Auck­land

Biodegrad­able, de­grade­able, com­postable… these terms are of­ten used in­ter­change­ably but they ac­tu­ally mean slightly dif­fer­ent things.

NZ Gardener - - Contents -

Jo McCar­roll is­sues a plas­tic-free gar­den chal­lenge.

Degrad­able sim­ply means some­thing will even­tu­ally break down – but al­most ev­ery sub­stance will break down if you wait long enough. Even plas­tic will de­grade un­der the right con­di­tions and over enough time, although it can leach po­ten­tially toxic chem­i­cals as it does so and also is prone to break­ing into what is just mil­lions of smaller pieces of plas­tic (of­ten called mi­cro-plas­tics) which end up in the oceans and build up in the soil.

Biodegrad­able means some­thing will de­grade due to the ac­tions of nat­u­rally oc­cur­ring micro­organ­isms – bac­te­ria and fungi. But some­thing can still be called biodegrad­able even if it will take a long time to break down and pos­si­bly leave po­ten­tially harm­ful residues be­hind.

Com­postable means a prod­uct is biodegrad­able and breaks down into the non-toxic com­po­nents of wa­ter, car­bon diox­ide and biomass. But prod­ucts that are la­belled as com­postable have usu­ally been tested un­der com­mer­cial com­post­ing con­di­tions where the tem­per­a­ture, mois­ture level and avail­able oxy­gen can be tightly con­trolled. Home com­post­ing is ob­vi­ously on a much smaller scale, so is un­likely to gen­er­ate as much heat. Some prod­ucts la­belled com­postable might not break down in a home sys­tem. Fi­nally a few prod­ucts or pack­ag­ing are classed as “home com­postable” which – as im­plies – mean they break down in your com­post bin.

These words are be­ing used a lot around plas­tic, espe­cially plas­tic pack­ag­ing.

Prob­a­bly be­cause of an in­creas­ing con­sumer con­cern, there’s been a huge in­crease in sin­gle use plas­tic items la­belled as biodegrad­able or com­postable. And at first that sounds like a good thing. But when ”biodegrad­able” doesn’t nec­es­sar­ily mean en­vi­ron­men­tally be­nign and ”com­postable” doesn‘t al­ways mean com­postable at home, it’s not quite so straight­for­ward. Plus New Zealand does not yet have a stan­dard that plas­tic needs to meet in or­der to be la­belled as biodegrad­able or com­postable (a work­ing group is cur­rently look­ing into whether we need one and cer­tain man­u­fac­tur­ers vol­un­tar­ily meet some of the ex­ist­ing in­ter­na­tional stan­dards). A re­port by the Par­lia­men­tary Com­mis­sioner for the Environment in July, Biodegrad­able and Com­postable Plas­tics in the Environment, sug­gests the ar­ray of en­vi­ron­men­tal claims be­ing made about some plas­tic pack­ag­ing ”might eas­ily lead to mis­un­der­stand­ings” and some of these new eco-plas­tic op­tions ”amount to lit­tle more than green­wash”.

What does all that have to do with gar­den­ing, you may ask?

Well, I think that gar­den­ers con­sider gar­den­ing to be an en­vi­ron­men­tally friendly thing to do. But I also think some gar­den­ers might be un­aware of how much plas­tic is used in their gar­den, and of­ten only used once – I was, when I stopped to think about it. Seed-rais­ing mix and fer­tiliser in plas­tic bags, gar­den sprays in plas­tic bot­tles, plas­tic plant pots and la­bels. Some can be re­cy­cled, true, but as is in­creas­ingly clear that’s not quite the com­plete so­lu­tion we once hoped. Paul Evans, chief ex­ec­u­tive of Waste Man­age­ment In­sti­tute New Zealand, com­ment­ing on the Par­lia­men­tary Com­mis­sioner’s re­port, puts it like this. ”No sin­gle-use op­tion is a good choice.”

Is it pos­si­ble then to have a plas­ticfree gar­den?

There’s cer­tainly a groundswell of in­ter­est in try­ing to. Ear­lier this year Bri­tish gar­den­ing celeb Monty Don called for gar­den­ers to re­duce their use of plas­tic and pledged to cut back the amount used on the TV show Gar­dener’s World, which he hosts, and in his own gar­den. A nurs­ery and gar­den cen­tre in the UK has vowed to go plas­tic free in 2019, the first one in the world to do so. At my place I’ve switched to wooden pop­si­cle stick plant la­bels (although I’m also still re-us­ing the plas­tic ones I al­ready had). I made my own seedling pots out of news­pa­per this year. I don’t have to ditch plas­tic weed mat since I’ve never been a fan (just mulch, mulch and mulch again). But I haven’t man­aged to avoid plas­tic com­pletely – ev­ery im­pulse plant buy is likely to bring in an­other plas­tic pot! So if you‘ve suc­cess­fully re­duced or elim­i­nated plas­tic from your gar­den, send me your prac­ti­cal tips. I’ll give them a go at my place… and pub­lish any par­tic­u­larly clever sug­ges­tions in a fu­ture is­sue.

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