YOUR “COMPOSTABLE” CUP ISN’T: Hot Pile, Cold Facts

Compostable is one of those words that looks saintly on a box and then misbehaves in the wild. Here’s the straight story: what the standards actually demand, how real facilities run, where home composting works (and doesn’t), why landfills are the wrong destination, and why we still tip our hats to the scientists grinding to make the tech better.

First, what “compostable” really means 

In the lab, compostability is a three-part trial by fire (well, heat + microbes): the item must disintegrate (no big fragments left), biodegrade (most carbon converted to CO₂ under aerobic conditions), and leave clean compost (no eco-tox). The big specs:

  • ASTM D6400 / D6868 (US) for plastics and coatings on paper.

  • EN 13432 (EU) for packaging, with nearly identical targets: ~90% disintegration in ~12 weeks and ~90% biodegradation in ≤6 months.

If you don’t see a trusted mark (BPI, OK compost, Seedling), treat the claim like a rental car contract—assume there’s fine print.

Industrial composting: where most certified items belong


Real facilities run aerobic systems—windrows, aerated static piles, or in-vessel—targeting ~58 °C during active phases. That heat plus oxygen is what certified packages are designed for. Lab tests assume months; facilities often move faster (think ~30–60 days active + curing) and screen finished compost at 3/8–1/2 inch. Translation: thin liners, food-soiled fiber, and well-designed serviceware tend to make the cut; thick, rigid plastics can get screened out as “overs” if they don’t break down quickly enough.

Good news: acceptance of certified food-contact items is climbing, especially at sites already taking food scraps. The catch is contamination—look-alike conventional plastics still jam the signal, so crystal-clear labeling matters.

Applause break: materials teams are tuning PHA families, blends, and coatings so they disintegrate faster in hot piles without harming compost quality. It’s not magic; it’s methodical chemistry, pilot after pilot.

Brand notes that actually help:

  • Put the certification + standard on-pack (e.g., “BPI, ASTM D6400/D6868”).

  • Say “Commercially compostable where accepted” and point people to a program finder (see “Where to compost” below).

  • Pressure-test the format with your local composters before you scale—your ops window is their reality.

Home composting: Cooler, slower, stricter

Backyard bins run cooler and wildly variable. Only items with home-compost certification (e.g., OK compost HOME, AS 5810 in Australia/NZ) belong there—these allow longer timeframes (up to ~12 months) and still require disintegration + eco-tox checks. Putting industrial-only plastics in the backyard is how you end up with confetti in your soil… and cranky neighbors.

Landfill: Wrong tool, wrong job

Landfills are anaerobic. Compostable packaging isn’t designed for that and won’t deliver soil benefits there. If it breaks down at all, it can generate methane, the climate gremlin we’re trying to avoid. The FTC also frowns on “degradable” claims for items that typically end up in landfills unless they completely break down in about a year (spoiler: they don’t). Bottom line: if your customers can’t access composting, don’t sell compostables as a climate fix—work on organics diversion first.

Quick copy you can live with

  • Industrial-only items: “Commercially compostable where accepted. Certified to ASTM D6400/D6868 (BPI). Not for home compost. Don’t recycle. Check local programs.”

  • Home-certified items: “Home-compostable (OK compost HOME/AS 5810). Conditions vary; allow extended time. Not recyclable.”

Where compostables shine today

  • Food-soiled fiber (pizza boxes, molded fiber), certified liners, and selected serviceware in communities with commercial composting.

  • Use caution with thick, rigid bioplastics unless your local facility confirms they’ll disintegrate within their cycle.

Scientists, keep going

Standards bodies refining tests. Polymer chemists adjusting backbones and blends. Field researchers closing the lab-to-pile gap. None of this is easy—and it’s moving the ball.

“Where to compost” (fast lookups you can share)

Use these to help readers find real outlets before they buy:

  • EPA “Find a Composter Near You” — launches the Excess Food Opportunities Map with many composting sites. (US EPA)

  • SPC Compost Maps — national overlays showing facilities and where compostable packaging is more likely accepted. (Sustainable Packaging Coalition)

  • BioCycle Drop-Off Locator — a growing database of neighborhood food-scrap drop-off sites. (BioCycle)

  • US Composting Council (state chapters & STA participants) — find local pros; ask what they accept. (Composting Council)

Sources (further reading & receipts)



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