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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010 edited
    I would love to see other forum users thoughts about these key points that I am working up in detail for my response to the AECB document on Biomass : http://www.aecb.net/new_releases/detail/?nId=9

    Putting aside the argument about whether or not we should still be erecting new buildings that require heating at all, it is clear that we still need and will continue to need for some time, sustainable heating solutions for our existing buildings stock. In my opinion, a key fuel for meeting this need is biomass, for five fundamental reasons:
    1. Biomass is a renewable fuel (within human timescales).
    2. Biomass can be grown locally close to the point where it is needed.
    3. Biomass is energy secure i.e no need to rely on supplies from other countries
    4. Biomass requires relatively simple technology and equipment to enable it to be grown harvested and burnt efficiently
    5. Biomass can provide employment, environmental protection of habitat and improved lumber production, all for use in the UK.

    Whereas on the other hand, gas, the fuel which the report has tried to convince us the only 'sustainable fuel' we should use, is unacceptable (to me) for the same five fundamental reasons:
    1. Gas is not a renewable fuel (in human timescales)
    2. Gas cannot be sourced locally or even easily for that matter.
    3. Gas is not energy secure and forces us to rely on imports from other countries and can be implicated in recent conflicts with other nations and the oppression of third world countries.
    4 Gas requires complex and increasingly sophisticated technology to extract, transport, store and burn efficiently.
    5. Gas provides for very little UK employment or for any habitat protection.
    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010 edited
    On a separate thread, I am grappling with the complexities of the carbon content of the two fuels so please take a look at that thread too as i need all the help I can get please.

    • CommentAuthorJTGreen
    • CommentTimeSep 19th 2010 edited
    I think you would have to take into account "green gas" (i.e. methane from anaerobic digestion) when saying gas cannot be sourced locally, and does not contribute to energy security. Natural gas almost certainly can't, given that UK natural gas has peaked as far as I understand it. But AD gas might.

    It's worth looking at how much land would be required to be given over to sustainably managed woodland to provide differents %s of current and projected demand (projected demand being +/- current demand, depending on various scenarios). It seems clear to me that that burning wood could easily be a larger % of the fuel mix than currently. And doesn't have to negatively impact on land for other purposes - we've had this discussion with regard to motorway-side coppice, for example. Creating a demand for wood for fuel from managed woodland would be a benefit in terms of providing habitat etc if it results in more new woodland being planted. At the same time, I think it is worth defining the natural limits. If we want to encourage local food production (which I think we do, for purposes of food security and reduced food miles - not withstanding ST's skeptism) AND local wood for fuel, then we have to define how much land is required for these different purposes.

    At present, I know I could put in a wood stove with back boiler, and source local enough wood at reasonable price from a tree surgeon working within and around the city. But it's not realistic to expect that everyone can meet their wood needs that way - and my county has smallest % of woodland in the country, so it wouldn't take much to tip the balance and put fuel prices through the roof. Or alternatively to create the demand for planting which would be a very good thing.
    • CommentAuthortony
    • CommentTimeSep 19th 2010
    I dont think that biofuel is a sustainable option for Britain as there is insufficient if everyone wanted to have some of it.

    Long term future it could help but only in conjunction with massive energy saving programmes.
    • CommentAuthorJTGreen
    • CommentTimeSep 19th 2010
    But are we talking about 'everyone wanting to have some of it' (what does that even mean?) or just a % of the mix alongside other fuels, all which are also unsustainable to a greater or lesser degree if 'everyone wanted to have some of it'?

    If everyone wanted a new build passive house, is that sustainable? Where will people live while the new passive houses are built? How long would it take to replace the entire housing stock, while also providing temporary shelter while new houses were built on the sites of old? Can it be done in a short enough timescale to make a difference to energy use any time soon? If not everyone can have one in short order, does that mean that no one should build a passive house, or that passive houses should not be incentivised in various ways?

    There are insufficient sites for wind turbines, if we wanted to get all our electricity from wind. Ditto every type of renewable. And certainly not everyone can use oil, gas and coal to the extent we have historically without a) depleting non-renewable resources b) producing lots of CO2 and c) drilling/mining in increasingly difficult locations with consequent environmental and human risks. So, we have to reduce demand, but we also have to think about the least bad source too.
    • CommentTimeSep 19th 2010 edited
    A quick look at the solar map will show how much energy is available to the country. About 1.025GWhkm^-2.
    If we are generous and say that all 242,900 km^2 is covered in forest that can be burnt for fuel then we have 248.9725 PWh of energy (that 10 with 15 zeros after it)
    Now we have to factor in the conversion factor for trees growing, this I have no idea about but probably around 3% or less.

    That gives us 7.46975TWh before we process it.

    Domestic energy use in the UK last year was 67.9 mtoe or 789.677 TWh

    Or the UK could supply in wood about 9.5% of our domestic energy needs.

    Now I appreciated that not all our domestic energy is for heating but I think you can see the problem.
    Even if we can cut out heating (30% of total) by 90% we still have a problem as we would need 23.69031TWh and that is relying on the UK being covered in forest.

    This works out at 789,677 tonnes of CO2 (what we would produce if we used todays energy use in wood)
    or 23,690 tonnes if we just take 30% for heating and reduce that by 90%

    Very large number.

    As always check my arithmetic, it is easy to make an error.
    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010
    Good points JTGreen. The discussion does refer specifically to natural gas so I'll add that to my paper.

    Also as you have said to Tony, the switchover to biomass (lets not confuse this with biofuels as they are different)could not be an instant thing but something we could work towards over a number of years. The authors of the AECB report have really been niggled by the governments encouragement of developers to install the equipment - kind of putting the cart before the horse. The government would do better to encourage more and better woodland management first.
    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010
    I would appreciate it if you could pick the faults out of this musing please.

    A quick simplistic calculation:
    If every household switched to heating their home with an efficient wood boiler then at a rough calculation and at best yield using short rotation coppice (20 tonnes per hectare per yr) we would need about 162,000,000 tonnes of biomass each year which would provide every home with 9 tonnes of wood fuel. This would equate to needing roughly 8,100,000 hectares of land under forest cover which is roughly one third of the UK land area.

    However, householders would soon learn ways to reduce their consumption because biomass burning requires some user input. Householders would also become fitter due to doing a bit of exercise.

    Community heating schemes if rolled out could improve (lower the consumption levels)
    • CommentTimeSep 19th 2010 edited
    See my previous post as I used a different methodology

    Your figures seem to give about 42,500 kWh/year
    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010 edited
    How far apart are we then because I got lost in all your figures SteamyTea.
    • CommentTimeSep 19th 2010 edited
    I looked at what the land area could supply and then used a conversion figure. I worked it out nationally rather than by household.
    If we say 30 million houses then the energy use for each house is, by my method, 26,300 kWh/year.
    If timber has an energy content of 1.7MJkg^-1 (0.472 kWh/kg) then (26,300/0.472)/1000=55.7 tonnes for all domestic energy use.

    Just checked the national figures and 77% is for heating (space and water). I assumed 30%, so it is worse.
    But on the bright side would only need 42.9 tonnes of wood.
    • CommentAuthorgcar90
    • CommentTimeSep 19th 2010
    Biomass is not a superior fuel to nat gas, quite the opposite, hence the worldwide demand for it rocketing over the past decade or so. Biomass is neither sustainable or green in today`s urbanised and populous society. Why are so many people hell bent on sending civilisation backwards with all these unrealistic “solutions“ to the energy needs required for a modern living standard. AECB are wrong to encourage greater dependency on gas but right to slate biomass as a solution to power, heat and light.
    • CommentTimeSep 19th 2010
    26.5 million households in the UK, roughly.

    Mean consumption of those on mains gas is ~18MWh/y which we can prob assume to be a fair estimate of average heat requirement, thus UK total domestic heat requirement ~480TWh (which is prob about right), but DUKES will have better numbers and is free and easy to get.


    • CommentTimeSep 19th 2010
    Have I made a schoolboy error and got a 12 and 15 superscript in the wrong place, very possible.
    • CommentAuthorJTGreen
    • CommentTimeSep 19th 2010
    Does this provide some useful data?


    For example, they say their research shows that 68% of aboricultural "arisings" don't find any market at present.
    • CommentTimeSep 19th 2010 edited
    This based on MacKay's book may be helpful:


    Implication is that ~200m^2, ie 5% of per-person inland area, could provide enough biomass for about 24kWh/d/person (24kWh/d is plenty to cover space and water heating for the *4* of us at my house for example).



    PS. Here is DUKES: http://www.decc.gov.uk/en/content/cms/statistics/publications/dukes/
    • CommentAuthorJTGreen
    • CommentTimeSep 19th 2010
    "energy needs required for a modern living standard"

    Would you care to define "modern living standard".
    • CommentAuthorJTGreen
    • CommentTimeSep 19th 2010
    I think MacKay is including food in that solar biomass though!
    • CommentTimeSep 19th 2010 edited
    200m^2*1050Wm^-2 = 210MWh/year/person

    What is the conversion factor for plants growing, always lead to believe it is very low, hence the 3% figure I used.

    Got my data for usage from:
    • CommentAuthorGavin_A
    • CommentTimeSep 19th 2010
    I don't think there's much point in attempting to guestimate these figures from first principles when others have already done the detailed calculations for us...

    "Results given in Table 3 show that at the UK level about 28TWh of biomass are
    potentially available from existing forestry and agricultural sources, amounting to
    about 1% of total UK primary energy consumption. With the inclusion of energy
    crops10 and waste wood, the resource could be increased to about 3% of UK
    primary energy, and if it were used to replace coal or oil from the current energy
    mix it would reduce UK carbon emissions respectively by about 22 MtCO2 and 18
    MtCO2 (6MtC and 5MtC), or about 4% and 3% of the UK’s CO2 emissions11."


    Lowest Estimate (PJ) Highest Estimate (PJ)
    Existing Biomass 194.0 198.0
    Set-Aside Land 0.124 0.253
    Changed Agricultural Use 717.8 1,465.2
    TOTAL 911.924 1,663.453
    Table 5. Estimated Total Potential Energy from Biomass in the UK.

    The total potential energy from biomass in the UK is therefore between 911 PJ and 1,664 PJ per year."

    - note, the existing biomass figure refers to the renewable biomass potential for land already used for growing wood that's not currently being used, ie it's in addition to current use of UK wood, but without any additional land needed. "British forests will be producing 10 million tonnes more wood than is currently used, against a backdrop of falling demand for British timber (RCEP, 2004). "

    google is your friend etc ;)
    • CommentAuthorGavin_A
    • CommentTimeSep 19th 2010
    anyway, back to the main thrust of the discussion...

    thinking about it, the major flaw to the argument about burning gas and using biomass as a carbon sink for the resulting CO2 is that eventually the gas is going to run out, at which point we'll probably have no option other than to burn the biomass that's supposedly locking up all that carbon from the gas.

    Also, burning biomass will reduce total demand for gas, which in turn is likely to keep the price from spiking too much, which in turn is likely to reduce the economic viability, and necessity of opening up new fields in the arctic etc, which gives us a better chance of that gas actually staying in the ground, reducing the overall volume of carbon that's likely to end up in the atmosphere / biosphere / oceans.
    • CommentAuthorGBP-Keith
    • CommentTimeSep 19th 2010 edited
    I thought it was 18 million households in the UK. Have housebuilders really been that busy since I last checked?

    Posted By: DamonHD26.5 million households in the UK, roughly.


    • CommentAuthormike7
    • CommentTimeSep 20th 2010 edited
    Posted By: SteamyTea
    If timber has an energy content of 1.7MJkg^-1 (0.472 kWh/kg)

    The energy content of wood is in the region of 4.7 kWh/kg, which looks to be 17.0MJ/kg.

    Biomass tends to be lumpy, awkward and a hassle to come by for the consumer compared with mains gas or electricity. Speaking from personal experience this lack of convenience is a significant incentive to reduce consumption by whatever means, eg less than total uniform comfort level, more insulation etc.

    I'd suggest gas burning is maybe not higher tech than biomass burning - if the same degree of 24/7 convenience is required.
    • CommentTimeSep 20th 2010
    Whoops, your right, so my figures are a factor or 10 out. I should not be allowed near numbers. And must get new glasses.

    So 5.6 tonnes of wood, much nearer Keith's figure.
    • CommentAuthorbiffvernon
    • CommentTimeSep 20th 2010
    Elizabethan houses are 400 years old, Georgian 200. It would be a smart thing to do if new builds were designed on the assumption that they will still be standing in 300 years time, when the energy mix available might be rather different. Future-proofing might involve building in a way that includes flexibility.
    • CommentAuthorJTGreen
    • CommentTimeSep 20th 2010
    There were 24.9 million households (in 2006), but households =/= houses. Defined by who you live with, not your living situation. Some of those households are one person living in a bedsit/converted flat and there may be four households in a house.

    One thing to mention is the potential amenity value of woodland over and above the value the wood for fuel. Woodland provides a different, and probably better, habitat for other species - and more access for human enjoyment - than air fields, golf courses and army training centres (to name three spaces we might want to convert locally if we had the chance).
    • CommentAuthorsune
    • CommentTimeSep 20th 2010
    I have a vested interest in this as I am involved in biomass heating for my job. Having said that I do not think for a second that this paper or discussion will have a serious impact on my living. The AECB and this forum are great and influencial of course but.....

    I detect a tendancy, not shared by all, to make sweeping, black or white statements when what is required is a mentally agile, realistic, point of view that can let one look at a blend of different solutions (which incorporate ecological, ethical, social needs), which will have to be slowly implemented?

    Wood is part of the solution. Part. We all knew that already though didn't we - its fairly obvious.

    The 'if everyone did it' argument would stop you ever letting anyone use your toilet as it would get a bit messy if everyone did wouldn't it. But that's stupid you say, everyone can't and wouldn't possibly use your toilet - I agree, its only small, at the most you could get 4 people in there. As it stands though I will still let someone use my toilet in general as I know not everyone will want to use it. Don't come round specially though please....

    It might not make sense everywhere - ie central London....again that is known. Are we perhaps wasting our time here retreading ground and stating obvious facts?

    Example 1: I have a friend with a woodland, 100 acres of which he uses for timber and recreation. He will soon be expanding into firewood as well as the 2 other uses. The firewood will power their 80kW log boiler district heating scheme - 3 houses - soon to be installed. They are all grade 2* listed buildings, we can upgrade the loft insulation which we are going to do but that's about it. There is already solar thermal for all the DHW.
    The rest of the firewood he will sell. The wood is lots of larch planted by his father in the 60s-70s. part of that boom in planting where people thought their children would earn a fortune. Well it didn't quiet go to plan and its been under used for years and, in common with lots of other forest, it has not been maintained - there are lots of side branches hence much of it is not good building timber, but firewood, as part of the use, is now starting to make sense again....great.

    But actually what he should do is forget the firewood thing but wait until the timber prices are good enough and till the price paid by the wood fibre insulation board manufacturers are offerring lots of ££'s. ie he should let the timber continue to fall, largely unused??
    Or should he await a carbon tax scheme and then get paid to build lots of stacks of wood with roofs on in order to lock up the carbon?
    He should also replace the current oil fired heating systems running the 3 houses there with some gas boilers, and have some big LPG tanks with trucked deliveries of fuel from really far away, even though he has a forest, literally, on his doorstep?
    Or do we like oil now as well, can he keep his oil boilers?
    Or should he build some PassivHaus houses on the site, vacate the existing buildings leaving them empty, and install a little gas boiler?

    In the future when the oil and gas run out - well more realistically when they start to cost too much - he could install a PV system to power a heat pump. It'll be his sons problem by then hopefully and PV will be cheaper. Plus it'll probably be a bit warmer anyway.

    Hang on - the gas and oil are getting scarce in this story - which probably means that everyone carried on using loads of fossil fuels globally. But hopefully locking up the carbon in a FEW new buildings did the trick to let us carry on using the gas boilers but still meet the currently un-meetable IPCC targets?

    Example 2: I heat my own house with a boiler stove - it was running on an old inefficient oil fired rayburn when I got it. The stove provides DHW and heating. Solar tubes do DHW too. The wood is from thinnings of a line of coppiced hedgerow running up my land. The wood is also from a site where they were clearing wood unsuited to make building timber from. I will be planting up the rest of the land with wood too - including some southern beech as Funcrusher writes about elsewhere - that will help biodiversity (we've already seen an increase in bird life, there are more owls, a local hedge hog in living in one of the piles of branches left around for that purpose).
    So what I should do is install a gas boiler, and then use the wood (I have to cut it as otherwise they can fall on the road you see) to, erm, use it to, well, sell it to someone I guess. It's not straight enough to build from so it will have to go to make insulating panels from. Anyone got the name of a manufacturer? - I'll give them a call and see what they will offer me. Hope they are local as I will need them to collect.
    Then the trees I'm planting I'll have to manage for making building timber so I will need to devote quite some time to it and densely plant it too. Might have to give up work on a day a month at least I guess? It's OK though because the timber will help my children earn money in the future.

    Example 3: My dad across the road is in the same situation although he runs a Vigas 40kW.
    So we'll install a big gas boiler for him too. Perhaps we can share a big tank which'll be nice.

    Example 4: Andy down the road also runs his house on a wood boiler stove, solar going in for DHW, accumulator tank, etc. We just put that in to replace an oil fired rayburn. We took the oil tank out of his house which freed up some space. The stove is very efficient and so he doesn't use much wood and the house is warmer and he has more hot water than he used to. He fires on slabwood offcuts from a local sawmill - provided by us at a 'Village rate' and branches etc that he finds.
    So shall we take the stove out and again put in the gas boiler? He'd need either a tank in the house or to dig up the road to get to his garden for the LPG.
    We can probably get a reduced rate from the installer for doing all three houses at once.

    I am not normally quite so sarcastic on here, but I get annoyed by silliness like everyone else from time to time!

    For the people that do not think that this is at least a partial waste of time and misguided please enlighten me as to what exactly my friends in Example 1 and 3, and what my father and I should do. Detailed, real world scenario responses only though - and they need to make financial sense as well or we won't feel inclined to do them.
    • CommentAuthorGavin_A
    • CommentTimeSep 20th 2010
    • CommentTimeSep 20th 2010
    *pip pip*

    Agreed: real-world solutions are a blend of many components: B&W thinking is rather 'teenage' and unhelpful.


    Are people trying to deny that wood contains carbon and emits carbon dioxide when burned? It sounds rather like it.

    On my reading, the report doesn't say
    Gas is good

    It says
    Wood is bad, and worse than most people think

    So why this obsession with trying to deny a claim which the report doesn't even make?

    BTW it would be much easier to have this discussion on one forum as it gets rather confusing slipping between here and aecb.net and back again.
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