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Home compostable

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Definition

Breaks down to become part of healthy soil in a home compost pile.

Overview

Compostable materials go a step beyond biodegradable materials by breaking down into natural components and becoming a part of healthy soil. Home compostable materials do not require the high heat (over 136° F)1 of industrial compost facilities to break down. They can biodegrade in the moderate heat (68-86° F) of home compost piles/bins. The concept of home compostability has come to carry extra weight as many commercial compost facilities are refusing to collect products designed for industrial compost8.

Tests for compostability measure material disintegration3, ensure the tested material has no adverse effects on plant growth, and account for toxicity by setting minimum amounts of heavy metals9.

Home composting certifications include TUV's OK compost HOME certification in Europe, and AS-5810 Home Compost standard6 in Australia. In the United States, BPI offers certification but only for industrially compostability.

Why choose it?

If it can meet your design needs, home compostable packaging is a better choice than industrially compostable packaging because there is a higher likelihood that the material will actually get composted — either at home or at a neighborhood dropoff.

The infrastructure is not yet in place in most US cities to properly process industrially compostable materials3. Some cities have local drop-off or compost pick-up services to meet the needs of cities that do not offer curbside compost collection4.

The purpose of composting is to return nutrients to soil and limit the amount of greenhouse gas released into the atmosphere as materials degrade in landfills. Compostable packaging is not nutrient-rich in the way that nitrogen-packed food waste or lawn trimmings are. Compostable packaging offers carbon to compost, which is a much smaller proportion.

However, compostable packaging can be particularly effective when designed in tandem with products that inherently return nutrients to the soil (i.e. containers for food waste or poly bags that double as food scrap bags)

Home compostable materials are also industrially compostable, though not all facilities accept compostable plastics8.

Why not choose it?

Some home compostable options, particularly compostable poly mailers, may not meet the long shelf-life needs of brands. On the other hand, compostable plastics take at least 12 months to break down in a home compost setting8.

Not everyone has access to composting, where as the recycling infrastructure is more robust and readily available5,6. When it comes to paper — which can recycled up to seven times — recycling can actually be a more sustainable way to sequester CO2 by extending the life of the material7.

Top 10 US States by Weight of Compost

Frequently asked questions

It comes down to lack of regulation and infrastructure as compostable plastic is a relatively new material. Compostable plastics take longer to degrade, which can hold up processing time in industrial facilities.

Contamination is also a risk due to labeling confusion and inconsistency11. Some compost facilities certify their compost to OMRI (Organic Materials Review Institute), which will only certify compost that’s free of polycoated papers (much compostable packaging).

There are a few factors to consider. If the paper is soiled with food grease, it’s no longer suited for the recycling stream and should be composted. If the paper is clean, recycling is probably a better option so it can be reused up to seven times, thereby sequestering CO2 and reducing the need for virgin materials.

Paper is part of the carbon ratio in compost, so you need much less of it than you do nitrogen (food scraps). Paper doesn’t add a lot of nutrients to the compost heap, which is bought and sold for its nutrients.

Yes, as long as the compost pile can get hot enough at its core. The colder the outside temperatures, the more volume (bigger pile) you need to generate heat.

CalRecycle has a good break down for how to set up a home composting system10.

Be wary of words like “compostable” or “biodegredable” with no further context. Look for a label from one of these certification bodies:

  • BPI: The Biodegradable Products Institute is a nonprofit that created the BPI certification and the US certification for industrial composting based on the ASTM test methods and specifications.
  • OK Compost Industrial: TÜV AUSTRIA is a for-profit company that purchased the certification from Vinçotte. The certification was created this European certification for industrial composting based on the harmonized EN 13432 standard.
  • OK Compost Home: This European certification for home composting is also licensed by TÜV AUSTRIA with the understanding that home composting is slower.

Also, beware of “oxo-degradable” plastic. Plastic with this label is traditional plastic with an agent added to accelerate degradation as it breaks down into small fragments (microplastics) that will never biodegrade.

TUV OK compost HOME standard requires packages to biodegrade 90% in 365 days at 20-30° C (68-86° F). This is a much lower temperature than the 58°C required by industrial composters. Similarly, Australia’s AS-5810 Home Compostability standard requires the same 90% biodegradability in the same 20-30°C but in just 180 days.

It depends on how the material is disposed. If landfilled, compostable plastic decomposing in an anaerobic environment (without oxygen) can produce methane, a powerful greenhouse gas. Paper-based materials, while compostable, are fiber based and can be easily recycled.

Yes. Compostable implies stricter rules on degradation time and soil health, meaning that the product can’t break down into anything that would inhibit plant growth.

Compost them at home or at a neighborhood dropoff. Landfill should be a last resort.

Industrially compostable plastic (PLA) will not break down in the ocean. Other home compostable polymers, starches, and paper will break down over time. ISO 18830 is the standard test to determine compostability in marine environments, but the test is not commonly performed by packaging manufacturers.