Compostable is the ability of matter to disintegrate over time into nutrient-rich organic material called humus.

Not to be confused with biodegradable.

Compostable products are all biodegradable, but they are specifically intended for a composting environment, and can break down faster than other biodegradable products (usually within 90 days in the right setting). 

pathways:

28.02.2024 / WasteDive / Synagro invests $50M to open 2 composting facilities

04.04.2022 / CompostNow.org / What’s safe to compost?

Wikipedia / Compost