Plastics on your allotment & the environment

By John Hodges

Many people will have been very concerned to see on the Blue Planet how plastics are having a devastating effect polluting our seas & oceans. Environmental groups like FOE & Greenpeace had been trying to alert people for many years to this growing disaster but it took the clout of David Attenborough to really make the general population finally sit up & take notice of the negative effects of a substance we use once & then throw away with gay abandon.

With the exception of PVC, the majority of plastics are relatively benign & non-toxic for their original purpose. They are after all widely used for food packaging. It’s what happens to them when they’re disposed of that is the real problem. It’s not enough to assume that it’s ok to keep on & on buying single use plastic & throwing it into the recycle bin. The recycling process is VERY imperfect. As little as a third of plastic sent for recycling in the UK is actually recycled. You the consumer have no control over whether your bottle ends up being turned into an inferior bottle, landfilled, incinerated or shipped to the far east & illegally dumped in a river or on a beach there. We should all be doing our utmost to reduce the amount of plastic we buy in our lives & bring onto our plots. Ultimately the only way to control the torrent of single use plastic is for governments to tax it into oblivion which will encourage the development of benign alternatives.

Looking around the back ends of member’s plots, there is a very worrying build-up of abandoned & decaying plastic & fibres from carpets around the whole of our allotment site. Information on the effects of plastic pollution in soil is still being researched but a few facts are worth considering:
It’s downhill all the way to the sea via our site’s drain. Plastic bags & particles, once they fall into water become ensnared & are carried away with the flow. Larger pieces may be filtered out at the sewage works but during storms, even these are carried with the overflow straight into the Thames.

Earth worms behave differently when the soil contains micro plastics.
In the marine environment, Persistent Organic Pollutants with hormonal effects have been observed to be adsorbed onto the surface of plastic micro particles. These particles are then ingested by simple organisms like plankton & so the POPs are carried further & further up the food chain & eventually into the fish we eat ourselves. Remember too that as plastic breaks down into smaller & smaller particles, its overall surface area increases. It’s very likely this process is happening in the soil too. Not hard to see why cancer rates are on the rise.

Nearly all plastics are affected over time by being exposed to the Ultra Violet content of sunlight. This typically causes the outer layer of plastic to weaken, become brittle & flake off thereby exposing fresh plastic underneath. Transparent & light coloured plastics generally have the least resistance to the effects of UV. Always try to buy dark or preferably black plastic items that you want to last. The dark pigment reduces UV penetration. A good example of this is an orange builder’s bucket I had that obviously came from the same mould in the same factory as my regular black ones but after only 2 or so years it became bleached, then cracked & useless whereas the black buckets are still perfect. Don’t go for the gaudy option if you want items to last. Always try to store all your plastic items – watering cans, hose, sacks etc – away from the sun. Some plastics have additives to resist the effects of UV but infuriatingly, there are no markings to indicate this. You must be prepared to keep an eye out for evidence of the decay of all plastics on your plot over time. If this seems tedious to you then seriously reduce the amount of plastic you have there.

The following notes on the stability & longevity of the different types of plastic commonly encountered on allotments are mostly based on observations & mistakes made by me over the years. I’ve spent many hours on my knees picking up scraps of decaying plastic & particularly tufts of carpet from my own soil & compost. Never bring hessian backed synthetic carpets onto site. In fact all carpets are likely to contain toxic fire retardants that leach into the soil. Best use giant cardboard boxes from bike shops for smothering weeds & covering compost heaps. Plot holders should always have a bucket near to hand to collect bits of plastic, fibres & glass into whenever they’re working their soil or compost. The codes & full chemical names of plastics are given below so people can do their own further research.

Polythene, Polyethylene, LDPE & HDPE
This, the simplest plastic exists in High Density & Low Density forms. Used for cheap greenhouses, bubble wrap, milk bottles, the thicker non-rustling type of plastic bags, compost sacks & smooth heavy-duty sheeting. Polythene in its non-UV stabilised form appears to degrade in the sun faster than any other plastic. It can lose all its strength & fragment entirely away in about two years. Black (builders) HDPE sheeting seems the most stable form & is useful for warming the soil & excluding light from weeds.

Polypropylene, PP
Widely used for many larger moulded plastic products on allotments – compost bins, watering cans, buckets, plant pots, clematis netting, hose reels, bottle tops, vermin netting, woven Ikea blue bags, giant cubic metre builder’s aggregate sacks & estate agent sale boards. It’s also used to make the twisted film type of plastic string & rope. Probably due to its high surface area in this state, PP string & rope degrades particularly rapidly in sunlight – shedding tiny fibres from the outside which blow around or drop into the soil & the string completely disintegrates in as little as 2 years of sunlight exposure. Don’t use such string or rope for the long term tieing together of things unless you’re prepared to renew it every year or two. Best use natural jute string for tieing plants, runner bean poles etc.

All of the plastic netting I’ve encountered seems to be UV stable but the consequences of it not being so are so serious that you should avoid buying it from cheap sources such as the hateful pound shops that sell mostly short-lived rubbish that soon breaks & ends up in landfill. Also never buy the very wasteful plastic climbing pea & bean netting as it gets thrown in the skip after a single season. There are always twigs & sticks to be had from the green waste heap.

I find the giant PP builder’s bags particularly useful for containing leaves rotting down into leaf mould. Kept in a shady position these can last 3 to 4 years. However, because of their limited life, it’s imperative that you should test them each year by attempting to rip them. If they tear or make a cracking sound then they should definitely be disposed of very soon. Don’t use these bags to store compost that contains food scraps as rats & mice will chew their way through the fabric to reach the food. The plastic fragments are particularly fiddly to pick up.

Corrugated estate agent sale boards crumble quickly so don’t bring onto site for making compost containers etc.

PET, Polyethylene Terephthalate
This is used to make the thin rustling plastic bags that blow everywhere & also the clear plastic used for drinks bottles that are used once then thrown away. Rats & mice like chewing up plastic bags into tiny pieces for their bedding so keep carrier bags etc in vermin proof containers such as a biscuit tin. I gather 5 litre mineral water PET bottles up as they blow around in the street near me, cut the bottoms off & use them as cloches to protect tender seedlings from slugs & cold nights. Never be tempted to leave the caps on as I lost most of my seedlings one year through overheating in the sun. Remove film labels as these disintegrate very quickly. Such bottles used to quickly yellow & go brittle in the sun but modern ones seem good for about 5 years but you must always keep checking them for brittleness.

On no account buy hideously destructive bottled water yourself as clueless people with more money than sense can be relied on to keep doing this & then scatter such bottles around. If you’re concerned that tap water is polluted then it’s because there are diesel burning, water laden lorries thundering across Europe & plastics factories turning oil into bottles at a furious rate. Bleeding obvious. I laughed out loud when I read that bottled water contains plastic particles.

PVC, polyvinyl chloride
Used for hose pipe, cling film, cable insulation, window frames & waste & rainwater pipes & guttering. Like many halogenated organic compounds, the manufacturing process for PVC is very polluting involving carcinogenic ingredients. If PVC finds its way to an incineration plant then it releases carcinogenic dioxin into the environment. This is why I get particularly annoyed to find perfectly good hosepipe regularly thrown away in the skip.

If a section of your hose leaks or splits then it’s very easy to cut the damaged section out & join the two ends with a hose joiner rather than buy an entire new hose & cause several more kilos of polluting PVC to be manufactured. PVC is generally one of the more light stable plastics but after many years of exposure to UV the surface of some PVC can start to dull & have a crazed appearance. PVC should be disposed of when this happens as it’s likely to shed toxic micro particles into the environment & your soil.

Compostable plastic bags made from corn starch
These have the look & feel of condoms. They’re supposed to naturally decompose but in practice this only happens in properly hot compost heaps so best put these into council compost bins rather than your own heap.

If you’re desperate to know the type of plastic an unmarked item is made from then the simplest way is to melt a tiny sample & compare the smell to that from a known sample. Be cautious of breathing in PVC vapour though because of its toxicity.

Finally please remember that our skips go straight to landfill & are therefore an ABSOLUTE LAST RESORT FOR DISPOSAL that should only be used for mucky non-recyclable items. People living within a mile of landfill sites have a 15% raised chance of developing leukemia. Casually dumping recyclables in the skip is lazy, thoughtless & selfish as we all have to pay about £300 each time it’s unnecessarily bulked up & filled & we’re presently filling about four skips a year. Put such rubbish in your domestic bins at home. Your council will properly dispose of any item you take to their recycling depot for FREE.