Compostable means that material is certified according to the European standards EN 13432 (packaging) and EN 14995 (products) and is composted in industrial plants. In most cases biodegradable plastics will only degrade in industrial composting plants under specific conditions, because compostability or biodegradability does not automatically mean that a product will degrade in any environment.
Degradation is dependent on factors such as temperature, time, humidity and the presence of bacteria and fungi in the specific environment. These factors can be controlled only in industrial composting plants. Nevertheless some products might be suitable for home composting. Even though a European standard for home composting does not yet exist, there are a few standards on national level already in place. Two examples for home composting labels are:
Composting of bio-based plastics only makes sense for specific applications where recycling is too difficult, for instance, because the packaging is highly contaminated with organic residues. An example where composting makes sense is the use of tea bags. To seal tea bags, most tea bags consist of 20-30% of the fossil plastic PP (polypropylene). These tea bags often end up in the composting bin, although they are not compostable. By replacing the PP with PLA the tea bag becomes fully industrially compostable.