We have a large compost pile, about 1m x 3m and 50cm deep, with brick
walls. It's covered by three sloping wood panels. I was wondering
whether changing them for corrugated plastic ones would help warm up the
heap and thereby speed up the composting, or if it would be detrimental,
so I'd be grateful for any advice.

Daniele
--
Apple Juice www.apple-juice.co.uk
Chapter Arts Centre
Market Road
Cardiff CF5 1QE

In article ,
michael adams wrote:

Painting the brick walls and wood panels black would allow them to
better absorb any heat - without reflecting it away unlike a paler
colour - while still insulating the pile against heat loss at
night and retaining any necessary moisture in the heap.

That assumes that the net radiation into the heap is positive - a VERY
debatable matter.


Regards,
Nick Maclaren.

The message
from "michael adams" contains these words:
"Nick Maclaren" wrote in message
...
In article ,
michael adams wrote:

Painting the brick walls and wood panels black would allow them to
better absorb any heat - without reflecting it away unlike a paler
colour - while still insulating the pile against heat loss at
night and retaining any necessary moisture in the heap.

That assumes that the net radiation into the heap is positive - a VERY
debatable matter.

Hence the use there, of the words "would" and "any".

And in direct sunlight, possibly correct. However, when the environment
cools, the black surface will radiate heat better.

Since the heap is likely to be out of direct strong sunlight longer than
in it each day, the net effect of painting it black would be negative.

If you feel any overwhelming desire to furnish any actual evidence
or data in support of your claim, please don't hesitate to do so.

Claim? If you mean by that "a VERY debatable matter.", I would
wholeearted ly agree with Nick - it *IS* debatable, and we are both
debating it. Enough evidence for you?

After all, we're all friends here.

Allegedly.

Well, most of us are, mot of the time.

--
Rusty
Emus to: horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

The message
from "michael adams" contains these words:

That assumes that the net radiation into the heap is positive - a VERY
debatable matter.

That isn't the issue.

If the brick walls are painted black they'll absorb solar
radiation rather than reflecting it straight back and warming
the surrounding atmospere. The warmer the brick walls are, the
less heat will pass from the heap into the walls, given that
less heat passes from a hot body to a warm body, than to a cool
body. And so less heat will be lost from the heap overall, as
result of paining the walls black - and more solar radiation
will be absorbed from day one, when the heap isn't actualy
generating any heat of its own.

Thank you for your helpful contribution, nevertheless.

I consider it a very helpful contribution and well-thught-out, and even
if you could arrange for the black face/faces to be presented to the sun
at right-angles to its elevation while it is playing on it/them, and the
heap is at a normal temperature (for compost heaps) the balace has to be
a net loss of heat.

I'll no doubt rejoin this later - England wants eleven runs to win - Oz
wants three wickets.

--
Rusty
Emus to: horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

In message , michael adams
writes

"Janet Baraclough" wrote in message
...
The message
from "michael adams" contains these words:


"Nick Maclaren" wrote in message
...
In article ,
michael adams wrote:

Painting the brick walls and wood panels black would allow them to
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

better absorb any heat - without reflecting it away unlike a paler
colour - while still insulating the pile against heat loss at
night and retaining any necessary moisture in the heap.

That assumes that the net radiation into the heap is positive - a VERY
debatable matter.

That isn't the issue.

If the brick walls are painted black they'll absorb solar
radiation rather than reflecting it straight back and warming
the surrounding atmospere.


You haven't ascertained from the OP whether the structure gets any
direct sun at all. Even if it does, since the structure is only 50 cm
high, it seems unlikely that such low walls will get enough sun on them
for long enough to affect the heat of the contents. Even less if only
one one of the short walls (1 m) faces the sun.


michael adams wrote:

Painting the brick walls and wood panels *black
^^^^^^^^^^^^^^^
*On top of the structure as specified by the OP.

hint:see above

It would appear you're attempting to outdo Mr McLaren
in nitpicking.

Thats 0 - 3 in my favour, thus far I believe.

Would you be aware that surfaces that are good at absorbing radiation
are also good at radiating energy? A black compost heat container will
indeed absorb more heat when in direct sunlight. At night, and perhaps
when shaded, it will lose more heat. Given that a compost heap generates
heat internally, and therefore is above the equilibrium temperature for
a passive object on the surface of the earth, at first sight it seems
that painting the heap container black will reduce the time averaged
temperature.

How significant this is depends on a number of factors. For a well
insulated heap, such as one with brick walls, and wooden covers, it may
be negligible.

With respect to the OP's question, replacing the wooden panels with
corrugated plastic presumably allows heat loss from convection via the
ends of the corrugations. I imagine that plastic is thinner than the
wood, which would contribute to it being a poorer insulator. If clear,
it will allow visible light to pass through and heat the surface of the
compost directly, while absorbing radiated infra-red light. My intuition
is that better insulation is more important than exploiting the
greenhouse effect.
--
Stewart Robert Hinsley

In article ,
michael adams wrote:
"Stewart Robert Hinsley" wrote in message
...

A black compost heat container will indeed absorb more heat when
in direct sunlight. At night, and perhaps when shaded, it will lose
more heat.

Surely Mr Hinsley, as with cats, all compost heaps are black at night ?

I really do encourage you to write up your musings on science in book
form. You could become as well-respected as von Daniken or even
Velikovsky.


Regards,
Nick Maclaren.

The message
from "michael adams" contains these words:
"Nick Maclaren" wrote in message
...

I really do encourage you to write up your musings on science in book
form. You could become as well-respected as von Daniken or even
Velikovsky.

....

I'd certainly settle for their income, that's for sure.

But I'd imagine all the most highly respected authorities on most
subjects can be found posting in NewsGroups nevertheless. Offering
to share their invaluable knowledge with total strangers, and all
for free.

Naturally. It's not *QUITE* as positive as that though, it's just that
they hate to see people being misinformed.

--
Rusty
Emus to: horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

The message
from "michael adams" contains these words:
"Janet Baraclough" wrote in message
...
The message
from "michael adams" contains these words:


But I'd imagine all the most highly respected authorities on most
subjects can be found posting in NewsGroups nevertheless. Offering
to share their invaluable knowledge with total strangers, and all
for free.

It would save everyone's time if such experts marked all their posts
"This author's posts are certifiable. No discussion required".

Janet



Well done Janet.

Leading by example, as always.

5 - 0

Ah well, it won't be *THAT* long before school is back.

--
Rusty
Emus to: horrid dot squeak snailything zetnet point co full-stop uk
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