Which compostable plastic types can be composted at home?

Question

There often is confusion about compostable plastics (see for example this question on greenware items or this gardening question on plastic bags). 'Compostable' suggests that you can compost the plastic yourself, but most compostable plastics are made of PLA and that can only be composted in industrial composting facilities. This is because PLA requires high temperatures for several days to decompose. If you throw the plastic on your home compost pile it most likely won't degrade (or else very slowly) because the temperatures are often too low. However, plastics that can be composted at home do exist.

What plastic types can you compost safely at home? Or which labels/certification schemes guarantee that you can compost it yourself?

Please only answer if the label explicitly mentions that the plastic will break down in home compost piles, or if you've verified yourself that the plastic does break down. Please also include the method of composting (hot/cold composting).

Answer 1

Home compostable standards

1. Published in 2010, the Australian AS 5810 is the first standard that guarantees composting at low temperatures.

   Heavy metals and plant toxicity requirements are similar to those for industrial compostability (AS 4736). Biodegradation and disintegration however need to be performed at ambient temperature instead of at elevated temperature (source)

   The AS 5810 standard has it's own logo

   

2. UNI 11183:2006 is an Italian standard that defines:

   the requirements of the plastic materials used to make products that can be disposed by aerobic biodegradation at room temperature . The term "room temperature identify the range of temperature of temperate regions excluding the high temperatures these ones typical for composting. The requirements of ecotoxicity of the plastic materials are also considered in the standard.

   The UNI 11183:2006 doesn't seem to be used much (outside of Italy?) and doesn't seem to have a logo.

Logos

Besides official government standards, there are 3 logo's that guarantee that you can compost a plastic in your home compost pile and these are:

• in Europe TÜV AUSTRIA OK compost HOME label (this company was formerly called Vinçotte, so old logos with that name may be around)
• also in Europe DIN CERTCO Geprüft Home Compostable logo
• UK only AfOR Home Compostable Logo. I was not able to find any recent information on this label, so I'm not sure it still exists.

Note that the TÜV AUSTRIA logo must have the word 'HOME' on the left. Without it, the logo only guarantees that it is compostable in an industrial facility.

Plastic types

In the past TÜV AUSTRIA / Vinçotte published a long list of plastic types that are certified home compostable in this PDF, but it seems this list is no longer updated because of new European GPDR rules.

Compostable standards

There are several standards that are often mentioned on compostable plastics that guarantee that the plastic can be composted safely (with low levels of heavy metals and toxic substances in the resulting compost). These can theoretically be used in home composting but only when doing hot-composting for a longer period of time, so this won't work on the average home compost heap. Less strict standard first:

1. The US ASTM D6400

   degradation by biological processes during composting to yield CO2, water, inorganic compounds and biomass at a rate consistent with other compostable materials and leaves no visible, distinguishable or toxic residue.... 60% biodegradation within 180 days

2. The European EN 13432 / Seedling logo

   A biodegradation level of at least 90% must be reached in less than 6 months... fragmentation and loss of visibility in the final compost (absence of visible pollution)... absence of negative effects on the composting process... Low levels of heavy metals (below given max values) and absence of negative effects on the final compost.

3. The Australian AS 4736

   • minimum of 90% of plastic materials should disintegrate into less than 2mm pieces in compost within 12 weeks
   • no toxic effect of the resulting compost on plants and earthworms.
   • hazardous substances such as heavy metals should not be present above the maximum allowed levels
   • plastic materials should contain more than 50% organic materials.

Again, these 3 standards do not guarantee under which circumstances (temperature) the plastic will compost.