueldata.direct.gov.uk/search-new-or-used-cars.aspx), has done about 200,000 km.
    Trees seem to absorb CO2 at this rate http://www.carbon-info.org/pressrelease/_documents/100%20year%20absorption.pdf

    So my car emits about 3.1 tonnes of CO2 a year. 31 tonnes so far then.

    Now a tree seem to have a sweet spot when they are 20 to 55 years old, absorbing 14 kg/year.
    At the lower end, between 0 and 10 years (the age my car has been on the road) it is 0-5 year 2.5 kg/year and 6-10 years it is 10 kg/year.

    So to absorb all the CO2 my car emitted in year 1, I would have had to plant 1240 trees.
    The next 5 years those 1250 trees will be absorbing at twice the rate that I emit, so I could cut half of them down (620) and build with them, but not burn them, or just plant a few less in the beginning, about 500 of them.

    So to balance all that mileage I need a pretty large wood. Tree density is about 2,500 trees per hectare (http://www.forestry.gov.uk/forestry/INFD-6ARG5Y), so I would need 1/5th of a hectare (half an acre).

    Now my house, that is all electric now uses 4.5 MWh of EDFs finest a year, Grid electric is about 0.45 kg/kWh, so I emitted 2 tonnes last year, down from 4 tones when I moved in 7 years ago. Let us assume a mean of 3 tonnes/year.
    That is about the same as my car emits, so I would need to plant just 500 trees again. (edited as Ed found the error)

    There are about 34m cars and 25m houses in the UK, http://www.rac.co.uk/news-advice/motoring-news/post/2011/4/record-34m-vehicles-on-uks-roads/ and http://news.bbc.co.uk/1/shared/spl/hi/guides/456900/456991/html/

    So if we could halve the number km travelled or halve the CO2 emissions of vehicles we would be quids in compared to halving the emissions from houses.

    So I ask the question (other than check my sums), are we tackling the wrong area as we swap houses rather than replace them but we replace cars fairly often.
    Is it feasible to reduce the energy use in cars and houses at the same rate (edited to a second question because of sums error earlier).
    • CommentAuthorEd Davies
    • CommentTimeAug 4th 2012
     
    Posted By: SteamyTeaSo my car emits about 3.1 tonnes of CO2 a year.
    Now my house,... Let us assume a mean of 3 tonnes/year.
    That is about a tenth of what my car emits,

    How's 3 a tenth of 3.1?
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 4th 2012 edited
     
    Whoops, new something was nagging at me :shamed:

    So the house and car are about the same, shall edit that when back from sailing.
    • CommentAuthorRobL
    • CommentTimeAug 4th 2012
     
    We're in a similar position -
    One car family with a 13 year old mondeo, relatively low 7k/year mileage, total 90K miles - so far so good..
    208g CO2/km, clarkson would love it :-)
    From database figs ST linked to, it emitts 2.3tonnes CO2/year. Putting that in context:
    Our elec is 2700KWh/year, ie 1.2tonnes CO2/year
    and our gas is 7000KWh/year ie 1.5tonnes/year.

    Maybe I should lay off the insulation, and go buy a new car ?
    Or maybe become a vegan? Allegedly this saves 1.5Tonnes CO2/year

    Feel free to offer suggestions for the next RobL motor! Failing that, dietry advice welcomed :-)
    Car spec: Large family hatchback, used for motorway journeys, 2nd hand around £7K.
  5.  
    Posted By: RobLOr maybe become a vegan? Allegedly this saves 1.5Tonnes CO2/year
    But how many additional tonnes of methane does a vegan emit per year? :bigsmile:

    David
    •  
      CommentAuthorDamonHD
    • CommentTimeAug 6th 2012
     
    I do hope that it ain't tonnes(!), and in any case with less meat in my diet I think that any current duvet hovering is rather less unpleasant than before, though it may not be my opinion that matters here... %-P

    Rgds

    Damon
    • CommentAuthorJoiner
    • CommentTimeAug 6th 2012
     
    For anyone who wants to follow the last two onto the naughty step for REALLY bringing this discussion down to its lowest possible denominator, at least take the time to inform your opinions here...

    http://www.veganfitness.net/viewtopic.php?t=8830

    :crazy:
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 6th 2012
     
    What was that book Tom mentioned :thumbup:

    I find if I hold on to them long enough they go solid. If you don't believe me, give it a go.
  9.  
    Planting trees is lots of fun, very satisfying to see them grow, wildlife, windbreaks, change with the seasons, eventually firewood, great for the soul. Highly recommended - include plenty of tree space on your 'green build' plot plan!

    But (for the couple of hundred I planted) about 2/3 of them died in the first few years (mostly eaten by rabbits or drowned by nettles). Steamy, did your calculations include a mortality rate?!

    I guess this is as Nature intended, a single mature tree produces zillions of seedlings, so they cant all grow to maturity, and rabbits and nettles do support worthwhile food chains of their own..

    Seriously, it is quite cheap to buy low-grade agricultural land that can be used for tree planting (PP not as restrictive as for house building), tree seedlings are pence each if you buy quantity, and all kinds of grants can be had, and over time the land value might increase. I keep meaning to check out whether DIY tree planting might produce more CO2 savings per £, compared to heatpumps EWI MHRV 3G etc etc etc.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 6th 2012
     
    Posted By: SteamyTeaI find if I hold on to them long enough they go solid
    That's about as likely as long term success of underground CO2 sequestration! Don't kid yourself - it just leaks slowly till lo and behold it seems there's nothing there any more!
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 6th 2012 edited
     
    Posted By: fostertomit just leaks slowly

    Usually out my mouth when I am in public :shamed:

    Posted By: WillInAberdeendid your calculations include a mortality rate

    Not for drowned rabbits, I think it was for managed woodland, so included thinning. It is in the earlier link.

    You can't burn it if you have used it to sequester your emissions.
  12.  
    Right then, lets say agricultural land £5k/acre, tree seedlings 20p each. So your 1/2acre 500-tree wood will cost you £2600 up front. Grants of ~60% available (see Woodland Trust website) so thats £1k for you to pay. Cheaper than MHRV, and you'll get it back if you ever sell the woodland!

    Wheres the catch?

    (edited to avoid credit for Steamy's sums)
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 7th 2012
     
    Interesting way to look at it, can you find me half an acre for sale down here please :wink:

    Will the Woodland Trust really give me 60% of the land value in cash?
    • CommentAuthorEd Davies
    • CommentTimeAug 7th 2012
     
    Posted By: WillInAberdeenSo your 1/2acre 500-tree wood will ... make your car/house completely CO2-neutral.

    For how long? A stable woodland is carbon neutral - it only absorbs COâ‚‚ while it's growing unless wood is removed and sequestered with associated concerns about removing nutrients.

    Half an acre per household is about one fifth of the area of Great Britain.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 7th 2012
     
    Posted By: Ed DaviesHalf an acre per household is about one fifth of the area of Great Britain.
    Is that all? Two fifths forested would be very acceptable, another two fifths agricultural/char sequestration, the rest urbanised - something like that.
  16.  
    Posted By: Ed Davies
    Posted By: WillInAberdeenSo your 1/2acre 500-tree wood will ... make your car/house completely CO2-neutral.

    For how long? A stable woodland is carbon neutral - it only absorbs COâ‚‚ while it's growing unless wood is removed and sequestered with associated concerns about removing nutrients.


    That's Steamy's calculation, I'm not taking his credit for it! Edited my post. I just looked at the costs. I understood from his OP that he based it on the first 55 years of his forestry scheme, when the net rate of CO2 absorbtion is highest.

    After that time, indeed the rate of net CO2 absorbtion tails off and will no longer balance his car emissions. In the very long term (>>55 years) his wood will reach steady state and there will be no more net absorbtion. So he'll have to plant another half acre if he wants to carry on driving his Renault in 55 years from now.:bigsmile: Hence Ed's point, that if we all did that, then we'd run out of land.
  17.  
    My personal experience is that half an acre is not going to be enough. The saplings I planted, have visibly not absorbed tonnes of CO2.

    Instead, the saplings have themselves been absobed, mostly by bunnies, and in turn by buzzards foxes and stoat.

    Would still recommend tree planting though.
    • CommentAuthorJonti
    • CommentTimeAug 7th 2012
     
    Posted By: WillInAberdeen
    Instead, the saplings have themselves been absobed, mostly by bunnies



    Willie,

    try installing proper rabbit fencing. Also using protective tubing will help,

    Jonti
  19.  
    Posted By: Jontiprotective tubing


    :bigsmile: I put 600mm tall plastic tubing round each tree when I planted them, it worked fine as bunnies can only reach up 500mm high.

    But then we had 450mm of snow. That made the bunnies both hungrier and taller.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 7th 2012 edited
     
    Posted By: Ed DaviesFor how long?

    Based it on a ten year cycle, then chop down and store (not burn the timber).

    Posted By: fostertomIs that all? Two fifths forested would be very acceptable, another two fifths agricultural/char sequestration, the rest urbanised - something like that.

    If only.
    That is for my car/house, there are a lot of cars/house in the UK and not that much land suitable for growing timber (very little down here for instance, too windy). Then there is the rest of the 'energy' used in the UK. And I did not mention efficiency, my house is all electric, so a kilowatt in is a kilowatt out, that could be improved a bit with an HP, or made worse by a gas boiler (though more control may help a bit there, as would the lower CO2/kWh)

    The sweet spot does seem to be either side of about 55 year old trees, so if you can buy a woodland that is 30 years old, it coudl do you for 40 years with no replanting.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 7th 2012
     
    Posted By: SteamyTeanot that much land suitable for growing timber (very little down here for instance, too windy)
    Really? AFAIK the vast majority of the British Isles' area was covered with forest until cleared by man, apart from rocky high altitude. A bit of wind Dartmoor- or Cornwall-style is no prob to a tough small oak, given a chance and absence of over-stocked nibbling sheep.
    • CommentAuthorJonti
    • CommentTimeAug 7th 2012
     
    Posted By: WillInAberdeen
    Posted By: Jontiprotective tubing


    :bigsmile:" alt=":bigsmile:" src="http:///forum114/extensions/Vanillacons/smilies/standard/bigsmile.gif" >I put 600mm tall plastic tubing round each tree when I planted them, it worked fine as bunnies can only reach up 500mm high.

    But then we had 450mm of snow. That made the bunnies both hungrier and taller.


    :bigsmile:
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 7th 2012
     
    Bit hard to grow even a small oak on a granite outcrop, this end of Cornwall has always been treeless. True there has been a few small pockets of woodland down here, but nothing as large as is left in even Beechy Bucks today.
    Also, a small, slow growing tree will need more time/more planted/more land area to absorb the same amount of CO2.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 7th 2012
     
    Ok, so two fifths rather than one fifth, still room to grant you your bare bit of Cornish rock (could do with some sequestered charcoal?)
    •  
      CommentAuthorfostertom
    • CommentTimeAug 7th 2012
     
    Posted By: SteamyTeathis end of Cornwall has always been treeless
    Penwith - really? It's got quite a lot of trees nowadays, tho I admit I've not checked it out this year, but with Cabrio + heatwave, maybe it's time.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 7th 2012 edited
     
    Well some roads have a few tress along them, and there is Tehidy Wood, next to a golf course. There is a little bit on the Penzance to Helston road and some scrubby bits of bush where I was climbing Sunday, hardly forested though.
    Let us know if you come down.
    •  
      CommentAuthorDamonHD
    • CommentTimeAug 8th 2012
     
    • CommentAuthormike7
    • CommentTimeAug 9th 2012 edited
     
    Quoting Steamy:- "So to balance all that mileage I need a pretty large wood. Tree density is about 2,500 trees per hectare (http://www.forestry.gov.uk/forestry/INFD-6ARG5Y), so I would need 1/5th of a hectare (half an acre)."

    That means 4 m2 per tree, which is very small for a mature tree. They may be planted at that density to achieve early canopy closure and to promote tall straight boles with little side branching, but there will be far fewer trees once losses and thinning have taken place.

    Bearing in mind the length of a piece of string, I'd guess that half an acre would finish up with more like 100 trees (20m2 each) at the most, so your half acre would now need to be at least 2.5 acres. :sad:
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 9th 2012
     
    I tend to agree, planting density and fully grown density are probably very different, and as Damon's link above, what will happen to the ones that do not survive.

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