Recently several stores, such as Target, have made their plastic gift cards out of biodegradable plastic (despite them costing 3x as much as regular plastic), and Innocent Drinks have tested a 100% biodegradable bottle. But what does biodegradable actually mean?
For something to be biodegradable it has to be a organic substance that can be broken down by microorganisms, a great example being a leaf. In the case of biodegradable plastic, which is usually made from petrochemical compounds, they often use a substance called Mirel which is a corn-based product. They describe biodegradable as “the degradation of material from naturally occurring microorganisms, such as bacteria, fungi or algae over a period of time. Source: ASTM“.
For more information, check out the excellent Worldwise biodegradable article.