Dr Jeff Seadon: environmental scientist weighs in on recycling debate

Published Jan 28, 2025, 3:14 AM

It's a debate that has many households arguing - how clean should your recycling be before you put it in the right bins?

Contamination can create extra difficulties for recycling facilities, meaning it's important to clean the recyclable waste to save it from the landfill.

Environmental scientist Dr Jeff Seadon joined the Afternoons team to discuss.

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To rerap this up because it's been a good discussion about recycling, but we thought we'd get someone who knows what they're talking about to wrap up this hour. Doctor Jeff Seden is an independent environmental scientist and integrated waste management experty. Joins us on the line, get a doctor sedon.

Good afternoon, Nice to talk to you.

What percentage, doctor Seden, of items going through our wheelly bins are actually being recycled probably.

About eighty percent of what goes through, and the other twenty percent is due to contaminants. And the difficulty is, you know, people put things in a plastic bag and then put them into their recycling bin. And while they may have put everything correctly into that plastic bag, it's the plastic bag itself. It can't be recycled through that system.

Sen, Sorry, eighty percent is a really high number. I haven't seen that anywhere else. I'm hearing that eighty percent of what goes through. But if the machine has been there's only so much that you can do in any given day, and more comes through than they can deal with.

Is that?

Is that are you including that in your number? I?

Yes, I am, and including that, what we've got is this level of contamination, which is about twenty percent, and so that causes the difficulties.

So everything that isn't contaminated gets recycled, is that what you're saying?

Not necessarily If you have, say a plastic bag with stuff in it for recycling, it won't be recycled because the plastic bag itself can't be so they'll just put that aside and that ends up going to the landfill.

So what's the gross number then? So taking into that account into what's contaminated? I mean, so you're saying that eighty percent of stuff could be recycled, but what percentage is actually recycled and becomes another product?

Yeah, it is around about eighty percent. It's about twenty percent which contains stuff that can be recycled like that one's, two's fives in paper, et cetera. But they can also be in things like plastic bag, so that won't go through. And of course then there is the contaminated stuff people putting in the nappies and all sorts of stuff.

So just to get this straight just because I'm sorry, I'm a little bit confused here. So you're saying eighty percent of the rubbish that's put into recycling bins, say, for example in Auckland, goes through the processing part, doesn't end up in landfill and gets recycled and becomes another product.

Yeah, that's about right.

Wow, is it a change, doctor seed them? Because I the messaging from the Christian City Council, for example, before the standardized rules came into play, was that there was an allowance I believe, of ten percent content the nation in a recycling truck and if that was exceeded, the whole lot went into into landfill. Was that the case before the standardization?

Yep, that was the case. And you know, likewise they allow a certain amount of contamination. So if they can pick up the level of contamination as being above the ten percent, then the whole thing goes off to landfall. And what the what they're discovering is that we're still getting about eighty percent. But yes, there is a larger amount being sent to landfill than there used to be. It used to be about ten percent. But over about the last decade or so, people have been putting in more contaminants, and where are these.

Where are these recycled products going? Where are they coming out the other end?

Are they?

So you say, once it goes through the say the refuse transit center, eighty percent of it is that then sent to recycling companies that then do the work.

Well, yeah, it goes through the cycling companies and they sell it on to manufacturers, and those manufacturers are both local and international.

Is that system working well at the moment, doctor Seden or is there still a lot of flaws within that particular system.

Well, obviously, if you've got twenty percent of the material contaminated, then there are full flaws, and it has been increasing. The change to a nationwide single system has helped things nationally, but there's also been changes like, for example, in Auckland used to leave the lids on. In other countries and other parts of the country you had lids off bottles, and now with that change, that's some people haven't caught up with those sorts of changes, even though the publicity's been there.

Oh hey, thank you so much for you. We've got to go now, doctor, You've seen an independent environmental scientist.

Interesting discussion, but I'm still going to put my rubbers through the dishwasher because it makes me feel good about myself.

I'm still very skeptical.

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