Biodegradable materials are not necessarily compostable, and compostable materials are not necessarily compostable at home. This is a long but interesting article on the subject [www.growingcommunities.org
] and an article on misleading claims about biodegradability in plastic products [www.theguardian.com
That's not very hopeful, sorry! Maybe someone here has deeper knowledge and can suggest something but I suspect the best solution is to encourage people to bring their own?