Plastics You Could Eat - Recyling

Here is a biodegradable material that could be used for many things: shampoo bottles, plastic cups and packaging materials. But currently it's used for very little. One major factor limiting PHB's use is its brittleness. Drop a brick into a PHB shopping bag and it breaks. The other main factor limiting PHB's use is the cost: we'd have to pay a few pence extra for products packaged in PHB. But there are a few places where PHB is used. The US Navy, having despaired of trying to prevent staff throwing drinking containers overboard, has opted to use PHB cups. Now the sailors are free to throw their empty cups into the waves. In Japan, PHB has found its way into people's bathrooms and appears in the form of disposable razors. Apparently some Japanese women are so uncomfortable about body hair they remove every bit of it. The discretion surrounding the whole activity requires that the razors be thrown down a toilet, and instantly flushed away. PHB's rapid degradation in sewage clearly makes it the right choice.

PHB's success in market penetration could be greatly improved with new governmental legislation. A UN convention in 1973 required that all material thrown directly into the sea must be biodegradable, and it was this gradually coming into force that got the US navy interested in PHB. The Italian government taxes every non-biodegradable plastic bag 250 lira (about 15 US cents), and the Danish government has banned non-recyclable beverage containers. If moves like these continue, there's a better chance that we'll see PHB in our supermarkets.

Even if biodegradable plastics start to be used extensively our waste won't completely disappear. The places where our rubbish is supposed to end up, land-fill sites, are notoriously bad at enabling anything to degrade - even paper lasts decades. There aren't enough bacteria because there isn't enough oxygen around to keep them alive. Large-scale composting facilities will be needed and these cost money.

Using PHB in the Body

Since the bacteria in our own stomachs make PHB to store energy our bodies don't reject it. PHB can be used in medicine, in sutures for example, where the body gradually replaces PHB over time. The plastic could also be used as a material that slowly releases drugs into the body. After surgical implantation, its gradual degradation releases locked-in drugs, right at the point where they are needed most. The fact that the human body accepts PHB, means that you could eat the wrapper along with the chocolate bar.

Jamie Hobbs The exact form of the PHB spherulites depends on the temperature at which they crystallize: These grew at 80°, 55° and 40° respectively.