In a compost bin near you

We are interested in the compostability of nappies (well, in compostability generally - see 20/3/07). This is the latest bulletin from the front. I had to empty one of the bins the other day and some nasties were revealed.
First, above, what it should look like: rich, friable, odourless brown stuff with a few eggshells, chicken bones and twigs (and, this being more than a year old, teabags - see 22/6/07).


But lurking in the well-composted material was a large number of completely uncomposted Moltex nappies which had been put in last September, i.e. fourteen months ago, in the belief that they were biodegradable. So why did we think that they would compost?

I don't know of any claim that Moltex nappies are wholly or largely biodegradable, but there is a very clear one they will be broken down in few weeks by worms, and a cool compost bin normally functions as a wormery. The claim appears, for example, at naturebotts.co.uk,
"· NEW breathable backsheet which is 100% biodegradable · Compostable - proven to break down within 8 weeks in a wormery - tests carried out by ecobaby in Ireland, visit www.ecobaby.ie for further information". Here and elsewhere one receives a strong impression of at least partial compostability.

In fourteen months I really would have expected some sign of deterioration. After all, it is not as though the thing is sealed. The outside is polythene or polypropylene and so quite un-biodegradable. But the little bundle is only closed with Velcro, and then the whole point of the inside surface is that it is permeable. Nonetheless the nappies are still heavy and rubbery with no sign at all of biodegradation. I suspect that the problem is the gel, the super-absorbent polymer that is used in such quantity in Pampers and the like. No claim for biodegradability has ever been made for it, but it seems as though it acts as a barrier to microbial attack, so that cellulose (i.e. the wood pulp in the middle of the nappy) impregnated with gel will no longer decompose in the way one would otherwise expect. In brief, thumbs down to Moltex.

The bag is interesting too. Each one says on it, "100% degradable nappy bag", and lower down, "ECO DISPOSABLE", and at the bottom, again, "This bag is 100% degradable". So, compostable, you might think. But not at all. It doesn't say compostable nor indeed does it say biodegradable. The bags are made from a modified version of polythene for which the manufacturers, Symphony Environmental Technologies, do not make any compostability claim. And, indeed, the bags are quite unscathed by the same sojourn in the compost bin. Which just leaves the misleadingness of the Moltex wording.

Biodegradability

What does it mean to say something is biodegradable? Our answer is that if an object is still identifiable after a year in a fairly cool compost bin, it is not biodegradable in any useful sense.

But it is difficult to carry out a comparative trial in a compost bin, so we are trying a substitute approach, putting stuff on the soil surface, covering it with a black plastic bag, and keeping it moist. On 4 July we started with an Ecover bag (A); an M&S potato carton (B and C); a Kanga incontinence pad (D); and an Earthfriendly eco baby wipe (E). More recently we've added a Weenee nappy pad. All the products claim 100% bidegradability/compostability.

The pads seem to be entirely wood-based pulp and tissue, except that the Weenee admits to having some gel ("superabsorbent polymer" - crosslinked polyacrylate). The other items all seem to be made of a polymer derived from starch, poly(lactic acid), or PLA (trade name Ingeo).

So we'll have a look at how they are getting on every couple of months.

Teabags

We changed to Fairtrade tea a few years ago, buying both Teadirect and Clipper. I only recently realized that Clipper teabags are biodegradable while Teadirect's are not - they hang around perfectly identifiably after a year in the compost bin. I suppose after a longer time and more disturbance they would physically disintegrate, but that would just mean small pieces of nylon in the soil rather than large ones.

So, anyhow, we have become obligate Clipper teabag buyers. Happily both Somerfield and the Co-op on Camberwell New Road sell them.

Waste food

Last week's Southwark News had an item under the heading "Bin strike could mean smelly summer". And we've had concerns expressed about the possibility of less frequent rubbish collections, and that report about a third of food being thrown away.

But whatever food you throw away, if you throw it into a compost bin you don't have to worry about a smelly dustbin. Even the smallest garden can accommodate one of those nice plastic beehives which you can buy at a subsidized price of a few pounds.

On the other hand, composting remains resolutely unpopular. I was brought up to it and have always taken it for granted. But I suspect that for many people there is a quasi religious objection, religious not in the sense of any particular religion's doctrine but in a more primitive sense of taboo, of dirtiness, which may affect people who are fairly rational in other areas of their lives.

There is also the issue of what you can compost. The answer is almost anything: raw food, cooked food, meat, orange peel, teabags, nappies of the right kind, cotton clothes, woollen clothes, feathers from old pillows or duvets and of course all non-woody garden waste. Just bung it all in, and in a year or so you have a dark brown to black material, looking a bit like a mixture of dry coffee grounds and chopped straw, with no smell whatsoever.

Of course the books are full of don'ts, raising fears of rats and heaven knows what else. But the nice plastic beehive has a lid and I guess is pretty well rat proof. We have three and have never seen sign of rat in ten years. The rats will be more interested in the dustbins round the front with fresh supplies weekly of uncomposted waste.

Rats themselves of course are very much on the taboo, dirty side of the line - oddly unlike pigeons, which on any objective assessment are less desirable but which manage to seem "clean" so you can feed them in Trafalgar Square.