This thread contains boring wood/logs/biomass/heating calcs/energy stuff. Turn back now if this is a problem for you...
Last Saturday I hired a mate and his tractor and trailer to help me get all the wood from this winter's harvest at the coppice back to the house for seasoning.
Over the winter I had managed to fell about 0.4 of an acre (I have 3.5 acres at the coppice ready for clearing). I had wanted to do half an acre a year but ran out of time before the season passed.
Back at base
This week I have mostly been playing the biggest game of single player pick-up-stix in the county
Maths bit (particularly for Sharkbait and DD)
BTW, deadlydarcy, http://bit.ly/17tuT5n
this link covers the thing about all wood having pretty much the same net calorific value for a given moisture content.
The stack is 1.5m high, 9.6m long, and 1.5m deep. It's tightly stacked so assuming 10% loss of cross section to air space gives a total volume of around 19m3.
Poplar has a dry (c.10% moisture) density of c.450Kg/m3, so given water is 1,000Kg/m3 and the wood currently has a moisture content of around 30-35%, then the wood has a density of c.600Kg/m3 at the moment.
So I hefted 11 tons of wood into the trailer and then stacked it this week. No wonder I hurt.
When the poplar is air dry (12% moisture) it will have a net calorific value of around 4,000 kWh/ton, or 4kWh/Kg.
So that pile will produce something like 35,000 kWh of energy.
(just for the giggles: that's worth £5,500 in electricity, or £1,600 in gas or £2,500 in oil )
My deemed Central heating energy usage is about 15,000 kWh a year and for the domestic hot water requirement over the months when the solar thermal tubes aren't providing it I need another 3,600 kWh of energy.
So that one year of harvesting should cover just under two years of consumption. I think I'll take next year off then....maybe....
The hire of my mate and his kit cost £200, but I have also processed around 300 stakes for another mate who lays hedges and they're worth about £100. In future years my mate and I may come to a deal where I shall trade some timber for free delivery of the rest as he has plans to use a kindling processor for some of the poplar.