"Tumbleweed" wrote in message
. ..

"Nick Maclaren" wrote in message
...

In article , (dmc) writes:
| In article , Huge

wrote:
| (dmc) writes:
|
| Had a couple full of gravel at the bottom of the garden for a few
years.
| Both have gone very brittle - the one I attempted to empty and move
just
| crumbled.
|
| That's not biodegrading. The UV in the sunlight has destroyed them.
|
| Hmm. Good point. They had turned to dust though. Nasty poisonous dust
| maybe

No. Polythene and polypropylene break down into harmless chemicals,
and I believe that the other ingredients aren't particularly toxic
or permanent.

| What actually has to happen to something in order for it to have
"biodegraded"?
| Break down into component chemicals?

To have broken down as result of biological action.



Indeed. So something that is biodegradeable may break down to harmful
chemicals, whilst something that is inert (and thus not biodegradable),
for
example glass, may have no effect on the environment (after its
manufacture).

Usually (always?) there is an implicit 'its a good thing' associated with
the word biodegradeable, for no good reason AFAICS.

Biodegradation is being eaten by bugs, worms fungi etc. It is not breaking
down into harmful chemicals. Although I've never seen a chemical analysis of
worm dung. :-))

Steve

In article ,
shazzbat wrote:
"Tumbleweed" wrote in message
...

Usually (always?) there is an implicit 'its a good thing' associated with
the word biodegradeable, for no good reason AFAICS.

Biodegradation is being eaten by bugs, worms fungi etc. It is not breaking
down into harmful chemicals. Although I've never seen a chemical analysis of
worm dung. :-))

While some results of biodegradation can be harmful (e.g. "red tide"),
it isn't all that common. There are actually very good reasons to
regard biodegradability as "a good thing".


Regards,
Nick Maclaren.

"..........These bag things are supposed to bio-degrade, so only a solution
for a year or so ............"

They are not Bio degradable, it's the Ultra Violet (UV) light that breaks
down the white plastic they are made of. If the sunlight is kept off them
they will last 5 or 6 years.

For your stakes I would get the heavy grade of Roof batons, they have the
advantage of being tanalised as well and should last 3 or 4 years.

I use these bags for the debris from the shredder and leave it in the bags
for 6 months or so to start breaking down, works well, and you don't need to
make drainage holes as the water gets out of the woven fabric quite easily,
and if you have any doubts, try putting a hose into an empty bag and see if
you can fill it with water.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk

"Nick Maclaren" wrote in message
...
In article ,
shazzbat wrote:
"Tumbleweed" wrote in message
...

Usually (always?) there is an implicit 'its a good thing' associated
with
the word biodegradeable, for no good reason AFAICS.

Biodegradation is being eaten by bugs, worms fungi etc. It is not
breaking
down into harmful chemicals. Although I've never seen a chemical analysis
of
worm dung. :-))

While some results of biodegradation can be harmful (e.g. "red tide"),
it isn't all that common. There are actually very good reasons to
regard biodegradability as "a good thing".



What about biodegradation leading to over-fertilisation and resulting
problems such as eutrophication? Isnt that what can happen with
biodegradation of detergents for example? However, the core point is that
any biodegradation involves an interaction with the environment; whether you
regard that interaction as positive or negative probably depends on your
individual POV rather than any objective criteria.

--
Tumbleweed

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