Woodfuel Puzzle

[Amelanchier]

Can someone help me out here? I've been asked the following question;

 

"How much land would you need to sustain 10 average 3 bed dwellings with wood fuel?"

 

This is a serious problem put forward by policy bods who want to plan up an ecotown. (10 is an easy number to multiply as neccessary I suspect). I'm assuming they're thinking woodburners and logs but those of you who have experience with other mechanisms please show me the light.

 

If you could show the working that would be even better!

 

Any feedback would be gratefully appreciated from the collective wisdom of the site!!

Edited January 16, 2009 by Amelanchier

[Johny Walker]

Can someone help me out here? I've been asked the following question;

 

"How much land would you need to sustain 10 average 3 bed dwellings with wood fuel?"

 

This is a serious problem put forward by policy bods who want to plan up an ecotown. (10 is an easy number to multiply as neccessary I suspect). I'm assuming they're thinking woodburners and logs but those of you who have experience with other mechanisms please show me the light.

 

If you could show the working that would be even better!

 

Any feedback would be gratefully appreciated from the collective wisdom of the site!!

 

for starters , A LOT OFF LAND & A LOT MORE TREES well thats got you started

[john burgess]

Can someone help me out here? I've been asked the following question;

 

"How much land would you need to sustain 10 average 3 bed dwellings with wood fuel?"

 

This is a serious problem put forward by policy bods who want to plan up an ecotown. (10 is an easy number to multiply as neccessary I suspect). I'm assuming they're thinking woodburners and logs but those of you who have experience with other mechanisms please show me the light.

 

If you could show the working that would be even better!

 

Any feedback would be gratefully appreciated from the collective wisdom of the site!!

9 tons for one dwelling per year. coppice will yield 3 tons per year per hectare on a 15-20 years rotation

[Bundle 2]

so 3 hecs does 1 dwelling x1 yr=10 dwelling for 1 yr =30 hectares.....

how long do you want to sustain it? Its never as simple as that mate...if its sustainable, or even sustained...you cannot use that 30 hectares for another 15-20 yrs after first year.....logical conclusion then ( ie x 20 yrs ) = 600 hectares....

 

On a serious note mate, you could ask at Bayfield hall ( Norfolk/Holt )He is alright, and uses his own timber thinnings as fuel for a quite sophisticated biomass fuel system which heats a number of properties inc the Hall itself.

Edited January 16, 2009 by Bundle 2
additional info/afterthought

[Quickthorn]

so 3 hecs does 1 dwelling x1 yr=10 dwelling for 1 yr =30 hectares.....

how long do you want to sustain it? Its never as simple as that mate...if its sustainable, or even sustained...you cannot use that 30 hectares for another 15-20 yrs after first year.....logical conclusion then ( ie x 20 yrs ) = 600 hectares....

 

No..on a 15 yr rotation you divide your 30 hectares into coupes so you're cutting 1/15th of the total area of 30 hectares each year..so each area gets cut every 15 years. That would yield 30/15 hectares cut per year x 3 tons per year per hectare x 15 years = 90 tons for 10 dwellings..

 

If it's new planting, getting it started would take time initially.

Edited January 16, 2009 by Quickthorn

[Mr Ed]

If the dwelings are built along new super insulated guidelines (which they should be!), and you use a district heating system with a central boiler running on woodchips, then your efficiency starts to improve.

 

SO say each house needs approx 6 kwh - 16 hours a day, 7 months or 210 days per year = 20000kw per annum.

 

Wodchip at 30% moisture content will give over 4000kwh per tonne, so each property will need about 5 tonnes of chip per year.

 

Biomass on short rotation coppice yields from the FC website -http://www.forestry.gov.uk/srcsite/INFD-5L3CDQ

 

I would estimate over a 5 year period that 5 tonnes per hectare is achieveable.

 

Therefore, each property would need a hectare.

 

However, a single tree surgeon would be able to easily provide enough chip for such a scheme.

[Mark T]

Best stick to round / split logs as it can be problematic to get chip below required moisture content and pellet can be difficult to get hold of.

 

A good idea is to use solar hot water, geothermal ground-source heat pumps to keep room temps ticking over and top up when required with woodfuel boiler, this way they'll put less pressure on the wood supply... but then... I guess all that is out of your remit?!

[Mr Ed]

Best stick to round / split logs as it can be problematic to get chip below required moisture content and pellet can be difficult to get hold of.

 

A good idea is to use solar hot water, geothermal ground-source heat pumps to keep room temps ticking over and top up when required with woodfuel boiler, this way they'll put less pressure on the wood supply... but then... I guess all that is out of your remit?!

 

Jeez, its no wonder were so backward in this country. DOnt know where you get your info from, but on the continent they have had sophisticated woodchip and pellet boilers for 30 years without the issues you mention.

Chip is very easily dried in the round, however most district sized boilers will run on chip at 50% moisture content.

I could get 1000 tonnes of pellet tomorrow by picking up the technological marvel you might have heard of called a 'telephone'.

 

Solar indeed should be a prerequisite for any heating system, but ground-source heatpumps? absolute non starter. the conversion factor from electricity is very low, and electricity is mostly made by burning fossil fuels, so bit of a non starter if your thinking green.

[Buzz]

 

However, a single tree surgeon would be able to easily provide enough chip for such a scheme.

 

When a boiler is specced that will cope with it lol. I'd have coppice on rotation and dry it in the round before chipping.

 

A district system is the ONLY way to do it economically with a meter in each property.

[Mark T]

Jeez, its no wonder were so backward in this country. DOnt know where you get your info from, but on the continent they have had sophisticated woodchip and pellet boilers for 30 years without the issues you mention.

Chip is very easily dried in the round, however most district sized boilers will run on chip at 50% moisture content.

I could get 1000 tonnes of pellet tomorrow by picking up the technological marvel you might have heard of called a 'telephone'.

 

Solar indeed should be a prerequisite for any heating system, but ground-source heatpumps? absolute non starter. the conversion factor from electricity is very low, and electricity is mostly made by burning fossil fuels, so bit of a non starter if your thinking green.

 

Hey Mr Ed... been a long week or something?!

 

The 50% moiture content you speak of is news to me and obviously makes chip more feasible but might there be problems with space for storage of round material whilst it dries? Presumably, to kiln dry material, you would need significant energy input?

 

I know several people who have pellet boilers and they all have had issues with reliable, quality and affordable pellet supply (admittedly this was approx' 1 yr ago). Perhaps things have improved now? Do you regularly buy pellet? How do they work for you?

 

With regards to most electricity coming from fossil fuels... sure it does... but I source all my electricity from 100% renewable sources. Not a problem! In addition... any new development could of course generate its own electricity could it not?