Research on membership cards

We have regained our sometimes unhappy card printer but the main question has been "do we want plastic cards at all?"

I ordered some sample 'green' cards from www.eco-card.co.uk.

There is one made of PLA - a plastic made from plants instead of oil - which is compostable at the end of its life.
Looking deeper into bioplastics lead me into another minefield - the fact that much of this new technology is created using GM crops and could potentially contaminate the recycling stream if added to conventional plastic. However, it does seem to be a really important material which may ultimately solve our requirement for plastic in a post-petroleum world. Ingeo PLA (the type that eco-card uses) is meant to be one of the better ones and the company that produces it (www.natureworksllc.com) uses certified non-GM corn.

Another card is made of recycled PVC. Which certainly seems better than using the newly minted variety. Though maybe we want to get away from using plastic.

But what other options are there?
A wooden key fob with a barcode on it?
Tattooing our customers with their memebrship number? ;-)

We want something that is long lasting as well as environmentally friendly.
In the meantime, we'll be trying some of the eco-cards to see if they work in our existing printer and see where we go from here...