What is PLA? A plain-English guide to the bioplastic in your kitchen

PLA turns up on more and more packaging, usually next to words like "bioplastic" and "compostable". So what is it, is it safe near your food, and where does it go when you're done with it? Here's the short version, then the detail.

• What it is: polylactic acid, a bioplastic made from plant sugars rather than crude oil.
• BPA? No. PLA isn't made with bisphenol chemistry, so BPA isn't part of it.
• Where it goes: wherever its certification says. Some PLA products are certified industrially compostable, some (including ZERO's cling wrap) are certified home compostable. The label decides, not the polymer name.

What is PLA and how is it made?

PLA stands for polylactic acid. It starts life as plant starch or sugar, from crops such as sugarcane, corn or cassava. Microbes ferment those sugars into lactic acid (the same acid found in yoghurt). The lactic acid is converted into a ring-shaped molecule called lactide, and the lactide is linked into long chains. Those chains are PLA.

The result is a clear, strong material that can be made into films, bags, cups and trays. PLA also runs on much of the same equipment used for conventional plastics, which is a big part of why it's become common.

The PLA in ZERO Cling Wrap is made from sugarcane, specifically bagasse, the fibrous material left after the cane is crushed. On its own PLA is quite stiff, so the wrap includes about 20% PBAT to give it the stretch and cling you expect. (More on that pairing in PLA vs PBAT.)

Is PLA BPA free?

Yes. BPA (bisphenol A) is a building block of polycarbonate plastics and some epoxy resins. PLA is built from lactic acid, so BPA simply isn't part of its chemistry. That's a structural fact, not a marketing line.

The same goes for phthalates. These are additives used to make some conventional plastics, like PVC, soft and flexible. PLA isn't made with them.

One honest caveat: "BPA free" describes the base material. A finished product can also contain inks, colours or other additives. That's why it matters whether a finished product has been tested for food contact, not just the resin it started as.

Is PLA safe for food?

PLA has a long track record in food packaging. A published safety assessment of PLA as a food-contact polymer found that what migrates from it is mainly lactic acid and lactide, which breaks down to lactic acid, a substance already present in many foods.

In Australia, food-contact materials fall under the food standards administered by Food Standards Australia New Zealand (FSANZ), which require that packaging doesn't make food unsafe.

Practical tips for using any PLA product with food:

• Follow the usage guide on the pack, especially when it comes to heat.
• It's ideal for covering bowls, wrapping leftovers and keeping fruit and veg fresh in the fridge.

Want more detail on heat? See Does PLA cling film handle heat?

Is PLA compostable?

PLA is designed to break down. Water first breaks its chains into shorter pieces, then microbes digest those pieces into carbon dioxide, water and biomass. That's the big difference from conventional plastic, which can fragment but doesn't break down like this on any human timescale.

How fast that happens depends on the conditions and on the product itself: its thickness, its formulation and what it's blended with. That's why the certification on the pack is what counts.

• AS 4736 is the Australian standard for industrially compostable plastics, tested in the heat of a commercial composting facility.
• AS 5810 is the Australian standard for home compostable plastics, tested at the lower temperatures of a backyard bin.
• OK compost HOME (TÜV Austria) and DIN CERTCO's home compostable scheme are international home composting certifications.

Some PLA items, like thick cups and cutlery, are only certified for industrial composting. Others pass home composting tests. ZERO Cling Wrap is certified home compostable (DIN CERTCO; TÜV Austria OK compost HOME), so it can go in your home compost. For a closer look at the two Australian standards, read AS 4736 vs AS 5810.

How to dispose of PLA properly

1. Read the label. Look for the certification mark and whether it says home or industrial.
2. Certified home compostable? Into your compost it goes. With ZERO Cling Wrap, remove the detachable cutter blade first, then compost the film and the box.
3. Certified industrially compostable only? Check whether your council's FOGO (food organics and garden organics) bin accepts certified compostable packaging. Rules vary by council.
4. Never put PLA in kerbside recycling. It looks like conventional plastic but it isn't, and it can contaminate the recycling stream.

Not sure what your council accepts? Our guide to compostable bags and the green bin walks you through it.

Common PLA myths

"PLA can never go in a home compost." Not true. It depends on the product. Thin, certified PLA-based films like ZERO Cling Wrap are certified home compostable. Check the mark, not the material name.

"Plant-based means heat-proof." Where a material comes from has nothing to do with how it handles heat. Follow the usage guide on the pack.

"Compostable means it's fine to drop anywhere." No. Compostable materials are designed to break down in compost. Litter is still litter.

"PLA goes in the recycling bin." It doesn't. Compost it if it's certified, otherwise follow your council's advice.

The easy swap

If you use cling wrap, the switch is simple. ZERO Cling Wrap (30m or 60m, from $6.99) is made from bioplastic, mainly sugarcane-based PLA, and it's certified home compostable. The film is strong enough that a metal cutter would bend the box or pull away, so it comes with a detachable blade instead. Pop the blade out before composting the box and film, and you're done.

FAQ

Is PLA plastic?

PLA is a bioplastic. It behaves like a plastic in use, but it's made from plant sugars and is designed to break down into carbon dioxide, water and biomass in compost. There's no dedicated regulatory category for bioplastics, so they're often grouped with plastics.

Does PLA contain BPA?

No. PLA is made from lactic acid, not bisphenol chemistry.

Can I put PLA in my home compost?

If it's certified home compostable, yes. ZERO Cling Wrap is. If a PLA product is only certified to AS 4736 (industrial), check your council's FOGO rules instead.

Can I recycle PLA?

Not in kerbside recycling. Compost certified items according to their label.