Garden School:


Garden School:
Teaching this week: Rose pruning (as always!) and water management

Thursday, 3 May 2012

Biodegradable pots: no, they don't

I've referred to this subject before: I have what you might call Doubts about so-called biodegradable pots on the grounds that they are either soggily impossible to work with, or they simply don't degrade.

Here we are in the compost heap, digging out some of our Lovely Stuff to spread around on the beds, and what do I find?

Yes, it is one of those blasted coir pots, which has been on the compost heap for many months, and which has - as you can clearly see here - totally failed to rot.

I feel at this point that I ought to be composing a lecture on the subject "The Difference between Compostable and Biodegradable."

I can't tell you how many time I have found plastic bags on the various compost heaps in my charge:  and although a fair proportion are of the "slapped wrist" variety, quite a few are clearly printed as being suitable for adding to compost heaps.

However, there is a big difference between something labelled Biodegradable, and something that will actually rot on a normal domestic compost heap. Those ecover packets, for example: although they try to say that they are biodegradable, they need the very high heat generated by commercial composting facilities.

So even though something might be labelled as Biodegradable, or even Compostable, I would strongly suggest not wasting your time adding the following to your compost heap:

Corn-starch bags. They are perfect for the council's biowaste which goes to anaerobic digestion plant, or to what is called "in-vessel composting" which is held by law at over 60 degrees for a minimum of 48 hours. We just can't achieve that in normal garden compost heaps.

Ecover wrappings, biodegradable fabric washing-up cloths: I am forever fishing these out of compost heaps and throwing them onto bonfire heaps.

Eggshells: how many times to I have to say this? EGG SHELLS DO NOT COMPOST!  They remain intact, perfect, for months, years, maybe even decades. Don't believe me? Please see Exhibit A, below:


Yes, those are eggshells, a stack of them, inside compost that has been there so long that it has formed a compressed, peat-like mass. And yet the eggshells are completely undamaged. Or should that be "composed", as apposed to "de-composed"?

Anyway, yes, I have heard all about the quantities of good minerals and vitamins ("vitamins?") that are to be found in eggshells, and I have no doubt that they do contain at least some minerals: but not in any form that can be transferred to your domestic compost heap.

There is a small possibility that this would work if you crushed the eggshells up into tiny fragments, but frankly you are better off putting them in the food waste bin, and instead, pouring the water in which they were boiled over the compost heap. Or your potted plants. Once it has cooled down, of course.

I shouldn't have to say this, but just in case there are any casual viewers out there: here is my patent list of what NOT put on the compost heap:


What Not To Put In:
  1. No plastic, glass, metal....I shouldn't need to say this... this includes wine bottle corks, by the way.
  2. No plate scrapings - no meat, cooked or raw, it will attract RATS - and that includes bones, whether cooked or raw.
  3. No grease, cheese, butter, oil, or fat.
  4. No cat poo, dog poo,or nappies.
  5. No bindweed, ground elder or couch grass: otherwise everywhere you put the compost, they will appear.
  6. No egg shells - I know every book says to add them, but even if crushed finely, they don't rot!
  7. No citrus - that means grapefruit/orange/lemon/lime peel - they don't rot!
  8. No potato (that means no peelings either) or tomato - for risk of blight, plus you will get little plants everywhere the compost goes. 
There, are we all clear? Good!

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